grpc package - google.golang.org/grpc - Go Packages (original) (raw)

Package grpc implements an RPC system called gRPC.

See grpc.io for more information about gRPC.

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const ( SupportPackageIsVersion3 = true SupportPackageIsVersion4 = true SupportPackageIsVersion5 = true SupportPackageIsVersion6 = true SupportPackageIsVersion7 = true SupportPackageIsVersion8 = true SupportPackageIsVersion9 = true )

The SupportPackageIsVersion variables are referenced from generated protocol buffer files to ensure compatibility with the gRPC version used. The latest support package version is 9.

Older versions are kept for compatibility.

These constants should not be referenced from any other code.

Version is the current grpc version.

DefaultBackoffConfig uses values specified for backoff inhttps://github.com/grpc/grpc/blob/master/doc/connection-backoff.md.

Deprecated: use ConnectParams instead. Will be supported throughout 1.x.

EnableTracing controls whether to trace RPCs using the golang.org/x/net/trace package. This should only be set before any RPCs are sent or received by this program.

ErrClientConnTimeout indicates that the ClientConn cannot establish the underlying connections within the specified timeout.

Deprecated: This error is never returned by grpc and should not be referenced by users.

ErrServerStopped indicates that the operation is now illegal because of the server being stopped.

ClientSupportedCompressors returns compressor names advertised by the client via grpc-accept-encoding header.

The context provided must be the context passed to the server's handler.

Experimental

Notice: This function is EXPERIMENTAL and may be changed or removed in a later release.

Code returns the error code for err if it was produced by the rpc system. Otherwise, it returns codes.Unknown.

Deprecated: use status.Code instead.

ErrorDesc returns the error description of err if it was produced by the rpc system. Otherwise, it returns err.Error() or empty string when err is nil.

Deprecated: use status.Convert and Message method instead.

Errorf returns an error containing an error code and a description; Errorf returns nil if c is OK.

Deprecated: use status.Errorf instead.

Invoke sends the RPC request on the wire and returns after response is received. This is typically called by generated code.

DEPRECATED: Use ClientConn.Invoke instead.

Method returns the method string for the server context. The returned string is in the format of "/service/method".

MethodFromServerStream returns the method string for the input stream. The returned string is in the format of "/service/method".

NewContextWithServerTransportStream creates a new context from ctx and attaches stream to it.

Experimental

Notice: This API is EXPERIMENTAL and may be changed or removed in a later release.

SendHeader sends header metadata. It may be called at most once, and may not be called after any event that causes headers to be sent (see SetHeader for a complete list). The provided md and headers set by SetHeader() will be sent.

The error returned is compatible with the status package. However, the status code will often not match the RPC status as seen by the client application, and therefore, should not be relied upon for this purpose.

SetHeader sets the header metadata to be sent from the server to the client. The context provided must be the context passed to the server's handler.

Streaming RPCs should prefer the SetHeader method of the ServerStream.

When called multiple times, all the provided metadata will be merged. All the metadata will be sent out when one of the following happens:

SetHeader will fail if called after any of the events above.

The error returned is compatible with the status package. However, the status code will often not match the RPC status as seen by the client application, and therefore, should not be relied upon for this purpose.

SetSendCompressor sets a compressor for outbound messages from the server. It must not be called after any event that causes headers to be sent (see ServerStream.SetHeader for the complete list). Provided compressor is used when below conditions are met:

The context provided must be the context passed to the server's handler. It must be noted that compressor name encoding.Identity disables the outbound compression. By default, server messages will be sent using the same compressor with which request messages were sent.

It is not safe to call SetSendCompressor concurrently with SendHeader and SendMsg.

Experimental

Notice: This function is EXPERIMENTAL and may be changed or removed in a later release.

SetTrailer sets the trailer metadata that will be sent when an RPC returns. When called more than once, all the provided metadata will be merged.

The error returned is compatible with the status package. However, the status code will often not match the RPC status as seen by the client application, and therefore, should not be relied upon for this purpose.

BackoffConfig defines the parameters for the default gRPC backoff strategy.

Deprecated: use ConnectParams instead. Will be supported throughout 1.x.

type BidiStreamingClient[Req any, Res any] interface {

Send(*Req) [error](/builtin#error)


Recv() (*Res, [error](/builtin#error))


[ClientStream](#ClientStream)

}

BidiStreamingClient represents the client side of a bidirectional-streaming (many requests, many responses) RPC. It is generic over both the type of the request message stream and the type of the response message stream. It is used in generated code.

type BidiStreamingServer[Req any, Res any] interface {

Recv() (*Req, [error](/builtin#error))


Send(*Res) [error](/builtin#error)


[ServerStream](#ServerStream)

}

BidiStreamingServer represents the server side of a bidirectional-streaming (many requests, many responses) RPC. It is generic over both the type of the request message stream and the type of the response message stream. It is used in generated code.

To terminate the stream, return from the handler method and return an error from the status package, or use nil to indicate an OK status code.

type CallOption interface {

}

CallOption configures a Call before it starts or extracts information from a Call after it completes.

func CallContentSubtype added in v1.10.0

func CallContentSubtype(contentSubtype string) CallOption

CallContentSubtype returns a CallOption that will set the content-subtype for a call. For example, if content-subtype is "json", the Content-Type over the wire will be "application/grpc+json". The content-subtype is converted to lowercase before being included in Content-Type. See Content-Type onhttps://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md#requests for more details.

If ForceCodec is not also used, the content-subtype will be used to look up the Codec to use in the registry controlled by RegisterCodec. See the documentation on RegisterCodec for details on registration. The lookup of content-subtype is case-insensitive. If no such Codec is found, the call will result in an error with code codes.Internal.

If ForceCodec is also used, that Codec will be used for all request and response messages, with the content-subtype set to the given contentSubtype here for requests.

func CallCustomCodec(codec Codec) CallOption

CallCustomCodec behaves like ForceCodec, but accepts a grpc.Codec instead of an encoding.Codec.

Deprecated: use ForceCodec instead.

func FailFast(failFast bool) CallOption

FailFast is the opposite of WaitForReady.

Deprecated: use WaitForReady.

ForceCodec returns a CallOption that will set codec to be used for all request and response messages for a call. The result of calling Name() will be used as the content-subtype after converting to lowercase, unless CallContentSubtype is also used.

See Content-Type onhttps://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md#requests for more details. Also see the documentation on RegisterCodec and CallContentSubtype for more details on the interaction between Codec and content-subtype.

This function is provided for advanced users; prefer to use only CallContentSubtype to select a registered codec instead.

Experimental

Notice: This API is EXPERIMENTAL and may be changed or removed in a later release.

ForceCodecV2 returns a CallOption that will set codec to be used for all request and response messages for a call. The result of calling Name() will be used as the content-subtype after converting to lowercase, unless CallContentSubtype is also used.

See Content-Type onhttps://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md#requests for more details. Also see the documentation on RegisterCodec and CallContentSubtype for more details on the interaction between Codec and content-subtype.

This function is provided for advanced users; prefer to use only CallContentSubtype to select a registered codec instead.

Experimental

Notice: This API is EXPERIMENTAL and may be changed or removed in a later release.

Header returns a CallOptions that retrieves the header metadata for a unary RPC.

func MaxCallRecvMsgSize(bytes int) CallOption

MaxCallRecvMsgSize returns a CallOption which sets the maximum message size in bytes the client can receive. If this is not set, gRPC uses the default 4MB.

func MaxCallSendMsgSize(bytes int) CallOption

MaxCallSendMsgSize returns a CallOption which sets the maximum message size in bytes the client can send. If this is not set, gRPC uses the default `math.MaxInt32`.

func MaxRetryRPCBufferSize(bytes int) CallOption

MaxRetryRPCBufferSize returns a CallOption that limits the amount of memory used for buffering this RPC's requests for retry purposes.

Experimental

Notice: This API is EXPERIMENTAL and may be changed or removed in a later release.

func OnFinish(onFinish func(err error)) CallOption

OnFinish returns a CallOption that configures a callback to be called when the call completes. The error passed to the callback is the status of the RPC, and may be nil. The onFinish callback provided will only be called once by gRPC. This is mainly used to be used by streaming interceptors, to be notified when the RPC completes along with information about the status of the RPC.

Experimental

Notice: This API is EXPERIMENTAL and may be changed or removed in a later release.

Peer returns a CallOption that retrieves peer information for a unary RPC. The peer field will be populated *after* the RPC completes.

PerRPCCredentials returns a CallOption that sets credentials.PerRPCCredentials for a call.

func StaticMethod() CallOption

StaticMethod returns a CallOption which specifies that a call is being made to a method that is static, which means the method is known at compile time and doesn't change at runtime. This can be used as a signal to stats plugins that this method is safe to include as a key to a measurement.

Trailer returns a CallOptions that retrieves the trailer metadata for a unary RPC.

UseCompressor returns a CallOption which sets the compressor used when sending the request. If WithCompressor is also set, UseCompressor has higher priority.

Experimental

Notice: This API is EXPERIMENTAL and may be changed or removed in a later release.

func WaitForReady(waitForReady bool) CallOption

WaitForReady configures the RPC's behavior when the client is in TRANSIENT_FAILURE, which occurs when all addresses fail to connect. If waitForReady is false, the RPC will fail immediately. Otherwise, the client will wait until a connection becomes available or the RPC's deadline is reached.

By default, RPCs do not "wait for ready".

type ClientConn struct {

}

ClientConn represents a virtual connection to a conceptual endpoint, to perform RPCs.

A ClientConn is free to have zero or more actual connections to the endpoint based on configuration, load, etc. It is also free to determine which actual endpoints to use and may change it every RPC, permitting client-side load balancing.

A ClientConn encapsulates a range of functionality including name resolution, TCP connection establishment (with retries and backoff) and TLS handshakes. It also handles errors on established connections by re-resolving the name and reconnecting.

Dial calls DialContext(context.Background(), target, opts...).

Deprecated: use NewClient instead. Will be supported throughout 1.x.

DialContext calls NewClient and then exits idle mode. If WithBlock(true) is used, it calls Connect and WaitForStateChange until either the context expires or the state of the ClientConn is Ready.

One subtle difference between NewClient and Dial and DialContext is that the former uses "dns" as the default name resolver, while the latter use "passthrough" for backward compatibility. This distinction should not matter to most users, but could matter to legacy users that specify a custom dialer and expect it to receive the target string directly.

Deprecated: use NewClient instead. Will be supported throughout 1.x.

NewClient creates a new gRPC "channel" for the target URI provided. No I/O is performed. Use of the ClientConn for RPCs will automatically cause it to connect. Connect may be used to manually create a connection, but for most users this is unnecessary.

The target name syntax is defined inhttps://github.com/grpc/grpc/blob/master/doc/naming.md. e.g. to use dns resolver, a "dns:///" prefix should be applied to the target.

The DialOptions returned by WithBlock, WithTimeout, WithReturnConnectionError, and FailOnNonTempDialError are ignored by this function.

func (cc *ClientConn) CanonicalTarget() string

CanonicalTarget returns the canonical target string of the ClientConn.

Close tears down the ClientConn and all underlying connections.

func (cc *ClientConn) Connect()

Connect causes all subchannels in the ClientConn to attempt to connect if the channel is idle. Does not wait for the connection attempts to begin before returning.

Experimental

Notice: This API is EXPERIMENTAL and may be changed or removed in a later release.

func (cc *ClientConn) GetMethodConfig(method string) MethodConfig

GetMethodConfig gets the method config of the input method. If there's an exact match for input method (i.e. /service/method), we return the corresponding MethodConfig. If there isn't an exact match for the input method, we look for the service's default config under the service (i.e /service/) and then for the default for all services (empty string).

If there is a default MethodConfig for the service, we return it. Otherwise, we return an empty MethodConfig.

GetState returns the connectivity.State of ClientConn.

Invoke sends the RPC request on the wire and returns after response is received. This is typically called by generated code.

All errors returned by Invoke are compatible with the status package.

NewStream creates a new Stream for the client side. This is typically called by generated code. ctx is used for the lifetime of the stream.

To ensure resources are not leaked due to the stream returned, one of the following actions must be performed:

  1. Call Close on the ClientConn.
  2. Cancel the context provided.
  3. Call RecvMsg until a non-nil error is returned. A protobuf-generated client-streaming RPC, for instance, might use the helper function CloseAndRecv (note that CloseSend does not Recv, therefore is not guaranteed to release all resources).
  4. Receive a non-nil, non-io.EOF error from Header or SendMsg.

If none of the above happen, a goroutine and a context will be leaked, and grpc will not call the optionally-configured stats handler with a stats.End message.

func (cc *ClientConn) ResetConnectBackoff()

ResetConnectBackoff wakes up all subchannels in transient failure and causes them to attempt another connection immediately. It also resets the backoff times used for subsequent attempts regardless of the current state.

In general, this function should not be used. Typical service or network outages result in a reasonable client reconnection strategy by default. However, if a previously unavailable network becomes available, this may be used to trigger an immediate reconnect.

Experimental

Notice: This API is EXPERIMENTAL and may be changed or removed in a later release.

Target returns the target string of the ClientConn.

WaitForStateChange waits until the connectivity.State of ClientConn changes from sourceState or ctx expires. A true value is returned in former case and false in latter.

ClientConnInterface defines the functions clients need to perform unary and streaming RPCs. It is implemented by *ClientConn, and is only intended to be referenced by generated code.

ClientStream defines the client-side behavior of a streaming RPC.

All errors returned from ClientStream methods are compatible with the status package.

NewClientStream is a wrapper for ClientConn.NewStream.

type ClientStreamingClient[Req any, Res any] interface {

Send(*Req) [error](/builtin#error)


CloseAndRecv() (*Res, [error](/builtin#error))


[ClientStream](#ClientStream)

}

ClientStreamingClient represents the client side of a client-streaming (many requests, one response) RPC. It is generic over both the type of the request message stream and the type of the unary response message. It is used in generated code.

type ClientStreamingServer[Req any, Res any] interface {

Recv() (*Req, [error](/builtin#error))


SendAndClose(*Res) [error](/builtin#error)


[ServerStream](#ServerStream)

}

ClientStreamingServer represents the server side of a client-streaming (many requests, one response) RPC. It is generic over both the type of the request message stream and the type of the unary response message. It is used in generated code.

To terminate the RPC, call SendAndClose and return nil from the method handler or do not call SendAndClose and return an error from the status package.

Codec defines the interface gRPC uses to encode and decode messages. Note that implementations of this interface must be thread safe; a Codec's methods can be called from concurrent goroutines.

Deprecated: use encoding.Codec instead.

Compressor defines the interface gRPC uses to compress a message.

Deprecated: use package encoding.

func NewGZIPCompressor() Compressor

NewGZIPCompressor creates a Compressor based on GZIP.

Deprecated: use package encoding/gzip.

func NewGZIPCompressorWithLevel(level int) (Compressor, error)

NewGZIPCompressorWithLevel is like NewGZIPCompressor but specifies the gzip compression level instead of assuming DefaultCompression.

The error returned will be nil if the level is valid.

Deprecated: use package encoding/gzip.

type CompressorCallOption struct { CompressorType string }

CompressorCallOption is a CallOption that indicates the compressor to use.

Experimental

Notice: This type is EXPERIMENTAL and may be changed or removed in a later release.

ConnectParams defines the parameters for connecting and retrying. Users are encouraged to use this instead of the BackoffConfig type defined above. See here for more details:https://github.com/grpc/grpc/blob/master/doc/connection-backoff.md.

Experimental

Notice: This type is EXPERIMENTAL and may be changed or removed in a later release.

type ContentSubtypeCallOption added in v1.11.0

type ContentSubtypeCallOption struct { ContentSubtype string }

ContentSubtypeCallOption is a CallOption that indicates the content-subtype used for marshaling messages.

Experimental

Notice: This type is EXPERIMENTAL and may be changed or removed in a later release.

type CustomCodecCallOption struct { Codec Codec }

CustomCodecCallOption is a CallOption that indicates the codec used for marshaling messages.

Experimental

Notice: This type is EXPERIMENTAL and may be changed or removed in a later release.

Decompressor defines the interface gRPC uses to decompress a message.

Deprecated: use package encoding.

func NewGZIPDecompressor() Decompressor

NewGZIPDecompressor creates a Decompressor based on GZIP.

Deprecated: use package encoding/gzip.

type DialOption interface {

}

DialOption configures how we set up the connection.

func FailOnNonTempDialError(f bool) DialOption

FailOnNonTempDialError returns a DialOption that specifies if gRPC fails on non-temporary dial errors. If f is true, and dialer returns a non-temporary error, gRPC will fail the connection to the network address and won't try to reconnect. The default value of FailOnNonTempDialError is false.

FailOnNonTempDialError only affects the initial dial, and does not do anything useful unless you are also using WithBlock().

Use of this feature is not recommended. For more information, please see:https://github.com/grpc/grpc-go/blob/master/Documentation/anti-patterns.md

Deprecated: this DialOption is not supported by NewClient. This API may be changed or removed in a later release.

WithAuthority returns a DialOption that specifies the value to be used as the :authority pseudo-header and as the server name in authentication handshake.

func WithBackoffConfig(b BackoffConfig) DialOption

WithBackoffConfig configures the dialer to use the provided backoff parameters after connection failures.

Deprecated: use WithConnectParams instead. Will be supported throughout 1.x.

WithBackoffMaxDelay configures the dialer to use the provided maximum delay when backing off after failed connection attempts.

Deprecated: use WithConnectParams instead. Will be supported throughout 1.x.

func WithBlock() DialOption

WithBlock returns a DialOption which makes callers of Dial block until the underlying connection is up. Without this, Dial returns immediately and connecting the server happens in background.

Use of this feature is not recommended. For more information, please see:https://github.com/grpc/grpc-go/blob/master/Documentation/anti-patterns.md

Deprecated: this DialOption is not supported by NewClient. Will be supported throughout 1.x.

func WithChainStreamInterceptor(interceptors ...StreamClientInterceptor) DialOption

WithChainStreamInterceptor returns a DialOption that specifies the chained interceptor for streaming RPCs. The first interceptor will be the outer most, while the last interceptor will be the inner most wrapper around the real call. All interceptors added by this method will be chained, and the interceptor defined by WithStreamInterceptor will always be prepended to the chain.

func WithChainUnaryInterceptor(interceptors ...UnaryClientInterceptor) DialOption

WithChainUnaryInterceptor returns a DialOption that specifies the chained interceptor for unary RPCs. The first interceptor will be the outer most, while the last interceptor will be the inner most wrapper around the real call. All interceptors added by this method will be chained, and the interceptor defined by WithUnaryInterceptor will always be prepended to the chain.

WithChannelzParentID returns a DialOption that specifies the channelz ID of current ClientConn's parent. This function is used in nested channel creation (e.g. grpclb dial).

Experimental

Notice: This API is EXPERIMENTAL and may be changed or removed in a later release.

func WithCodec(c Codec) DialOption

WithCodec returns a DialOption which sets a codec for message marshaling and unmarshaling.

Deprecated: use WithDefaultCallOptions(ForceCodec(_)) instead. Will be supported throughout 1.x.

func WithCompressor(cp Compressor) DialOption

WithCompressor returns a DialOption which sets a Compressor to use for message compression. It has lower priority than the compressor set by the UseCompressor CallOption.

Deprecated: use UseCompressor instead. Will be supported throughout 1.x.

func WithConnectParams(p ConnectParams) DialOption

WithConnectParams configures the ClientConn to use the provided ConnectParams for creating and maintaining connections to servers.

The backoff configuration specified as part of the ConnectParams overrides all defaults specified inhttps://github.com/grpc/grpc/blob/master/doc/connection-backoff.md. Consider using the backoff.DefaultConfig as a base, in cases where you want to override only a subset of the backoff configuration.

WithContextDialer returns a DialOption that sets a dialer to create connections. If FailOnNonTempDialError() is set to true, and an error is returned by f, gRPC checks the error's Temporary() method to decide if it should try to reconnect to the network address.

Note: All supported releases of Go (as of December 2023) override the OS defaults for TCP keepalive time and interval to 15s. To enable TCP keepalive with OS defaults for keepalive time and interval, use a net.Dialer that sets the KeepAlive field to a negative value, and sets the SO_KEEPALIVE socket option to true from the Control field. For a concrete example of how to do this, see internal.NetDialerWithTCPKeepalive().

For more information, please see issue 23459 in the Go GitHub repo.

WithCredentialsBundle returns a DialOption to set a credentials bundle for the ClientConn.WithCreds. This should not be used together with WithTransportCredentials.

Experimental

Notice: This API is EXPERIMENTAL and may be changed or removed in a later release.

func WithDecompressor(dc Decompressor) DialOption

WithDecompressor returns a DialOption which sets a Decompressor to use for incoming message decompression. If incoming response messages are encoded using the decompressor's Type(), it will be used. Otherwise, the message encoding will be used to look up the compressor registered via encoding.RegisterCompressor, which will then be used to decompress the message. If no compressor is registered for the encoding, an Unimplemented status error will be returned.

Deprecated: use encoding.RegisterCompressor instead. Will be supported throughout 1.x.

func WithDefaultCallOptions(cos ...CallOption) DialOption

WithDefaultCallOptions returns a DialOption which sets the default CallOptions for calls over the connection.

func WithDefaultServiceConfig(s string) DialOption

WithDefaultServiceConfig returns a DialOption that configures the default service config, which will be used in cases where:

1. WithDisableServiceConfig is also used, or

2. The name resolver does not provide a service config or provides an invalid service config.

The parameter s is the JSON representation of the default service config. For more information about service configs, see:https://github.com/grpc/grpc/blob/master/doc/service_config.mdFor a simple example of usage, see: examples/features/load_balancing/client/main.go

WithDialer returns a DialOption that specifies a function to use for dialing network addresses. If FailOnNonTempDialError() is set to true, and an error is returned by f, gRPC checks the error's Temporary() method to decide if it should try to reconnect to the network address.

Deprecated: use WithContextDialer instead. Will be supported throughout 1.x.

func WithDisableHealthCheck() DialOption

WithDisableHealthCheck disables the LB channel health checking for all SubConns of this ClientConn.

Experimental

Notice: This API is EXPERIMENTAL and may be changed or removed in a later release.

func WithDisableRetry() DialOption

WithDisableRetry returns a DialOption that disables retries, even if the service config enables them. This does not impact transparent retries, which will happen automatically if no data is written to the wire or if the RPC is unprocessed by the remote server.

func WithDisableServiceConfig() DialOption

WithDisableServiceConfig returns a DialOption that causes gRPC to ignore any service config provided by the resolver and provides a hint to the resolver to not fetch service configs.

Note that this dial option only disables service config from resolver. If default service config is provided, gRPC will use the default service config.

WithIdleTimeout returns a DialOption that configures an idle timeout for the channel. If the channel is idle for the configured timeout, i.e there are no ongoing RPCs and no new RPCs are initiated, the channel will enter idle mode and as a result the name resolver and load balancer will be shut down. The channel will exit idle mode when the Connect() method is called or when an RPC is initiated.

A default timeout of 30 minutes will be used if this dial option is not set at dial time and idleness can be disabled by passing a timeout of zero.

Experimental

Notice: This API is EXPERIMENTAL and may be changed or removed in a later release.

func WithInitialConnWindowSize(s int32) DialOption

WithInitialConnWindowSize returns a DialOption which sets the value for initial window size on a connection. The lower bound for window size is 64K and any value smaller than that will be ignored.

func WithInitialWindowSize(s int32) DialOption

WithInitialWindowSize returns a DialOption which sets the value for initial window size on a stream. The lower bound for window size is 64K and any value smaller than that will be ignored.

func WithInsecure() DialOption

WithInsecure returns a DialOption which disables transport security for this ClientConn. Under the hood, it uses insecure.NewCredentials().

Note that using this DialOption with per-RPC credentials (through WithCredentialsBundle or WithPerRPCCredentials) which require transport security is incompatible and will cause grpc.Dial() to fail.

Deprecated: use WithTransportCredentials and insecure.NewCredentials() instead. Will be supported throughout 1.x.

WithKeepaliveParams returns a DialOption that specifies keepalive parameters for the client transport.

Keepalive is disabled by default.

func WithMaxCallAttempts(n int) DialOption

WithMaxCallAttempts returns a DialOption that configures the maximum number of attempts per call (including retries and hedging) using the channel. Service owners may specify a higher value for these parameters, but higher values will be treated as equal to the maximum value by the client implementation. This mitigates security concerns related to the service config being transferred to the client via DNS.

A value of 5 will be used if this dial option is not set or n < 2.

func WithMaxHeaderListSize(s uint32) DialOption

WithMaxHeaderListSize returns a DialOption that specifies the maximum (uncompressed) size of header list that the client is prepared to accept.

func WithMaxMsgSize(s int) DialOption

WithMaxMsgSize returns a DialOption which sets the maximum message size the client can receive.

Deprecated: use WithDefaultCallOptions(MaxCallRecvMsgSize(s)) instead. Will be supported throughout 1.x.

func WithNoProxy() DialOption

WithNoProxy returns a DialOption which disables the use of proxies for this ClientConn. This is ignored if WithDialer or WithContextDialer are used.

Experimental

Notice: This API is EXPERIMENTAL and may be changed or removed in a later release.

WithPerRPCCredentials returns a DialOption which sets credentials and places auth state on each outbound RPC.

func WithReadBufferSize(s int) DialOption

WithReadBufferSize lets you set the size of read buffer, this determines how much data can be read at most for each read syscall.

The default value for this buffer is 32KB. Zero or negative values will disable read buffer for a connection so data framer can access the underlying conn directly.

WithResolvers allows a list of resolver implementations to be registered locally with the ClientConn without needing to be globally registered via resolver.Register. They will be matched against the scheme used for the current Dial only, and will take precedence over the global registry.

Experimental

Notice: This API is EXPERIMENTAL and may be changed or removed in a later release.

func WithReturnConnectionError() DialOption

WithReturnConnectionError returns a DialOption which makes the client connection return a string containing both the last connection error that occurred and the context.DeadlineExceeded error. Implies WithBlock()

Use of this feature is not recommended. For more information, please see:https://github.com/grpc/grpc-go/blob/master/Documentation/anti-patterns.md

Deprecated: this DialOption is not supported by NewClient. Will be supported throughout 1.x.

func WithSharedWriteBuffer(val bool) DialOption

WithSharedWriteBuffer allows reusing per-connection transport write buffer. If this option is set to true every connection will release the buffer after flushing the data on the wire.

Experimental

Notice: This API is EXPERIMENTAL and may be changed or removed in a later release.

func WithStatsHandler added in v1.2.0

WithStatsHandler returns a DialOption that specifies the stats handler for all the RPCs and underlying network connections in this ClientConn.

func WithStreamInterceptor(f StreamClientInterceptor) DialOption

WithStreamInterceptor returns a DialOption that specifies the interceptor for streaming RPCs.

WithTimeout returns a DialOption that configures a timeout for dialing a ClientConn initially. This is valid if and only if WithBlock() is present.

Deprecated: this DialOption is not supported by NewClient. Will be supported throughout 1.x.

WithTransportCredentials returns a DialOption which configures a connection level security credentials (e.g., TLS/SSL). This should not be used together with WithCredentialsBundle.

func WithUnaryInterceptor(f UnaryClientInterceptor) DialOption

WithUnaryInterceptor returns a DialOption that specifies the interceptor for unary RPCs.

WithUserAgent returns a DialOption that specifies a user agent string for all the RPCs.

func WithWriteBufferSize(s int) DialOption

WithWriteBufferSize determines how much data can be batched before doing a write on the wire. The default value for this buffer is 32KB.

Zero or negative values will disable the write buffer such that each write will be on underlying connection. Note: A Send call may not directly translate to a write.

type EmptyCallOption struct{}

EmptyCallOption does not alter the Call configuration. It can be embedded in another structure to carry satellite data for use by interceptors.

type EmptyDialOption struct{}

EmptyDialOption does not alter the dial configuration. It can be embedded in another structure to build custom dial options.

Experimental

Notice: This type is EXPERIMENTAL and may be changed or removed in a later release.

type EmptyServerOption struct{}

EmptyServerOption does not alter the server configuration. It can be embedded in another structure to build custom server options.

Experimental

Notice: This type is EXPERIMENTAL and may be changed or removed in a later release.

type FailFastCallOption struct { FailFast bool }

FailFastCallOption is a CallOption for indicating whether an RPC should fail fast or not.

Experimental

Notice: This type is EXPERIMENTAL and may be changed or removed in a later release.

ForceCodecCallOption is a CallOption that indicates the codec used for marshaling messages.

Experimental

Notice: This type is EXPERIMENTAL and may be changed or removed in a later release.

ForceCodecV2CallOption is a CallOption that indicates the codec used for marshaling messages.

Experimental

Notice: This type is EXPERIMENTAL and may be changed or removed in a later release.

type GenericClientStream[Req any, Res any] struct { ClientStream }

GenericClientStream implements the ServerStreamingClient, ClientStreamingClient, and BidiStreamingClient interfaces. It is used in generated code.

func (*GenericClientStream[Req, Res]) CloseAndRecv added in v1.64.0

func (x *GenericClientStream[Req, Res]) CloseAndRecv() (*Res, error)

CloseAndRecv closes the sending side of the stream, then receives the unary response from the server. The type of message which it returns is determined by the Res type parameter of the GenericClientStream receiver.

func (x *GenericClientStream[Req, Res]) Recv() (*Res, error)

Recv reads one message from the stream of responses generated by the server. The type of the message returned is determined by the Res type parameter of the GenericClientStream receiver.

func (x *GenericClientStream[Req, Res]) Send(m *Req) error

Send pushes one message into the stream of requests to be consumed by the server. The type of message which can be sent is determined by the Req type parameter of the GenericClientStream receiver.

type GenericServerStream[Req any, Res any] struct { ServerStream }

GenericServerStream implements the ServerStreamingServer, ClientStreamingServer, and BidiStreamingServer interfaces. It is used in generated code.

func (x *GenericServerStream[Req, Res]) Recv() (*Req, error)

Recv reads one message from the stream of requests generated by the client. The type of the message returned is determined by the Req type parameter of the clientStreamServer receiver.

func (x *GenericServerStream[Req, Res]) Send(m *Res) error

Send pushes one message into the stream of responses to be consumed by the client. The type of message which can be sent is determined by the Res type parameter of the serverStreamServer receiver.

func (*GenericServerStream[Req, Res]) SendAndClose added in v1.64.0

func (x *GenericServerStream[Req, Res]) SendAndClose(m *Res) error

SendAndClose pushes the unary response to the client. The type of message which can be sent is determined by the Res type parameter of the clientStreamServer receiver.

type HeaderCallOption struct { }

HeaderCallOption is a CallOption for collecting response header metadata. The metadata field will be populated *after* the RPC completes.

Notice: This type is EXPERIMENTAL and may be changed or removed in a later release.

type MaxHeaderListSizeDialOption struct { }

MaxHeaderListSizeDialOption is a DialOption that specifies the maximum (uncompressed) size of header list that the client is prepared to accept.

type MaxHeaderListSizeServerOption struct { }

MaxHeaderListSizeServerOption is a ServerOption that sets the max (uncompressed) size of header list that the server is prepared to accept.

type MaxRecvMsgSizeCallOption struct { MaxRecvMsgSize int }

MaxRecvMsgSizeCallOption is a CallOption that indicates the maximum message size in bytes the client can receive.

Experimental

Notice: This type is EXPERIMENTAL and may be changed or removed in a later release.

type MaxRetryRPCBufferSizeCallOption struct { MaxRetryRPCBufferSize int }

MaxRetryRPCBufferSizeCallOption is a CallOption indicating the amount of memory to be used for caching this RPC for retry purposes.

Experimental

Notice: This type is EXPERIMENTAL and may be changed or removed in a later release.

type MaxSendMsgSizeCallOption struct { MaxSendMsgSize int }

MaxSendMsgSizeCallOption is a CallOption that indicates the maximum message size in bytes the client can send.

Experimental

Notice: This type is EXPERIMENTAL and may be changed or removed in a later release.

type MethodDesc struct { MethodName string Handler methodHandler }

MethodDesc represents an RPC service's method specification.

type MethodInfo struct {

Name [string](/builtin#string)

IsClientStream [bool](/builtin#bool)

IsServerStream [bool](/builtin#bool)

}

MethodInfo contains the information of an RPC including its method name and type.

type OnFinishCallOption struct { OnFinish func(error) }

OnFinishCallOption is CallOption that indicates a callback to be called when the call completes.

Experimental

Notice: This type is EXPERIMENTAL and may be changed or removed in a later release.

type PeerCallOption struct { PeerAddr *peer.Peer }

PeerCallOption is a CallOption for collecting the identity of the remote peer. The peer field will be populated *after* the RPC completes.

Experimental

Notice: This type is EXPERIMENTAL and may be changed or removed in a later release.

PerRPCCredsCallOption is a CallOption that indicates the per-RPC credentials to use for the call.

Experimental

Notice: This type is EXPERIMENTAL and may be changed or removed in a later release.

type PreparedMsg struct {

}

PreparedMsg is responsible for creating a Marshalled and Compressed object.

Experimental

Notice: This type is EXPERIMENTAL and may be changed or removed in a later release.

Encode marshalls and compresses the message using the codec and compressor for the stream.

Server is a gRPC server to serve RPC requests.

func NewServer(opt ...ServerOption) *Server

NewServer creates a gRPC server which has no service registered and has not started to accept requests yet.

func (s *Server) GetServiceInfo() map[string]ServiceInfo

GetServiceInfo returns a map from service names to ServiceInfo. Service names include the package names, in the form of ..

func (s *Server) GracefulStop()

GracefulStop stops the gRPC server gracefully. It stops the server from accepting new connections and RPCs and blocks until all the pending RPCs are finished.

func (s *Server) RegisterService(sd *ServiceDesc, ss any)

RegisterService registers a service and its implementation to the gRPC server. It is called from the IDL generated code. This must be called before invoking Serve. If ss is non-nil (for legacy code), its type is checked to ensure it implements sd.HandlerType.

Serve accepts incoming connections on the listener lis, creating a new ServerTransport and service goroutine for each. The service goroutines read gRPC requests and then call the registered handlers to reply to them. Serve returns when lis.Accept fails with fatal errors. lis will be closed when this method returns. Serve will return a non-nil error unless Stop or GracefulStop is called.

Note: All supported releases of Go (as of December 2023) override the OS defaults for TCP keepalive time and interval to 15s. To enable TCP keepalive with OS defaults for keepalive time and interval, callers need to do the following two things:

ServeHTTP implements the Go standard library's http.Handler interface by responding to the gRPC request r, by looking up the requested gRPC method in the gRPC server s.

The provided HTTP request must have arrived on an HTTP/2 connection. When using the Go standard library's server, practically this means that the Request must also have arrived over TLS.

To share one port (such as 443 for https) between gRPC and an existing http.Handler, use a root http.Handler such as:

if r.ProtoMajor == 2 && strings.HasPrefix( r.Header.Get("Content-Type"), "application/grpc") { grpcServer.ServeHTTP(w, r) } else { yourMux.ServeHTTP(w, r) }

Note that ServeHTTP uses Go's HTTP/2 server implementation which is totally separate from grpc-go's HTTP/2 server. Performance and features may vary between the two paths. ServeHTTP does not support some gRPC features available through grpc-go's HTTP/2 server.

Experimental

Notice: This API is EXPERIMENTAL and may be changed or removed in a later release.

Stop stops the gRPC server. It immediately closes all open connections and listeners. It cancels all active RPCs on the server side and the corresponding pending RPCs on the client side will get notified by connection errors.

type ServerOption interface {

}

A ServerOption sets options such as credentials, codec and keepalive parameters, etc.

func ChainStreamInterceptor(interceptors ...StreamServerInterceptor) ServerOption

ChainStreamInterceptor returns a ServerOption that specifies the chained interceptor for streaming RPCs. The first interceptor will be the outer most, while the last interceptor will be the inner most wrapper around the real call. All stream interceptors added by this method will be chained.

func ChainUnaryInterceptor(interceptors ...UnaryServerInterceptor) ServerOption

ChainUnaryInterceptor returns a ServerOption that specifies the chained interceptor for unary RPCs. The first interceptor will be the outer most, while the last interceptor will be the inner most wrapper around the real call. All unary interceptors added by this method will be chained.

ConnectionTimeout returns a ServerOption that sets the timeout for connection establishment (up to and including HTTP/2 handshaking) for all new connections. If this is not set, the default is 120 seconds. A zero or negative value will result in an immediate timeout.

Experimental

Notice: This API is EXPERIMENTAL and may be changed or removed in a later release.

Creds returns a ServerOption that sets credentials for server connections.

func CustomCodec(codec Codec) ServerOption

CustomCodec returns a ServerOption that sets a codec for message marshaling and unmarshaling.

This will override any lookups by content-subtype for Codecs registered with RegisterCodec.

Deprecated: register codecs using encoding.RegisterCodec. The server will automatically use registered codecs based on the incoming requests' headers. See alsohttps://github.com/grpc/grpc-go/blob/master/Documentation/encoding.md#using-a-codec. Will be supported throughout 1.x.

ForceServerCodec returns a ServerOption that sets a codec for message marshaling and unmarshaling.

This will override any lookups by content-subtype for Codecs registered with RegisterCodec.

See Content-Type onhttps://github.com/grpc/grpc/blob/master/doc/PROTOCOL-HTTP2.md#requests for more details. Also see the documentation on RegisterCodec and CallContentSubtype for more details on the interaction between encoding.Codec and content-subtype.

This function is provided for advanced users; prefer to register codecs using encoding.RegisterCodec. The server will automatically use registered codecs based on the incoming requests' headers. See alsohttps://github.com/grpc/grpc-go/blob/master/Documentation/encoding.md#using-a-codec. Will be supported throughout 1.x.

Experimental

Notice: This API is EXPERIMENTAL and may be changed or removed in a later release.

ForceServerCodecV2 is the equivalent of ForceServerCodec, but for the new CodecV2 interface.

Will be supported throughout 1.x.

Experimental

Notice: This API is EXPERIMENTAL and may be changed or removed in a later release.

HeaderTableSize returns a ServerOption that sets the size of dynamic header table for stream.

Notice: This API is EXPERIMENTAL and may be changed or removed in a later release.

func InTapHandle added in v1.0.5

InTapHandle returns a ServerOption that sets the tap handle for all the server transport to be created. Only one can be installed.

Experimental

Notice: This API is EXPERIMENTAL and may be changed or removed in a later release.

func InitialConnWindowSize(s int32) ServerOption

InitialConnWindowSize returns a ServerOption that sets window size for a connection. The lower bound for window size is 64K and any value smaller than that will be ignored.

func InitialWindowSize(s int32) ServerOption

InitialWindowSize returns a ServerOption that sets window size for stream. The lower bound for window size is 64K and any value smaller than that will be ignored.

KeepaliveEnforcementPolicy returns a ServerOption that sets keepalive enforcement policy for the server.

KeepaliveParams returns a ServerOption that sets keepalive and max-age parameters for the server.

func MaxConcurrentStreams(n uint32) ServerOption

MaxConcurrentStreams returns a ServerOption that will apply a limit on the number of concurrent streams to each ServerTransport.

MaxHeaderListSize returns a ServerOption that sets the max (uncompressed) size of header list that the server is prepared to accept.

func MaxMsgSize(m int) ServerOption

MaxMsgSize returns a ServerOption to set the max message size in bytes the server can receive. If this is not set, gRPC uses the default limit.

Deprecated: use MaxRecvMsgSize instead. Will be supported throughout 1.x.

func MaxRecvMsgSize(m int) ServerOption

MaxRecvMsgSize returns a ServerOption to set the max message size in bytes the server can receive. If this is not set, gRPC uses the default 4MB.

func MaxSendMsgSize(m int) ServerOption

MaxSendMsgSize returns a ServerOption to set the max message size in bytes the server can send. If this is not set, gRPC uses the default `math.MaxInt32`.

func NumStreamWorkers(numServerWorkers uint32) ServerOption

NumStreamWorkers returns a ServerOption that sets the number of worker goroutines that should be used to process incoming streams. Setting this to zero (default) will disable workers and spawn a new goroutine for each stream.

Experimental

Notice: This API is EXPERIMENTAL and may be changed or removed in a later release.

func RPCCompressor(cp Compressor) ServerOption

RPCCompressor returns a ServerOption that sets a compressor for outbound messages. For backward compatibility, all outbound messages will be sent using this compressor, regardless of incoming message compression. By default, server messages will be sent using the same compressor with which request messages were sent.

Deprecated: use encoding.RegisterCompressor instead. Will be supported throughout 1.x.

func RPCDecompressor(dc Decompressor) ServerOption

RPCDecompressor returns a ServerOption that sets a decompressor for inbound messages. It has higher priority than decompressors registered via encoding.RegisterCompressor.

Deprecated: use encoding.RegisterCompressor instead. Will be supported throughout 1.x.

func ReadBufferSize(s int) ServerOption

ReadBufferSize lets you set the size of read buffer, this determines how much data can be read at most for one read syscall. The default value for this buffer is 32KB. Zero or negative values will disable read buffer for a connection so data framer can access the underlying conn directly.

func SharedWriteBuffer(val bool) ServerOption

SharedWriteBuffer allows reusing per-connection transport write buffer. If this option is set to true every connection will release the buffer after flushing the data on the wire.

Experimental

Notice: This API is EXPERIMENTAL and may be changed or removed in a later release.

func StatsHandler added in v1.2.0

StatsHandler returns a ServerOption that sets the stats handler for the server.

func StreamInterceptor(i StreamServerInterceptor) ServerOption

StreamInterceptor returns a ServerOption that sets the StreamServerInterceptor for the server. Only one stream interceptor can be installed.

func UnaryInterceptor(i UnaryServerInterceptor) ServerOption

UnaryInterceptor returns a ServerOption that sets the UnaryServerInterceptor for the server. Only one unary interceptor can be installed. The construction of multiple interceptors (e.g., chaining) can be implemented at the caller.

func UnknownServiceHandler added in v1.2.0

func UnknownServiceHandler(streamHandler StreamHandler) ServerOption

UnknownServiceHandler returns a ServerOption that allows for adding a custom unknown service handler. The provided method is a bidi-streaming RPC service handler that will be invoked instead of returning the "unimplemented" gRPC error whenever a request is received for an unregistered service or method. The handling function and stream interceptor (if set) have full access to the ServerStream, including its Context.

func WaitForHandlers added in v1.61.0

func WaitForHandlers(w bool) ServerOption

WaitForHandlers cause Stop to wait until all outstanding method handlers have exited before returning. If false, Stop will return as soon as all connections have closed, but method handlers may still be running. By default, Stop does not wait for method handlers to return.

Experimental

Notice: This API is EXPERIMENTAL and may be changed or removed in a later release.

func WriteBufferSize(s int) ServerOption

WriteBufferSize determines how much data can be batched before doing a write on the wire. The default value for this buffer is 32KB. Zero or negative values will disable the write buffer such that each write will be on underlying connection. Note: A Send call may not directly translate to a write.

ServerStream defines the server-side behavior of a streaming RPC.

Errors returned from ServerStream methods are compatible with the status package. However, the status code will often not match the RPC status as seen by the client application, and therefore, should not be relied upon for this purpose.

type ServerStreamingClient[Res any] interface {

Recv() (*Res, [error](/builtin#error))


[ClientStream](#ClientStream)

}

ServerStreamingClient represents the client side of a server-streaming (one request, many responses) RPC. It is generic over the type of the response message. It is used in generated code.

type ServerStreamingServer[Res any] interface {

Send(*Res) [error](/builtin#error)


[ServerStream](#ServerStream)

}

ServerStreamingServer represents the server side of a server-streaming (one request, many responses) RPC. It is generic over the type of the response message. It is used in generated code.

To terminate the response stream, return from the handler method and return an error from the status package, or use nil to indicate an OK status code.

ServerTransportStream is a minimal interface that a transport stream must implement. This can be used to mock an actual transport stream for tests of handler code that use, for example, grpc.SetHeader (which requires some stream to be in context).

See also NewContextWithServerTransportStream.

Experimental

Notice: This type is EXPERIMENTAL and may be changed or removed in a later release.

ServerTransportStreamFromContext returns the ServerTransportStream saved in ctx. Returns nil if the given context has no stream associated with it (which implies it is not an RPC invocation context).

Experimental

Notice: This API is EXPERIMENTAL and may be changed or removed in a later release.

ServiceConfig is provided by the service provider and contains parameters for how clients that connect to the service should behave.

Deprecated: Users should not use this struct. Service config should be received through name resolver, as specified herehttps://github.com/grpc/grpc/blob/master/doc/service_config.md

type ServiceDesc struct { ServiceName string

HandlerType [any](/builtin#any)
Methods     [][MethodDesc](#MethodDesc)
Streams     [][StreamDesc](#StreamDesc)
Metadata    [any](/builtin#any)

}

ServiceDesc represents an RPC service's specification.

type ServiceInfo struct { Methods []MethodInfo

Metadata [any](/builtin#any)

}

ServiceInfo contains unary RPC method info, streaming RPC method info and metadata for a service.

type ServiceRegistrar interface {

RegisterService(desc *[ServiceDesc](#ServiceDesc), impl [any](/builtin#any))

}

ServiceRegistrar wraps a single method that supports service registration. It enables users to pass concrete types other than grpc.Server to the service registration methods exported by the IDL generated code.

type StaticMethodCallOption struct { EmptyCallOption }

StaticMethodCallOption is a CallOption that specifies that a call comes from a static method.

Stream defines the common interface a client or server stream has to satisfy.

Deprecated: See ClientStream and ServerStream documentation instead.

StreamClientInterceptor intercepts the creation of a ClientStream. Stream interceptors can be specified as a DialOption, using WithStreamInterceptor() or WithChainStreamInterceptor(), when creating a ClientConn. When a stream interceptor(s) is set on the ClientConn, gRPC delegates all stream creations to the interceptor, and it is the responsibility of the interceptor to call streamer.

desc contains a description of the stream. cc is the ClientConn on which the RPC was invoked. streamer is the handler to create a ClientStream and it is the responsibility of the interceptor to call it. opts contain all applicable call options, including defaults from the ClientConn as well as per-call options.

StreamClientInterceptor may return a custom ClientStream to intercept all I/O operations. The returned error must be compatible with the status package.

type StreamDesc struct {

StreamName [string](/builtin#string)        
Handler    [StreamHandler](#StreamHandler) 


ServerStreams [bool](/builtin#bool) 
ClientStreams [bool](/builtin#bool)

}

StreamDesc represents a streaming RPC service's method specification. Used on the server when registering services and on the client when initiating new streams.

type StreamHandler

type StreamHandler func(srv any, stream ServerStream) error

StreamHandler defines the handler called by gRPC server to complete the execution of a streaming RPC.

If a StreamHandler returns an error, it should either be produced by the status package, or be one of the context errors. Otherwise, gRPC will use codes.Unknown as the status code and err.Error() as the status message of the RPC.

type StreamServerInfo struct {

FullMethod [string](/builtin#string)

IsClientStream [bool](/builtin#bool)

IsServerStream [bool](/builtin#bool)

}

StreamServerInfo consists of various information about a streaming RPC on server side. All per-rpc information may be mutated by the interceptor.

type StreamServerInterceptor func(srv any, ss ServerStream, info *StreamServerInfo, handler StreamHandler) error

StreamServerInterceptor provides a hook to intercept the execution of a streaming RPC on the server. info contains all the information of this RPC the interceptor can operate on. And handler is the service method implementation. It is the responsibility of the interceptor to invoke handler to complete the RPC.

Streamer is called by StreamClientInterceptor to create a ClientStream.

type TrailerCallOption struct { TrailerAddr *metadata.MD }

TrailerCallOption is a CallOption for collecting response trailer metadata. The metadata field will be populated *after* the RPC completes.

Experimental

Notice: This type is EXPERIMENTAL and may be changed or removed in a later release.

UnaryClientInterceptor intercepts the execution of a unary RPC on the client. Unary interceptors can be specified as a DialOption, using WithUnaryInterceptor() or WithChainUnaryInterceptor(), when creating a ClientConn. When a unary interceptor(s) is set on a ClientConn, gRPC delegates all unary RPC invocations to the interceptor, and it is the responsibility of the interceptor to call invoker to complete the processing of the RPC.

method is the RPC name. req and reply are the corresponding request and response messages. cc is the ClientConn on which the RPC was invoked. invoker is the handler to complete the RPC and it is the responsibility of the interceptor to call it. opts contain all applicable call options, including defaults from the ClientConn as well as per-call options.

The returned error must be compatible with the status package.

type UnaryHandler

UnaryHandler defines the handler invoked by UnaryServerInterceptor to complete the normal execution of a unary RPC.

If a UnaryHandler returns an error, it should either be produced by the status package, or be one of the context errors. Otherwise, gRPC will use codes.Unknown as the status code and err.Error() as the status message of the RPC.

UnaryInvoker is called by UnaryClientInterceptor to complete RPCs.

type UnaryServerInfo struct {

Server [any](/builtin#any)

FullMethod [string](/builtin#string)

}

UnaryServerInfo consists of various information about a unary RPC on server side. All per-rpc information may be mutated by the interceptor.

UnaryServerInterceptor provides a hook to intercept the execution of a unary RPC on the server. info contains all the information of this RPC the interceptor can operate on. And handler is the wrapper of the service method implementation. It is the responsibility of the interceptor to invoke handler to complete the RPC.