Release Notes for MongoDB 5.0 (original) (raw)

Note

MongoDB 5.0 Released July 13, 2021

Warning

Past Release Limitations

The Critical Advisories below affect some prior MongoDB versions. If your deployment depends on features impacted by a Critical Advisory, upgrade to the latest available patch release.

Important

Improper neutralization of null bytes may lead to buffer over-reads in MongoDB Server

In MongoDB 5.0 prior to 5.0.30, an authorized user may trigger crashes or receive the contents of buffer over-reads of Server memory by issuing specially crafted requests that construct malformed BSON in the MongoDB Server.

This issue affects MongoDB Server versions:

Important

Fix for CSFLE and Queryable Encryption self-lookup may send values in subpipelines as plaintext instead of ciphertext

Due to CVE-2024-8013, in MongoDB 5.0 prior to 5.0.28, a bug in query analysis of certain complex self-referential $lookup subpipelines may result in literal values in expressions for encrypted fields being sent to the server malformed.

Should this occur, no documents are returned or written. This issue affects the mongocryptd binary and mongo_crypt_v1shared library in the following MongoDB Server versions:

CVSS Score: 2.2

CWE: CWE-319: Cleartext Transmission of Sensitive Information

Important

Fix for MongoDB Server may allow successful untrusted connection

Due to CVE-2024-1351, in MongoDB 5.0 prior to 5.0.25, under certain configurations of --tlsCAFile andCAFile, MongoDB Server may skip peer certificate validation which may result in untrusted connections to succeed.

This may effectively reduce the security guarantees provided by TLS and open connections that should have been closed due to failing certificate validation. This issue affects the following MongoDB Server versions:

CVSS Score: 8.8

CWE: CWE-295: Improper Certificate Validation

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The rest of this page provides the 5.0.0 release notes:

MongoDB 5.0 introduces time series collections which efficiently store sequences of measurements over a period of time. Compared to normal collections, storing time series data in time series collections improves query efficiency and reduces disk usage for your data and indexes.

MongoDB 5.0 introduces the following aggregation operators:

MongoDB 5.0 introduces the $setWindowFields pipeline stage, allowing you to perform operations on a specified span of documents in a collection, known as a window. The operation returns the results based on the chosen window operator.

For example, you can use the $setWindowFields stage to output the:

Starting in MongoDB 5.0, the $eq, $lt,$lte, $gt, and $gte operators placed in an $expr operator can use indexes to improve performance.

Starting in MongoDB 5.0, you can specify multiple input expressions for the $ifNull expression before returning a replacement expression.

Starting in MongoDB 5.0, the aggregate command anddb.collection.aggregate() helper method have a let option to specify a list of variables that can be used elsewhere in the aggregation pipeline. This allows you to improve command readability by separating the variables from the query text.

Starting in MongoDB 5.0, an aggregation pipeline $lookupstage supports concise correlated subqueries that improve joins between collections.

Starting in MongoDB 5.0, for an uncorrelated subquery in a$lookup pipeline stage containing a $samplestage, the $sampleRate operator, or the$rand operator, the subquery is always run again if repeated. Previously, depending on the subquery output size, either the subquery output was cached or the subquery was run again.

See Perform an Uncorrelated Subquery with $lookup.

Starting in MongoDB 5.0, the query optimizer pushes down the results of a $project stage into the $sort stage. As a result,$sort operations can require less RAM when used with the project stage and avoid Sort exceeded memory limit errors.

MongoDB 5.0 adds the ability to configure auditing filters at runtime.

Starting in MongoDB 5.0:

Starting in MongoDB 5.0, the implicit delete operations for replica set capped collections are processed by the primary and replicated to the secondary members.

Starting in MongoDB 5.0.7, you can delete documents from capped collections using delete methods.

Starting in MongoDB 5.0, Change Eventscontain the field updateDescription.truncatedArrays to record array truncations.

Starting in MongoDB 5.0, multiplepartial indexescan be created using the same key pattern as long as the partialFilterExpressionfields do not express equivalent filters.

In earlier versions of MongoDB, creating multiplepartial indexes is not allowed when using the same key pattern with differentpartialFilterExpressions.

Starting in MongoDB 5.0, unique sparseand unique non-sparse indexes with the samekey pattern can exist on a single collection.

See unique sparse index creation

The db.collection.dropIndexes() command cannot dropready indexesif there are any in-progress index builds.

When run on a MongoDB deployment,db.collection.validate() attempts to fixmultikey metadata inconsistenciesof standalone deployments.

MongoDB 5.0 removes the deprecated geoHaystack index andgeoSearch command. Use a 2d index with$geoNear or one of the supported geospatial query operators instead.

Upgrading your MongoDB instance to 5.0 and settingfeatureCompatibilityVersion to 5.0 will delete any pre-existing geoHaystack indexes.

The db.collection.createIndex() and db.collection.createIndexes()operations have new error messages when options are specified incorrectly.

If a node in a replica set is cleanly shutdown or rolls back during an index build, the index build progress is nowsaved to disk. When the server restarts, index creation resumes from the saved position.

Starting in MongoDB 5.0, the reIndex command and thedb.collection.reIndex() shell method may only be run onstandalone instances.

Starting in MongoDB 5.0, these database commands andmongo shell helper methods are removed:

Starting in MongoDB 5.0, non-transaction reads are not allowed on the config.transactions collection with the following read concerns and options:

Starting in MongoDB 5.0, thehello command and the db.hello() method were introduced as replacements for the isMaster command and the db.isMaster() method. The new topology metricconnections.exhaustHello tracks this inconnections.

Starting in MongoDB 5.0, mongod and mongosenter a quiesce period to allow any ongoing database operations to complete before shutting down.

Starting in MongoDB 5.0, the members[n]._id field may be any integer value greater than or equal to 0. Previously, this value was limited to an integer between 0 and 255 inclusive.

Starting in MongoDB 5.0,enableMajorityReadConcern and--enableMajorityReadConcern cannot be changed and are always set to true due to storage engine improvements.

In earlier versions of MongoDB,enableMajorityReadConcern and--enableMajorityReadConcern are configurable and can be set to false to prevent storage cache pressure from immobilizing a deployment with a three-member primary-secondary-arbiter (PSA) architecture.

If you are using a three-member primary-secondary-arbiter (PSA) architecture, consider the following:

Starting in MongoDB 5.0, you can use the newreplWriterMinThreadCount server parameter to allow idle threads above this minimum to be closed. When replWriterMinThreadCount is configured with a value less than replWriterThreadCount, idle threads above replWriterMinThreadCount are timed out.

When reconfiguring primary-secondary-arbiter (PSA) replica sets or changing to a PSA architecture, it is now in some cases required to perform the reconfiguration in a two-step change. MongoDB 5.0 introduces the rs.reconfigForPSASet() method which performs both steps. If you cannot use the helper method, follow the procedure inModify a Self-Managed PSA Replica Set Safely.

maxNumSyncSourceChangesPerHour determines how many sync source changes can happen per hour before the node temporarily stops re-evaluating a sync source. This parameter will not prevent a node from starting to sync from another node if it doesn't have a sync source.

Starting in MongoDB 5.0.2, you can set the newenableOverrideClusterChainingSetting server parameter totrue to allow secondary members to replicate data from other secondary members even if settings.chainingAllowed isfalse.

Starting in MongoDB 5.0, you may now rotate the following TLS certificates on demand without first needing to stop your runningmongod or mongos instance:

To rotate these certificates, replace the certificate files on your filesystem with updated versions, then use therotateCertificates command or thedb.rotateCertificates() shell method to trigger certificate rotation.

Rotating certificates in this manner does not require downtime, and does not drop any active remote connections.

See Online Certificate Rotation for full details.

MongoDB 5.0 introduces the opensslCipherSuiteConfigparameter to enable configuration of the supported cipher suites OpenSSL should permit when using TLS 1.3 encryption.

Starting in MongoDB 5.0, mongod and mongos now issue a startup warning when their certificates do not include aSubject Alternative Name attribute.

The following platforms do not support common name validation:

Clients using these platforms will notauthenticate to MongoDB servers that use X.509 certificates whose hostnames arespecified by CommonName attributes.

MongoDB 5.0 introduces the applyOpsprivilege action which is inherited by dbAdminAnyDatabase.

The applyOps action permits users to run theapplyOps database command.

The ideal shard key allows MongoDB to distribute documents evenly throughout the cluster while facilitating common query patterns. A suboptimal shard key can lead to performance or scaling issues due to uneven data distribution. Starting in MongoDB 5.0, you can use thereshardCollection command to change the shard key for a collection to change the distribution of your data across your cluster.

Starting in MongoDB 5.0, the $currentOp aggregation stage (and the currentOp command and db.currentOp()shell method) include additional information about the status of ongoing resharding operations for the resharding coordinator and the donor and recipient shards.

Starting in MongoDB 5.0, the $currentOp aggregation stage is used when running the helper method db.currentOp()with mongosh.

Starting in MongoDB 5.0, MongoDB adds the parameter option "automatic" as the new default for the ShardingTaskExecutorPoolReplicaSetMatching. When set for a mongos, the instance follows the behavior specified for the "matchPrimaryNode" option. When set for amongod, the instance follows the behavior specified for the "disabled" option.

Starting in MongoDB 5.0, you can use the renameCollectioncommand to change the name of a sharded collection.

When renaming a sharded or unsharded collection in a sharded cluster, the source and target collections are exclusively locked on every shard. Subsequent operations on the source and target collections must wait until the rename operation completes.

Starting in MongoDB 5.0, when using the movePrimary command to remove a shard from a sharded cluster, writes to the original shard will generate an error message.

Starting in MongoDB 5.0, documents in the config.changelogcollection forsplit andmerge operations contain an owningShard field. The owningShard field shows theshardId of the shard that owns the chunks that were split or merged.

The owningShard field helps identify shards where split or merge operations frequently occur.

Starting in MongoDB 5.0, you can set themaxCatchUpPercentageBeforeBlockingWrites to specify the maximum allowed percentage of data not yet migrated during a moveChunk operation when compared to the total size (in MBs) of the chunk being transferred.

This parameter can affect the behavior of:

The mongo shell has been deprecated in MongoDB v5.0. The replacement shell is mongosh. The legacy mongo shell will be removed in a future release.

Shell packaging also changes in MongoDB v5.0. Refer to theinstallation instructions for further details.

Starting in MongoDB 5.0, the Google Cloud Platform KMS and Azure Key Vault are supported in both mongosh and the legacy mongo shell asKey Management Service (KMS)providers for Client-Side Field Level Encryption.

Using a KMS, you can centrally and securely store Customer Master Keys (CMKs), which are used to encrypt and decrypt data encryption keys as part of the client-side field level encryption workflow.

In addition, a configured KMS allows for the use ofHow CSFLE Decrypts Documents of data fields when used with MongoDB Enterprise.

To learn more, see Configure a KMS provider using mongosh.

Starting in MongoDB 5.0, read concern "snapshot" is supported for some read operations outside of multi-document transactions on primaries and secondaries. SeePerform Long-Running Snapshot Queries.

Starting in MongoDB 5.0, you can use theminSnapshotHistoryWindowInSeconds parameter to control how long WiredTiger keeps the snapshot history.

The server parametercoordinateCommitReturnImmediatelyAfterPersistingDecisioncontrols when transaction commit decisions are returned to the client.

The parameter was introduced in MongDB 5.0 with a default value oftrue. In MongoDB 6.1 the default value changes to false.

When coordinateCommitReturnImmediatelyAfterPersistingDecision isfalse, the shard transaction coordinator waits for all members to acknowledge a multi-document transaction commit before returning the commit decision to the client.

Starting in February 2022, the "Versioned API" terminology was changed to "Stable API". All concepts and features remain the same with this naming change.

MongoDB 5.0 adds execution plan statistics for queries that use a $lookuppipeline stage.

MongoDB 5.0 adds improved support for field names that are ($) prefixed or that contain (.) characters. The validation rules for storing data have been updated to make it easier to work with data sources that use these characters.

Starting in MongoDB 5.0, once the Cluster Wide Write Concern (CWWC) is set via the setDefaultRWConcern command the write concern cannot be unset.

Starting in MongoDB 5.0, the implicit defaultwrite concern isw: majority. However, special considerations are made for deployments containingarbiters:

Specifically, MongoDB uses the following formula to determine the default write concern:


if [ (#arbiters > 0) AND (#non-arbiters <= majority(#voting-nodes)) ]

    defaultWriteConcern = { w: 1 }

else

    defaultWriteConcern = { w: "majority" }

For example, consider the following deployments and their respective default write concerns:

Non-Arbiters Arbiters Voting Nodes Majority of Voting Nodes Implicit Default Write Concern
2 1 3 2 { w: 1 }
4 1 5 3 { w: "majority" }

The { w: "majority" } defaultwrite concern provides a stronger durability guarantee in the event of an election, or if replica set members become unavailable.

Starting in MongoDB 5.0, the new parametermongosShutdownTimeoutMillisForSignaledShutdown specifies the time in milliseconds to wait for any ongoing database operations to complete before initiating a shutdown of mongos.

MongoDB 5.0 introduces thezstdCompressionLevelconfiguration file option which allows for configurable compression levels whenblockCompressor is set to zstd.

Starting in MongoDB 5.0, the following read operations are not blocked when another operation holds an exclusive (X) write lock on the collection:

When writing to a collection, mapReduce andaggregate hold an intent exclusive (IX) lock. Therefore, if an exclusive X lock is already held on a collection,mapReduce and aggregate write operations are blocked.

MongoDB 5.0 adds detailed explanations when a document failsschema validation.

Starting in MongoDB 5.0, the validate command anddb.collection.validate() helper method have a new repair option for repairing a collection that has inconsistencies.

The validate command and db.collection.validate()helper method also return a new repaired boolean value that is true if the collection was repaired.

Starting in MongoDB 5.0, validate anddb.collection.validate() validates documents in a collection. The commands report if anyschema validation rules are violated.

Starting in MongoDB 5.0, the --repair option for mongod validates the collections to find any inconsistencies and fixes them if possible, which avoids rebuilding the indexes. See the --repair option for usage and limitations.

Starting in MongoDB 5.0, the validate command anddb.collection.validate() helper method return a newcorruptRecords field that contains an array ofRecordId values for corrupt documents.

Starting in MongoDB 5.0, the setParametercommand has a new maxValidateMemoryUsageMB parameter, which sets the maximum memory usage for the validate command.

Starting in MongoDB 5.0, you can use thefindChunksOnConfigTimeoutMS parameter to change the timeout for find operations on chunks.

Starting in MongoDB 5.0, you can set a filter option for thedatabase profiler to determine which operations are profiled and logged. You can use the filterexpression in place of the slowms and sampleRate profiler options.

See:

Starting in MongoDB 5.0, changes made to the database profiler level, slowms, sampleRate, orfilter using the profile command ordb.setProfilingLevel() wrapper method are recorded in thelog file.

Starting in MongoDB 5.0, when auditing is enabled, you may now rotate the server and audit logs independently using the logRotate command. Previously, logRotate would rotate the two logs together.

Starting in MongoDB 5.0, slow operation log messages include aremote field specifying client IP address.

Starting in MongoDB 5.0, you can use the remoteOpWaitMillis log field to obtain the wait time for results from shards.

Starting in MongoDB 5.0, log messages for slow queries on viewsinclude a resolvedViews field that contains the view details.

Starting in MongoDB 5.0, the following commands have a let option to define a list of variables. This allows you to improve command readability by separating the variables from the query text.

The update command also has a c field to define a list of variables.

Starting in MongoDB 5.0, the userToDNMappingconfiguration file option and the --ldapUserToDNMapping command line option formongod / mongos and mongoldapnow map the authenticated username as the LDAP DN by default if an empty mapping document (i.e. an empty string or empty array) is specified to the option. Previously, providing an empty mapping document would cause mapping to fail.

Starting in MongoDB 5.0, the dbStats command outputs these additional statistics:

serverStatus includes the following new fields in its output:

Aggregation Metrics

API Version Metrics

Replication Metrics

Read Concern Counters

Write Concern Counters

Number of Threaded Connections

Resharding Statistics

Service Executor Metrics

Cursor Metrics

Security Counter

Repl

Starting in MongoDB 5.0, theplan cache will save full plan cacheentries only if the cumulative size of the plan caches for all collections is lower than 0.5 GB. When the cumulative size of theplan caches for all collections exceeds this threshold, additionalplan cache entries are stored without certain debug information.

The estimated size in bytes of a plan cache entry is available in the output of $planCacheStats.

Starting in MongoDB 5.0, cursors created within aclient session close when the corresponding server sessionends with the killSessions command, if the session times out, or if the client has exhausted the cursor. See Iterate a Cursor in mongosh.

MongoDB 5.0 adds the validateDBMetadata command. ThevalidateDBMetadata command checks that the stored metadata of a database or a collection is valid within a particular API version.

MongoDB 5.0 changes the default write concern to{ w: "majority" }. The new default write concern might impact performance since MongoDB acknowledges writes only after acalculated majority of replica set members have executed and persisted the write to disk.

If your application relies on performance-sensitive writes, you can override the default write concern at the cost of data durability guarantees. To override this setting, you can:

Warning

If write operations use { w: 1 } write concern, the rollback directory may exclude writes submitted after anoplog hole if the primary restarts before the write operation completes.

Starting in MongoDB 5.0, "local" is the default read concern level for read operations against the primary and secondaries. In MongoDB 4.4, queries targeting sharded cluster secondaries use read concern "available" and can returnorphaned documents.

This may introduce a significant latency increase for count queries that use a filter and for covered queries.

You can opt out of this behavior by setting the cluster-wide read concern with setDefaultRWConcern.

MongoDB 5.0 increases the default value ofminSnapshotHistoryWindowInSeconds to 300, which might negatively impact performance. If you aren't using read concern"snapshot", you can reduce the value of theminSnapshotHistoryWindowInSeconds parameter to 5 on allmongod instances. For more information, seeSnapshot History Retention.

Note

If you are running a sharded cluster, do not changeminSnapshotHistoryWindowInSeconds on config servers.

MongoDB 5.0 introduces the following minimum microarchitecture requirements:

CPU Minimum Supported Microarchitecture
Intel x86_64 MongoDB 5.0 requires one of:Intel Sandy Bridge or later Core processor, orIntel Tiger Lake or later Celeron or Pentium processor.
AMD x86_64 MongoDB 5.0 requires AMD Bulldozer or later.
ARM arm64 MongoDB 5.0 requires ARMv8.2-A or later.

MongoDB v5.0 is not supported on x86_64 or arm64 platforms that do not meet these minimum microarchitecture requirements.

See x86_64 Platform Support for more information.

MongoDB 5.0 removes support for the following platforms:

See Platform Support for the full list of platforms and architectures supported in MongoDB 5.0.

Some changes can affect compatibility and may require user actions. For a detailed list of compatibility changes, seeCompatibility Changes in MongoDB 5.0.

Important

Feature Compatibility Version

To upgrade to MongoDB 5.0 from a 4.4 deployment, the 4.4 deployment must have featureCompatibilityVersion set to 4.4. To check the version:


db.adminCommand( { getParameter: 1, featureCompatibilityVersion: 1 } )

To upgrade to MongoDB 5.0, refer to the upgrade instructions specific to your MongoDB deployment:

If you need guidance on upgrading to 5.0, MongoDB professional services offer major version upgrade support to help ensure a smooth transition without interruption to your MongoDB application.

MongoDB only supports single-version downgrades. You cannot downgrade to a release that is multiple versions behind your current release.

For example, you can downgrade a 5.0-series to a 4.4-seriesdeployment. However, further downgrading that 4.4-series deployment to a 4.2-series deployment is not supported.

To download MongoDB 5.0, go to the MongoDB Download Center.

See also:

In Version Issues Status
5.0.0 SERVER-58171: A Time Series collection's granularityparameter cannot be modified after the collection is created. Fixed in 5.0.1
5.0.0 SERVER-58392: An ongoing resharding operation may prevent a backup or restore operation from succeeding. Fixed in 5.0.3

To report an issue, see the MongoDB GitHub repository for instructions on how to file a JIRA ticket for the MongoDB server or one of the related projects.