RFR 9: 8077350 Process API Updates Implementation Review (original) (raw)

Peter Levart peter.levart at gmail.com
Thu May 14 12:19:40 UTC 2015

Hi Roger,

The new API using Optional(s) looks fine. In particular for the ProcessHandle returning methods. They now either return Stream or Optional.

At some point in the development of this API, the implementation introduced the AsyncExecutor to execute synchronous continuations of the onExit() returned CompletableFuture(s). What was the main motivation for this given that:

Would an alternative be to define two overloaded onExit() methods in the style of CompletableFuture itself?

 CompletableFuture<ProcessHandle> onExit();
 CompletableFuture<ProcessHandle> onExit(Executor executor);

...and give the user a chance to supply it's own Executor if the default ForkJoinPoll.commonPool() does not fit?

Is there expectation that ForkJoinPoll.commonPool() will not fit in the common case?

Regards, Peter

On 05/13/2015 04:16 PM, Roger Riggs wrote:

Hi,

Are there any comments about the use of java.util.Optional in the ProcessHandle API? Or a review of the changes? Thanks, Roger

On 5/11/2015 11:49 AM, Roger Riggs wrote: Please review clarifications and updates to the proposed Precess API.

A few loose ends in the ProcessHandle API were identified. 1) The ProcessHandle.parent() method currently returns null if the parent cannot be determined and the ProcessHandle.of(PID) method returns null if the PID does not exist. It has been suggested to return an Optional to make these methods more flexible and allow a fluent style and work better with streams. 2) The behavior of Processhandle.destroy and destroyForcibly are different than Process.destroy and destroyForcibly. Those functions always succeed because they are children of the spawning process. In contrast, ProcessHandle.destroy and destroyForcible are requests to destroy the process and may not succeed due to operating system restrictions such as the process not being a child or not having enough privilege. The description of the methods needs to be clarified that it is a request to destroy and it may not succeed, In that case the destroy and destroyForcibly methods should indicate that the request was not successful. In particular, the caller may not want to wait for the process to terminate (its not going to). The proposed update is to return an Optional . It can be streamed and can take advantage of the conditional operations on the Optional. 3) Using Optional is also attractive for the return values of the information about a ProcessHandles, since not all values are available from every OS. The returns values of Info.command, arguments, startInstant, totalDuration, and user are proposed to be updated to return Optional. It allows for more compact code and fewer explicit checks for null. Please review and comment: Webrev: http://cr.openjdk.java.net/~rriggs/webrev-ph/ javadoc: http://cr.openjdk.java.net/~rriggs/ph-apidraft/ Diffs of the spec/javadoc from previous draft: http://cr.openjdk.java.net/~rriggs/ph-diffs-2015-05-11/overview-summary.html

Thanks, Roger

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