Repository navigation
[PIP-149] Making the REST Admin API fully asyncĀ #14365
Description
Co-author: @mattisonchao @Technoboy-
Motivation
The Rest API was originally designed to be implemented asynchronously, but with the iteration of functions, some synchronous implementations were added, resulting in many asynchronous methods called synchronous implementations. Also, many synchronous calls do not add timeouts. This greatly reduces concurrency, user operations, and experience.
In order to prevent more problems, and improve code readability and maintainability, we intend to refactor these synchronous calls and standardize the implementation of the API.
Related discussion: https://lists.apache.org/thread/pkkz2jgwtzpksp6d4rdm1pyxzb3z6vmg
Goals
- Try to avoid synchronous method calls in asynchronous methods.
- Async variable (AsyncResponse) is placed in the first parameter position.
- Async variable (AsyncResponse) cannot be substituted into method implementations.
- Add more tests and increase the coverage.
Modification
-
Avoid synchronous method calls in asynchronous methods.
protected void internalDeleteNamespace(boolean authoritative) { validateTenantOperation(namespaceName.getTenant(), TenantOperation.DELETE_NAMESPACE); validatePoliciesReadOnlyAccess(); }Suggest to do like this:
protected CompletableFuture<Void> internalDeleteNamespace(boolean authoritative) { return validateTenantOperationAsync(namespaceName.getTenant(), TenantOperation.DELETE_NAMESPACE) .thenCompose(__ -> validatePoliciesReadOnlyAccessAsync()); } -
Async variable (AsyncResponse) is placed in the first parameter position
public void deleteNamespace(@Suspended final AsyncResponse asyncResponse, @PathParam("tenant") String tenant, @PathParam("namespace") String namespace, @QueryParam("force") @DefaultValue("false") boolean force, @QueryParam("authoritative") @DefaultValue("false") boolean authoritative) { -
Async variable (AsyncResponse) cannot be substituted into method implementations
internalCreateNonPartitionedTopicAsync(asyncResponse, authoritative, properties);Suggest to do like this:
internalCreateNonPartitionedTopicAsync(authoritative, properties) .thenAccept(__ -> asyncResponse.resume(Response.noContent().build())) .exceptionally(ex -> { resumeAsyncResponseExceptionally(asyncResponse, ex.getCause()); return null; }); -
Exception
Some methods will validate ownership, like namespace ownership, topic ownership, so will throw REDIRECT exception. we need to filter this exception and not print log.
internalCreateNonPartitionedTopicAsync(authoritative, properties)
.thenAccept(__ -> asyncResponse.resume(Response.noContent().build()))
.exceptionally(ex -> {
if (!isRedirectException(ex)) {
log.error("Failed to xxx");
}
resumeAsyncResponseExceptionally(asyncResponse, ex.getCause());
return null;
});
Task tracking
In order to unify the modification and track the modified part, it's better to open an issue to track, like #14353, #14013, #13854.
Activity
Technoboy- commentedon Feb 18, 2022
@codelipenghui @lhotari @eolivelli @BewareMyPower @nodece @mattisonchao
I have opened this issue to discuss first then decide to make to PIP
lhotari commentedon Feb 18, 2022
Thank you @Technoboy- . Good work. I shared my thoughts and some expectations in yesterdays Pulsar Community meeting, you can find the discussion and @merlimat's responses of the rationale for the changes. It would be good to document the arguments that Matteo explained why mixing async and blocking (sync) causes issues.
Please check the last 35 minutes from the recording of the meeting (it's not available yet, @merlimat could you please add the recording on https://github.com/apache/pulsar/wiki/Community-Meetings#recordings ?)
I'll be able to follow up at the beginning of March the next time. There's no need to wait for me to reply.
While digging into the Jetty settings in Pulsar, I noticed a few gaps in backpressure handling, which are relevant when there are more requests which are handled asynchronously. I have a draft PR #14353 . I'll resume work on that in March. The current values for queue sizes and thread pool sizes are just guesses. Most likely we will use much lower values to prevent the broker taking in too much work in parallel. That's the essence of back pressure that it limits the in progress work so that incoming requests also slow down. Currently that is not the case since the thread pool queue can grow in an unbounded way (LinkedBlockingQueue is used under the covers). There are several kludges that attempt to add backpressure, but they aren't very effective in Pulsar currently. #14353 will help address backpressure issues in Pulsar Admin API. These problems will come more evident when there are more APIs which are implemented using asynchronous Servlet API. /cc @merlimat @codelipenghui
codelipenghui commentedon Feb 23, 2022
Is it better to combine this one and #14353 want to do to one PIP such as PIP-142?
WDYT? @Technoboy- @lhotari @merlimat
The advantage is that we can provide a clearer image to the community that what we want to improve for the REST API part.
Technoboy- commentedon Feb 23, 2022
Yes, agree.
eolivelli commentedon Feb 23, 2022
I agree with this proposal and @codelipenghui 's proposal
One formality...
If this is a discussion it should stay on the mailing list.
This looks like a PIP doc.
I suggest to rename this to a PIP and let the discussion happen mostly on the dev@ list
[-][DISCUSS] Standardize Admin REST API[/-][+][PIP-142] Standardize Admin REST API[/+]mattisonchao commentedon Mar 15, 2022
Hi, @lhotari @Technoboy-
Is there any news in this PIP?
[-][PIP-142] Standardize Admin REST API[/-][+][PIP-143] Standardize Admin REST API[/+][-][PIP-143] Standardize Admin REST API[/-][+][PIP-144] Standardize Admin REST API[/+][-][PIP-144] Standardize Admin REST API[/-][+][PIP-149] Standardize Admin REST API[/+][-][PIP-149] Standardize Admin REST API[/-][+][PIP-149] Making the REST Admin API fully async[/+]lhotari commentedon Apr 11, 2022
When more and more asynchronous request handling is happening, it is importance of having a backpressure handling that prevents too much work entering the system. Backpressure handling is broken at the moment. Please review PR #14353. It is fixes bugs in the Admin API / Jetty backpressure configuration.
frankjkelly commentedon Apr 11, 2022
Great point @lhotari I would also suggest that thread pool monitoring is also critical to understand
So we'll probably need to make sure the appropriate metrics are exposed as well as ensure there is documentation on the monitoring of these threads and what to do if thread pools are exhausted, threads are blocked etc.
[improve][broker] Make some methods in NamespacesBase async. (#15518)
[improve][broker] Make some methods in SchemasResourceBase async. (#1ā¦
github-actions commentedon Jun 2, 2022
The issue had no activity for 30 days, mark with Stale label.
[improve][broker] Make Namespaces.deleteNamespaceBundle async (#16287)
[improve][broker] Make Namespaces.deleteNamespaceBundle async (apacheā¦
[improve][broker] Make Namespaces.deleteNamespaceBundle async (apacheā¦
Technoboy- commentedon Dec 25, 2023
Close this as we have done all the tracking works
[improve][broker] Make Namespaces.deleteNamespaceBundle async (apacheā¦
[improve][broker] Make Namespaces.deleteNamespaceBundle async (apacheā¦
[improve][broker] Make Namespaces.deleteNamespaceBundle async (apacheā¦
[improve][broker] Make some methods in NamespacesBase async. (apache#ā¦