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Revert DefaultDocumentationRequestHandler to be blocking again (#824)
Back in January, we changed the blocking DDRH to be non-blocking (fail requests sent during initialization) to solve an edge-case issue of request thread pool exhaustion. This started causing a lot more complaints, as many more use cases were now seeing errors for OPTIONS calls that would otherwise be successful. This change brings back the old blocking behavior as default, and adds NonBlockingDocumentationRequestHandler as a subclass of the DDRH which users can configure if they see thread pool exhaustion in their use case.
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62
...cgen/src/main/java/com/linkedin/restli/docgen/NonBlockingDocumentationRequestHandler.java
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| Original file line number | Diff line number | Diff line change |
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| /* | ||
| Copyright (c) 2022 LinkedIn Corp. | ||
| Licensed under the Apache License, Version 2.0 (the "License"); | ||
| you may not use this file except in compliance with the License. | ||
| You may obtain a copy of the License at | ||
| http://www.apache.org/licenses/LICENSE-2.0 | ||
| Unless required by applicable law or agreed to in writing, software | ||
| distributed under the License is distributed on an "AS IS" BASIS, | ||
| WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| See the License for the specific language governing permissions and | ||
| limitations under the License. | ||
| */ | ||
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| package com.linkedin.restli.docgen; | ||
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| import com.linkedin.common.callback.Callback; | ||
| import com.linkedin.r2.message.RequestContext; | ||
| import com.linkedin.r2.message.rest.RestRequest; | ||
| import com.linkedin.r2.message.rest.RestResponse; | ||
| import com.linkedin.restli.common.HttpStatus; | ||
| import com.linkedin.restli.server.RestLiDocumentationRequestHandler; | ||
| import com.linkedin.restli.server.RestLiServiceException; | ||
| import java.util.concurrent.atomic.AtomicBoolean; | ||
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| /** | ||
| * Non-blocking extension of the default {@link RestLiDocumentationRequestHandler} that is needed in special use cases. | ||
| * This implementation blocks on the request thread that lazily initializes the renderers, but refuses to block | ||
| * subsequent request threads, failing the requests instead. | ||
| * | ||
| * The advantage of this approach is that the request thread pool may avoid exhaustion in the case of lengthy initialization. | ||
| * The downside is that requests sent during initialization will fail, which may cause client problems and confusion. | ||
| * | ||
| * @author Evan Williams | ||
| */ | ||
| public class NonBlockingDocumentationRequestHandler extends DefaultDocumentationRequestHandler | ||
| { | ||
| private final AtomicBoolean _shouldInitialize = new AtomicBoolean(true); | ||
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| @Override | ||
| public void handleRequest(RestRequest request, RequestContext requestContext, Callback<RestResponse> callback) | ||
| { | ||
| // The first request thread should perform the initialization and render the response | ||
| if (_shouldInitialize.getAndSet(false)) | ||
| { | ||
| super.handleRequest(request, requestContext, callback); | ||
| } | ||
| // For subsequent requests sent during initialization, immediately return a failure response | ||
| else if (!isInitialized()) | ||
| { | ||
| callback.onError(new RestLiServiceException(HttpStatus.S_503_SERVICE_UNAVAILABLE, "Documentation renderers have not yet been initialized.")); | ||
| } | ||
| // For all requests received after initialization has completed, render the response | ||
| else | ||
| { | ||
| super.handleRequest(request, requestContext, callback); | ||
| } | ||
| } | ||
| } |