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fix: prevent potential thread starvation in SessionPool (#85)
* fix: prevent thread starvation in session pool * fix: prevent test from blocking on close * fix: wait for executor to shutdown
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google-cloud-spanner/src/test/java/com/google/cloud/spanner/BackendExhaustedTest.java
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| /* | ||
| * Copyright 2020 Google LLC | ||
| * | ||
| * 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. | ||
| */ | ||
|
|
||
| package com.google.cloud.spanner; | ||
|
|
||
| import static com.google.common.truth.Truth.assertThat; | ||
|
|
||
| import com.google.api.gax.grpc.testing.LocalChannelProvider; | ||
| import com.google.cloud.NoCredentials; | ||
| import com.google.cloud.grpc.GrpcTransportOptions; | ||
| import com.google.cloud.grpc.GrpcTransportOptions.ExecutorFactory; | ||
| import com.google.cloud.spanner.MockSpannerServiceImpl.SimulatedExecutionTime; | ||
| import com.google.cloud.spanner.MockSpannerServiceImpl.StatementResult; | ||
| import com.google.cloud.spanner.TransactionRunner.TransactionCallable; | ||
| import com.google.protobuf.ListValue; | ||
| import com.google.spanner.v1.ResultSetMetadata; | ||
| import com.google.spanner.v1.StructType; | ||
| import com.google.spanner.v1.StructType.Field; | ||
| import com.google.spanner.v1.TypeCode; | ||
| import io.grpc.Server; | ||
| import io.grpc.Status; | ||
| import io.grpc.inprocess.InProcessServerBuilder; | ||
| import java.io.IOException; | ||
| import java.util.concurrent.Executors; | ||
| import java.util.concurrent.ScheduledExecutorService; | ||
| import java.util.concurrent.ScheduledThreadPoolExecutor; | ||
| import java.util.concurrent.TimeUnit; | ||
| import org.junit.After; | ||
| import org.junit.AfterClass; | ||
| import org.junit.Before; | ||
| import org.junit.BeforeClass; | ||
| import org.junit.Test; | ||
| import org.junit.runner.RunWith; | ||
| import org.junit.runners.JUnit4; | ||
|
|
||
| /** | ||
| * Tests that a degraded backend that can no longer create any new sessions will not cause an | ||
| * application that already has a healthy session pool to stop functioning. | ||
| */ | ||
| @RunWith(JUnit4.class) | ||
| public class BackendExhaustedTest { | ||
| private static final String TEST_PROJECT = "my-project"; | ||
| private static final String TEST_INSTANCE = "my-instance"; | ||
| private static final String TEST_DATABASE = "my-database"; | ||
| private static MockSpannerServiceImpl mockSpanner; | ||
| private static Server server; | ||
| private static LocalChannelProvider channelProvider; | ||
| private static final Statement UPDATE_STATEMENT = | ||
| Statement.of("UPDATE FOO SET BAR=1 WHERE BAZ=2"); | ||
| private static final Statement INVALID_UPDATE_STATEMENT = | ||
| Statement.of("UPDATE NON_EXISTENT_TABLE SET BAR=1 WHERE BAZ=2"); | ||
| private static final long UPDATE_COUNT = 1L; | ||
| private static final Statement SELECT1 = Statement.of("SELECT 1 AS COL1"); | ||
| private static final ResultSetMetadata SELECT1_METADATA = | ||
| ResultSetMetadata.newBuilder() | ||
| .setRowType( | ||
| StructType.newBuilder() | ||
| .addFields( | ||
| Field.newBuilder() | ||
| .setName("COL1") | ||
| .setType( | ||
| com.google.spanner.v1.Type.newBuilder() | ||
| .setCode(TypeCode.INT64) | ||
| .build()) | ||
| .build()) | ||
| .build()) | ||
| .build(); | ||
| private static final com.google.spanner.v1.ResultSet SELECT1_RESULTSET = | ||
| com.google.spanner.v1.ResultSet.newBuilder() | ||
| .addRows( | ||
| ListValue.newBuilder() | ||
| .addValues(com.google.protobuf.Value.newBuilder().setStringValue("1").build()) | ||
| .build()) | ||
| .setMetadata(SELECT1_METADATA) | ||
| .build(); | ||
| private Spanner spanner; | ||
| private DatabaseClientImpl client; | ||
|
|
||
| @BeforeClass | ||
| public static void startStaticServer() throws IOException { | ||
| mockSpanner = new MockSpannerServiceImpl(); | ||
| mockSpanner.setAbortProbability(0.0D); // We don't want any unpredictable aborted transactions. | ||
| mockSpanner.putStatementResult(StatementResult.update(UPDATE_STATEMENT, UPDATE_COUNT)); | ||
| mockSpanner.putStatementResult(StatementResult.query(SELECT1, SELECT1_RESULTSET)); | ||
| mockSpanner.putStatementResult( | ||
| StatementResult.exception( | ||
| INVALID_UPDATE_STATEMENT, | ||
| Status.INVALID_ARGUMENT.withDescription("invalid statement").asRuntimeException())); | ||
|
|
||
| String uniqueName = InProcessServerBuilder.generateName(); | ||
| server = | ||
| InProcessServerBuilder.forName(uniqueName) | ||
| // We need to use a real executor for timeouts to occur. | ||
| .scheduledExecutorService(new ScheduledThreadPoolExecutor(1)) | ||
| .addService(mockSpanner) | ||
| .build() | ||
| .start(); | ||
| channelProvider = LocalChannelProvider.create(uniqueName); | ||
| } | ||
|
|
||
| @AfterClass | ||
| public static void stopServer() throws InterruptedException { | ||
| // Force a shutdown as there are still requests stuck in the server. | ||
| server.shutdownNow(); | ||
| server.awaitTermination(); | ||
| } | ||
|
|
||
| @Before | ||
| public void setUp() throws Exception { | ||
| SpannerOptions options = | ||
| SpannerOptions.newBuilder() | ||
| .setProjectId(TEST_PROJECT) | ||
| .setChannelProvider(channelProvider) | ||
| .setCredentials(NoCredentials.getInstance()) | ||
| .build(); | ||
| ExecutorFactory<ScheduledExecutorService> executorFactory = | ||
| ((GrpcTransportOptions) options.getTransportOptions()).getExecutorFactory(); | ||
| ScheduledThreadPoolExecutor executor = (ScheduledThreadPoolExecutor) executorFactory.get(); | ||
| options = | ||
| options | ||
| .toBuilder() | ||
| .setSessionPoolOption( | ||
| SessionPoolOptions.newBuilder() | ||
| .setMinSessions(executor.getCorePoolSize()) | ||
| .setMaxSessions(executor.getCorePoolSize() * 3) | ||
| .setWriteSessionsFraction(0.0f) | ||
| .build()) | ||
| .build(); | ||
| executorFactory.release(executor); | ||
|
|
||
| spanner = options.getService(); | ||
| client = | ||
| (DatabaseClientImpl) | ||
| spanner.getDatabaseClient(DatabaseId.of(TEST_PROJECT, TEST_INSTANCE, TEST_DATABASE)); | ||
| // Wait until the session pool has initialized. | ||
| while (client.pool.getNumberOfSessionsInPool() | ||
| < spanner.getOptions().getSessionPoolOptions().getMinSessions()) { | ||
| Thread.sleep(1L); | ||
| } | ||
| } | ||
|
|
||
| @After | ||
| public void tearDown() throws Exception { | ||
| mockSpanner.reset(); | ||
| mockSpanner.removeAllExecutionTimes(); | ||
| // This test case force-closes the Spanner instance as it would otherwise wait | ||
| // forever on the BatchCreateSessions requests that are 'stuck'. | ||
| try { | ||
| ((SpannerImpl) spanner).close(100L, TimeUnit.MILLISECONDS); | ||
| } catch (SpannerException e) { | ||
| // ignore any errors during close as they are expected. | ||
| } | ||
| } | ||
|
|
||
| @Test | ||
| public void test() throws Exception { | ||
| // Simulate very heavy load on the server by effectively stopping session creation. | ||
| mockSpanner.setBatchCreateSessionsExecutionTime( | ||
| SimulatedExecutionTime.ofMinimumAndRandomTime(Integer.MAX_VALUE, 0)); | ||
| // Create an executor that can handle twice as many requests as the minimum number of sessions | ||
| // in the pool and then start that many read requests. That will initiate the creation of | ||
| // additional sessions. | ||
| ScheduledExecutorService executor = | ||
| Executors.newScheduledThreadPool( | ||
| spanner.getOptions().getSessionPoolOptions().getMinSessions() * 2); | ||
| // Also temporarily freeze the server to ensure that the requests that can be served will | ||
| // continue to be in-flight and keep the sessions in the pool checked out. | ||
| mockSpanner.freeze(); | ||
| for (int i = 0; i < spanner.getOptions().getSessionPoolOptions().getMinSessions() * 2; i++) { | ||
| executor.submit(new ReadRunnable()); | ||
| } | ||
| // Now schedule as many write requests as there can be sessions in the pool. | ||
| for (int i = 0; i < spanner.getOptions().getSessionPoolOptions().getMaxSessions(); i++) { | ||
| executor.submit(new WriteRunnable()); | ||
| } | ||
| // Now unfreeze the server and verify that all requests can be served using the sessions that | ||
| // were already present in the pool. | ||
| mockSpanner.unfreeze(); | ||
| executor.shutdown(); | ||
| assertThat(executor.awaitTermination(10, TimeUnit.SECONDS)).isTrue(); | ||
| } | ||
|
|
||
| private final class ReadRunnable implements Runnable { | ||
| @Override | ||
| public void run() { | ||
| try (ResultSet rs = client.singleUse().executeQuery(SELECT1)) { | ||
| while (rs.next()) {} | ||
| } | ||
| } | ||
| } | ||
|
|
||
| private final class WriteRunnable implements Runnable { | ||
| @Override | ||
| public void run() { | ||
| TransactionRunner runner = client.readWriteTransaction(); | ||
| runner.run( | ||
| new TransactionCallable<Long>() { | ||
| @Override | ||
| public Long run(TransactionContext transaction) throws Exception { | ||
| return transaction.executeUpdate(UPDATE_STATEMENT); | ||
| } | ||
| }); | ||
| } | ||
| } | ||
| } |