[accumulo] branch main updated: fixes #1320 adds a stress test for ZooReaderWriter.mutateOrCreate() (#1851)

[kt...@apache.org]

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kturner pushed a commit to branch main
in repository https://gitbox.apache.org/repos/asf/accumulo.git


The following commit(s) were added to refs/heads/main by this push:
     new e51a611  fixes #1320 adds a stress test for ZooReaderWriter.mutateOrCreate() (#1851)
e51a611 is described below

commit e51a611f6cc0faebd7261bb2eb197ee86f71e429
Author: Keith Turner <kt...@apache.org>
AuthorDate: Wed Jan 6 15:29:07 2021 -0500

    fixes #1320 adds a stress test for ZooReaderWriter.mutateOrCreate() (#1851)
---
 .../accumulo/test/functional/ZooMutatorIT.java     | 158 +++++++++++++++++++++
 1 file changed, 158 insertions(+)

diff --git a/test/src/main/java/org/apache/accumulo/test/functional/ZooMutatorIT.java b/test/src/main/java/org/apache/accumulo/test/functional/ZooMutatorIT.java
new file mode 100644
index 0000000..114dc27
--- /dev/null
+++ b/test/src/main/java/org/apache/accumulo/test/functional/ZooMutatorIT.java
@@ -0,0 +1,158 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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 org.apache.accumulo.test.functional;
+
+import static java.nio.charset.StandardCharsets.UTF_8;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+
+import org.apache.accumulo.core.client.Accumulo;
+import org.apache.accumulo.core.clientImpl.ClientContext;
+import org.apache.accumulo.core.conf.Property;
+import org.apache.accumulo.fate.zookeeper.ZooReaderWriter;
+import org.apache.accumulo.harness.AccumuloClusterHarness;
+import org.apache.accumulo.test.categories.MiniClusterOnlyTests;
+import org.junit.Test;
+import org.junit.experimental.categories.Category;
+
+import com.google.common.hash.Hashing;
+
+@Category(MiniClusterOnlyTests.class)
+public class ZooMutatorIT extends AccumuloClusterHarness {
+  /**
+   * This test uses multiple threads to update the data in a single zookeeper node using
+   * {@link ZooReaderWriter#mutateOrCreate(String, byte[], org.apache.accumulo.fate.zookeeper.ZooReaderWriter.Mutator)}
+   * and tries to detect errors and race conditions in that code. Each thread uses
+   * {@link #nextValue(String)} to compute a new value for the ZK node based on the current value,
+   * producing a new unique value. Its expected that multiple threads calling
+   * {@link #nextValue(String)} as previously described should yield the same final value as a
+   * single thread repeatedly calling {@link #nextValue(String)} the same number of times. There are
+   * many things that can go wrong in the multithreaded case. This test tries to ensure the
+   * following are true for the multithreaded case.
+   *
+   * <ul>
+   * <li>All expected updates are made, none were skipped.
+   * <li>No updates are made twice. For example if two threads wrote the exact same value to the
+   * node this should be detected by the test. Would expect each update to be unique.
+   * <li>The updates are made in the same order as a single thread repeatedly calling
+   * {@link #nextValue(String)}.
+   * </ul>
+   *
+   * <p>
+   * If any of the expectations above are not met it should cause the hash, count, and/or count
+   * tracking done in the test to not match the what is computed by the single threaded code at the
+   * end of the test.
+   *
+   * <p>
+   * A hash and a counter are stored in ZK. The hashes form a chain of hashes as each new value is
+   * written because its a hash of the previous value. The chain of hashes is useful for detecting
+   * missing and out of order updates, but not duplicates. The counter and associated map that
+   * tracks which counts were seen is useful for detecting missing and duplicate updates. The
+   * counter is also used to weakly check for out of order updates, but the chain of hashes provides
+   * a much strong check for this.
+   */
+  @Test
+  public void concurrentMutatorTest() throws Exception {
+    try (var client = Accumulo.newClient().from(getClientProps()).build();
+        var context = (ClientContext) client) {
+      String secret = cluster.getSiteConfiguration().get(Property.INSTANCE_SECRET);
+
+      ZooReaderWriter zk = new ZooReaderWriter(context.getZooKeepers(),
+          context.getZooKeepersSessionTimeOut(), secret);
+
+      var executor = Executors.newFixedThreadPool(16);
+
+      String initialData = hash("Accumulo Zookeeper Mutator test data") + " 0";
+
+      List<Future<?>> futures = new ArrayList<>();
+
+      // This map is used to ensure multiple threads do not successfully write the same value and no
+      // values are skipped. The hash in the value also verifies similar things in a different way.
+      ConcurrentHashMap<Integer,Integer> countCounts = new ConcurrentHashMap<>();
+
+      for (int i = 0; i < 16; i++) {
+        futures.add(executor.submit(() -> {
+          try {
+
+            int count = -1;
+            while (count < 200) {
+              byte[] val =
+                  zk.mutateOrCreate("/test-zm", initialData.getBytes(UTF_8), this::nextValue);
+              int nextCount = getCount(val);
+              assertTrue("nextCount <= count " + nextCount + " " + count, nextCount > count);
+              count = nextCount;
+              countCounts.merge(count, 1, Integer::sum);
+            }
+
+          } catch (Exception e) {
+            throw new RuntimeException(e);
+          }
+        }));
+      }
+
+      // wait and check for errors in background threads
+      for (Future<?> future : futures) {
+        future.get();
+      }
+      executor.shutdown();
+
+      byte[] actual = zk.getData("/test-zm");
+      int settledCount = getCount(actual);
+
+      assertTrue(settledCount >= 200);
+
+      String expected = initialData;
+
+      assertEquals(1, (int) countCounts.get(0));
+
+      for (int i = 1; i <= settledCount; i++) {
+        assertEquals(1, (int) countCounts.get(i));
+        expected = nextValue(expected);
+      }
+
+      assertEquals(settledCount + 1, countCounts.size());
+      assertEquals(expected, new String(actual, UTF_8));
+    }
+  }
+
+  private String hash(String data) {
+    return Hashing.sha256().hashString(data, UTF_8).toString();
+  }
+
+  private String nextValue(String currString) {
+    String[] tokens = currString.split(" ");
+    String currHash = tokens[0];
+    int count = Integer.parseInt(tokens[1]);
+    return (hash(currHash) + " " + (count + 1));
+  }
+
+  private byte[] nextValue(byte[] curr) {
+    return nextValue(new String(curr, UTF_8)).getBytes(UTF_8);
+  }
+
+  private int getCount(byte[] val) {
+    return Integer.parseInt(new String(val, UTF_8).split(" ")[1]);
+  }
+}