[GitHub] [kafka] ableegoldman commented on a change in pull request #11787: KAFKA-12738: track processing errors and implement constant-time task backoff

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ableegoldman commented on a change in pull request #11787:
URL: https://github.com/apache/kafka/pull/11787#discussion_r815264270



##########
File path: streams/src/main/java/org/apache/kafka/streams/processor/internals/TaskExecutionMetadata.java
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@@ -0,0 +1,98 @@
+/*
+ * 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.kafka.streams.processor.internals;
+
+import org.apache.kafka.common.utils.LogContext;
+import org.apache.kafka.streams.processor.TaskId;
+
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
+import org.slf4j.Logger;
+
+import static org.apache.kafka.streams.processor.internals.TopologyMetadata.UNNAMED_TOPOLOGY;
+
+/**
+ * Multi-threaded class that tracks the status of active tasks being processed. A single instance of this class is
+ * shared between all StreamThreads.
+ */
+public class TaskExecutionMetadata {
+    private final boolean hasNamedTopologies;
+    // map of topologies experiencing errors/currently under backoff
+    private final ConcurrentHashMap<String, NamedTopologyMetadata> topologyNameToErrorMetadata = new ConcurrentHashMap<>();
+
+    public TaskExecutionMetadata(final Set<String> allTopologyNames) {
+        this.hasNamedTopologies = !(allTopologyNames.size() == 1 && allTopologyNames.contains(UNNAMED_TOPOLOGY));
+    }
+
+    public boolean canProcessTask(final Task task, final long now) {
+        final String topologyName = task.id().topologyName();
+        if (!hasNamedTopologies) {
+            // TODO implement error handling/backoff for non-named topologies (needs KIP)
+            return true;
+        } else {
+            final NamedTopologyMetadata metadata = topologyNameToErrorMetadata.get(topologyName);
+            return metadata == null || (metadata.canProcess() && metadata.canProcessTask(task, now));
+        }
+    }
+
+    public void registerTaskError(final Task task, final Throwable t, final long now) {
+        if (hasNamedTopologies) {
+            final String topologyName = task.id().topologyName();
+            topologyNameToErrorMetadata.computeIfAbsent(topologyName, n -> new NamedTopologyMetadata(topologyName))
+                .registerTaskError(task, t, now);
+        }
+    }
+
+    class NamedTopologyMetadata {
+        private final Logger log;
+        private final Map<TaskId, Long> tasksToErrorTime = new ConcurrentHashMap<>();
+
+        public NamedTopologyMetadata(final String topologyName) {
+            final LogContext logContext = new LogContext(String.format("topology-name [%s] ", topologyName));
+            this.log = logContext.logger(NamedTopologyMetadata.class);
+        }
+
+        public boolean canProcess() {
+            // TODO: during long task backoffs, pause the full topology to avoid it getting out of sync
+            return true;
+        }
+
+        public boolean canProcessTask(final Task task, final long now) {
+            // TODO: implement exponential backoff, for now we just wait 15s
+            final Long errorTime = tasksToErrorTime.get(task.id());
+            if (errorTime == null) {
+                return true;
+            } else if (now - errorTime > 15000L) {

Review comment:
       Because it was actually taking the thread 10s to come back up (in the integration test where we overrode `session.timeout` to 10s) before we had https://github.com/apache/kafka/pull/11801
   
   Now with that fix it takes under .5s for the thread to be replaced, so there's no particular reason to have it be 15s. I think it makes sense to lower it to maybe 5s for now, and then when we have the true exponential backoff obviously it can start lower and grow from there.




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