[GitHub] [kafka] guozhangwang commented on a change in pull request #10683: KAFKA-12648: Pt. 2 - Introduce TopologyMetadata to wrap InternalTopologyBuilders of named topologies

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guozhangwang commented on a change in pull request #10683:
URL: https://github.com/apache/kafka/pull/10683#discussion_r677784769



##########
File path: streams/src/main/java/org/apache/kafka/streams/processor/internals/TopologyMetadata.java
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@@ -16,10 +16,294 @@
  */
 package org.apache.kafka.streams.processor.internals;
 
+import org.apache.kafka.clients.consumer.OffsetResetStrategy;
+import org.apache.kafka.common.TopicPartition;
+import org.apache.kafka.streams.StreamsConfig;
+import org.apache.kafka.streams.errors.TopologyException;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.TaskId;
+import org.apache.kafka.streams.processor.internals.InternalTopologyBuilder.TopicsInfo;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
 import java.util.Objects;
+import java.util.Set;
+import java.util.SortedMap;
+import java.util.TreeMap;
+import java.util.function.Consumer;
+import java.util.function.Function;
+import java.util.regex.Pattern;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+// TODO KAFKA-12648:
+//  1) synchronize on these methods instead of individual InternalTopologyBuilder methods, where applicable
 
 public class TopologyMetadata {
-    //TODO KAFKA-12648: the TopologyMetadata class is filled in by Pt. 2 (PR #10683)
+    private final Logger log = LoggerFactory.getLogger(TopologyMetadata.class);
+
+    // the '_' character is not allowed for topology names, thus it's safe to use to indicate that it's not a named topology
+    private static final String UNNAMED_TOPOLOGY = "__UNNAMED_TOPOLOGY__";
+    private static final Pattern EMPTY_ZERO_LENGTH_PATTERN = Pattern.compile("");
+
+    private final StreamsConfig config;
+    private final SortedMap<String, InternalTopologyBuilder> builders; // Keep sorted by topology name for readability
+
+    private ProcessorTopology globalTopology;
+    private Map<String, StateStore> globalStateStores = new HashMap<>();
+    final Set<String> allInputTopics = new HashSet<>();
+
+    public TopologyMetadata(final InternalTopologyBuilder builder, final StreamsConfig config) {
+        this.config = config;
+        builders = new TreeMap<>();
+        if (builder.hasNamedTopology()) {
+            builders.put(builder.namedTopology(), builder);
+        } else {
+            builders.put(UNNAMED_TOPOLOGY, builder);
+        }
+    }
+
+    public TopologyMetadata(final SortedMap<String, InternalTopologyBuilder> builders, final StreamsConfig config) {
+        this.config = config;
+        this.builders = builders;
+        if (builders.isEmpty()) {
+            log.debug("Building KafkaStreams app with no empty topology");
+        }
+    }
+
+    public int getNumStreamThreads(final StreamsConfig config) {
+        final int configuredNumStreamThreads = config.getInt(StreamsConfig.NUM_STREAM_THREADS_CONFIG);
+
+        // If the application uses named topologies, it's possible to start up with no topologies at all and only add them later
+        if (builders.isEmpty()) {
+            if (configuredNumStreamThreads != 0) {
+                log.info("Overriding number of StreamThreads to zero for empty topology");
+            }
+            return 0;
+        }
+
+        // If there are topologies but they are all empty, this indicates a bug in user code
+        if (hasNoNonGlobalTopology() && !hasGlobalTopology()) {

Review comment:
       Yeah what I meant is that, if we can ever reach this condition then it seems the extra check is redundant. I will check the current logic again.




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