Get better concurrency with parallelStream
@@ -15,11 +15,13 @@ import java.time.Clock;
import java.time.Duration;
import java.time.Instant;
import java.util.HashSet;
+import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.function.Function;
import java.util.stream.Collectors;
+import java.util.stream.Stream;
/**
* Administers a host (for now only docker hosts) and its nodes (docker containers nodes).
@@ -130,7 +132,7 @@ public class NodeAdminImpl implements NodeAdmin {
}
// Use filter with count instead of allMatch() because allMatch() will short circuit on first non-match
- boolean allNodeAgentsConverged = nodeAgentWithSchedulerByHostname.values().parallelStream()
+ boolean allNodeAgentsConverged = parallelStreamOfNodeAgentWithScheduler()
.filter(nodeAgentScheduler -> !nodeAgentScheduler.setFrozen(wantFrozen, freezeTimeout))
.count() == 0;
@@ -158,9 +160,7 @@ public class NodeAdminImpl implements NodeAdmin {
@Override
public void stopNodeAgentServices() {
// Each container may spend 1-1:30 minutes stopping
- nodeAgentWithSchedulerByHostname.values()
- .parallelStream()
- .forEach(NodeAgentWithScheduler::stopForHostSuspension);
+ parallelStreamOfNodeAgentWithScheduler().forEach(NodeAgentWithScheduler::stopForHostSuspension);
}
@Override
@@ -171,7 +171,18 @@ public class NodeAdminImpl implements NodeAdmin {
@Override
public void stop() {
// Stop all node-agents in parallel, will block until the last NodeAgent is stopped
- nodeAgentWithSchedulerByHostname.values().parallelStream().forEach(NodeAgentWithScheduler::stopForRemoval);
+ parallelStreamOfNodeAgentWithScheduler().forEach(NodeAgentWithScheduler::stopForRemoval);
+ }
+
+ /**
+ * Returns a parallel stream of NodeAgentWithScheduler.
+ *
+ * <p>Why not just call nodeAgentWithSchedulerByHostname.values().parallelStream()? Experiments
+ * with Java 11 have shown that with 10 nodes and forEach(), there are a maximum of 3 concurrent
+ * threads. With HashMap it produces 5. With List it produces 10 concurrent threads.</p>
+ */
+ private Stream<NodeAgentWithScheduler> parallelStreamOfNodeAgentWithScheduler() {
+ return List.copyOf(nodeAgentWithSchedulerByHostname.values()).parallelStream();
}
// Set-difference. Returns minuend minus subtrahend.
