cameronlee314 commented on a change in pull request #1027: SAMZA-2046:
Startpoint fan out implementation
URL: https://github.com/apache/samza/pull/1027#discussion_r283543587
##########
File path:
samza-core/src/main/java/org/apache/samza/startpoint/StartpointManager.java
##########
@@ -173,71 +226,151 @@ public void deleteStartpoint(SystemStreamPartition ssp,
TaskName taskName) {
Preconditions.checkState(!stopped, "Underlying metadata store not
available");
Preconditions.checkNotNull(ssp, "SystemStreamPartition cannot be null");
- metadataStore.delete(toStoreKey(ssp, taskName));
+ readWriteStore.delete(toReadWriteStoreKey(ssp, taskName));
}
/**
- * For {@link Startpoint}s keyed only by {@link SystemStreamPartition}, this
method re-maps the Startpoints from
- * SystemStreamPartition to SystemStreamPartition+{@link TaskName} for all
tasks provided by the {@link JobModel}
+ * The Startpoints that are written to with {@link
#writeStartpoint(SystemStreamPartition, Startpoint)} and with
+ * {@link #writeStartpoint(SystemStreamPartition, TaskName, Startpoint)} are
moved from a "read-write" namespace
+ * to a "fan out" namespace.
* This method is not atomic or thread-safe. The intent is for the Samza
Processor's coordinator to use this
* method to assign the Startpoints to the appropriate tasks.
- * @param jobModel The {@link JobModel} is used to determine which {@link
TaskName} each {@link SystemStreamPartition} maps to.
- * @return The list of {@link SystemStreamPartition}s that were fanned out
to SystemStreamPartition+TaskName.
+ * @param taskToSSPs Determines which {@link TaskName} each {@link
SystemStreamPartition} maps to.
+ * @return The set of active {@link TaskName}s that were fanned out to.
*/
- public Set<SystemStreamPartition> fanOutStartpointsToTasks(JobModel
jobModel) {
+ public Set<TaskName> fanOut(Map<TaskName, Set<SystemStreamPartition>>
taskToSSPs) {
Preconditions.checkState(!stopped, "Underlying metadata store not
available");
- Preconditions.checkNotNull(jobModel, "JobModel cannot be null");
-
- HashSet<SystemStreamPartition> sspsToDelete = new HashSet<>();
-
- // Inspect the job model for TaskName-to-SSPs mapping and re-map
startpoints from SSP-only keys to SSP+TaskName keys.
- for (ContainerModel containerModel: jobModel.getContainers().values()) {
- for (TaskModel taskModel : containerModel.getTasks().values()) {
- TaskName taskName = taskModel.getTaskName();
- for (SystemStreamPartition ssp :
taskModel.getSystemStreamPartitions()) {
- Startpoint startpoint = readStartpoint(ssp); // Read SSP-only key
- if (startpoint == null) {
- LOG.debug("No Startpoint for SSP: {} in task: {}", ssp, taskName);
- continue;
- }
-
- LOG.info("Grouping Startpoint keyed on SSP: {} to tasks determined
by the job model.", ssp);
- Startpoint startpointForTask = readStartpoint(ssp, taskName);
- if (startpointForTask == null ||
startpointForTask.getCreationTimestamp() < startpoint.getCreationTimestamp()) {
- writeStartpoint(ssp, taskName, startpoint);
- sspsToDelete.add(ssp); // Mark for deletion
- LOG.info("Startpoint for SSP: {} remapped with task: {}.", ssp,
taskName);
- } else {
- LOG.info("Startpoint for SSP: {} and task: {} already exists and
will not be overwritten.", ssp, taskName);
- }
+ Preconditions.checkArgument(MapUtils.isNotEmpty(taskToSSPs), "taskToSSPs
cannot be null or empty");
+
+ // construct fan out with the existing readWriteStore entries and mark the
entries for deletion after fan out
+ Instant now = Instant.now();
+ HashMultimap<SystemStreamPartition, TaskName> deleteKeys =
HashMultimap.create();
+ HashMap<TaskName, StartpointFanOut> fanOuts = new HashMap<>();
+ for (TaskName taskName : taskToSSPs.keySet()) {
+ Set<SystemStreamPartition> ssps = taskToSSPs.get(taskName);
+ if (CollectionUtils.isEmpty(ssps)) {
+ LOG.warn("No SSPs are mapped to taskName: {}", taskName.getTaskName());
+ continue;
+ }
+ for (SystemStreamPartition ssp : ssps) {
+ Startpoint startpoint = readStartpoint(ssp); // Read SSP-only key
+ if (startpoint != null) {
+ deleteKeys.put(ssp, null);
+ }
+
+ Startpoint startpointForTask = readStartpoint(ssp, taskName); // Read
SSP+taskName key
+ if (startpointForTask != null) {
+ deleteKeys.put(ssp, taskName);
+ }
+
+ Startpoint startpointWithPrecedence =
resolveStartpointPrecendence(startpoint, startpointForTask);
+ if (startpointWithPrecedence == null) {
+ continue;
+ }
+
+ fanOuts.putIfAbsent(taskName, new StartpointFanOut(now, new
HashMap<>()));
+ fanOuts.get(taskName).getFanOuts().put(ssp, startpointWithPrecedence);
+ }
+ }
+
+ if (fanOuts.isEmpty()) {
+ LOG.debug("No fan outs created.");
+ return ImmutableSet.of();
+ }
+
+ LOG.info("Fanning out to {} tasks", fanOuts.size());
+
+ StartpointFanOut.StartpointFanOutSerde startpointFanOutSerde = new
StartpointFanOut.StartpointFanOutSerde();
+ for (TaskName taskName : fanOuts.keySet()) {
+ String fanOutKey = toFanOutStoreKey(taskName);
+ StartpointFanOut newFanOut = fanOuts.get(taskName);
+ byte[] fanOutFromStoreInBytes = fanOutStore.get(fanOutKey);
+
+ if (ArrayUtils.isNotEmpty(fanOutFromStoreInBytes)) {
+ // Merge new fan out with existing fan out. This is not a typical
scenario but it can happen when the job
Review comment:
Is there any concern here regarding non-atomic merge? Is there a case where
the job coordinator could be merging a startpoint at the same time as a
processing container deleting a startpoint?
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