dnishimura commented on a change in pull request #1027: SAMZA-2046: Startpoint
fan out implementation
URL: https://github.com/apache/samza/pull/1027#discussion_r284074779
##########
File path:
samza-core/src/main/java/org/apache/samza/startpoint/StartpointManager.java
##########
@@ -173,71 +205,148 @@ 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) throws IOException {
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, StartpointFanOutPerTask> 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 StartpointFanOutPerTask(now));
+ 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());
+
+ // Fan out to store
+ for (TaskName taskName : fanOuts.keySet()) {
+ String fanOutKey = toFanOutStoreKey(taskName);
+ StartpointFanOutPerTask newFanOut = fanOuts.get(taskName);
+ fanOutStore.put(fanOutKey, objectMapper.writeValueAsBytes(newFanOut));
+ }
+
+ for (SystemStreamPartition ssp : deleteKeys.keySet()) {
+ for (TaskName taskName : deleteKeys.get(ssp)) {
+ if (taskName != null) {
+ deleteStartpoint(ssp, taskName);
+ } else {
+ deleteStartpoint(ssp);
}
}
}
- // Delete SSP-only keys
- sspsToDelete.forEach(ssp -> {
- deleteStartpoint(ssp);
- LOG.info("All Startpoints for SSP: {} have been grouped to the
appropriate tasks and the SSP was deleted.");
- });
+ return ImmutableSet.copyOf(fanOuts.keySet());
+ }
- return ImmutableSet.copyOf(sspsToDelete);
+ /**
+ * Read the fanned out {@link Startpoint}s for the given {@link TaskName}
+ * @param taskName to read the fan out Startpoints for
+ * @return fanned out Startpoints
+ */
+ public Map<SystemStreamPartition, Startpoint> getFanOutForTask(TaskName
taskName) throws IOException {
+ Preconditions.checkState(!stopped, "Underlying metadata store not
available");
+ Preconditions.checkNotNull(taskName, "TaskName cannot be null");
+
+ byte[] fanOutBytes = fanOutStore.get(toFanOutStoreKey(taskName));
+ if (ArrayUtils.isEmpty(fanOutBytes)) {
+ return ImmutableMap.of();
+ }
+ StartpointFanOutPerTask startpointFanOutPerTask =
objectMapper.readValue(fanOutBytes, StartpointFanOutPerTask.class);
+ return ImmutableMap.copyOf(startpointFanOutPerTask.getFanOuts());
}
/**
- * Relinquish resources held by the underlying {@link MetadataStore}
+ * Deletes the fanned out {@link Startpoint} for the given {@link TaskName}
+ * @param taskName to delete the fan out Startpoints for
*/
- public void stop() {
- stopped = true;
- // Metadata store lifecycle is managed outside of the StartpointManager,
so not closing it.
+ public void removeFanOutForTask(TaskName taskName) {
+ Preconditions.checkState(!stopped, "Underlying metadata store not
available");
+ Preconditions.checkNotNull(taskName, "TaskName cannot be null");
+
+ fanOutStore.delete(toFanOutStoreKey(taskName));
}
@VisibleForTesting
MetadataStore getMetadataStore() {
return metadataStore;
}
- private static String toStoreKey(SystemStreamPartition ssp, TaskName
taskName) {
- return new String(new JsonSerdeV2<>().toBytes(new StartpointKey(ssp,
taskName)));
+ @VisibleForTesting
+ MetadataStore getReadWriteStore() {
+ return readWriteStore;
+ }
+
+ @VisibleForTesting
+ MetadataStore getFanOutStore() {
+ return fanOutStore;
+ }
+
+ @VisibleForTesting
+ ObjectMapper getObjectMapper() {
+ return objectMapper;
+ }
+
+ private static Startpoint resolveStartpointPrecendence(Startpoint
startpoint1, Startpoint startpoint2) {
+ if (startpoint1 != null && startpoint2 != null) {
Review comment:
I'm a little confused. Isn't the offset resolution done in the offset
manager? The resolution here is the resolution between two startpoints, not a
startpoint and the resolved offset. Also how would we support startpoint with
broadcast here?
In a follow on PR, I'll be integrating the fan out with the JobCoordinators
to use the info in the job model to fan out the startpoints, which should take
care of broadcast streams. Once the startpoints are fanned out, the actual
offset resolution itself happens in the offset manager.
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