dnishimura commented on a change in pull request #1027: SAMZA-2046: Startpoint
fan out implementation
URL: https://github.com/apache/samza/pull/1027#discussion_r284074495
##########
File path:
samza-core/src/main/java/org/apache/samza/startpoint/StartpointManager.java
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@@ -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
Review comment:
It's not just the older value, but it's marking the startpoints keyed by SSP
and SSP+TaskName for deletion after they are moved to the fan out store. If we
don't delete them, the fan out will happen again on subsequent restarts. Once
the startpoints are moved to the fan out, they are no longer valid in the
readWriteStore.
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