C0urante commented on code in PR #13429:
URL: https://github.com/apache/kafka/pull/13429#discussion_r1175123889
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connect/mirror/src/main/java/org/apache/kafka/connect/mirror/OffsetSyncStore.java:
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@@ -139,10 +171,103 @@ public void close() {
protected void handleRecord(ConsumerRecord<byte[], byte[]> record) {
OffsetSync offsetSync = OffsetSync.deserializeRecord(record);
TopicPartition sourceTopicPartition = offsetSync.topicPartition();
- offsetSyncs.put(sourceTopicPartition, offsetSync);
+ offsetSyncs.computeIfAbsent(sourceTopicPartition, ignored ->
createInitialSyncs(offsetSync));
+ offsetSyncs.compute(sourceTopicPartition, (ignored, syncs) ->
updateExistingSyncs(syncs, offsetSync));
+ }
+
+ private OffsetSync[] updateExistingSyncs(OffsetSync[] syncs, OffsetSync
offsetSync) {
+ // Make a copy of the array before mutating it, so that readers do not
see inconsistent data
+ // TODO: batch updates so that this copy can be performed less often
for high-volume sync topics.
+ OffsetSync[] mutableSyncs = Arrays.copyOf(syncs, Long.SIZE);
+ updateSyncArray(mutableSyncs, offsetSync);
+ if (log.isTraceEnabled()) {
+ StringBuilder stateString = new StringBuilder();
+ stateString.append("[");
+ for (int i = 0; i < Long.SIZE; i++) {
+ if (i != 0) {
+ stateString.append(",");
+ }
+ if (i == 0 || i == Long.SIZE - 1 || mutableSyncs[i] !=
mutableSyncs[i - 1]) {
+ // Print only if the sync is interesting, a series of
repeated syncs will appear as ,,,,,
+ stateString.append(mutableSyncs[i].upstreamOffset());
+ stateString.append(":");
+ stateString.append(mutableSyncs[i].downstreamOffset());
+ }
+ }
+ stateString.append("]");
+ log.trace("New sync {} applied, new state is {}", offsetSync,
stateString);
+ }
+ return mutableSyncs;
+ }
+
+ private OffsetSync[] createInitialSyncs(OffsetSync firstSync) {
+ OffsetSync[] syncs = new OffsetSync[Long.SIZE];
+ clearSyncArray(syncs, firstSync);
+ return syncs;
+ }
+
+ private void clearSyncArray(OffsetSync[] syncs, OffsetSync offsetSync) {
+ for (int i = 0; i < Long.SIZE; i++) {
+ syncs[i] = offsetSync;
+ }
+ }
+
+ private void updateSyncArray(OffsetSync[] syncs, OffsetSync offsetSync) {
+ long upstreamOffset = offsetSync.upstreamOffset();
+ // Old offsets are invalid, so overwrite them all.
+ if (!readToEnd || syncs[0].upstreamOffset() > upstreamOffset) {
Review Comment:
I think the most convincing point in favor of monotonicity is that
violations of it will seem like a bug to users and will almost certainly lead
to Jira tickets being logged in the future asking us to fix that behavior.
I think it's important to keep in mind that exactly-once offset syncing is
impossible no matter what, and in addition, any consumer applications that
cannot tolerate data loss should already have `auto.offset.reset` set to
`earliest`, regardless of whether we make this change or not.
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