JacksonYao287 commented on pull request #2611:
URL: https://github.com/apache/ozone/pull/2611#issuecomment-914268170
> Can you explain the problem in bit detail here?
thanks @bshashikant for the review! when i investigate some issues in our
production cluster, i find the log below, which is in
`SequenceIdGenerator.java`
2021-09-03 12:50:38,632
[1114efaf-c975-4ea0-bc8b-c3309a57cc8d@group-58D600BFB107-StateMachineUpdater]
WARN org.apache.hadoop.hdds.scm.ha.SequenceIdGenerator: Failed to allocate a
batch for localId, **expected lastId is 0**, actual lastId is
107544261438510000.
let us see the code below
```
public Boolean allocateBatch(String sequenceIdName,
Long expectedLastId, Long newLastId) {
Long lastId = sequenceIdToLastIdMap.computeIfAbsent(sequenceIdName,
key -> {
try {
Long idInDb = this.sequenceIdTable.get(key);
return idInDb != null ? idInDb : INVALID_SEQUENCE_ID;
} catch (IOException ioe) {
throw new RuntimeException("Failed to get lastId from db",
ioe);
}
});
if (!lastId.equals(expectedLastId)) {
LOG.warn("Failed to allocate a batch for {}, expected lastId is {},"
+
" actual lastId is {}.", sequenceIdName, expectedLastId, lastId);
return false;
}
```
`expected lastId is 0` means `sequenceIdToLastIdMap` does not contains
`sequenceIdName`(localId), and thus `INVALID_SEQUENCE_ID`(0) is assigned to
`lastId`. this is a long run ozone cluster , so local id should exist in
sequenceIdToLastIdMap.
for now , when leader reelection happens , the new leader will call
`reinitialize` , but in current `SequenceIdGenerator` does not initialize
`sequenceIdToLastIdMap` , which hold the latest state of `lastId`. so this is
what this patch does.
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