BsoBird commented on code in PR #9546:
URL: https://github.com/apache/iceberg/pull/9546#discussion_r1482554243
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core/src/main/java/org/apache/iceberg/hadoop/HadoopTableOperations.java:
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@@ -289,64 +377,153 @@ Path versionHintFile() {
return metadataPath(Util.VERSION_HINT_FILENAME);
}
- private void writeVersionHint(int versionToWrite) {
+ @VisibleForTesting
+ boolean writeVersionHint(FileSystem fs, Integer versionToWrite) throws
Exception {
Path versionHintFile = versionHintFile();
- FileSystem fs = getFileSystem(versionHintFile, conf);
-
+ Path tempVersionHintFile = metadataPath(UUID.randomUUID() +
"-version-hint.temp");
try {
- Path tempVersionHintFile = metadataPath(UUID.randomUUID().toString() +
"-version-hint.temp");
writeVersionToPath(fs, tempVersionHintFile, versionToWrite);
- fs.delete(versionHintFile, false /* recursive delete */);
- fs.rename(tempVersionHintFile, versionHintFile);
- } catch (IOException e) {
- LOG.warn("Failed to update version hint", e);
+ // We can accept that version Hint fails to write, but we can't accept
that version Hint
+ // writes the wrong version.
+ if (fs.exists(versionHintFile) || findVersionWithOutVersionHint(fs) !=
versionToWrite) {
+ throw new AlreadyExistsException(
Review Comment:
If the versionHint comes up, it means that another client is committing.
Even if I don't block it, there's a good chance that fs.rename will get an
error. This is because the v+1 version has been committed by another client.
Also, we need to check to see if a new version has been committed before we
commit. If we don't do this, then we have a situation where client B commits
version V+2, but has some problems writing to versionHint, and the operation is
slow. Client A doesn't have this problem, it's committing V+1. And the
versionHint is written successfully. Eventually, versionHint < maxVersion.
```
client A ------------> COMMIT V+1 ---> COMMIT V+2 ---> TTL CLEAN V+1-->
COMMIT V+3-----------> WRITE TEMP VERSION HINT ---------------->RENAME VERSION
HINT
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CLIENT B --> READ VERSION -----> COMMIT V+1------>WRITE TEMP VERSION
HINT-------------------------------------------->RENAME VERSION HINT
final: maxVersion = v+3 versionHint = v+1
```
At present, there is only one situation left that we have not resolved:
```
client A --> COMMIT V+1 --------------> WRITE TEMP VERSION HINT
---------------->RENAME VERSION HINT-------------
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CLIENT B ----------------> READ VERSION -----> COMMIT V+2------>WRITE TEMP
VERSION HINT------>RENAME VERSION HINT (FAILED)
final: maxVersion = v+2 versionHint = v+1
```
In this case, although I can't stop it from happening at the moment, all
commits will fail if there is such a problem. But no data will be lost. When
the user resubmits the task, I will clean up the incorrect versionHint.
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