private Translog openTranslog(EngineConfig engineConfig, IndexWriter writer) throws IOException {
final TranslogConfig translogConfig = engineConfig.getTranslogConfig();
Translog.TranslogGeneration generation = null;
if (openMode == EngineConfig.OpenMode.OPEN_INDEX_AND_TRANSLOG) {
generation = loadTranslogIdFromCommit(writer);
// We expect that this shard already exists, so it must already have an existing translog else
// something is badly wrong!
if (generation == null) {
throw new IllegalStateException(
"no translog generation present in commit data but translog is expected to exist");
}
if (generation != null && generation.translogUUID == null) {
throw new IndexFormatTooOldException(
"trasnlog",
"translog has no generation nor a UUID - this might be an index from a previous version consider upgrading to N-1 first");
}
}
final Translog translog = new Translog(translogConfig, generation);
if (generation == null || generation.translogUUID == null) {
assert openMode != EngineConfig.OpenMode.OPEN_INDEX_AND_TRANSLOG
: "OpenMode must not be " + EngineConfig.OpenMode.OPEN_INDEX_AND_TRANSLOG;
if (generation == null) {
logger.debug("no translog ID present in the current generation - creating one");
} else if (generation.translogUUID == null) {
logger.debug(
"upgraded translog to pre 2.0 format, associating translog with index - writing translog UUID");
}
boolean success = false;
try {
commitIndexWriter(
writer,
translog,
openMode == EngineConfig.OpenMode.OPEN_INDEX_CREATE_TRANSLOG
? writer.getCommitData().get(SYNC_COMMIT_ID)
: null);
success = true;
} finally {
if (success == false) {
IOUtils.closeWhileHandlingException(translog);
}
}
}
return translog;
}
/**
* Reads the current stored translog ID from the IW commit data. If the id is not found, recommits
* the current translog id into lucene and returns null.
*/
@Nullable
private Translog.TranslogGeneration loadTranslogIdFromCommit(IndexWriter writer)
throws IOException {
// commit on a just opened writer will commit even if there are no changes done to it
// we rely on that for the commit data translog id key
final Map<String, String> commitUserData = writer.getCommitData();
if (commitUserData.containsKey("translog_id")) {
assert commitUserData.containsKey(Translog.TRANSLOG_UUID_KEY) == false
: "legacy commit contains translog UUID";
return new Translog.TranslogGeneration(
null, Long.parseLong(commitUserData.get("translog_id")));
} else if (commitUserData.containsKey(Translog.TRANSLOG_GENERATION_KEY)) {
if (commitUserData.containsKey(Translog.TRANSLOG_UUID_KEY) == false) {
throw new IllegalStateException("commit doesn't contain translog UUID");
}
final String translogUUID = commitUserData.get(Translog.TRANSLOG_UUID_KEY);
final long translogGen = Long.parseLong(commitUserData.get(Translog.TRANSLOG_GENERATION_KEY));
return new Translog.TranslogGeneration(translogUUID, translogGen);
}
return null;
}