}
// Before we do compaction, try to get rid of unneeded files to simplify things.
removeUnneededFiles();
CompactionContext compaction = storeEngine.createCompaction();
CompactionRequest request = null;
this.lock.readLock().lock();
try {
synchronized (filesCompacting) {
// First, see if coprocessor would want to override selection.
if (this.getCoprocessorHost() != null) {
List<StoreFile> candidatesForCoproc = compaction.preSelect(this.filesCompacting);
boolean override = this.getCoprocessorHost().preCompactSelection(
this, candidatesForCoproc, baseRequest);
if (override) {
// Coprocessor is overriding normal file selection.
compaction.forceSelect(new CompactionRequest(candidatesForCoproc));
}
}
// Normal case - coprocessor is not overriding file selection.
if (!compaction.hasSelection()) {
boolean isUserCompaction = priority == Store.PRIORITY_USER;
boolean mayUseOffPeak = offPeakHours.isOffPeakHour() &&
offPeakCompactionTracker.compareAndSet(false, true);
try {
compaction.select(this.filesCompacting, isUserCompaction,
mayUseOffPeak, forceMajor && filesCompacting.isEmpty());
} catch (IOException e) {
if (mayUseOffPeak) {
offPeakCompactionTracker.set(false);
}
throw e;
}
assert compaction.hasSelection();
if (mayUseOffPeak && !compaction.getRequest().isOffPeak()) {
// Compaction policy doesn't want to take advantage of off-peak.
offPeakCompactionTracker.set(false);
}
}
if (this.getCoprocessorHost() != null) {
this.getCoprocessorHost().postCompactSelection(
this, ImmutableList.copyOf(compaction.getRequest().getFiles()), baseRequest);
}
// Selected files; see if we have a compaction with some custom base request.
if (baseRequest != null) {
// Update the request with what the system thinks the request should be;
// its up to the request if it wants to listen.
compaction.forceSelect(
baseRequest.combineWith(compaction.getRequest()));
}
// Finally, we have the resulting files list. Check if we have any files at all.
request = compaction.getRequest();
final Collection<StoreFile> selectedFiles = request.getFiles();
if (selectedFiles.isEmpty()) {
return null;
}