// close and read are synchronized because can not call close on the data source while it is in
// use
// this could lead to the case where file iterators that are in use by a thread are returned
// to the pool... this would be bad
public boolean close() {
options.getInterruptFlag().set(true);
boolean obtainedLock = false;
try {
obtainedLock = scannerSemaphore.tryAcquire(10, TimeUnit.MILLISECONDS);
if (!obtainedLock) return false;
scanClosed = true;
if (isolatedDataSource != null) isolatedDataSource.close(false);
} catch (InterruptedException e) {
return false;
} finally {
if (obtainedLock) scannerSemaphore.release();
}
return true;
}
public ScanBatch read() throws IOException, TabletClosedException {
ScanDataSource dataSource = null;
Batch results = null;
try {
try {
scannerSemaphore.acquire();
} catch (InterruptedException e) {
sawException = true;
}
// sawException may have occurred within close, so we cannot assume that an interrupted
// exception was its cause
if (sawException)
throw new IllegalStateException("Tried to use scanner after exception occurred.");
if (scanClosed) throw new IllegalStateException("Tried to use scanner after it was closed.");
if (options.isIsolated()) {
if (isolatedDataSource == null) isolatedDataSource = new ScanDataSource(tablet, options);
dataSource = isolatedDataSource;
} else {
dataSource = new ScanDataSource(tablet, options);
}
SortedKeyValueIterator<Key, Value> iter;
if (options.isIsolated()) {
if (isolatedIter == null) isolatedIter = new SourceSwitchingIterator(dataSource, true);
else isolatedDataSource.reattachFileManager();
iter = isolatedIter;
} else {
iter = new SourceSwitchingIterator(dataSource, false);
}
results =
tablet.nextBatch(
iter, range, options.getNum(), options.getColumnSet(), options.getBatchTimeOut());
if (results.getResults() == null) {
range = null;
return new ScanBatch(new ArrayList<KVEntry>(), false);
} else if (results.getContinueKey() == null) {
return new ScanBatch(results.getResults(), false);
} else {
range =
new Range(
results.getContinueKey(),
!results.isSkipContinueKey(),
range.getEndKey(),
range.isEndKeyInclusive());
return new ScanBatch(results.getResults(), true);
}
} catch (IterationInterruptedException iie) {
sawException = true;
if (tablet.isClosed()) throw new TabletClosedException(iie);
else throw iie;
} catch (IOException ioe) {
if (tablet.shutdownInProgress()) {
log.debug("IOException while shutdown in progress ", ioe);
throw new TabletClosedException(
ioe); // assume IOException was caused by execution of HDFS shutdown hook
}
sawException = true;
dataSource.close(true);
throw ioe;
} catch (RuntimeException re) {
sawException = true;
throw re;
} finally {
// code in finally block because always want
// to return mapfiles, even when exception is thrown
if (null != dataSource && !options.isIsolated()) {
dataSource.close(false);
} else if (null != dataSource) {
dataSource.detachFileManager();
}
if (results != null && results.getResults() != null)
tablet.updateQueryStats(results.getResults().size(), results.getNumBytes());
scannerSemaphore.release();
}
}
