dataBlockEncoder.getDataBlockEncoding(),
expectedBlockType);
boolean useLock = false;
IdLock.Entry lockEntry = null;
TraceScope traceScope = Trace.startSpan("HFileReaderV2.readBlock");
try {
while (true) {
if (useLock) {
lockEntry = offsetLock.getLockEntry(dataBlockOffset);
}
// Check cache for block. If found return.
if (cacheConf.isBlockCacheEnabled()) {
// Try and get the block from the block cache. If the useLock variable is true then this
// is the second time through the loop and it should not be counted as a block cache miss.
HFileBlock cachedBlock = (HFileBlock) cacheConf.getBlockCache().getBlock(cacheKey,
cacheBlock, useLock, updateCacheMetrics);
if (cachedBlock != null) {
validateBlockType(cachedBlock, expectedBlockType);
if (cachedBlock.getBlockType().isData()) {
HFile.dataBlockReadCnt.incrementAndGet();
// Validate encoding type for data blocks. We include encoding
// type in the cache key, and we expect it to match on a cache hit.
if (cachedBlock.getDataBlockEncoding() != dataBlockEncoder.getDataBlockEncoding()) {
throw new IOException("Cached block under key " + cacheKey + " "
+ "has wrong encoding: " + cachedBlock.getDataBlockEncoding() + " (expected: "
+ dataBlockEncoder.getDataBlockEncoding() + ")");
}
}
return cachedBlock;
}
// Carry on, please load.
}
if (!useLock) {
// check cache again with lock
useLock = true;
continue;
}
if (Trace.isTracing()) {
traceScope.getSpan().addTimelineAnnotation("blockCacheMiss");
}
// Load block from filesystem.
long startTimeNs = System.nanoTime();
HFileBlock hfileBlock = fsBlockReader.readBlockData(dataBlockOffset, onDiskBlockSize, -1,
pread);
validateBlockType(hfileBlock, expectedBlockType);
final long delta = System.nanoTime() - startTimeNs;
HFile.offerReadLatency(delta, pread);
// Cache the block if necessary
if (cacheBlock && cacheConf.shouldCacheBlockOnRead(hfileBlock.getBlockType().getCategory())) {
cacheConf.getBlockCache().cacheBlock(cacheKey, hfileBlock, cacheConf.isInMemory());
}
if (updateCacheMetrics && hfileBlock.getBlockType().isData()) {
HFile.dataBlockReadCnt.incrementAndGet();
}
return hfileBlock;
}
} finally {
traceScope.close();
if (lockEntry != null) {
offsetLock.releaseLockEntry(lockEntry);
}
}
}