private DNAddrPair chooseDataNode(LocatedBlock block) throws IOException {
while (true) {
DatanodeInfo[] nodes = block.getLocations();
try {
DatanodeInfo chosenNode = bestNode(nodes, deadNodes);
InetSocketAddress targetAddr = NetUtils.createSocketAddr(chosenNode.getXferAddr());
return new DNAddrPair(chosenNode, targetAddr);
} catch (IOException ie) {
String blockInfo = block.getBlock() + " file=" + src;
if (failures >= dfsClient.getMaxBlockAcquireFailures()) {
throw new BlockMissingException(
src, "Could not obtain block: " + blockInfo, block.getStartOffset());
}
if (nodes == null || nodes.length == 0) {
DFSClient.LOG.info("No node available for block: " + blockInfo);
}
DFSClient.LOG.info(
"Could not obtain block "
+ block.getBlock()
+ " from any node: "
+ ie
+ ". Will get new block locations from namenode and retry...");
try {
// Introducing a random factor to the wait time before another retry.
// The wait time is dependent on # of failures and a random factor.
// At the first time of getting a BlockMissingException, the wait time
// is a random number between 0..3000 ms. If the first retry
// still fails, we will wait 3000 ms grace period before the 2nd retry.
// Also at the second retry, the waiting window is expanded to 6000 ms
// alleviating the request rate from the server. Similarly the 3rd retry
// will wait 6000ms grace period before retry and the waiting window is
// expanded to 9000ms.
double waitTime =
timeWindow * failures
+ // grace period for the last round of attempt
timeWindow
* (failures + 1)
* DFSUtil.getRandom().nextDouble(); // expanding time window for each failure
DFSClient.LOG.warn(
"DFS chooseDataNode: got # "
+ (failures + 1)
+ " IOException, will wait for "
+ waitTime
+ " msec.");
Thread.sleep((long) waitTime);
} catch (InterruptedException iex) {
}
deadNodes.clear(); // 2nd option is to remove only nodes[blockId]
openInfo();
block = getBlockAt(block.getStartOffset(), false);
failures++;
continue;
}
}
}
DFSInputStream(DFSClient dfsClient, String src, int buffersize, boolean verifyChecksum)
throws IOException, UnresolvedLinkException {
this.dfsClient = dfsClient;
this.verifyChecksum = verifyChecksum;
this.buffersize = buffersize;
this.src = src;
this.socketCache = dfsClient.socketCache;
prefetchSize = dfsClient.getConf().prefetchSize;
timeWindow = dfsClient.getConf().timeWindow;
nCachedConnRetry = dfsClient.getConf().nCachedConnRetry;
openInfo();
}