/**
* The crux of the matter...
*
* @param host {@link MapHost} from which we need to shuffle available map-outputs.
*/
@VisibleForTesting
protected void copyFromHost(MapHost host) throws IOException {
// Get completed maps on 'host'
List<TaskAttemptID> maps = scheduler.getMapsForHost(host);
// Sanity check to catch hosts with only 'OBSOLETE' maps,
// especially at the tail of large jobs
if (maps.size() == 0) {
return;
}
if (LOG.isDebugEnabled()) {
LOG.debug("Fetcher " + id + " going to fetch from " + host + " for: " + maps);
}
// List of maps to be fetched yet
Set<TaskAttemptID> remaining = new HashSet<TaskAttemptID>(maps);
// Construct the url and connect
DataInputStream input = null;
try {
URL url = getMapOutputURL(host, maps);
openConnection(url);
if (stopped) {
abortConnect(host, remaining);
return;
}
// generate hash of the url
String msgToEncode = SecureShuffleUtils.buildMsgFrom(url);
String encHash = SecureShuffleUtils.hashFromString(msgToEncode, shuffleSecretKey);
// put url hash into http header
connection.addRequestProperty(SecureShuffleUtils.HTTP_HEADER_URL_HASH, encHash);
// set the read timeout
connection.setReadTimeout(readTimeout);
// put shuffle version into http header
connection.addRequestProperty(
ShuffleHeader.HTTP_HEADER_NAME, ShuffleHeader.DEFAULT_HTTP_HEADER_NAME);
connection.addRequestProperty(
ShuffleHeader.HTTP_HEADER_VERSION, ShuffleHeader.DEFAULT_HTTP_HEADER_VERSION);
connect(connection, connectionTimeout);
// verify that the thread wasn't stopped during calls to connect
if (stopped) {
abortConnect(host, remaining);
return;
}
input = new DataInputStream(connection.getInputStream());
// Validate response code
int rc = connection.getResponseCode();
if (rc != HttpURLConnection.HTTP_OK) {
throw new IOException(
"Got invalid response code "
+ rc
+ " from "
+ url
+ ": "
+ connection.getResponseMessage());
}
// get the shuffle version
if (!ShuffleHeader.DEFAULT_HTTP_HEADER_NAME.equals(
connection.getHeaderField(ShuffleHeader.HTTP_HEADER_NAME))
|| !ShuffleHeader.DEFAULT_HTTP_HEADER_VERSION.equals(
connection.getHeaderField(ShuffleHeader.HTTP_HEADER_VERSION))) {
throw new IOException("Incompatible shuffle response version");
}
// get the replyHash which is HMac of the encHash we sent to the server
String replyHash = connection.getHeaderField(SecureShuffleUtils.HTTP_HEADER_REPLY_URL_HASH);
if (replyHash == null) {
throw new IOException("security validation of TT Map output failed");
}
LOG.debug("url=" + msgToEncode + ";encHash=" + encHash + ";replyHash=" + replyHash);
// verify that replyHash is HMac of encHash
SecureShuffleUtils.verifyReply(replyHash, encHash, shuffleSecretKey);
LOG.info("for url=" + msgToEncode + " sent hash and received reply");
} catch (IOException ie) {
boolean connectExcpt = ie instanceof ConnectException;
ioErrs.increment(1);
LOG.warn("Failed to connect to " + host + " with " + remaining.size() + " map outputs", ie);
// If connect did not succeed, just mark all the maps as failed,
// indirectly penalizing the host
scheduler.hostFailed(host.getHostName());
for (TaskAttemptID left : remaining) {
scheduler.copyFailed(left, host, false, connectExcpt);
}
// Add back all the remaining maps, WITHOUT marking them as failed
for (TaskAttemptID left : remaining) {
scheduler.putBackKnownMapOutput(host, left);
}
return;
}
try {
// Loop through available map-outputs and fetch them
// On any error, faildTasks is not null and we exit
// after putting back the remaining maps to the
// yet_to_be_fetched list and marking the failed tasks.
TaskAttemptID[] failedTasks = null;
while (!remaining.isEmpty() && failedTasks == null) {
failedTasks = copyMapOutput(host, input, remaining);
}
if (failedTasks != null && failedTasks.length > 0) {
LOG.warn("copyMapOutput failed for tasks " + Arrays.toString(failedTasks));
scheduler.hostFailed(host.getHostName());
for (TaskAttemptID left : failedTasks) {
scheduler.copyFailed(left, host, true, false);
}
}
// Sanity check
if (failedTasks == null && !remaining.isEmpty()) {
throw new IOException(
"server didn't return all expected map outputs: " + remaining.size() + " left.");
}
input.close();
input = null;
} finally {
if (input != null) {
IOUtils.cleanup(LOG, input);
input = null;
}
for (TaskAttemptID left : remaining) {
scheduler.putBackKnownMapOutput(host, left);
}
}
}
private void abortConnect(MapHost host, Set<TaskAttemptID> remaining) {
for (TaskAttemptID left : remaining) {
scheduler.putBackKnownMapOutput(host, left);
}
closeConnection();
}