add a standard handler for socket connection problems which improves diagnostics
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Key: HADOOP-7469
URL: https://issues.apache.org/jira/browse/HADOOP-7469
Project: Hadoop Common
Issue Type: Sub-task
Components: util
Affects Versions: 0.20.203.0
Reporter: Steve Loughran
Priority: Minor
connection refused, connection timed out, no route to host, etc, are classic
IOExceptions that can be raised in a lot of parts of the code. The standard JDK
exceptions are useless for debugging as they
# don't include the destination (host, port) that can be used in diagnosing
service dead/blocked problems
# don't include any source hostname that can be used to handle routing issues
# assume the reader understands the TCP stack.
It's obvious from the -user lists that a lot of people hit these problems and
don't know how to fix them. Sometimes the source has been patched to insert the
diagnostics, but it may be convenient to have a single method to translate some
{code}
SocketException processIOException(SocketException e, String destHost, int
destPort) {
String localhost = getLocalHostname();
String details = "From "+ localhost +" to "+ desthost + ":"+destPort;
if (e instanceof ConnectException) {
return new ConnectException(details
+ " -- see http://wiki.apache.org/hadoop/ConnectionRefused --" + e,
e);
}
if (e instanceof UnknownHostException) {
return new UnknownHostException(details
+ " -- see http://wiki.apache.org/hadoop/UnknownHost --" + e, e);
}
// + handlers for other common socket exceptions
//and a default that returns an unknown class unchanged
return e;
}
{code}
Testing: try to connect to an unknown host, a local port that isn't live, etc.
It's hard to replicate all failures consistently. It may be simpler just to
verify that if you pass in a specific exception, the string is expanded and the
class is unchanged.
This code could then be patched in to places where IO takes place. Note that
Http Components and HttpClient libs already add some destination details on
some operation failures, with their own HttpException tree: it's simplest to
leave these alone.
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