Implement timeout for dns hostname lookup #179
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lemnik
requested changes
Jul 7, 2022
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| ExecutorService lookupService = Executors.newSingleThreadExecutor(new DaemonThreadFactory()); | ||
| Future<String> future = lookupService.submit(new Callable<String>() { | ||
| @Override | ||
| public String call() throws UnknownHostException { | ||
| return InetAddress.getLocalHost().getHostName(); | ||
| } | ||
| }); |
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Instead of adding a timeout to the lookupHostname method, maybe we should instead wrap the "startup" cache in a daemon thread?
public static void initializeCache() {
Thread hostnameLookup = new Thread("Hostname Lookup") {
@Override
public void run() {
getHostnameValue();
}
};
hostnameLookup.setDaemon(true);
hostnameLookup.start();
}There was a problem hiding this comment.
As discussed, I've moved the cache init to a daemon thread to prevent blocking on initialization, but retained the timeout on the hostname lookup as getHostnameValue may also be called from elsewhere before the cache is initialized.
lemnik
reviewed
Jul 7, 2022
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| Thread resolverThread = new Thread(future, "Hostname Resolver"); | ||
| resolverThread.setDaemon(true); | ||
| resolverThread.start(); | ||
| future.run(); |
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This will need to be threaded. future.run() will wait for the hostname to be resolved before returning, which means that future.get(HOSTNAME_LOOKUP_TIMEOUT... will return immediately (and never timeout).
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Goal
This PR aims to fix a freeze reported in #176.
DNS hostname lookups with
InetAddress.getLocalHost()can be very slow to run in certain situations and this can cause apps to hang on initialisation when determiningdevice.hostnameDesign
Added a 10s timeout when performing the DNS hostname lookup. If it cannot be resolved in that time then the metadata is simply not set. The timeout period here is fairly arbitrary.
Testing
Couldn't reproduce the slow DNS lookup, but ran unit tests and manually tested with the example app to confirm that DNS hostname still resolves successfully.