Praveen Krishna created HADOOP-16114:
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Summary: NetUtils#canonicalizeHost gives different value for same
host
Key: HADOOP-16114
URL: https://issues.apache.org/jira/browse/HADOOP-16114
Project: Hadoop Common
Issue Type: Bug
Components: net
Affects Versions: 3.1.2, 2.7.6
Reporter: Praveen Krishna
In NetUtils#canonicalizeHost uses ConcurrentHashMap#putIfAbsent to add an entry
to the cache
{code:java}
private static String canonicalizeHost(String host) {
// check if the host has already been canonicalized
String fqHost = canonicalizedHostCache.get(host);
if (fqHost == null) {
try {
fqHost = SecurityUtil.getByName(host).getHostName();
// slight race condition, but won't hurt
canonicalizedHostCache.putIfAbsent(host, fqHost);
} catch (UnknownHostException e) {
fqHost = host;
}
}
return fqHost;
}
{code}
If two different threads were invoking this method for the first time (so the
cache is empty) and if SecurityUtil#getByName()#getHostName gives two different
value for the same host , only one fqHost would be added in the cache and an
invalid fqHost would be given to one of the thread which might cause some APIs
to fail for the first time `FileSystem#checkPath` even if the path is in the
given file system. It might be better if we modify the above method to this
{code:java}
private static String canonicalizeHost(String host) {
// check if the host has already been canonicalized
String fqHost = canonicalizedHostCache.get(host);
if (fqHost == null) {
try {
fqHost = SecurityUtil.getByName(host).getHostName();
// slight race condition, but won't hurt
canonicalizedHostCache.putIfAbsent(host, fqHost);
fqHost = canonicalizedHostCache.get(host);
} catch (UnknownHostException e) {
fqHost = host;
}
}
return fqHost;
}
{code}
So even if other thread get a different host name it will be updated to the
cached value/
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