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https://issues.apache.org/jira/browse/HADOOP-11387?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14249044#comment-14249044
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Jonathan Eagles commented on HADOOP-11387:
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Can you post the findbugs warning. I prefer to fix the warning rather that
switch the underlying cache implementation. For small number hosts, this change
is overkill. For large number of hosts, this implementation under-performs.
> Simplify NetUtils#canonicalizeHost()
> ------------------------------------
>
> Key: HADOOP-11387
> URL: https://issues.apache.org/jira/browse/HADOOP-11387
> Project: Hadoop Common
> Issue Type: Bug
> Reporter: Haohui Mai
> Assignee: Li Lu
> Attachments: HADOOP-11387-121514-1.patch,
> HADOOP-11387-121514-2.patch, HADOOP-11387-121514.patch
>
>
> Currently {{NetUtils#canonicalizeHost}} uses a {{ConcurrentHashMap}} to cache
> the canonicalized hostname.
> {code}
> 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.put(host, fqHost);
> } catch (UnknownHostException e) {
> fqHost = host;
> }
> }
> return fqHost;
> }
> {code}
> The code triggers a findbugs warning. The cache is used for caching NN
> resolution for the client-side {{FileSystem}} objects. In most of the use
> cases there are at most one or two instances in the cache. This jira proposes
> to eliminate the findbugs warnings and to simplify the code using
> {{CacheMap}}.
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