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https://issues.apache.org/jira/browse/HBASE-18214?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16049607#comment-16049607
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Enis Soztutar commented on HBASE-18214:
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Indeed, this fails with
{code}
Exception AtomicHashMap is full.
{code}
If we use std::unordered_map, we need to use a mutex as well. One other option
is to bring in the TBB library as a dependency. I would say that let's do the
mutex + unordered_map for now, and worry about optimizing this later if we
measure that this part is a bottleneck.
> Replace the folly::AtomicHashMap usage in the RPC layer
> -------------------------------------------------------
>
> Key: HBASE-18214
> URL: https://issues.apache.org/jira/browse/HBASE-18214
> Project: HBase
> Issue Type: Sub-task
> Reporter: Devaraj Das
> Assignee: Devaraj Das
>
> In my tests, I saw that folly::AtomicHashMap usage is not appropriate for
> one, rather common use case. It'd become sort of unusable (inserts would
> hang) after a bunch of inserts and erases. This hashmap is used to keep track
> of call-Id after a connection is set up in the RPC layer (insert a
> call-id/msg pair when an RPC is sent, and erase the pair when the
> corresponding response is received). Here is a simple program that will
> demonstrate the issue:
> {code}
> folly::AtomicHashMap<int, int> f(100);
> int i = 0;
> while (i < 10000) {
> try {
> f.insert(i,100);
> LOG(INFO) << "Inserted " << i << " " << f.size();
> f.erase(i);
> LOG(INFO) << "Deleted " << i << " " << f.size();
> i++;
> } catch (const std::exception &e) {
> LOG(INFO) << "Exception " << e.what();
> break;
> }
> }
> {code}
> After poking around a little bit, it is indeed called out as a limitation
> here
> https://github.com/facebook/folly/blob/master/folly/docs/AtomicHashMap.md
> (grep for 'erase'). Proposal is to replace this with something that will fit
> in in the above usecase (thinking of using std::unordered_map).
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