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From "Jonathan Ellis (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-4708) StorageProxy slow-down and memory leak
Date Mon, 24 Sep 2012 15:20:07 GMT


Jonathan Ellis commented on CASSANDRA-4708:

did a quick audit of NBHM usage elsewhere.  think we're okay, everything else has a pretty
tiny amount of possible keys.  the main "large" maps are in the column containers where NBHM
is a non-candidate since we need sorting.
> StorageProxy slow-down and memory leak
> --------------------------------------
>                 Key: CASSANDRA-4708
>                 URL:
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Daniel Norberg
>            Assignee: Daniel Norberg
>             Fix For: 1.1.6
>         Attachments: 0001-MessagingService-don-t-use-NBHM-in-ExpiringMap.patch
> I am consistently observing slow-downs in StorageProxy caused by the NonBlockingHashMap
used indirectly by MessagingService via the callbacks ExpiringMap.
> This seems do be due to NBHM having unbounded memory usage in the face of workloads with
high key churn. As monotonically increasing integers are used as callback id's by MessagingService,
the backing NBHM eventually ends up growing the backing store unboundedly. This causes it
to also do very large and expensive backing store reallocation and migrations, causing throughput
to drop to tens of operations per second, lasting seconds or even minutes. 
> This behavior is especially noticable for high throughput workloads where the dataset
is completely in ram and I'm doing up to a hundred thousand reads per second.
> Replacing NBHM in ExpiringMap with the java standard library ConcurrentHashMap resolved
the issue and allowed me to keep a consistent high throughput.
> An open issue on NBHM can be seen here:

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