[jira] [Resolved] (HTRACE-308) Deserialize WriteSpans requests incrementally rather than all at once to optimize GC

["Colin Patrick McCabe (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HTRACE-308?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Colin Patrick McCabe resolved HTRACE-308.
-----------------------------------------
       Resolution: Fixed
    Fix Version/s: 4.1

> Deserialize WriteSpans requests incrementally rather than all at once to optimize GC
> ------------------------------------------------------------------------------------
>
>                 Key: HTRACE-308
>                 URL: https://issues.apache.org/jira/browse/HTRACE-308
>             Project: HTrace
>          Issue Type: Improvement
>          Components: htraced
>    Affects Versions: 4.0
>            Reporter: Colin Patrick McCabe
>            Assignee: Colin Patrick McCabe
>             Fix For: 4.1
>
>         Attachments: HTRACE-308.001.patch, HTRACE-308.002.patch, HTRACE-308.003.patch, HTRACE-308.004.patch
>
>
> We should deserialize WriteSpans requests incrementally rather than all at once.  Currently, we can deserialize 63 MB of spans all at once, which immediately creates somewhere between 60k and 600k spans, depending on span size.  This is hard on the garbage collector because it's a lot of allocations all at once, and because it allocates a very large array to hold it all.
> It would be better to deserialize spans one at a time and feed them into the datastore via the BatchIngestor. This will ensure that we don't have to allocate giant arrays of spans all at once.  If the datastore lags behind the rate of span ingestion, this will avoid us needing to allocate a bunch of memory "up front" which can lead to further slowdowns due to GC.
> Also, we should reuse buffers for the RPC handlers, and use buffering while deserializing to avoid making lots of small reads from the socket.



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