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https://issues.apache.org/jira/browse/COUCHDB-1258?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13090466#comment-13090466
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Paul Joseph Davis commented on COUCHDB-1258:
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Sounds reasonable. A map function that emits no keys coupled with a lot of
deleted documents means that the partial_update frequency will be quite large.
couch_work_queue's behave quite poorly when the dequeue side is faster than the
queue side and end up basically not bulking updates together. A quick test
would be to guard the partial_update message to only fire at most every 1000
writes. A quick hack to store calls in the process dict in do_writes should
give a quick idea if it's the partial updates.
A should_flush for every partial update seems a bit extreme. Although I can't
think of a better solution that doesn't just make an equivalent to should_flush
that's more specific to this case.
> eheap_alloc OOM errors when attempting to build selected views
> --------------------------------------------------------------
>
> Key: COUCHDB-1258
> URL: https://issues.apache.org/jira/browse/COUCHDB-1258
> Project: CouchDB
> Issue Type: Bug
> Affects Versions: 1.1
> Environment: CentOS 5.6, 1GB RAM (approx 800MB free)
> CouchDb 1.1.0, Erlang R14B-03, js lib 1.7.0-8 EPEL RPM build
> Couch database exhibiting this behaviour:
> {"db_name":"activity_new","doc_count":593274,"doc_del_count":4743352,"update_seq":10559287,"purge_seq":0,"compact_running":false,"disk_size":3366396013,"instance_start_time":"1314097423985726","disk_format_version":5,"committed_update_seq":10559287}
> Reporter: James Cohen
> Priority: Critical
>
> We spotted OOM errors crashing our CouchDb instance when attempting to
> rebuild selected views. CouchDb was dying with the following messages (worth
> noting that the type reported varies between heap/old_heap
> eheap_alloc: Cannot allocate 478288480 bytes of memory (of type "heap").
> eheap_alloc: Cannot allocate 597860600 bytes of memory (of type "heap").
> eheap_alloc: Cannot allocate 747325720 bytes of memory (of type "old_heap").
> eheap_alloc: Cannot allocate 597860600 bytes of memory (of type "old_heap").
> By modifying the view I was able to find a view that could consistently crash
> the server and another that ran fine. They are as follows:
> Runs out of memory v.quickly
> {
> "_id": "_design/cleanup",
> "_rev": "5-e004fbab278355e9d08763877e5a8295",
> "views": {
> "byDate": {
> "map": "function(doc) { if (! doc.action) emit([doc.date], doc); }"
> }
> }
> }
> Runs fine with minimal memory usage (returns 88128 docs in the view)
> {
> "_id": "_design/cleanup",
> "_rev": "6-3823be6b72ca2441e235addfece6900c",
> "views": {
> "byDate": {
> "map": "function(doc) { if (doc.action) emit([doc.date], doc); }"
> }
> }
> }
> The only difference between the two is the negation of the if conditional.
> memory usage was monitored with top on the machine while the view was being
> built. Under correct behaviour I could see beam.smp using just 3 or 4% of the
> server's memory. With the view that causes problems that memory usage
> increased until the RAM/swap on the server was exhausted (as you can see from
> the error messages around 500/700MB)
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