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From "Filipe Manana (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (COUCHDB-1258) eheap_alloc OOM errors when attempting to build selected views
Date Wed, 24 Aug 2011 19:08:29 GMT

    [ https://issues.apache.org/jira/browse/COUCHDB-1258?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13090410#comment-13090410
] 

Filipe Manana commented on COUCHDB-1258:
----------------------------------------

I have a similar case. Database with about 2.6 million deleted documents.
The map function is not emitting any key/value and memory consumption goes to about 4Gb.
After the indexer finishes, and the system goes idle, memory usage stays at about 2Gb forever.
Inspecting the erlang processes, a couch_view_group process is using about 2Gb of memory:

7> process_info(list_to_pid("<0.276.0>")).
[{current_function,{gen_server,loop,6}},
 {initial_call,{proc_lib,init_p,5}},
 {status,waiting},
 {message_queue_len,0},
 {messages,[]},
 {links,[<0.278.0>,<0.132.0>]},
 {dictionary,[{'$ancestors',[<0.275.0>]},
              {'$initial_call',{couch_view_group,init,1}}]},
 {trap_exit,true},
 {error_handler,error_handler},
 {priority,normal},
 {group_leader,<0.37.0>},
 {total_heap_size,323345205},
 {heap_size,38263080},
 {stack_size,9},
 {reductions,1041902893},
 {garbage_collection,[{min_bin_vheap_size,46368},
                      {min_heap_size,233},
                      {fullsweep_after,65535},
                      {minor_gcs,538}]},
 {suspending,[]}]
8> 

Manually invoking the garbage collector against this process releases memory and after that
the process is using only about 7Kb of memory:

8> erlang:garbage_collect(list_to_pid("<0.276.0>")).
true
9> process_info(list_to_pid("<0.276.0>")).          
[{current_function,{gen_server,loop,6}},
 {initial_call,{proc_lib,init_p,5}},
 {status,waiting},
 {message_queue_len,0},
 {messages,[]},
 {links,[<0.278.0>,<0.132.0>]},
 {dictionary,[{'$ancestors',[<0.275.0>]},
              {'$initial_call',{couch_view_group,init,1}}]},
 {trap_exit,true},
 {error_handler,error_handler},
 {priority,normal},
 {group_leader,<0.37.0>},
 {total_heap_size,987},
 {heap_size,987},
 {stack_size,9},
 {reductions,1041902893},
 {garbage_collection,[{min_bin_vheap_size,46368},
                      {min_heap_size,233},
                      {fullsweep_after,65535},
                      {minor_gcs,0}]},
 {suspending,[]}]
10> 

I have no idea why the view group is using so much memory.
My best call is that we need to call couch_util:should_flush/1 everytime we receive a partial_update
message in the view group.
This was with OT R14B03.

> 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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