Nothing to see here, the message queue stat from Adam's advice is accurate.
Note that you should run this only when there is already an unreasonable
amount memory leaked/consumed.
But now I realise you had "processes":1877591424 before restart from the
stats above which is less than 2G. Are you using only 2 gigs of RAM? I got
confused by the initial comment and I thought you had 15GB RAM. If you are
only using 2 gigs of RAM, it's probably not enough for your workload.
On Mon, Jun 17, 2019 at 12:15 PM Jérôme Augé <jerome.a...@anakeen.com>
wrote:
> That command seems to work, and here is the output:
>
> --8<--
> # /opt/couchdb/bin/remsh < debug.2.remsh
> Eshell V7.3 (abort with ^G)
> (remsh22574@127.0.0.1)1> [{0,<0.0.0>},
> {0,<0.3.0>},
> {0,<0.6.0>},
> {0,<0.7.0>},
> {0,<0.9.0>},
> {0,<0.10.0>},
> {0,<0.11.0>},
> {0,<0.12.0>},
> {0,<0.14.0>},
> {0,<0.15.0>},
> {0,<0.16.0>},
> {0,<0.17.0>},
> {0,<0.18.0>},
> {0,<0.19.0>},
> {0,<0.20.0>},
> {0,<0.21.0>},
> {0,<0.22.0>},
> {0,<0.23.0>},
> {0,<0.24.0>},
> {0,<0.25.0>},
> {0,<0.26.0>},
> {0,<0.27.0>},
> {0,<0.28.0>},
> {0,<0.29.0>},
> {0,<0.31.0>},
> {0,<0.32.0>},
> {0,<0.33.0>},
> {0,...},
> {...}]
> (remsh22574@127.0.0.1)2> {0,<0.38.0>}
> (remsh22574@127.0.0.1)3> [{current_function,{erl_eval,do_apply,6}},
> {initial_call,{erlang,apply,2}},
> {status,running},
> {message_queue_len,0},
> {messages,[]},
> {links,[<0.32.0>]},
> {dictionary,[]},
> {trap_exit,false},
> {error_handler,error_handler},
> {priority,normal},
> {group_leader,<0.31.0>},
> {total_heap_size,5172},
> {heap_size,2586},
> {stack_size,24},
> {reductions,24496},
> {garbage_collection,[{min_bin_vheap_size,46422},
> {min_heap_size,233},
> {fullsweep_after,65535},
> {minor_gcs,1}]},
> {suspending,[]}]
> (remsh22574@127.0.0.1)4> *** Terminating erlang ('remsh22574@127.0.0.1')
> -->8--
>
> What should I be looking for in this output?
>
> Le ven. 14 juin 2019 à 17:30, Vladimir Ralev <vladimir.ra...@gmail.com> a
> écrit :
>
> > That means your couch is creating and destroying processes too rapidly. I
> > haven't seen this, however I think Adam's message_queues stat above does
> > the same thing. I didn't notice you can get it from there.
> >
> > Either way it will be useful if you can get the shell to work:
> > Try this command instead for the first, the rest will be the same:
> >
> > MQSizes2 = lists:map(fun(A) -> {_,B} = case
> > process_info(A,message_queue_len) of {XV,XB} -> {XV, XB}; _ERR ->
> > io:format("~p",[_ERR]),{ok, 0} end, {B,A} end, processes()).
> >
> > On Fri, Jun 14, 2019 at 5:52 PM Jérôme Augé <jerome.a...@anakeen.com>
> > wrote:
> >
> > > I tried the following, but it seems to fail on the first command:
> > >
> > > --8<--
> > > # /opt/couchdb/bin/remsh
> > > Erlang/OTP 18 [erts-7.3] [source-d2a6d81] [64-bit] [smp:8:8]
> > > [async-threads:10] [hipe] [kernel-poll:false]
> > >
> > > Eshell V7.3 (abort with ^G)
> > > (couchdb@127.0.0.1)1> MQSizes2 = lists:map(fun(A) -> {_,B} =
> > > process_info(A,message_queue_len), {B,A} end, processes()).
> > > ** exception error: no match of right hand side value undefined
> > > -->8--
> > >
> > >
> > > Le ven. 14 juin 2019 à 16:08, Vladimir Ralev <vladimir.ra...@gmail.com
> >
> > a
> > > écrit :
> > >
> > > > Hey guys. I bet it's a mailbox leaking memory. I am very interested
> in
> > > > debugging issues like this too.
> > > >
> > > > I can suggest to get an erlang shell and run these commands to see
> the
> > > top
> > > > memory consuming processes
> > > > https://www.mail-archive.com/user@couchdb.apache.org/msg29365.html
> > > >
> > > > One issue I will be reporting soon is if one of your nodes is down
> for
> > > some
> > > > amount of time, it seems like all databases independently try and
> retry
> > > to
> > > > query the missing node and fail, resulting in printing a lot of logs
> > for
> > > > each db which can overwhelm the logger process. If you have a lot of
> > DBs
> > > > this makes the problem worse, but it doesn't happen right away for
> some
> > > > reason.
> > > >
> > > > On Fri, Jun 14, 2019 at 4:25 PM Adrien Vergé <
> adrien.ve...@tolteck.com
> > >
> > > > wrote:
> > > >
> > > > > Hi Jérôme and Adam,
> > > > >
> > > > > That's funny, because I'm investigating the exact same problem
> these
> > > > days.
> > > > > We have a two CouchDB setups:
> > > > > - a one-node server (q=2 n=1) with 5000 databases
> > > > > - a 3-node cluster (q=2 n=3) with 50000 databases
> > > > >
> > > > > ... and we are experiencing the problem on both setups. We've been
> > > having
> > > > > this problem for at least 3-4 months.
> > > > >
> > > > > We've monitored:
> > > > >
> > > > > - The number of open files: it's relatively low (both the system's
> > > total
> > > > > and or fds opened by beam.smp).
> > > > > https://framapic.org/wQUf4fLhNIm7/oa2VHZyyoPp9.png
> > > > >
> > > > > - The usage of RAM, total used and used by beam.smp
> > > > > https://framapic.org/DBWIhX8ZS8FU/MxbS3BmO0WpX.png
> > > > > It continuously grows, with regular spikes, until killing CouchDB
> > > with
> > > > an
> > > > > OOM. After restart, the RAM usage is nice and low, and no spikes.
> > > > >
> > > > > - /_node/_local/_system metrics, before and after restart. Values
> > that
> > > > > significantly differ (before / after restart) are listed here:
> > > > > - uptime (obviously ;-))
> > > > > - memory.processes : + 3732 %
> > > > > - memory.processes_used : + 3735 %
> > > > > - memory.binary : + 17700 %
> > > > > - context_switches : + 17376 %
> > > > > - reductions : + 867832 %
> > > > > - garbage_collection_count : + 448248 %
> > > > > - words_reclaimed : + 112755 %
> > > > > - io_input : + 44226 %
> > > > > - io_output : + 157951 %
> > > > >
> > > > > Before CouchDB restart:
> > > > > {
> > > > > "uptime":2712973,
> > > > > "memory":{
> > > > > "other":7250289,
> > > > > "atom":512625,
> > > > > "atom_used":510002,
> > > > > "processes":1877591424,
> > > > > "processes_used":1877504920,
> > > > > "binary":177468848,
> > > > > "code":9653286,
> > > > > "ets":16012736
> > > > > },
> > > > > "run_queue":0,
> > > > > "ets_table_count":102,
> > > > > "context_switches":1621495509,
> > > > > "reductions":968705947589,
> > > > > "garbage_collection_count":331826928,
> > > > > "words_reclaimed":269964293572,
> > > > > "io_input":8812455,
> > > > > "io_output":20733066,
> > > > > ...
> > > > >
> > > > > After CouchDB restart:
> > > > > {
> > > > > "uptime":206,
> > > > > "memory":{
> > > > > "other":6907493,
> > > > > "atom":512625,
> > > > > "atom_used":497769,
> > > > > "processes":49001944,
> > > > > "processes_used":48963168,
> > > > > "binary":997032,
> > > > > "code":9233842,
> > > > > "ets":4779576
> > > > > },
> > > > > "run_queue":0,
> > > > > "ets_table_count":102,
> > > > > "context_switches":1015486,
> > > > > "reductions":111610788,
> > > > > "garbage_collection_count":74011,
> > > > > "words_reclaimed":239214127,
> > > > > "io_input":19881,
> > > > > "io_output":13118,
> > > > > ...
> > > > >
> > > > > Adrien
> > > > >
> > > > > Le ven. 14 juin 2019 à 15:11, Jérôme Augé <jerome.a...@anakeen.com
> >
> > a
> > > > > écrit :
> > > > >
> > > > > > Ok, so I'll setup a cron job to journalize (every minute?) the
> > output
> > > > > from
> > > > > > "/_node/_local/_system" and wait for the next OOM kill.
> > > > > >
> > > > > > Any property from "_system" to look for in particular?
> > > > > >
> > > > > > Here is a link to the memory usage graph:
> > > > > > https://framapic.org/IzcD4Y404hlr/06rm0Ji4TpKu.png
> > > > > >
> > > > > > The memory usage varies, but the general trend is to go up with
> > some
> > > > > > regularity over a week until we reach OOM. When "beam.smp" is
> > killed,
> > > > > it's
> > > > > > reported as consuming 15 GB (as seen in the kernel's OOM trace in
> > > > > syslog).
> > > > > >
> > > > > > Thanks,
> > > > > > Jérôme
> > > > > >
> > > > > > Le ven. 14 juin 2019 à 13:48, Adam Kocoloski <
> kocol...@apache.org>
> > a
> > > > > > écrit :
> > > > > >
> > > > > > > Hi Jérôme,
> > > > > > >
> > > > > > > Thanks for a well-written and detailed report (though the
> mailing
> > > > list
> > > > > > > strips attachments). The _system endpoint provides a lot of
> > useful
> > > > data
> > > > > > for
> > > > > > > debugging these kinds of situations; do you have a snapshot of
> > the
> > > > > output
> > > > > > > when the system was consuming a lot of memory?
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
> http://docs.couchdb.org/en/stable/api/server/common.html#node-node-name-system
> > > > > > >
> > > > > > > Adam
> > > > > > >
> > > > > > > > On Jun 14, 2019, at 5:44 AM, Jérôme Augé <
> > > jerome.a...@anakeen.com>
> > > > > > > wrote:
> > > > > > > >
> > > > > > > > Hi,
> > > > > > > >
> > > > > > > > I'm having a hard time figuring out the high memory usage of
> a
> > > > > CouchDB
> > > > > > > server.
> > > > > > > >
> > > > > > > > What I'm observing is that the memory consumption from the
> > > > "beam.smp"
> > > > > > > process gradually rises until it triggers the kernel's OOM
> > > > > > (Out-Of-Memory)
> > > > > > > which kill the "beam.smp" process.
> > > > > > > >
> > > > > > > > It also seems that many databases are not compacted: I've
> made
> > a
> > > > > script
> > > > > > > to iterate over the databases to compute de fragmentation
> factor,
> > > and
> > > > > it
> > > > > > > seems I have around 2100 databases with a frag > 70%.
> > > > > > > >
> > > > > > > > We have a single CouchDB v2.1.1server (configured with q=8
> n=1)
> > > and
> > > > > > > around 2770 databases.
> > > > > > > >
> > > > > > > > The server initially had 4 GB of RAM, and we are now with 16
> GB
> > > w/
> > > > 8
> > > > > > > vCPU, and it still regularly reaches OOM. From the monitoring I
> > see
> > > > > that
> > > > > > > with 16 GB the OOM is almost triggered once per week (c.f.
> > attached
> > > > > > graph).
> > > > > > > >
> > > > > > > > The memory usage seems to increase gradually until it reaches
> > > OOM.
> > > > > > > >
> > > > > > > > The Couch server is mostly used by web clients with the
> PouchDB
> > > JS
> > > > > API.
> > > > > > > >
> > > > > > > > We have ~1300 distinct users and by monitoring the
> netstat/TCP
> > > > > > > established connections I guess we have around 100 (maximum)
> > users
> > > at
> > > > > any
> > > > > > > given time. From what I understanding of the application's
> logic,
> > > > each
> > > > > > user
> > > > > > > access 2 private databases (read/write) + 1 common database
> > > > > (read-only).
> > > > > > > >
> > > > > > > > On-disk usage of CouchDB's data directory is around 40 GB.
> > > > > > > >
> > > > > > > > Any ideas on what could cause such behavior (increasing
> memory
> > > > usage
> > > > > > > over the course of a week)? Or how to find what is happening
> > behind
> > > > the
> > > > > > > scene?
> > > > > > > >
> > > > > > > > Regards,
> > > > > > > > Jérôme
> > > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
>
