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
> > > > >
> > > >
> > >
> >
>
