I am running a server with 20 cpu cores and 96 GB of ram. I have configured Postgresql and Pgbouncer to handle 1000 connections at a time.
However when the connections increase (even though they are well below the 1000 limit I have set) I start getting failed connections. I checked the pgbouncer log and I noticed the following
ERROR accept() failed: Too many open files
What limit do I need to increase to solve this issue? I am running Debian 8
Increate the operating system limit of the maximum number of open files for the user under which pgBouncer is running.
I added the below parameters in the pgBouncer service. After that, pgbanch was run again. So problems was solved.
The file limit size depend on your Linux file size. You checked your system with these codes.
cat /proc/sys/fs/file-max
ulimit -n
ulimit -Sn
ulimit -Hn
vim /lib/systemd/system/pgbouncer.service
[Service]
LimitNOFILE=64000
LimitNOFILESoft=64000
how could I relaunch mongodb service after killed by OOM
I couldn't find the reason why the mongodb service killed by OS about every 2 days.
is there any workaround to launch the mongodb service when it got killed
I've already set some system configs to avoid killing the mongodb service
thanks so much
/etc/security/limits.conf
* hard nofile unlimited
* soft nofile unlimited
root hard nofile unlimited
root soft nofile unlimited
/etc/sysctl.conf
vm.oom-kill = 0
vm.overcommit_memory = 1
Try to add these lines in /etc/init/mongod.conf
respawn
respawn limit 10 100
it will retry restart the service in 100 seconds
I am trying to create a docker image for Couchbase and i get the following error with the dockerfile on CentOS image.
# expose default port
EXPOSE 8091
ENV PATH $PATH:/opt/couchbase/bin
RUN cd /var/tmp &&\
wget http://packages.couchbase.com/releases/2.5.0/couchbase-server-enterprise_2.5.0_x86_64.rpm &&\
rpm -ivh couchbase-server-enterprise_2.5.0_x86_64.rpm &&\
chkconfig couchbase-server on &&\
service couchbase-server start
#add start script to the container
ADD start /start
#make the script executable
RUN chmod 0755 /start
EXPOSE 11211 11210 11209 4369 8092 18091 18092 11214 11215
#start mysql service and launch the command console
CMD ["/start"]
When building it, i am getting the following error ..
ulimit: open files: cannot modify limit: Operation not permitted
ulimit: max locked memory: cannot modify limit: Operation not permitted
I saw in a forum that we can set these values in docker.conf files. But i tried creating this file /etc/init/docker.conf and put the following lines in that file-
limit memlock unlimited unlimited
limit nofile 262144
but still i get the same error.
If i follow the same steps manually on CentOS VM, it works. So i guess i need to set something on Docker CentOS image.
Resolved the issue by setting the ulimit on the Docker host using the following command:
ulimit -l unlimited
ulimit -n 10240
ulimit -c unlimited
Then restart the Docker service on the CentOS. That fixed the issue since these values of the host will be inherited by the container.
Only root can increase the hard upper limit, and you have to be logged in as root, sudo won't work.
su root
ulimit -n 10240
My application uses MongoDB as database. We are expecting 20K+ simultaneous connections to mongodb cluster. How should I config the server if I want to run the mongodb on 20 servers and shard the cluster 20 ways?
Here is what I've done so far:
On each of my 20 servers, I have one mongos (router) running on port 30000, and on 3 servers I run mongo config servers on port 20000. Then on each server, I run 3 instances of mongod. One of the is the primary. In order words, I have 20 mongos, 3 mongo-config, 60 mongod servers (20 primary and 40 replica).
Then in my application (which also run on each server and connect to the localhost:30000 mongos), I set the mongoOptions such that the connectionsPerHost = 1000.
10-15 minutes after all services start, some of them became no longer ssh-able. These servers are still ping-able. I suspect there were too many connections, and it caused the server to die.
My own analysis is as follows:
1K connections per connection pool means for each shard's primary, it will have 1K * 20 (shards) = 20K simultaneous connections open. A few servers will probably have more than one primary running on it, which will double or triple the number of connections to 60K. Somehow mongod cannot handle these many connections although I changed my system settings to allow each process to open way more files.
Here are what 'ulimit -a' shows:
core file size (blocks, -c) 0
data seg size (kbytes, -d) unlimited
scheduling priority (-e) 20
file size (blocks, -f) unlimited
pending signals (-i) 16382
max locked memory (kbytes, -l) 64000000
max memory size (kbytes, -m) unlimited
open files (-n) 320000
pipe size (512 bytes, -p) 8
POSIX message queues (bytes, -q) 819200
real-time priority (-r) 0
stack size (kbytes, -s) 8192
cpu time (seconds, -t) unlimited
max user processes (-u) unlimited
virtual memory (kbytes, -v) unlimited
file locks (-x) unlimited
BTW, I didn't specify --maxConns when I start up mongod/mongos, I also didn't change MONGO.POOLSIZE.
A side question: if my reasoning is correct, the total number of simultaneous connection requirement will be posed on each primary, which doesn't seem right to me, it almost means mongodb cluster is not scalable at all. Someone tell me I'm wrong please?
Aout your cluster architecture :
Running several instances of mongod on the same server is usually not a good idea, do you any particular reason to do this ? The primary server of each shard will put some heavy pressure on your server, the replication also add io pressure, so mixing them won't be really good for performance. IMO, you should rather have 6 shards (1 master - 2 secondaries) and give each instance their own server. (Conf and arbiter instance are not very resources consomming so its ok to leave them on the same servers).
Sometimes the limits don't apply to the process itself. As a test go onto one of the servers and get the pid for the mongo service you want to check on by doing
ps axu | grep mongodb
and then do
cat /proc/{pid}/limit
That will tell you if the limits have taken effect. If the limit isn't un effect then you need to specify the limit in the startup file and then stop - start the mongo service and test again.
A sure-fire way to know if this is happening is to tail -f the mongo log on a dying server and watch for those "too many files" messages.
We set our limit to 20000 per server and do the same on all mongod and mongos instances and this seems to work.
We're running a 4-shard replicaset on 4 machines. We have 2 shard primaries on 2 hosts, 2 shard replicas on the other 2 boxes, arbiters and config servers spread out).
We're getting messages:
./checkMongo.bash: fork: retry: Resource temporarily unavailable
./checkMongo.bash: fork: retry: Resource temporarily unavailable
./checkMongo.bash: fork: retry: Resource temporarily unavailable
Write failed: Broken pipe
Checking ulimit -a:
core file size (blocks, -c) 0
data seg size (kbytes, -d) unlimited
scheduling priority (-e) 0
file size (blocks, -f) unlimited
pending signals (-i) 773713
max locked memory (kbytes, -l) 64
max memory size (kbytes, -m) unlimited
open files (-n) 4096
pipe size (512 bytes, -p) 8
POSIX message queues (bytes, -q) 819200
real-time priority (-r) 0
stack size (kbytes, -s) 10240
cpu time (seconds, -t) unlimited
max user processes (-u) 1024
virtual memory (kbytes, -v) unlimited
file locks (-x) unlimited
Okay, so we're possibly hitting a process limit because of the fork message. Here's how to check that:
$ ps axo pid,ppid,rss,vsz,nlwp,cmd | egrep mongo
27442 1 36572 59735772 275 /path/mongod --shardsvr --replSet shard-00 --dbpath /path/rs-00-p --port 30000 --logpath /path/rs-00-p.log --fork
27534 1 4100020 59587548 295 /path/mongod --shardsvr --replSet shard-02 --dbpath /path/rs-02-p --port 30200 --logpath /path/rs-02-p.log --fork
27769 1 57948 13242560 401 /path/mongod --configsvr --dbpath /path/configServer_1 --port 35000 --logpath /path/configServer_1.log --fork
So, you can see the mongod's have 275, 295, and 401 subprocesses/threads each. though I'm not hitting a limit now, I probably was earlier. So, the solution: change the system's ulimit for the user we're running under from 1024 to 2048 (or even unlimited). You can't change via
ulimit -u unlimited
unless you sudo first or something; I don't have privs to do that.
i am using memcached on my centos server , my project is large and has objects more than 1MB which i need to save to memcached , well , i can't ! because the max_item_size is 1MB , anyway to edit that ?
Thank you
You can change the limit quickly by edit the configuration file [/etc/memcached.conf] adding:
# Increase limit
-I 128M
Or if you have trouble with SO config run it with command line directly
memcached -I 128M
If you are using Memcache >= 1.4.2, this is now configurable. Here is an example of how to set this in your init script for starting Memcache on CentOS: http://www.alphadevx.com/a/387-Changing-the-maximum-item-size-allowed-by-Memcache
You can compile memcached and change the memory allocation setting to use POWER_BLOCK's, in the slabs.c file (or you can recompile and user malloc/free, but that is the greater of the evils).
http://code.google.com/p/memcached/wiki/FAQ#Why_are_items_limited_to_1_megabyte_in_size?
I would seriously consider what you are caching and how it can be more modular, > 1MB in active memory is large.
Spent tons of time to figure this out:
in /etc/sysconfig/memcached edit options
OPTIONS="-l 127.0.0.1 -I 3m"
then systemctl restart memcached to take effect.
Would recommend option -l 127.0.0.1 it secures to localhost usage only and -I 3m increases the limit as described above.
With Centos 7 I had no luck with these paths /etc/memcached.conf /etc/default/memcached