pthread_create failed: errno:11 Resource temporarily unavailable

[Darshan Shah]

Hi,

Intermittently I see the below error message in the logs:

2016-05-05T08:11:03.408-0400 I NETWORK  [initandlisten] pthread_create failed: errno:11 Resource temporarily unavailable

2016-05-05T08:11:03.408-0400 I NETWORK  [initandlisten] failed to create thread after accepting new connection, closing connection

This message is continuously printed multiple times in the log and then everything seems to be fine after 15-30 seconds. This pattern recurs at varying intervals in the log several times.

I am running MongoDb 3.2.5 WiredTiger with --wiredTigerCacheSizeGB 20 on CentOS 7.1 and the setup is 3 config servers, 28 shards with each shard being a 3 node replicaset and 30 mongos processes. The mongo related processes are started with numactl --interleave=all 

The limits on the boxes have been cranked up as below:

$ 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) 1546963

max locked memory       (kbytes, -l) unlimited

max memory size         (kbytes, -m) unlimited

open files                      (-n) 131072

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

$ cat /etc/security/limits.d/20-nproc.conf

# Default limit for number of user's processes to prevent

# accidental fork bombs.

# See rhbz #432903 for reasoning.

*          soft    nproc     4096

root       soft    nproc     unlimited

oasprod soft nofile unlimited

#oasprod hard nofile 65535

oasprod hard nofile 131072

oasprod soft nproc unlimited

oasprod hard nproc unlimited

oasprod soft fsize unlimited

oasprod hard fsize unlimited

oasprod soft memlock unlimited

oasprod hard memlock unlimited

oasprod soft cpu unlimited

oasprod hard cpu unlimited

oasprod soft as unlimited

oasprod hard as unlimited

# Sample limits of a Mongod process

$ cat /proc/44954/limits

Limit                     Soft Limit           Hard Limit           Units

Max cpu time              unlimited            unlimited            seconds

Max file size             unlimited            unlimited            bytes

Max data size             unlimited            unlimited            bytes

Max stack size            8388608              unlimited            bytes

Max core file size        0                    unlimited            bytes

Max resident set          unlimited            unlimited            bytes

Max processes             unlimited            unlimited            processes

Max open files            131072               131072               files

Max locked memory         unlimited            unlimited            bytes

Max address space         unlimited            unlimited            bytes

Max file locks            unlimited            unlimited            locks

Max pending signals       1546963              1546963              signals

Max msgqueue size         819200               819200               bytes

Max nice priority         0                    0

Max realtime priority     0                    0

Max realtime timeout      unlimited            unlimited            us

Other parameters of the system are:

$ cat /proc/sys/net/ipv4/ip_local_port_range

32768   61000

$ cat /proc/sys/vm/max_map_count

65530

$ cat /proc/sys/net/ipv4/tcp_keepalive_time

35

$ cat /proc/sys/kernel/threads-max

3093926

All help is highly appreciated!

Thanks!

[Darshan Shah]

Another observation - this happens randomly with either MongoS, Primary MongoD, Secondary MongoD or Arbiter MongoD and sometimes the problem lasts longer over a few minutes too.

Thanks!

[Wan Bachtiar]

pthread_create failed: errno:11 Resource temporarily unavailable

This message is continuously printed multiple times in the log and then everything seems to be fine after 15-30 seconds.

Hi Darshan,

Generally the error message is an indication that the OS runs out of sockets for mongod to open (pthread_create returns EAGAIN see linux pthread_create:ERRORS).

$ cat /proc/sys/kernel/threads-max
3093926

Based on your /proc/sys/kernel/threads-max, you have increased the maximum number of threads on the system to be 3093926. Depending on your hardware specs and applications requirements, you need to ensure that this is a reasonable number. Try tuning the number of maximum threads accordingly.

$ cat /etc/security/limits.d/20-nproc.conf

• soft nproc 4096
  root soft nproc unlimited

Based on the output of /etc/security/limits.d/20-nproc.conf, although you have the root user setting to unlimited, generally mongod in CentOS is executed via mongod user. Check whether the mongod process is actually under the soft limits of 4096.

Another thing to check, sometimes multiple short-lived connections can caused the machine to reach the system limits. Check on how your applications utilise the connections. i.e. depending on your use case see Bulk() operations.

You may also be benefited from reading these deployments/operational resources:

• MongoDB Production Notes
• MongoDB Whitepaper: Operations Best Practices

Kind regards,

Wan.

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