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AWS SSM Agent - Connection Error

Vu Dao
Awesome Devops || AWS SA || CloudOpz
Updated on ・3 min read

When trying to access EC2 instance using AWS ssm cli or SSM connect manager and get error Plugin with name Standard_Stream not found. Step name: Standard_Stream. No worry, this post shows you how to trouble shoot

What’s In This Document


🚀 What is the error

  • We got error when trying access EC2 instance using SSM and AWS CLI
⚡ $ aws ssm start-session --target i-123abc456efd789xx --region ap-northeast-2

Starting session with SessionId: userdev-004f77465f262084d


SessionId: userdev-004f77465f262084d : Plugin with name Standard_Stream not found. Step name: Standard_Stream
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  • Even from console

Alt-text

🚀 Investigate and Apply solution

  • So far you need to access the EC2 using SSH with key-pem to debug (ask your admin)

    • Running tail -f got issue

      tail: inotify resources exhausted
      tail: inotify cannot be used, reverting to polling
      
    • Restart ssm-agent service also got issue No space left on device but it's not about disk space

      [root@env-test ec2-user]# systemctl restart amazon-ssm-agent.service
      Error: No space left on device
      
      [root@env-test ec2-user]# df -h |grep dev
      devtmpfs         32G     0   32G   0% /dev
      tmpfs            32G     0   32G   0% /dev/shm
      /dev/nvme0n1p1  100G   82G   18G  83% /
      
  • So the error itself means that system is getting low on inotify watches, that enable programs to monitor file/dirs changes. To see the currently set limit (including output on my machine)

⚡ $ cat /proc/sys/fs/inotify/max_user_watches
8192
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  • Check which processes using inotify to improve your apps or increase max_user_watches
# for foo in /proc/*/fd/*; do readlink -f $foo; done | grep inotify | sort | uniq -c | sort -nr
      5 /proc/1/fd/anon_inode:inotify
      2 /proc/7126/fd/anon_inode:inotify
      2 /proc/5130/fd/anon_inode:inotify
      1 /proc/4497/fd/anon_inode:inotify
      1 /proc/4437/fd/anon_inode:inotify
      1 /proc/4151/fd/anon_inode:inotify
      1 /proc/4147/fd/anon_inode:inotify
      1 /proc/4028/fd/anon_inode:inotify
      1 /proc/3913/fd/anon_inode:inotify
      1 /proc/3841/fd/anon_inode:inotify
      1 /proc/31146/fd/anon_inode:inotify
      1 /proc/2829/fd/anon_inode:inotify
      1 /proc/21259/fd/anon_inode:inotify
      1 /proc/1934/fd/anon_inode:inotify
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  • Notice that the above inotify list include PID of ssm-agent processes, it explains why we got issue with SSM when max_user_watches reached limit
# ps -ef |grep ssm-ag
root      3841     1  0 00:02 ?        00:00:05 /usr/bin/amazon-ssm-agent
root      4497  3841  0 00:02 ?        00:00:33 /usr/bin/ssm-agent-worker
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- Final Solution: Permanent solution (preserved across restarts)

echo "fs.inotify.max_user_watches=1048576" >> /etc/sysctl.conf
sysctl -p
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  • Verify:
⚡ $ aws ssm start-session --target i-123abc456efd789xx --region ap-northeast-2

Starting session with SessionId: userdev-03ccb1a04a6345bf5
sh-4.2$
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🚀 Conclusion

  • This issue comes from EC2 instance not about SSM agent
  • Go to 🔗 to undestanding SSM agent in 2 minutes.

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