Service keepalive with a Cloud Assistant plugin-Elastic Compute Service(ECS)-阿里云帮助中心

How it works

The Cloud Assistant ecs-tool-servicekeepalive plugin uses systemd, the Linux service manager, to automatically restart an interrupted service or script, ensuring service reliability and continuity. To use the plugin for keepalive, provide a startup command. The plugin then generates the required systemd service configuration, starts the service, and enables auto-start on boot. No manual file editing is necessary.

Note

systemd is a service manager in Linux that can perform tasks such as enabling auto-start on boot and restarting services that stop unexpectedly. For more information, see the official systemd documentation.

Procedure

Enable service keepalive

After you deploy your service, run the Cloud Assistant pluginecs-tool-servicekeepalive as the root user.

Run as root

sudo acs-plugin-manager --exec --plugin ecs-tool-servicekeepalive --params "start,'<cmd>'"

<cmd>: The startup command for the service. See the examples below.

Shell script: (/bin/bash /home/ecs-user/keepalive-simple/test-keepalive.sh).
Python script: (python /home/root/main.py).

Run as specified user

sudo acs-plugin-manager --exec --plugin ecs-tool-servicekeepalive --params "start,execstart='<cmd>',user=<user_name>,group=<group_name>"

<cmd>: The startup command for the service. See the examples below.
- Shell script: (/bin/bash /home/ecs-user/keepalive-simple/test-keepalive.sh).
- Python script: (python /home/root/main.py).
<user_name>: The username that runs the service. Runcut -d: -f1 /etc/passwd to view existing users.
<group_name>: The group name for the service. Runcut -d: -f1 /etc/group to view existing user groups.

Warning

You must use an absolute path for the script or program file.
If enabling keepalive fails, first query the keepalive status of the service and then disable keepalive for the service for the failed entry before you try again. This prevents multiple service processes from starting, which can cause issues with your application.

Query keepalive status

Run the following command to check the keepalive status.

sudo acs-plugin-manager --exec --plugin ecs-tool-servicekeepalive --params "status"

The following example output indicates that keepalive is enabled.

service_name                   execstart            user  group status              
ecs_keepalive_1744262359.service /bin/bash /home/ecs-user/keepalive-simple/test-keepalive.sh /home/ecs-user/keepalive-simple/test-keepalive.log              active (running) since Thu 2025-04-10 13

Disable service keepalive

If you need to disable keepalive, run the following command.

sudo acs-plugin-manager --exec --local --plugin ecs-tool-servicekeepalive --params "stop <service_name>"

<service_name>: The name of the service configuration. This value is in the service_name column of the output from the Query keepalive status step.

Note

When you disable keepalive, the service process is terminated, the auto-start configuration is removed, and the service configuration file created by the ecs-tool-servicekeepalive plugin is deleted.

Example

Prepare a test service script.

This script uses/home/ecs-user as the working directory. Replace it with your actual working directory.

# Create the keepalive-simple directory in the /home/ecs-user directory and create the test-keepalive.sh script in the directory.
sudo mkdir -p /home/ecs-user/keepalive-simple && \
sudo tee /home/ecs-user/keepalive-simple/test-keepalive.sh > /dev/null << 'EOF'
#!/bin/bash
# Write one log line per second to the log file that you specify.
while true
do
   sudo echo "$(date '+%Y-%m-%d %H:%M:%S') progress is alive" >> $1
    sleep 1
done
EOF
# Grant execute permissions to the script.
sudo chmod +x /home/ecs-user/keepalive-simple/test-keepalive.sh

(Optional) Query the service running status.

Run the following command to query the service running status.
```
ps aux | grep test-keepalive.sh
```
The following example output indicates that the service is not running.
```
ecs-user    2207  0.0  0.0 221528   916 pts/0    S+   11:34   0:00 grep --color=auto test-keepalive.sh
```

Enable keepalive for the service.

sudo acs-plugin-manager --exec --plugin ecs-tool-servicekeepalive --params "start,'/bin/bash /home/ecs-user/keepalive-simple/test-keepalive.sh /home/ecs-user/keepalive-simple/test-keepalive.log'"

The following example output indicates that keepalive is enabled.

Created symlink /etc/systemd/system/multi-user.target.wants/ecs_keepalive_1744256544.service → /etc/systemd/system/ecs_keepalive_1744256544.service.
Start systemd service for "/bin/bash /home/ecs-user/keepalive-simple/test-keepalive.sh /home/ecs-user/keepalive-simple/test-keepalive.log" success

Query the keepalive status and service running status.

Run the following command to query the keepalive status.

sudo acs-plugin-manager --exec --plugin ecs-tool-servicekeepalive --params "status"

The following example output indicates that keepalive is enabled and the service is running.

service_name                   execstart            user  group status              
ecs_keepalive_1744256544.service /bin/bash /home/ecs-user/keepalive-simple/test-keepalive.sh /home/ecs-user/keepalive-simple/test-keepalive.log              active (running) since Thu 2025-04-10 11

Run the following command to query the service running status.

ps aux | grep test-keepalive.sh

The following example output indicates that the service is running.

root        3144  0.0  0.0 222200  3420 ?        Ss   11:42   0:00 /bin/bash /home/ecs-user/keepalive-simple/test-keepalive.sh /home/ecs-user/keepalive-simple/test-keepalive.log
ecs-user    6841  0.0  0.0 221660   968 pts/0    S+   11:49   0:00 grep --color=auto test-keepalive.sh

(Optional) Verify keepalive.
1. Manually stop the service to verify that Cloud Assistant automatically restarts its process.
  Method 1: Restart ECS instance
  
  Restart the instance to simulate an unexpected instance restart.
  Method 2: Terminate the process
  
  Run the following command to terminate the test-keepalive.sh process. Replace <PID> with the PID of the program that is returned by the ps command.
```
sudo date && kill -9 <PID>
```
2. Run the following command to query the service running status.
```
ps aux | grep test-keepalive.sh
```
  The following example output indicates that the service is running.
```
root       33061  0.0  0.0 222200  3504 ?        Ss   13:19   0:00 /bin/bash /home/ecs-user/keepalive-simple/test-keepalive.sh /home/ecs-user/keepalive-simple/test-keepalive.log
ecs-user   34558  0.0  0.0 221660  2556 pts/0    S+   13:23   0:00 grep --color=auto test-keepalive.sh
```

Disable keepalive for the service.

Run the following command to disable keepalive.

sudo acs-plugin-manager --exec --local --plugin ecs-tool-servicekeepalive --params "stop ecs_keepalive_1744256544.service"

The following example output indicates that the keepalive configuration is disabled.

service check ok, file:ecs_keepalive_1744256544.service is valid
Removed /etc/systemd/system/multi-user.target.wants/ecs_keepalive_1744256544.service.
stop service ok, service:ecs_keepalive_1744256544.service is stopped and removed

References

For more information about Cloud Assistant, see Cloud Assistant overview.