Mattermost Stops Working After Stopping MySQL Post-Migration to PostgreSQL

Problem

After migrating your Mattermost deployment from MySQL to PostgreSQL, you may encounter an issue where stopping the MySQL service causes the Mattermost application to shut down unexpectedly. This behavior persists even though the PostgreSQL migration appears successful and the application is configured to use PostgreSQL.

Cause

This issue is typically caused by the Mattermost systemd service configuration still referencing the MySQL service as a dependency. Specifically, the BindsTo and After directives in the systemd unit file are set to mysql.service. As a result, stopping MySQL also stops the Mattermost service.

Solution

To resolve the issue, you’ll need to update the systemd service file to reference postgresql.service instead of mysql.service.

1. Locate the Mattermost systemd service file
   This is usually located at:

   /lib/systemd/system/mattermost.service
   

   or

   /etc/systemd/system/mattermost.service
   

2. Open the file and review the contents.
   It may look something like this:

   [Unit]
   Description=Mattermost
   After=network.target
   After=mysql.service
   BindsTo=mysql.service
   
   [Service]
   Type=notify
   ExecStart=/opt/mattermost/bin/mattermost
   TimeoutStartSec=3600
   KillMode=mixed
   Restart=always
   RestartSec=10
   WorkingDirectory=/opt/mattermost
   User=mattermost
   Group=mattermost
   LimitNOFILE=49152
   
   [Install]
   WantedBy=mysql.service
   

3. Update all instances of mysql.service to postgresql.service:

   [Unit]
   Description=Mattermost
   After=network.target
   After=postgresql.service
   BindsTo=postgresql.service
   
   [Service]
   Type=notify
   ExecStart=/opt/mattermost/bin/mattermost
   TimeoutStartSec=3600
   KillMode=mixed
   Restart=always
   RestartSec=10
   WorkingDirectory=/opt/mattermost
   User=mattermost
   Group=mattermost
   LimitNOFILE=49152
   
   [Install]
   WantedBy=multi-user.target
   

    

4. After updating the service configuration, make sure to restart the Mattermost service to apply the changes.