Application Logs

Once an application is started with PM2 you can consult and manage logs easily.

Log files are located in the folder $HOME/.pm2/logs.

Log Views

To display application’s log you can use the command pm2 logs

  Usage: logs [options] [id|name|namespace]

  stream logs file. Default stream all logs

  Options:

    --json                json log output
    --format              formatted log output
    --raw                 raw output
    --err                 only shows error output
    --out                 only shows standard output
    --lines <n>           output the last N lines, instead of the last 15 by default
    --timestamp [format]  add timestamps (default format YYYY-MM-DD-HH:mm:ss)
    --nostream            print logs without launching the log stream
    --highlight [value]   highlights the given value
    -h, --help            output usage information

Some important commands:

# Display all apps logs in realtime
pm2 logs

# Display only `api` application logs
pm2 logs api

# Display new logs in json
pm2 logs --json

# Display 1000 lines of api log file
pm2 logs big-api --lines 1000

# Display logs of all apps whose name matches a regex
pm2 logs "/^api-/"

You can also check logs with the CLI dashboard:

pm2 monit

For each application line this metadata will be printed:

{
   "message": "echo\n",                     // the actual message that has been `console.log`
   "timestamp": "2017-02-06T14:51:38.896Z", // timestamp of the message, can be formatted
   "type": "out",                           // the type of logs, can be `err`, `out` or `PM2`
   "process_id": 0,                         // the process id used by PM2
   "app_name": "one-echo"                   // the application name
}

The module pm2-logrotate automatically rotate and keep all the logs file using a limited space on disk.

To install it:

pm2 install pm2-logrotate

Flushing logs

This will empty the current application logs managed by PM2:

pm2 flush

pm2 flush <api> # Clear the logs for the app with name/id matching <api>

Application log options

When starting an application you can specify many options on how

CLI

When running pm2 start app.js [OPTIONS] you can pass any of this options to the CLI:

-l --log [path]              specify filepath to output both out and error logs
-o --output <path>           specify out log file
-e --error <path>            specify error log file
--time                       prefix logs with standard formatted timestamp
--log-date-format <format>   prefix logs with custom formatted timestamp
--merge-logs                 when running multiple process with same app name, do not split file by id
--log-type <type>            log output style (raw by default, json optional)
--disable-logs               drop all app output (no log file, nothing in pm2 logs)

Auto prefixing logs with Date

To easily prefix logs of apps you can pass the option --time:

$ pm2 start app.js --time
# Or a running app
$ pm2 restart app --time

Configuration file

Via configuration file you can pass the options:

Field	Type	Example	Description
error_file	(string)		error file path (default to $HOME/.pm2/logs/<app name>-error.log, suffixed with the pm_id unless merge_logs is set: <app name>-error-<pm_id>.log)
out_file	(string)		output file path (default to $HOME/.pm2/logs/<app name>-out.log, suffixed with the pm_id unless merge_logs is set)
log_file	(string or boolean)		file path for both output and error logs (disabled by default). `true` writes to $HOME/.pm2/logs/<app name>.log
pid_file	(string)		pid file path (default to $HOME/.pm2/pids/<app name>-<pm_id>.pid, always suffixed with the pm_id)
merge_logs	boolean	true	if set to true, avoid to suffix logs file with the pm_id. Default to true when `exec_mode` is not cluster and `instances` is unset or 0, false otherwise
log_date_format	(string)	“YYYY-MM-DD HH:mm Z”	log date format (see log section)
log_type	(string)	“json”	specify log output style, possible value: ‘json’ (will log raw by default)
disable_logs	boolean	true	false by default. If true app output is dropped: nothing is written to disk nor shown by `pm2 logs`

Disabling log suffix

For app in cluster mode (node.js) only; If you want that all instances of a clustered process logs into the same file you can use the option --merge-logs or merge_logs: true

Disable logging

To disable all logs to be written in disk you can set the option out_file and error_file to /dev/null

module.exports = {
  apps : [{
    name: 'Business News Watcher',
    script: 'app.js',
    instances: 1,
    out_file: "/dev/null",
    error_file: "/dev/null"
    cron_restart: '0 0 * * *'
    [...]
  }]
}

You can provide /dev/null or NULL as output of logs (not depending on the platform, they are a hardcoded string).

To also stop the output from reaching pm2 logs, use disable_logs: true (or --disable-logs).

Setting up a native logrotate

sudo pm2 logrotate -u user

This will write a basic logrotate configuration to /etc/logrotate.d/pm2-user that will look like this:

/home/user/.pm2/pm2.log /home/user/.pm2/logs/*.log {
        rotate 12
        weekly
        missingok
        notifempty
        compress
        delaycompress
        copytruncate
        create 0640 user user
}

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Log Management