cronmutex

README

cronmutex

cronmutex is a simple cron daemon and command runner used to prevent a command (e.g. a cronjob) from running on multiple nodes simultaneously by placing a lock in a central redis server. Inspired by (and its command runner mode is similar to) cronlock, but supporting connecting to SSL-tunneled redis hosts natively and allowing running it as a cron daemon.

Usage

Usage:
  cronmutex [command]

Available Commands:
  daemon      Cron daemon mode
  help        Help about any command
  run         Run command
  version     Print the version number of cronmutex

Flags:
  -c, --config string   config file (default is /etc/cronmutex.yml)
  -h, --help            help for cronmutex

Global options

• --config Set path to config file instead of using the default /etc/cronmutex.yml

daemon

Run cronmutex in daemon mode, running configured cronjobs.

 Usage:
  cronmutex daemon <cron.yml> [flags]

Example cron.yml file:

- name: job-name
  cron: 0,10,20,30,40,50 * * * * *
  command:
    - sleep
    - 50
  options:
    randomwait: 2
    fireandforget: false
    mutexttl: 14
    ttl: 10
- name: job-name 2
  cron: 5,15,25,35,45,55 * * * * *
  command:
    - sleep
    - 20
  options:
    randomwait: 2
    ttl: 10

See https://pkg.go.dev/github.com/robfig/cron?tab=doc for the cron entry format.

run

Usage:
  cronmutex run [flags] <mutex-name> <command>

Flags:
  -f, --fire-n-forget     Don't hold (extend) the lock while the command is running
  -h, --help              help for run
  -m, --mutex-ttl int     The TTL of the lock in X seconds
  -n, --noout             Don't dump STDOUT and STDERR from command
  -w, --random-wait int   Wait for a random duration between 0 and X seconds before acquiring the lock and starting the command
  -t, --ttl int           Kill command after X seconds. Default is to wait until the command finishes by itself
  -v, --verbose           Tell what's happening with cronmutex

• --fire-n-forget Don't hold (extend) the lock while the command is running. Just keep lock until the lock's TTL (--mutex-ttl) expires and continue running the command without holding the lock (unless a --ttl is set and the command gets killed before).

• --mutex-ttl X The TTL of the lock in X seconds. Note that unless --fire-n-forget is set as well, the lock keeps getting extended by this amount before it expires until the command finishes and the lock gets released.

• --noout Don't dump STDOUT and STDERR from command.

• --random-wait X Wait for a random duration between 0 and X seconds before acquiring the lock and starting the command.

• --ttl X Kill command after X seconds. Default is to wait until the command finishes by itself.

• --verbose Tell what's happening with cronmutex.

• --version Print version and exit

Configuration

Unless overwritten by the --config option, cronmutex looks for a cronmutex.yml in /etc, $HOME/.config and current working directory.

Example config:

redis:
  uri: redis://127.0.0.1:6379
  #password: thepasswordifneeeded
mutex:
  prefix: EXAMPLEPREFIX.
  defaultTTL: 300

Use rediss:// scheme to connect to a TLS-tunneled redis host.

Build

On Linux:

$ git clone github.com/emgag/cronmutex 
$ cd cronmutex
$ make 

License

cronmutex is licensed under the MIT License.