An example of how to implement user-scheduled jobs for running Firebase Functions
I ran into needing this solution after working on a project which required users to have the ability to schedule functions to run at any time and at repeating intervals if necessary. The Firebase blog includes a method for running cron-jobs, but it is only for predefined Firebase functions.
The main Firebase function, scheduleJobs, works by iterating over all jobs defined in the node /scheduledJobs in Firebase's realtime database.
If a job's scheduled time is before or at the current time, the jobs information is copied over to the node /runningJobs in the database.
If a job is set to repeat on an interval, the job's run time is set to the next interval.
If a job is only supposed to run once, or it is set to stop repeating after a time which has passed, it is deleted from /scheduledJobs.
Another Firebase function, executeJobs, uses a hook listening for the creation of each job in /runningJobs, when a new job is added,
it runs the associated function in custom-functions.ts. After the function has completed, it is deleted from /runningJobs.
- Deploy the functions to Firebase
- Setup your Realtime Database to use the same format as example-firebase-export.json
- Get the url for the scheduleJobs function from the functions dashboard page, it should be a url similar to https://SERVERLOCATION-PROJECTNAME.cloudfunctions.net/scheduleJobs
- Setup a cron-job service to hit the function url every minute
Example cron-job service: https://cron-job.org/en/
If your functions in custom-functions.ts take longer than 9 minutes to complete, you will need to extend the timeout time of the executeJobs function, which can be done from the Google Cloud Functions dashboard by clicking on executeJobs and then clicking edit.
{
"scheduledJobs" : {
"ABC" : {
"args" : {
"logMe" : "Hello, this is a basic job!"
},
"runAt" : 1537356593000,
"worker" : "logArg"
},
"DEF" : {
"args" : {
"logMe" : "This is a job that repeats every 2 minutes forever!"
},
"repeat" : {
"interval" : 2
},
"runAt" : 1537356593000,
"worker" : "logArg"
},
"GHI" : {
"args" : {
"logMe" : "This is a repeating job that repeats every 3 minutes until the unix time: 1538356660!"
},
"repeat" : {
"endOn" : 1538356660000,
"interval" : 3
},
"runAt" : 1537356660000,
"worker" : "logArg"
}
}
}
worker is the function that will be called when it is the job's turn to run, and args are the arguments that will be passed to the function. They are equivalent to calling worker(args).
runAt and repeat.endOn are the millisecond representation of the unix time of a date and time.
repeat.interval is an optional integer for how often to repeat the job in minutes. As the cron-job service only activates the function once a minute, it is not possible to use sub-minute specification.