Crons Convex Component

Note: Convex Components are currently in beta.

This Convex component provides functionality for registering and managing cron jobs at runtime. Convex comes with built-in support for cron jobs but they must be statically defined at deployment time. This library allows for dynamic registration of cron jobs at runtime.

It supports intervals in milliseconds as well as cron schedules with the same format as the unix cron command:

 *  *  *  *  *  *
 ┬  ┬  ┬  ┬  ┬  ┬
 │  │  │  │  │  |
 │  │  │  │  │  └── day of week (0 - 7, 1L - 7L) (0 or 7 is Sun)
 │  │  │  │  └───── month (1 - 12)
 │  │  │  └──────── day of month (1 - 31, L)
 │  │  └─────────── hour (0 - 23)
 │  └────────────── minute (0 - 59)
 └───────────────── second (0 - 59, optional)

Design

The design of this component is based on the Cronvex demo app that's described in this Stack post.

Convex App

You'll need a Convex App to use the component. Run npm create convex or follow any of the Convex quickstarts to set one up.

Installation

Install the component package:

npm install @convex-dev/crons

Create a convex.config.ts file in your app's convex/ folder and install the component by calling use:

// convex/convex.config.js
import { defineApp } from "convex/server";
import crons from "@convex-dev/crons/convex.config";

const app = defineApp();
app.use(crons);

export default app;

Usage

A Crons wrapper can be instantiated within your Convex code as:

import { components } from "./_generated/api";
import { Crons } from "@convex-dev/crons";

const crons = new Crons(components.crons);

The Crons wrapper class provides the following methods:

• register(ctx, schedule, fn, args, name?): Registers a new cron job.
• get(ctx, { name | id }): Gets a cron job by name or ID.
• list(ctx): Lists all cron jobs.
• delete(ctx, { name | id }): Deletes a cron job by name or ID.

Example usage:

import { v } from "convex/values";
import { internalMutation } from "./_generated/server";
import { internal } from "./_generated/api";

// Dummy function that we're going to schedule.
export const logStuff = internalMutation({
  args: {
    message: v.string(),
  },
  handler: async (_ctx, args) => {
    console.log(args.message);
  },
});

// Run a bunch of cron operations as a test. Note that this function runs as a
// transaction and cleans up after itself so you won't actually see these crons
// showing up in the database while it's in progress.
export const doSomeStuff = internalMutation({
  handler: async (ctx) => {
    // Register some crons.
    const namedCronId = await crons.register(
      ctx,
      { kind: "interval", ms: 3600000 },
      internal.example.logStuff,
      { message: "Hourly cron test" },
      "hourly-test"
    );
    console.log("Registered new cron job with ID:", namedCronId);
    const unnamedCronId = await crons.register(
      ctx,
      { kind: "cron", cronspec: "0 * * * *" },
      internal.example.logStuff,
      { message: "Minutely cron test" }
    );
    console.log("Registered new cron job with ID:", unnamedCronId);

    // Get the cron job by name.
    const cronByName = await crons.get(ctx, { name: "hourly-test" });
    console.log("Retrieved cron job by name:", cronByName);

    // Get the cron job by ID.
    const cronById = await crons.get(ctx, { id: unnamedCronId });
    console.log("Retrieved cron job by ID:", cronById);

    // List all cron jobs.
    const allCrons = await crons.list(ctx);
    console.log("All cron jobs:", allCrons);

    // Delete the cron jobs.
    await crons.delete(ctx, { name: "hourly-test" });
    console.log("Deleted cron job by name:", "hourly-test");
    await crons.delete(ctx, { id: unnamedCronId });
    console.log("Deleted cron job by ID:", unnamedCronId);

    // Verify deletion.
    const deletedCronByName = await crons.get(ctx, { name: "hourly-test" });
    console.log("Deleted cron job (should be null):", deletedCronByName);
    const deletedCronById = await crons.get(ctx, { id: unnamedCronId });
    console.log("Deleted cron job (should be null):", deletedCronById);
  },
});

If you'd like to statically define cronjobs like in the built-in crons.ts Convex feature you can do so via an init script that idempotently registers a cron with a given name. e.g., in an init.ts file that gets run on every deploy via convex dev --run init.

// Register a daily cron job. This could be called from an init script to make
// sure it's always registered, like the built-in crons in Convex.
export const registerDailyCron = internalMutation({
  handler: async (ctx) => {
    if ((await crons.get(ctx, { name: "daily" })) === null) {
      await crons.register(
        ctx,
        { kind: "cron", cronspec: "0 0 * * *" },
        internal.example.logStuff,
        {
          message: "daily cron",
        },
        "daily"
      );
    }
  },
});

Crons are created transactionally and will be guaranteed to exist after the mutation that creates them has run. It's thus possible to write workflows like the following that schedules a cron and then deletes itself as soon as it runs, without any additional error handling about the cron not existing.

// This will schedule a cron job to run every 10 seconds but then delete itself
// the first time it runs.
export const selfDeletingCron = internalMutation({
  handler: async (ctx) => {
    const cronId = await crons.register(
      ctx,
      { kind: "interval", ms: 10000 },
      internal.example.deleteSelf,
      { name: "self-deleting-cron" },
      "self-deleting-cron"
    );

    console.log("Registered self-deleting cron job with ID:", cronId);
  },
});

// Worker function that deletes a cron job.
export const deleteSelf = internalMutation({
  args: { name: v.string() },
  handler: async (ctx, { name }) => {
    console.log("Self-deleting cron job running. Name:", name);
    await crons.delete(ctx, { name });
    console.log("Self-deleting cron job has been deleted. Name:", name);
  },
});

🧑‍🏫 What is Convex?

Convex is a hosted backend platform with a built-in database that lets you write your database schema and server functions in TypeScript. Server-side database queries automatically cache and subscribe to data, powering a realtime useQuery hook in our React client. There are also clients for Python, Rust, ReactNative, and Node, as well as a straightforward HTTP API.

The database supports NoSQL-style documents with opt-in schema validation, relationships and custom indexes (including on fields in nested objects).

The query and mutation server functions have transactional, low latency access to the database and leverage our v8 runtime with determinism guardrails to provide the strongest ACID guarantees on the market: immediate consistency, serializable isolation, and automatic conflict resolution via optimistic multi-version concurrency control (OCC / MVCC).

The action server functions have access to external APIs and enable other side-effects and non-determinism in either our optimized v8 runtime or a more flexible node runtime.

Functions can run in the background via scheduling and cron jobs.

Development is cloud-first, with hot reloads for server function editing via the CLI, preview deployments, logging and exception reporting integrations, There is a dashboard UI to browse and edit data, edit environment variables, view logs, run server functions, and more.

There are built-in features for reactive pagination, file storage, reactive text search, vector search, https endpoints (for webhooks), snapshot import/export, streaming import/export, and runtime validation for function arguments and database data.

Everything scales automatically, and it’s free to start.