convex-cron-jobs

What this skill does

# Convex Cron Jobs

Schedule recurring functions for background tasks, cleanup jobs, data syncing, and automated workflows in Convex applications.

## Documentation Sources

Before implementing, do not assume; fetch the latest documentation:

- Primary: https://docs.convex.dev/scheduling/cron-jobs
- Scheduling Overview: https://docs.convex.dev/scheduling
- Scheduled Functions: https://docs.convex.dev/scheduling/scheduled-functions
- For broader context: https://docs.convex.dev/llms.txt

## Instructions

### Cron Jobs Overview

Convex cron jobs allow you to schedule functions to run at regular intervals or specific times. Key features:

- Run functions on a fixed schedule
- Support for interval-based and cron expression scheduling
- Automatic retries on failure
- Monitoring via the Convex dashboard

### Basic Cron Setup

```typescript
// convex/crons.ts
import { cronJobs } from "convex/server";
import { internal } from "./_generated/api";

const crons = cronJobs();

// Run every hour
crons.interval(
  "cleanup expired sessions",
  { hours: 1 },
  internal.tasks.cleanupExpiredSessions,
  {}
);

// Run every day at midnight UTC
crons.cron(
  "daily report",
  "0 0 * * *",
  internal.reports.generateDailyReport,
  {}
);

export default crons;
```

### Interval-Based Scheduling

Use `crons.interval` for simple recurring tasks:

```typescript
// convex/crons.ts
import { cronJobs } from "convex/server";
import { internal } from "./_generated/api";

const crons = cronJobs();

// Every 5 minutes
crons.interval(
  "sync external data",
  { minutes: 5 },
  internal.sync.fetchExternalData,
  {}
);

// Every 2 hours
crons.interval(
  "cleanup temp files",
  { hours: 2 },
  internal.files.cleanupTempFiles,
  {}
);

// Every 30 seconds (minimum interval)
crons.interval(
  "health check",
  { seconds: 30 },
  internal.monitoring.healthCheck,
  {}
);

export default crons;
```

### Cron Expression Scheduling

Use `crons.cron` for precise scheduling with cron expressions:

```typescript
// convex/crons.ts
import { cronJobs } from "convex/server";
import { internal } from "./_generated/api";

const crons = cronJobs();

// Every day at 9 AM UTC
crons.cron(
  "morning notifications",
  "0 9 * * *",
  internal.notifications.sendMorningDigest,
  {}
);

// Every Monday at 8 AM UTC
crons.cron(
  "weekly summary",
  "0 8 * * 1",
  internal.reports.generateWeeklySummary,
  {}
);

// First day of every month at midnight
crons.cron(
  "monthly billing",
  "0 0 1 * *",
  internal.billing.processMonthlyBilling,
  {}
);

// Every 15 minutes
crons.cron(
  "frequent sync",
  "*/15 * * * *",
  internal.sync.syncData,
  {}
);

export default crons;
```

### Cron Expression Reference

```
┌───────────── minute (0-59)
│ ┌───────────── hour (0-23)
│ │ ┌───────────── day of month (1-31)
│ │ │ ┌───────────── month (1-12)
│ │ │ │ ┌───────────── day of week (0-6, Sunday=0)
│ │ │ │ │
* * * * *
```

Common patterns:
- `* * * * *` - Every minute
- `0 * * * *` - Every hour
- `0 0 * * *` - Every day at midnight
- `0 0 * * 0` - Every Sunday at midnight
- `0 0 1 * *` - First day of every month
- `*/5 * * * *` - Every 5 minutes
- `0 9-17 * * 1-5` - Every hour from 9 AM to 5 PM, Monday through Friday

### Internal Functions for Crons

Cron jobs should call internal functions for security:

```typescript
// convex/tasks.ts
import { internalMutation, internalQuery } from "./_generated/server";
import { v } from "convex/values";

// Cleanup expired sessions
export const cleanupExpiredSessions = internalMutation({
  args: {},
  returns: v.number(),
  handler: async (ctx) => {
    const oneHourAgo = Date.now() - 60 * 60 * 1000;
    
    const expiredSessions = await ctx.db
      .query("sessions")
      .withIndex("by_lastActive")
      .filter((q) => q.lt(q.field("lastActive"), oneHourAgo))
      .collect();

    for (const session of expiredSessions) {
      await ctx.db.delete(session._id);
    }

    return expiredSessions.length;
  },
});

// Process pending tasks
export const processPendingTasks = internalMutation({
  args: {},
  returns: v.null(),
  handler: async (ctx) => {
    const pendingTasks = await ctx.db
      .query("tasks")
      .withIndex("by_status", (q) => q.eq("status", "pending"))
      .take(100);

    for (const task of pendingTasks) {
      await ctx.db.patch(task._id, {
        status: "processing",
        startedAt: Date.now(),
      });
      
      // Schedule the actual processing
      await ctx.scheduler.runAfter(0, internal.tasks.processTask, {
        taskId: task._id,
      });
    }

    return null;
  },
});
```

### Cron Jobs with Arguments

Pass static arguments to cron jobs:

```typescript
// convex/crons.ts
import { cronJobs } from "convex/server";
import { internal } from "./_generated/api";

const crons = cronJobs();

// Different cleanup intervals for different types
crons.interval(
  "cleanup temp files",
  { hours: 1 },
  internal.cleanup.cleanupByType,
  { fileType: "temp", maxAge: 3600000 }
);

crons.interval(
  "cleanup cache files",
  { hours: 24 },
  internal.cleanup.cleanupByType,
  { fileType: "cache", maxAge: 86400000 }
);

export default crons;
```

```typescript
// convex/cleanup.ts
import { internalMutation } from "./_generated/server";
import { v } from "convex/values";

export const cleanupByType = internalMutation({
  args: {
    fileType: v.string(),
    maxAge: v.number(),
  },
  returns: v.number(),
  handler: async (ctx, args) => {
    const cutoff = Date.now() - args.maxAge;
    
    const oldFiles = await ctx.db
      .query("files")
      .withIndex("by_type_and_created", (q) => 
        q.eq("type", args.fileType).lt("createdAt", cutoff)
      )
      .collect();

    for (const file of oldFiles) {
      await ctx.storage.delete(file.storageId);
      await ctx.db.delete(file._id);
    }

    return oldFiles.length;
  },
});
```

### Monitoring and Logging

Add logging to track cron job execution:

```typescript
// convex/tasks.ts
import { internalMutation } from "./_generated/server";
import { v } from "convex/values";

export const cleanupWithLogging = internalMutation({
  args: {},
  returns: v.null(),
  handler: async (ctx) => {
    const startTime = Date.now();
    let processedCount = 0;
    let errorCount = 0;

    try {
      const expiredItems = await ctx.db
        .query("items")
        .withIndex("by_expiresAt")
        .filter((q) => q.lt(q.field("expiresAt"), Date.now()))
        .collect();

      for (const item of expiredItems) {
        try {
          await ctx.db.delete(item._id);
          processedCount++;
        } catch (error) {
          errorCount++;
          console.error(`Failed to delete item ${item._id}:`, error);
        }
      }

      // Log job completion
      await ctx.db.insert("cronLogs", {
        jobName: "cleanup",
        startTime,
        endTime: Date.now(),
        duration: Date.now() - startTime,
        processedCount,
        errorCount,
        status: errorCount === 0 ? "success" : "partial",
      });
    } catch (error) {
      // Log job failure
      await ctx.db.insert("cronLogs", {
        jobName: "cleanup",
        startTime,
        endTime: Date.now(),
        duration: Date.now() - startTime,
        processedCount,
        errorCount,
        status: "failed",
        error: String(error),
      });
      throw error;
    }

    return null;
  },
});
```

### Batching for Large Datasets

Handle large datasets in batches to avoid timeouts:

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

const BATCH_SIZE = 100;

export const processBatch = internalMutation({
  args: {
    cursor: v.optional(v.string()),
  },
  returns: v.null(),
  handler: async (ctx, args) => {
    const result = await ctx.db
      .query("items")
      .withIndex("by_status", (q) => q.eq("status", "pending"))
      .paginate({ numItems: BATCH_SIZE, cursor: args.cursor ?? null });