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Timer Jobs¶

This recipe uses app.timer() with NCRONTAB scheduling, demonstrates the isPastDue pattern, and calls out hosting-plan time zone behavior.

Architecture¶

flowchart LR
    SCHED[NCRONTAB Schedule] --> TIMER[Timer Trigger]
    TIMER --> CHECK[isPastDue Check]
    CHECK --> JOB[Maintenance Logic]
    JOB --> LOG[App Insights Logs]

Prerequisites¶

Use extension bundle v4:

{
  "version": "2.0",
  "extensionBundle": {
    "id": "Microsoft.Azure.Functions.ExtensionBundle",
    "version": "[4.*, 5.0.0)"
  }
}

Optional time zone configuration:

az functionapp config appsettings set \
  --name $APP_NAME \
  --resource-group $RG \
  --settings "WEBSITE_TIME_ZONE=Korea Standard Time"

WEBSITE_TIME_ZONE support: - Windows plans: supported - Linux Premium and Dedicated: supported - Linux Consumption and Flex Consumption: not supported

Working Node.js v4 Code¶

const { app } = require("@azure/functions");

app.timer("nightlyReconciliation", {
  schedule: "0 0 2 * * *",
  runOnStartup: false,
  useMonitor: true,
  handler: async (timer, context) => {
    if (timer.isPastDue) {
      context.warn("Timer invocation is running later than scheduled.", {
        scheduleStatus: timer.scheduleStatus
      });
    }

    context.log("Starting nightly reconciliation", {
      last: timer.scheduleStatus?.last,
      next: timer.scheduleStatus?.next
    });

    // Execute maintenance workload here.
  }
});

Implementation Notes¶

Timer expressions are NCRONTAB ({second} {minute} {hour} {day} {month} {day-of-week}), not classic 5-field cron.
timer.isPastDue is the signal for delayed execution due to scale or host restart conditions.
Keep jobs idempotent; timers can overlap with retries after transient failures.
On Linux Consumption/Flex, use UTC schedules because WEBSITE_TIME_ZONE is unsupported.

See Also¶

Sources¶