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Azure Event Grid script with preprocessor template

Template for scripts triggered by Azure Event Grid. Uses a preprocessor to unpack CloudEvents envelope fields into individual `main()` arguments. Payload is already the parsed CloudEvents `data` field (or the base64 string if the publisher used `data_base64`).

Script windmill Verified

by hugo989 · 4/23/2026

Use in Windmill

The script

Submitted by hugo989 Bun

Verified 19 days ago

All edits

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/**
 * General Trigger Preprocessor
 *
 * ⚠️ This function runs BEFORE the main function.
 *
 * It processes raw trigger data (e.g., Azure Event Grid, MQTT, HTTP, SQS)
 * before passing it to `main()`.
 * Common tasks:
 * - Extract metadata
 * - Filter messages
 * - Add timestamps/context
 *
 * The returned object determines `main()` parameters:
 * - `{a: 1, b: 2}` → `main(a, b)`
 * - `{payload}` → `main(payload)`
 *
 * @param event - Azure Event Grid trigger data. `payload` is the already-parsed
 *   CloudEvent `data` field (object / array / string / number / null) when the
 *   publisher used `data`. If the publisher used `data_base64` instead (binary
 *   payload), `payload` contains the base64 string — decode it here if needed.
 */
export async function preprocessor(event: {
	payload: any
	kind: 'azure'
	id: string
	source: string
	type: string
	subject?: string
	time?: string
	specversion: string
	datacontenttype?: string
	dataschema?: string
	headers?: Record<string, string>
	delivery_type: 'push' | 'pull'
	trigger_path: string
}) {
	if (event.kind !== 'azure') {
		// We assume the script is triggered by an Azure Event Grid message. If you
		// also want to wire it to other trigger kinds, extend this branch.
		throw new Error(`Expected azure trigger kind got: ${event.kind}`)
	}

	return {
		payload: event.payload,
		eventType: event.type,
		subject: event.subject,
		source: event.source,
		eventId: event.id,
		time: event.time,
		deliveryType: event.delivery_type
	}
}

/**
 * Main Function — handles processed Azure Event Grid events.
 *
 * Called AFTER `preprocessor()` with its return values.
 *
 * @param payload - The CloudEvent `data` field (parsed JSON) or base64 string.
 * @param eventType - e.g. `Microsoft.Storage.BlobCreated`.
 * @param subject - CloudEvents subject; for Azure system topics this is often
 *   a resource path (blob path, key vault secret id, etc.).
 * @param source - CloudEvents source; usually the producer resource.
 * @param eventId - Unique event id (useful for deduplication).
 * @param time - Event time (RFC 3339).
 * @param deliveryType - 'push' when Azure delivered via webhook, 'pull' when
 *   Windmill fetched from a Namespace queue.
 */
export async function main(
	payload: any,
	eventType: string,
	subject: string | undefined,
	source: string,
	eventId: string,
	time: string | undefined,
	deliveryType: 'push' | 'pull'
) {
	console.log(`[${deliveryType}] ${eventType} from ${source} (${eventId})`)
	return { received: payload, type: eventType, subject }
}


`1`	`/**`
`2`	`* General Trigger Preprocessor`
`3`	`*`
`4`	`* ⚠️ This function runs BEFORE the main function.`
`5`	`*`
`6`	`* It processes raw trigger data (e.g., Azure Event Grid, MQTT, HTTP, SQS)`
`7`	* before passing it to `main()`.
`8`	`* Common tasks:`
`9`	`* - Extract metadata`
`10`	`* - Filter messages`
`11`	`* - Add timestamps/context`
`12`	`*`
`13`	* The returned object determines `main()` parameters:
`14`	* - `{a: 1, b: 2}` → `main(a, b)`
`15`	* - `{payload}` → `main(payload)`
`16`	`*`
`17`	* @param event - Azure Event Grid trigger data. `payload` is the already-parsed
`18`	* CloudEvent `data` field (object / array / string / number / null) when the
`19`	* publisher used `data`. If the publisher used `data_base64` instead (binary
`20`	* payload), `payload` contains the base64 string — decode it here if needed.
`21`	`*/`
`22`	`export async function preprocessor(event: {`
`23`	`payload: any`
`24`	`kind: 'azure'`
`25`	`id: string`
`26`	`source: string`
`27`	`type: string`
`28`	`subject?: string`
`29`	`time?: string`
`30`	`specversion: string`
`31`	`datacontenttype?: string`
`32`	`dataschema?: string`
`33`	`headers?: Record<string, string>`
`34`	`delivery_type: 'push' \| 'pull'`
`35`	`trigger_path: string`
`36`	`}) {`
`37`	`if (event.kind !== 'azure') {`
`38`	`// We assume the script is triggered by an Azure Event Grid message. If you`
`39`	`// also want to wire it to other trigger kinds, extend this branch.`
`40`	throw new Error(`Expected azure trigger kind got: ${event.kind}`)
`41`	`}`
`42`
`43`	`return {`
`44`	`payload: event.payload,`
`45`	`eventType: event.type,`
`46`	`subject: event.subject,`
`47`	`source: event.source,`
`48`	`eventId: event.id,`
`49`	`time: event.time,`
`50`	`deliveryType: event.delivery_type`
`51`	`}`
`52`	`}`
`53`
`54`	`/**`
`55`	`* Main Function — handles processed Azure Event Grid events.`
`56`	`*`
`57`	* Called AFTER `preprocessor()` with its return values.
`58`	`*`
`59`	* @param payload - The CloudEvent `data` field (parsed JSON) or base64 string.
`60`	* @param eventType - e.g. `Microsoft.Storage.BlobCreated`.
`61`	`* @param subject - CloudEvents subject; for Azure system topics this is often`
`62`	`* a resource path (blob path, key vault secret id, etc.).`
`63`	`* @param source - CloudEvents source; usually the producer resource.`
`64`	`* @param eventId - Unique event id (useful for deduplication).`
`65`	`* @param time - Event time (RFC 3339).`
`66`	`* @param deliveryType - 'push' when Azure delivered via webhook, 'pull' when`
`67`	`* Windmill fetched from a Namespace queue.`
`68`	`*/`
`69`	`export async function main(`
`70`	`payload: any,`
`71`	`eventType: string,`
`72`	`subject: string \| undefined,`
`73`	`source: string,`
`74`	`eventId: string,`
`75`	`time: string \| undefined,`
`76`	`deliveryType: 'push' \| 'pull'`
`77`	`) {`
`78`	console.log(`[${deliveryType}] ${eventType} from ${source} (${eventId})`)
`79`	`return { received: payload, type: eventType, subject }`
`80`	`}`
`81`