Compute > Cloud Functions > Trigger Guide

This document describes the trigger types available in Cloud Functions and how to set them up.

Trigger Overview

Trigger is an event source to execute functions. Cloud Functions provide various triggers to allow you to call functions in multiple ways.

Supported Triggers

Types	Descriptions	Built-in
HTTP	Execute a function via an HTTP request	Yes
Timer	Execute a function at a specified time or interval	No
API Gateway	Execute a function via API Gateway	No

HTTP Trigger

HTTP trigger is built-in when creating a function, and you can execute the function with an HTTP request.

Features

• When creating a function, it will be automatically created.
• It cannot be deleted but only enabled or disabled.
• GET, POST methods are supported.

URL Format of HTTP Trigger

https://{userdomain}/{function name}

Examples

Request GET

curl -X GET "https://{userdomain}/{function name}?param1=value1&param2=value2"

Request POST

curl -X POST "https://{userdomain}/{function name}" \
  -H "Content-Type: application/json" \
  -d '{"key": "value"}'

Enable/disable HTTP Trigger

1. Select a function from the Cloud Functions console.
2. Go to Trigger tab.
3. Click Enable/Disable toggle for HTTP triggers.

[Note]
If you send a request with a disabled HTTP trigger, the function will not execute.

Timer Trigger

Timer trigger executes a function automatically at the specified time or cycle. You can set up the cycle by using the Cron expression.

Create Timer Trigger

1. Select a function from the Cloud Functions console.
2. Go to Trigger tab.
3. Click Generate Trigger.
4. Select the type as Timer.
5. Enter Cron expression in Value.
6. Click Create.

Cron Expression Format

Cron expression follows the format as below:

* * * * * *
│ │ │ │ │ │
│ │ │ │ │ └─ Day of week (0-6 or SUN-SAT, 0: sunday)
│ │ │ │ └─── Month (1-12 or JAN-DEC)
│ │ │ └───── Day of month (1-31)
│ │ └─────── hour (0-23)
│ └───────── minute (0-59)
└─────────── second (0-59)

Cron Expression Field

Field	Required	Allowed vale	Allowed special character
Seconds	Yes	0-59	* / , -
Minutes	Yes	0-59	* / , -
Hours	Yes	0-23	* / , -
Day of month	Yes	1-31	* / , - ?
Month	Yes	1-12 or JAN-DEC	* / , -
Day of week	Yes	0-6 or SUN-SAT	* / , - ?

Special Characters Details

*

Indicate that all values ​​in the field match. For example, using * in the 5th field (month) means all months.

/

Used to indicate the increment of a range. For example, using 3-59/15 in the 2nd field (minutes) means it will execute every 15 minutes starting at 3 minutes (3, 18, 33, and 48 minutes). For */... format, it matches first-last/... format and indicates that the increment for the largest range of the field. For N/... format, it indicates N-MAX/..., using increments starting from N to the end of the range. Once you go beyond the range, you won't go back to the beginning.

,

Used to separate items in a list. For example, using MON,WED,FRI in the 6th field (day of the week) means Monday, Wednesday, and Friday.

-

Used to define scope. For example, using 9-17 in the third field (hours) means all hours from 9 AM to 5 PM (inclusive).

?

You can use * instead of leaving the Day of month or Day of week field blank.

Example of Cron Expression

Cron Expression	Description
0 * * * * *	Execute every minute (at 0 seconds)
0 0 * * * *	Execute every hour on the hour
0 0 0 * * *	Execute every midnight
0 0 9 * * MON	Execute every Monday at 9:00 AM
0 0 0 1 * *	Execute every 1st of every month at midnight
0 */5 * * * *	Execute every 5 minutes
0 0 9-18 * * MON-FRI	Execute every hour from 9:00 AM to 6:00 PM on weekdays (Mon-Fri)
30 0 12 * * *	Execute every day at 12:00:30 PM
0 0 0 1 JAN *	Execute every January 1st at midnight

Modify Timer Trigger

1. Select a function from the Cloud Functions console.
2. Go to Trigger tab.
3. Select the Timer trigger to be modified.
4. Click Modify Trigger.
5. Modify the Cron expression of the Value.
6. Click Modify.

[Note]
The Month and Day of week field values ​​are case-insensitive. "SUN", "Sun", "sun" are all recognized equally.

API Gateway Trigger

API Gateway triggers can execute functions by leveraging the API Gateway service in the same project. API Gateway enables more detailed API management and control.

Prerequisites

• The API Gateway service must be enabled in the same project.
• If it isn't enabled, you can enable it when creating a trigger.

Create API Gateway Trigger

1. Select a function from the Cloud Functions console.
2. Go to Trigger tab.
3. Click Generate Trigger.
4. Select API Gateway from the type.
5. Enter the path to use.
6. Duplicate path is unavailable.
7. Click Create.

API Gateway Trigger URL Format

https://{stageurl}/{path}

Examples

Request GET

curl -X GET "https://{stageurl}/{path}?param1=value1&param2=value2"

Request POST

curl -X POST "https://{stageurl}/{path}" \
  -H "Content-Type: application/json" \
  -d '{"key": "value"}'

Features of API Gateway Trigger

• You can leverage various features of API Gateway.
• Manage authentication and permission
• Convert request/response
• Manage usage plan and API key
• Request restriction
• You can manage API settings from the API Gateway console.
• Integrating functions is available only in a single automatically generated service.
• The service supports GET and POST methods, same as HTTP triggers.

Modify API Gateway Trigger

1. Select a function from the Cloud Functions console.
2. Go to Trigger tab.
3. Select API Gateway trigger to modify.
4. Click Modify Trigger.
5. Changes the path.
6. Click Modify.

[Note]
Modifying an API Gateway trigger involves deleting the existing trigger within the API Gateway service and then creating a new one.
It results in deleting all plugins applied to the corresponding resource.
If you want to change the resource path to which the plugin is applied, we recommend adding a new trigger instead of modifying it.

Use with API Gateway

Once you create an API Gateway trigger, you can configure additional settings in the API Gateway console.

For more details, please refer to the API Gateway Guide.

Delete Trigger

How to Delete Trigger

1. Select a function from the Cloud Functions console.
2. Go to Trigger tab.
3. Select the trigger to delete (multiple choices available).
4. Click Delete Trigger.
5. Click Delete from the modal window of Delete Trigger.

Cautions

• You cannot delete HTTP trigger. HTTP trigger is built-in, only being enabled or disabled.
• If deleting the trigger, you cannot execute the function through the event.
• Deleted triggers cannot be recovered.

Restrictions

Restrictions for API Gateway Trigger

• You can only connect API Gateways within the same project.
• A single API Gateway resource can only be connected with one function. A single function can register multiple API Gateway triggers.
• You can register multiple API Gateway triggers for a single function.
• If the API Gateway service is disabled or the associated resource is deleted or modified, the trigger will no longer work.
• In this case, the trigger cannot be modified, so you must delete it and re-register it.