Triggers¶
OpenFaaS functions can be triggered easily by any kind of event. The most common use-case is HTTP which acts as a lingua franca between internet-connected systems.
Connectors map one or more topics, subjects or queues from a stateful messaging system or event-source to a number of functions in your cluster.
Can't find the event-source or trigger that you were looking for? Contact us for more info
Built-in triggers¶
HTTP / webhooks¶
This is the default, and standard method for interacting with your Functions.
The function URL follows the pattern of:
https://<gateway URL>:<port>/function/<function name>
Async / JetStream¶
You can execute a function or microservice asynchronously by replacing /function/ with /async-function/ when accessing the endpoint via the OpenFaaS gateway.
The function URL follows the pattern of:
https://<gateway URL>:<port>/async-function/<function name>
You can also pass an X-Callback-Url header with the URL of another endpoint for the response.
More on async: Async Functions
CLI¶
Trigger a function using the faas-cli by using the function name
echo "triggered" | faas-cli invoke figlet
CLI invocation can also be async by passing the
-aflag to theinvokecall
Find out more: faas-cli on GitHub
OpenFaaS Pro triggers¶
With the connector patterns, you can trigger functions from any event-source or messaging system, without having to add SDKs or subscription code to each of your functions.
This means a function can be triggered by Apache Kafka, AWS SNS and Cron, without having any direct coupling to of these systems. As functions scale, there is no additional load generated on the underlying event sources.
Pictured: Event-connector pattern. Each topic, subject or queue can be broadcast to one or many functions.
Apache Kafka¶
Trigger your functions via Apache Kafka topics.
See also:
- Staying on topic: trigger your OpenFaaS functions with Apache Kafka
- Event-driven OpenFaaS with Managed Kafka from Aiven
Postgres¶
Trigger functions based upon Postgres events including: insert, update and delete. The default mode uses the efficient Write Ahead Log (WAL) that is also used by Postgres for replication.
AWS SQS¶
Trigger your functions from events within AWS by publishing events to AWS SQS queues.
AWS SNS¶
Trigger OpenFaaS functions based upon many different types of events generated in AWS using an AWS SNS subscription. Events are sent by AWS via HTTPS and the connector will require as public endpoint to be accessible. Events are verified using the AWS public key and TLS ensures encryption of messages.
If you are unable to expose a public endpoint for any reason, and still need events from AWS, we recommend using the SQS connector instead.
RabbitMQ¶
Trigger your functions from messages published to RabbitMQ queues.
Cron Connector¶
The cron-connector can be used to trigger functions on a timed schedule. It uses traditional cron expressions.
When using the Community Edition (CE) of the connector, functions can only be invoked by the cron connector, however OpenFaaS Pro customers can set up a function to be invoked by Cron and any other connectors that they need.
See also: Scheduling function runs in the docs.
Community Triggers¶
MQTT Connector¶
The MQTT Connector can be used in conjunction with an MQTT broker such as emitter.io or similar to respond to events from IoT devices and MQTT message producers.
Example usage: Drone tracking project for Packet.com's session CES 2020.
Minio / S3¶
You can trigger OpenFaaS functions using Minio's webhook or Kafka integration.
For S3 on AWS, see the AWS SQS Connector.
NATS Pub/sub¶
OpenFaaS Pro has a built-in queue and integration with NATS JetStream, however you can also invoke functions using the pub/sub mechanism of NATS Core.
View the nats-connector
CloudEvents¶
CloudEvents is a specification for describing event data in a common way.
No connector is required to trigger OpenFaaS functions using CloudEvents.
Follow this example to learn how to trigger functions using the Azure EventGrid and CloudEvents: johnmccabe/cloudevents-slack-demo
VMware vCenter¶
The vcenter-connector by OpenFaaS is an event connector built to consume events from VMware's vCenter product.
With this project your functions can subscribe to events generated by the changes in your vCenter installation - for instance a VM being created, turned on or deleted. By using the connector you can extend the behaviours and functionality of vCenter and create custom workflows for your platform.
Status: if you require support for this project, reach out to us for more info
Link: openfaas-vcenter-connector
Pushbullet (third-party project)¶
Invoke functions from Pushbullet channels. This is a third party project.
More information in the repository: MrSimonEmms/openfaas-pushbullet-connector
IFTTT¶
You can trigger OpenFaaS functions using webhooks sent via the (if this, then that) service.
An example may be triggering a function which forwards Tweets about your brand or project to a given Slack channel. For this combination use the "Twitter search" Applet and have it trigger the "Make a web request" Applet giving the public URL of your OpenFaaS gateway and the receiver function such as https://gw.my-company.com/function/slack-forwarder
See an example of a function built to forward Tweets from IFTTTT to Slack using Golang: filter-tweets.
Visit ifttt.com to learn more.