Experimental SQS trigger for Spin

Install from release

spin plugins install --url https://github.com/fermyon/spin-trigger-sqs/releases/download/canary/trigger-sqs.json

Build from source

You will need Rust and the pluginify plugin (spin plugins install --url https://github.com/itowlson/spin-pluginify/releases/download/canary/pluginify.json).

cargo build --release
spin pluginify --install

Test

The trigger uses the AWS configuration environment variables - these must be set before running.

You will also need to change the queue_url in spin.toml to a queue you have access to.

cd guest
spin build --up

Limitations

This trigger is currently built using Spin 2.0.1. You will need that version of Spin or above.

Custom triggers, such as this one, can be run in the Spin command line, but cannot be deployed to Fermyon Cloud. For other hosts, check the documentation.

Configuration

The SQS trigger uses the AWS credentials from the standard AWS configuration environment variables. These variables must be set before you run spin up. The credentials must grant access to all queues that the application wants to monitor. The credentials must allow for reading messages and deleting read messages.

The trigger assumes that the monitored queues exist: it does not create them.

spin.toml

The trigger type is sqs, and there are no application-level configuration options.

The following options are available to set in the [[trigger.sqs]] section:

Name	Type	Required?	Description
queue_url	string	required	The queue to which this trigger listens and responds.
max_messages	number	optional	The maximum number of messages to fetch per AWS queue request. The default is 10. This refers specifically to how messages are fetched from AWS - the component is still invoked separately for each message.
idle_wait_seconds	number	optional	How long (in seconds) to wait between checks when the queue is idle (i.e. when no messages were received on the last check). The default is 2. If the queue is not idle, there is no wait between checks. The idle wait is also applied if an error occurs.
system_attributes	array of strings	optional	The list of system-defined attributes to fetch and make available to the component.
message_attributes	array of strings	optional	The list of message attributes to fetch and make available to the component. Only string and binary values are supported.
component	string or table	required	The component to run when a queue message is received. (This is the standard Spin trigger component field.)

For example:

spin_manifest_version = 2

[application]
name = "test"
version = "0.1.0"

# One [[trigger.sqs]] section for each queue to monisot1
[[trigger.sqs]]
queue_url = "https://sqs.us-west-2.amazonaws.com/12345/testqueue"
max_messages = 1
system_attributes = ["All"]
component = "test"

[component.test]
source = "..."

spin up command line options

There are no custom command line options for this trigger.

Writing SQS components

There is no SDK for SQS guest components. Use the sqs.wit file to generate a trigger binding for your language. Your Wasm component must export the handle-queue-message function. See guest/src/lib.rs for how to do this in Rust.

Note: In the current WIT, a message has a single message-attributes field. This contains both system and message attributes. Feedback is welcome on this design decision.

Your handler must return a message-action (or an error). The message-action values are:

Name	Description
delete	The message has been processed and should be removed from the queue.
leave	The message should be kept on the queue.

The trigger renews the message lease for as long as the handler is running.

Note: The current trigger implementation does not make the message visible immediately if the handler returns leave or an error; it lets the message become visible through the normal visibility timeout mechanism.