score-eg-thumbnail-service

score-eg-thumbnail-service

An example service that accepts reads a queue of image events and responds to them with generated thumbnails. This is used by https://github.com/astromechza/score-eg-image-service.

The message protocol is very simple:

Input message

Exchange: "" (default exchange)

Routing Key: thumbnail-generation (OR the value of $AMQP_THUMBNAILING_ROUTING_KEY)

Message Body: the raw png, jpeg, or gif contents, the size can be up to the rabbitmq max message size (usually 128MB to 2GB)

Reply-To: the routing key to send the output message to

Message-Id: an optional message id to include in the logs -- use this to match responses to requests

Output message

Exchange: "" (default exchange)

Routing Key: whatever the input message declared in Reply-To

Message Body: either the raw 200x200 jpeg bytes, or an errorCode

Correlation-Id: a copy of the message id that resulted in this response -- use this to match responses to requests

Testing with Score

score-compose init
score-compose generate score.yaml --build main=. \
    --override-property 'resources.queue.metadata.annotations.compose\.score\.dev/publish-port="15672"' \
    --override-property 'resources.queue.metadata.annotations.compose\.score\.dev/publish-management-port="16672"'
docker compose up -d --build
score-compose resources get-outputs 'amqp.default#shared' | jq

Browse to the management interface at http://localhost:16672/ login with the username and password and open the vhost with the unique ID.

Then send a new message on the default exchange to the thumbnail-generation routing key with the contents of cat lenna.png | base64.

Or run the automated test script:

AMQP_CONNECTION=$(score-compose resources get-outputs 'amqp.default#shared' --format 'amqp://{{.username}}:{{.password}}@localhost:15672/{{.vhost}}') \
    AMQP_THUMBNAILING_ROUTING_KEY=thumbnail-generation \
    go test ./

This will run the test and then write the output thumbnail to the local directory.