Health check endpoint

[hasufell]

For https://jira.iohk.io/browse/ADP-496 it would be interesting to have an inexpensive and unambiguous health check endpoint.

I couldn't find any in https://github.com/input-output-hk/smash/blob/master/src/Lib.hs

[ksaric]

There is a health check endpoint using Prometheus - https://github.com/input-output-hk/smash/blob/master/src/Cardano/Metrics.hs
Called from -

smash/src/Cardano/SmashDbSync.hs

Line 407 in bd36af6

(metrics, server) <- registerMetricsServer 8080

So by default, you have port 8080 as the health check port (http://localhost:8080/), not sure if it's exported through the HTTP proxy:

# TYPE action_queue_length_post gauge
action_queue_length_post  0.0
# TYPE action_queue_length_post_write gauge
action_queue_length_post_write  748.0
# TYPE action_queue_length_pre gauge
action_queue_length_pre  0.0
# TYPE db_block_height gauge
db_block_height  4820725.0
# TYPE remote_tip_height gauge
remote_tip_height  4822338.0

[hasufell]

But does that tell me this is a an actual smash server and it understands my API calls?

[ksaric]

But does that tell me this is a an actual smash server and it understands my API calls?

No, the SMASH server tells you it's a SMASH server by understanding your API calls 😄

What is that you want to check here?
A call which results in?

An example would do wonders here.

[hasufell]

No, the SMASH server tells you it's a SMASH server by understanding your API calls smile

The wallet wants to have a health check when a user sets a SMASH server, knowing that it's a valid SMASH server without doing expensive API calls and validating this prior to any metadata syncing.

[ksaric]

@hasufell Sure, propose the format of such health check.

[hasufell]

paths:
  /status:
    get:
    summary: Get
    description:  Query status/health of the SMASH server
    responses:
      200:
        description: Ok
        content:
          application/json:
            schema:
              type: object
              required:
                - smash_status
                - smash_version
             properties:
               smash_status:
                 description: the status of the SMASH server
                 type: string
                 enum:
                   - ok
                   - booting
                 example: ok
               smash_version:
                 description: The "git describe" version of the SMASH server
                 type: string
                 example: 0.1.0-rc-99-gb7fa2fe
               smash_message:
                 description: A custom message set by the operator
                 type: string
                 example: I'm a SMASH server for cardano

1. whether booting makes sense or not as a value, I don't know, it's optional I guess
2. I'm avoiding generic status field, so we can identify from the object keys that it's a smash server

[ksaric]

@hasufell That looks solid, will implement it in this sprint, and get back to you.

[ksaric]

Implemented in #101

[hasufell]

many thanks