What does this PR do?

This PR fixes #30729 by always emitting heartbeat/summary documents when a command exits without journey/end.

These documents have the following message:

journey did not finish executing, X steps ran

Why is it important?

Such a change will cause the Uptime UI to be able to display correct results even if a journey execution exits successfully but doesn't manage to write a journey/end event to the desired descriptor. Such a situation could happen when the synthetics runner buffer was full and wasn't emptied on time before the command's exit, as described in elastic/synthetics#446 and fixed in elastic/synthetics#465

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (Does not apply)
• I have made corresponding change to the default configuration files (Does not apply)
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in CHANGELOG.next.asciidoc or CHANGELOG-developer.next.asciidoc.

Author's Checklist

I've done so myself, but would like reviewers to verify the following:

• Running journeys on the latest version of the synthetics runner works fine for journeys which emit journey/end
• Running journeys on the latest version of the synthetics runner works fine for journeys which exit with status code > 0 and do not emit journey/end
• Running journeys on the latest version of the synthetics runner works fine for journeys which exit with status code == 0 and emit journey/end

How to test this PR locally

To test this PR locally you must have a version of the synthetics runner which does not emit journey/end events once its finished. Then, you'll use that version to run a browser monitor and verify that the documents in Kibana do contain summaries with the following error message:

journey did not finish executing, X steps ran

1. Update your local version of the synthetics package by removing these lines which are responsible for emitting journey/end events: https://github.com/elastic/synthetics/blob/e594196f4b083917fb7e44d67e208e1a87ea29a5/src/reporters/json.ts#L474-L484 (just comment them).
2. Copy the journey below and run it locally using pbpaste | elastic-synthetics --screenshots off --inline --rich-events | jq .type

   step("no journey end", async () => { await page.goto("https://bbc.co.uk") });

   You should ensure that no journey/end is emitted when running this journey. You must verify that because when running heartbeat you want to simulate what would happen when journeys exit without emitting journey/end.
3. Checkout this branch and build heartbeat.
4. Run the heartbeat executable you just compiled with the following monitor:

   heartbeat.monitors:
   - type: browser
     id: test-no-end-emitted
     name: test-no-end-emitted
     schedule: '@every 1m'
     source:
       inline:
         script: |-
           step("no journey end", async () => {
             await page.goto('https://www.bbc.co.uk');
           });

   You can use ELASTIC_SYNTHETICS_CAPABLE=true ./heartbeat -c /tmp/heartbeat.yml -e -d "*" for that.
5. Go to Kibana and ensure that there is a summary for this monitor which mentions it didn't run to completion.

Related issues

• Closes Heartbeat: report summary event when synthetics doesn't emit end event #30729

Screenshots