[Synthetics] Add lightweight params support

[shahzad31]

Summary

Fixes #147467

Users will be able to specify params in following format in project monitors or UI

- type: http
  name: Admin Check
  url: ...
  username: ${admin_user:admin}
  password: ${admin_password}

[elasticmachine]

Pinging @elastic/uptime (Team:uptime)

[dominiqueclarke]

My first basic test didn't seem to work for me.

I tried created an UI HTTP monitor.

I started out with setting the url to ${url:https://google.com}, before setting any params.

This worked as expected, as it fell back to https://google.com.

However, after adding a url param, the monitor did not update to use the param.

Upon further inspection, I noticed that the url param did not seem to be added at all. I removed the default and just used ${url}. When inspecting the config sent to the service, I noticed that the url is empty.

As a side note, we may want to prevent monitors before being saved with a configuration that results in an empty string for required values, such as url, hosts, and name for http, tcp, and icmp monitors. Otherwise, it could cause issues on the service side.

You can see my monitor config here.

And you can see I have my param set here

And you can see it's still running with the default here

[dominiqueclarke]

Doesn't work for http headers, where I would expect it to, for example to work with auth headers or other sensitive headers.

[dominiqueclarke]

@dominiqueclarke @shahzad31

Regarding: #148634 (review)

Doesn't work for http headers, where I would expect it to, for example to work with auth headers or other sensitive headers.

Is this being addressed as part of this PR? Would users be able to use global params in request headers for lightweight monitors?

It is being addressed in this PR.

[dominiqueclarke]

I don't understand why params is being passed to variableParser.parse.

I took a look at the defining for that function, it seems it takes input and an options object, but options doesn't seem to have anything to do with params.

Can you explain this for me?

I see params being used down below in replaceVarsWithParams(formatter, params) which makes perfect sense to me.

[shahzad31]

this was just a leftover. i will clean it

[dominiqueclarke]

I think this should maybe be logger?.warn and also I wonder if we want to log the actual error too. Since I ran into issues with my params, that would be helpful.

[dominiqueclarke]

When creating UI or project monitors in a non-default space, the "All spaces" params do not work. All spaces params do appear to work in the default space.

[dominiqueclarke]

LGTM. The issue with all the non-default space is being handled in a separate PR.

[kibana-ci]

💚 Build Succeeded

• Buildkite Build
• Commit: 14946ae

Metrics [docs]

Module Count

Fewer modules leads to a faster build time

id	before	after	diff
synthetics	1357	1360	+3

Async chunks

Total size of all lazy-loaded chunks that will be downloaded as the user navigates the app

id	before	after	diff
synthetics	1.4MB	1.4MB	+1.5KB

Unknown metric groups

ESLint disabled line counts

id	before	after	diff
securitySolution	433	436	+3
synthetics	92	104	+12
total			+15

Total ESLint disabled count

id	before	after	diff
securitySolution	513	516	+3
synthetics	98	110	+12
total			+15

History

• 💔 Build #116070 failed fbbf23c
• 💔 Build #115906 failed c517ade
• 💚 Build #115592 succeeded c050f05
• 💛 Build #115425 was flaky c2cf72d
• 💚 Build #115355 succeeded ef0d75a

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