Support configuration overrides for troubleshooting

[francoisferrand]

Any configuration field should be changeable per process, without a new image or release, so that support can adjust a setting on a running platform. The named settings only cover the knobs a schema field exists for, and cannot reach objects with unconstrained keys, such as the librdkafka producer parameters.

BACKBEAT_CONFIG_OVERRIDES now holds a JSON document applied to the configuration as a JSON Merge Patch, before validation: the merged result is validated as a whole, so a typo or a wrong type fails at startup rather than leaving the setting silently ignored. Each schema is given the fraction of the patch covering its own fields, applied after the environment variables derived from it, so that nothing silently overrides the escape hatch someone reached for precisely because the usual path did not work.

It is applied over the configuration file and any other setting, so that nothing silently overrides the escape hatch someone reached for precisely because the usual path did not work.

This stays an escape hatch: the named settings remain the supported way to configure backbeat.

Issue: BB-809

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.10%. Comparing base (d054ab6) to head (4b0d390).

Additional details and impacted files

Files with missing lines	Coverage Δ
lib/Config.js	81.81% <100.00%> (+0.67%)	⬆️
lib/config/configOverrides.js	100.00% <100.00%> (ø)
lib/config/envOverrides.js	98.70% <100.00%> (+0.01%)	⬆️

... and 2 files with indirect coverage changes

Components	Coverage Δ
Bucket Notification	80.25% <ø> (ø)
Core Library	82.36% <100.00%> (+0.04%)	⬆️
Ingestion	71.37% <ø> (ø)
Lifecycle	80.45% <ø> (ø)
Oplog Populator	85.80% <ø> (ø)
Replication	62.13% <ø> (ø)
Bucket Scanner	85.76% <ø> (ø)

@@                 Coverage Diff                 @@
##           development/9.6    #2810      +/-   ##
===================================================
+ Coverage            76.07%   76.10%   +0.03%     
===================================================
  Files                  203      204       +1     
  Lines                14024    14051      +27     
===================================================
+ Hits                 10669    10694      +25     
- Misses                3345     3347       +2     
  Partials                10       10              

Flag	Coverage Δ
api:retry	9.46% <29.03%> (+0.01%)	⬆️
api:routes	9.22% <29.03%> (+0.01%)	⬆️
bucket-scanner	85.76% <ø> (ø)
ft_test:queuepopulator	10.84% <29.03%> (-0.62%)	⬇️
ingestion	12.59% <29.03%> (+0.01%)	⬆️
lib	9.21% <29.03%> (+0.01%)	⬆️
lifecycle	19.61% <29.03%> (-0.01%)	⬇️
notification	1.01% <0.00%> (-0.01%)	⬇️
oplogPopulator	0.13% <0.00%> (-0.01%)	⬇️
replication	19.16% <29.03%> (-0.01%)	⬇️
unit	55.57% <100.00%> (+0.09%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[SylvainSenechal]

• I think this will need a small artesca ticket to document it ? Unless we only want CS to use it and not clients directly 🤔
• We may wanna exercise config overrides in zenko functional tests. No need to create new specific tests, but for example we have a variable timeFactor to turn one day into a second that maybe we could use it on ?

[bert-e]

Hello francoisferrand,

My role is to assist you with the merge of this
pull request. Please type @bert-e help to get information
on this process, or consult the user documentation.

Available options

name	description	privileged	authored
/after_pull_request	Wait for the given pull request id to be merged before continuing with the current one.
/bypass_author_approval	Bypass the pull request author's approval	⭐
/bypass_build_status	Bypass the build and test status	⭐
/bypass_commit_size	Bypass the check on the size of the changeset TBA	⭐
/bypass_incompatible_branch	Bypass the check on the source branch prefix	⭐
/bypass_jira_check	Bypass the Jira issue check	⭐
/bypass_peer_approval	Bypass the pull request peers' approval	⭐
/bypass_leader_approval	Bypass the pull request leaders' approval	⭐
/approve	Instruct Bert-E that the author has approved the pull request.		✍️
/create_pull_requests	Allow the creation of integration pull requests.
/create_integration_branches	Allow the creation of integration branches.
/no_octopus	Prevent Wall-E from doing any octopus merge and use multiple consecutive merge instead
/unanimity	Change review acceptance criteria from one reviewer at least to all reviewers
/wait	Instruct Bert-E not to run until further notice.

Available commands

name	description	privileged
/help	Print Bert-E's manual in the pull request.
/status	Print Bert-E's current status in the pull request.
/clear	Remove all comments from Bert-E from the history TBA
/retry	Re-start a fresh build TBA
/build	Re-start a fresh build TBA
/force_reset	Delete integration branches & pull requests, and restart merge process from the beginning.
/reset	Try to remove integration branches unless there are commits on them which do not appear on the source branch.

Status report is not available.

[bert-e]

Waiting for approval

The following approvals are needed before I can proceed with the merge:

• the author

• 2 peers