Add support for graceful halt via server config

[alexanderbez]

Add support for a halt-height in the node's server-config/CLI to gracefully halt and shutdown a node.

closes: #3981

---

• Targeted PR against correct branch (see CONTRIBUTING.md)

• Linked to github-issue with discussion and accepted design OR link to spec that describes this work.

• Wrote tests

• Updated relevant documentation (docs/)

• Added a relevant changelog entry: sdkch add [section] [stanza] [message]

• rereviewed Files changed in the github PR explorer

---

For Admin Use:

• Added appropriate labels to PR (ex. wip, ready-for-review, docs)
• Reviewers Assigned
• Squashed all commits, uses message "Merge pull request #XYZ: [title]" (coding standards)

[alexanderbez]

@ebuchman given the BaseApp has knowledge of the height to halt at, where is the most appropriate to check and gracefully exit while respecting the ABCI semantics? Commit?

[codecov]

Codecov Report

Merging #4059 into develop will decrease coverage by 0.03%.
The diff coverage is 20%.

@@             Coverage Diff             @@
##           develop    #4059      +/-   ##
===========================================
- Coverage    60.21%   60.17%   -0.04%     
===========================================
  Files          212      212              
  Lines        15155    15165      +10     
===========================================
  Hits          9126     9126              
- Misses        5405     5414       +9     
- Partials       624      625       +1

[rigelrozanski]

Is there a document describing how a validator would change the halting height on a live node? I'm assuming one would just write to the config live somehow

[alexanderbez]

@rigelrozanski I'll add a section to the docs somewhere on this new config feature. There currently isn't a way to do it live. You must, set the config and start (or restart) your node for the change to pickup.

[alexanderbez]

@rigelrozanski I added a section to the validator-setup.md docs.

[sabau]

👍

[sabau]

This can be set only at boot time right? Do you think will be possible to undo this at runtime, or to set/change this flag at runtime, let's say a governance proposal that proposed to update at height X got downvoted but I started a node with this this --halt-height X

Probably even if it's true it makes sense to do it in a separate PR

[alexanderbez]

Good question @sabau. This value can be set at any time really but the node would have to be restarted for it to take effect. There currently isn't a way to do this at runtime. I think there is some crossover functionality between this and the software upgrade module/process we plan to have. Essentially, to do this at runtime, it would have to be parameter somewhere.

[sabau]

I left a question more than a comment, if it makes sense probably should be addressed as a following PR

[alexanderbez]

Answered your (good) question @sabau. I think it's safe to merge this PR for now until we have a more established software upgrade process. I'm thinking we should maybe even get this into a v0.34.2 patch release along with some other small bits.