Backend: No pipelines created when matrix var is longer than 114 chars
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### Summary
After spending hours trying to understand what was going wrong, I came to the conclusion I found a specific edge case where GitLab does not throw any error messages and simply gets bugged.
When these conditions are met:
* There is a `needs` relations between two jobs
* The parent job has a matrix
* The total number of characters in the matrix variables values is greater than 114
...no pipelines are created, without any notifications of what could have gone wrong.
### Steps to reproduce
<!-- Describe how one can reproduce the issue - this is very important. Please use an ordered list. -->
1. Create a project with this minimal `.gitlab-ci.yml`:
````yaml
Parent job:
stage: build
parallel:
matrix:
- FOO: "fooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo"
script:
- echo "Hello world"
Child job:
stage: test
needs: ["Parent job"]
script:
- echo "Hello world"
````
2. Commit & push -> It creates a pipeline
3. Add a `o` to the `FOO` variable
4. Commit & push -> no pipelines
When multiple variables are defined, the issue occurs when the sum of the variables characters is above 114 :
<details><summary>Click to expand</summary>
````yaml
Parent job:
stage: build
parallel:
matrix:
- FOO: "fooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo"
BAR: "oooooooooooo"
script:
- echo "Hello world"
Child job:
stage: test
needs: ["Parent job"]
script:
- echo "Hello world"
````
</details>
### Example Project
Here is the project : https://gitlab.com/vdsbenoit/needs-matrix
We can see that no pipelines ran for this commit : https://gitlab.com/vdsbenoit/needs-matrix/-/commit/49ebea1e039ddaacd8136f9c0ccd51198bf26cdd
### What is the current *bug* behavior?
No pipelines are created
### What is the expected *correct* behavior?
A pipeline should be created
### Output of checks
This bug happens on GitLab.com
### Possible fixes
I don't have any fixes to this issue. The best workaround I found is to remove the `needs` instruction while waiting for a fix.
* Surface the error when no pipeline is created when matrix reaches limit
* Match job name chars limit
### Note
We are a 150 seats ~"GitLab Premium" customer. Support on this issue would be much appreciated 🙏
## Proposal
| Iteration | Description | Limitations |
| --------- | ----------- | ----------- |
| Step 1: Surface the error | Ensure that an error message is surfaced when character limits are exceeded. | Does not solve the problem to allow for long matrix section. Users still need to use identified workaround of variable indirection. |
| Step 2: Make the character limits match | | Does not solve the problem to allow for long matrix section. Users still need to use identified workaround of variable indirection. |
| Step 3: Update UI to show variables | Add UI elements to expose the variables used, rather than relying on the name. This may require updating the API to contain the information if not already available | Does not solve the problem to allow for long matrix section. Users still need to use identified workaround of variable indirection. |
| Step 4: Allow Custom Matrix Names | Exact details to be determined. Allow the user to assign names to the various configurations through the config. This allows for names that are meaningful. When names aren't provided default to names by variable - same behaviour as today. | Requires the UI update from step 3 to maintain parity with existing experience of viewing variables, but does fix the issue of being limited in matrix variables. |
### Questions to Answer
- [ ] UX thoughts on updated yml - @carolinesimpson to add details of question for @v_mishra
## Implementation Table
<!--
_NOTE: If the issue is not part of an epic, the implementation table can be removed. If it is part of an epic, make sure that the implementation table below mirrors the corresponding epic's implementation table content._
-->
| Group | Issue Link |
| ------ | ------ |
| ~backend | :point_left: You are here |
| ~backend | https://gitlab.com/gitlab-org/gitlab/-/issues/420669+ |
| ~backend / ~frontend | https://gitlab.com/gitlab-org/gitlab/-/issues/428165+ |
| ~backend | https://gitlab.com/gitlab-org/gitlab/-/issues/428169+ |
issue