Add guidance on how to address a CI failure.

README.md

@@ -2,6 +2,8 @@
 
 Continuous integration for OpenConfig models.
 
+[Guidance on how to address a CI failure](docs/addressing_ci_failures.md)
+
 ## Usage Notes and Versioning
 
 In order to avoid backwards-incompatible new changes from affecting and breaking
@@ -169,6 +171,9 @@ This script is aware of the results format for each validator. It parses each
 result uniquely for each validator, and posts the information as a gist on the
 GitHub PR.
 
+The logs for this step resides in the same step as the "Validator Script
+Execution" step.
+
 ## How Each Validator is Installed
 
 Validator         | Installation

docs/addressing_ci_failures.md

@@ -0,0 +1,53 @@
+# Addressing CI Failures
+
+The recommend way of resolving failures is 1) root causing via checking the
+logs, 2) determining the appropriate action, and 3) making changes to the CI
+pipeline if needed.
+
+## Root Causing via Checking Logs
+
+Logs are exposed via GCB in a link that’s accessible via the “Details” link of
+the `public-pr` GitHub CI status. If the results are for some reason not
+available, then you can check the build results by opening the Cloud project to
+find the corresponding build.
+
+When checking the logs, it is helpful to keep in mind the
+[CI steps outlined here](https://github.com/openconfig/models-ci?tab=readme-ov-file#ci-steps)
+to know where the error occurred in the CI pipeline.
+
+## Determining the Appropriate Action
+
+While incidents can be due to bugs in the CI pipeline’s implementation, GitHub
+or GCB can also be the culprit. For example, if too many GitHub calls are made
+(due to CI running too many concurrently-running PRs), then some statuses might
+remain in the “pending” state, which just necessitates a re-run. GCB might have
+a backward-incompatible change
+[that needs updating](https://github.com/openconfig/public/pull/1047/files). In
+the past, GitHub has changed its private/public key pair, necessitating
+[a change](https://github.com/openconfig/public/pull/838) to the `known_hosts`
+file required for GCB to run.
+
+## Making a Change to the CI Pipeline
+
+If you determine that a change is required to the
+[CI pipeline](https://github.com/openconfig/models-ci), then understand
+[which step](https://github.com/openconfig/models-ci?tab=readme-ov-file#ci-steps)
+needs to change and open a PR with the fix. You can test the fix by opening a
+test PR in openconfig/public and
+[changing the branch](https://github.com/openconfig/public/blob/c00868ed96e8e48993e26d8fba20f093722c0e39/cloudbuild.yaml#L55)
+used when pulling the CI pipeline code. Once it is approved, cut a new release
+of the CI pipeline based on
+[these guidelines](https://github.com/openconfig/models-ci?tab=readme-ov-file#usage-notes-and-versioning).
+Lastly, submit a PR in the openconfig/public repo if needed, for example to bump
+the CI pipeline version used.
+
+Example 1: [Making a fix](https://github.com/openconfig/models-ci/pull/98)
+
+Example 2:
+[Adding a feature to the CI pipeline](https://github.com/openconfig/models-ci/pull/92)
+
+Example 3:
+[Adding a validator to the CI pipeline](https://github.com/openconfig/models-ci/pull/93)
+
+Example 4:
+[Building the CI image at a regular frequency to avoid stale dependencies](https://github.com/openconfig/models-ci/pull/91)