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Zebra/book/src/dev/continuous-integration.md

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Zebra Continuous Integration

Overview

Zebra has extensive continuous integration tests for node syncing and lightwalletd integration.

On every PR change, Zebra runs these Docker tests:

  • Zebra update syncs from a cached state Google Cloud tip image
  • lightwalletd full syncs from a cached state Google Cloud tip image
  • lightwalletd update syncs from a cached state Google Cloud tip image
  • lightwalletd integration with Zebra JSON-RPC and Light Wallet gRPC calls

When a PR is merged to the main branch, we also run a Zebra full sync test from genesis. Some of our builds and tests are repeated on the main branch, due to:

  • GitHub's cache sharing rules,
  • our cached state sharing rules, or
  • generating base coverage for PR coverage reports.

Currently, each Zebra and lightwalletd full and update sync will updates cached state images, which are shared by all tests. Tests prefer the latest image generated from the same commit. But if a state from the same commit is not available, tests will use the latest image from any branch and commit, as long as the state version is the same.

Zebra also does a smaller set of tests on tier 2 platforms using GitHub actions runners.

Automated Merges

We use Mergify to automatically merge most pull requests. To merge, a PR has to pass all required main branch protection checks, and be approved by a Zebra developer.

We try to use Mergify as much as we can, so all PRs get consistent checks.

Some PRs don't use Mergify:

  • Mergify config updates
  • Admin merges, which happen when there are multiple failures on the main branch
  • Manual merges

We use workflow conditions to skip some checks on PRs, Mergify, or the main branch. For example, some workflow changes skip Rust code checks.

Manually Using Google Cloud

Some Zebra developers have access to the Zcash Foundation's Google Cloud instance, which also runs our automatic CI.

Please shut down large instances when they are not being used.

Automated Deletion

The Delete GCP Resources workflow automatically deletes instance templates, disks, and images older than a few days.

Running instances and their disks are protected from deletion.

If you want to keep instance templates, disks, or images in Google Cloud, name them so they don't match the automated names:

  • deleted instance templates and disks end in a commit hash, so use a name ending in - or -[^0-9a-f]+
  • deleted images start with zebrad-cache or lwd-cache, so use a name starting with anything else

Our other Google Cloud projects don't have automated deletion, so you can also use them for experiments or production deployments.

Troubleshooting

To improve CI performance, some Docker tests are stateful.

Tests can depend on:

  • built Zebra and lightwalletd docker images
  • cached state images in Google cloud
  • jobs that launch Google Cloud instances for each test
  • multiple jobs that follow the logs from Google Cloud (to work around the 6 hour GitHub actions limit)
  • a final "Run" job that checks the exit status of the Rust acceptance test
  • the current height and user-submitted transactions on the blockchain, which changes every minute

To support this test state, some Docker tests depend on other tests finishing first. This means that the entire workflow must be re-run when a single test fails.

Finding Errors

Look for the earliest job that failed, and find the earliest failure.

For example, this failure doesn't tell us what actually went wrong:

Error: The template is not valid. ZcashFoundation/zebra/.github/workflows/build-docker-image.yml@8bbc5b21c97fafc83b70fbe7f3b5e9d0ffa19593 (Line: 52, Col: 19): Error reading JToken from JsonReader. Path '', line 0, position 0.

https://github.com/ZcashFoundation/zebra/runs/8181760421?check_suite_focus=true#step:41:4

But the specific failure is a few steps earlier:

#24 2117.3 error[E0308]: mismatched types ...

https://github.com/ZcashFoundation/zebra/runs/8181760421?check_suite_focus=true#step:8:2112

The earlier failure can also be in another job, check out the whole workflow run for details. (Use the "Summary" button on the top left of the job details, and zoom in.)

Fixing CI Sync Timeouts

CI sync jobs near the tip will take different amounts of time as:

  • the blockchain grows, and
  • Zebra's checkpoints are updated.

To fix a CI sync timeout, follow these steps until the timeouts are fixed:

  1. Check for recent PRs that could have caused a performance decrease

  2. Update Zebra's checkpoints

  3. Wait for a full or update sync to finish with the new checkpoints

  4. The GitHub actions job limit is 6 hours, so the ideal job time is 4-5 hours. If any GitHub actions job times out, or takes over 5 hours:

    a. Split the job based on the sync height, or

    b. Adjust the sync heights in existing jobs.

  5. If a Rust test fails with "command did not log any matches for the given regex, within the ... timeout":

    a. If it's the full sync test, increase the full sync timeout

    b. If it's an update sync test, increase the update sync timeouts

Fixing Duplicate Dependencies in Check deny.toml bans

Zebra's CI checks for duplicate crate dependencies: multiple dependencies on different versions of the same crate. If a developer or dependabot adds a duplicate dependency, the Check deny.toml bans CI job will fail.

You can view Zebra's entire dependency tree using cargo tree. It can also show the active features on each dependency.

To fix duplicate dependencies, follow these steps until the duplicate dependencies are fixed:

  1. Check for updates to the crates mentioned in the Check deny.toml bans logs, and try doing them in the same PR. For an example, see PR #5009.

    a. Check for open dependabot PRs, and

    b. Manually check for updates to those crates on https://crates.io .

  2. If there are still duplicate dependencies, try removing those dependencies by disabling crate features:

    a. Check for features that Zebra activates in its Cargo.toml files, and try turning them off, then

    b. Try adding default-features = false to Zebra's dependencies (see PR #4082).

  3. If there are still duplicate dependencies, add or update the exceptions in deny.toml:

    a. Prefer exceptions for dependencies that are closer to Zebra in the dependency tree (sometimes this resolves other duplicates as well),

    b. Add or update exceptions for the earlier version of duplicate dependencies, not the later version, and

    c. Add a comment about why the dependency exception is needed: what was the dependency update that caused it?

    d. For an example, see PR #4890.

  4. Repeat step 3 until the dependency warnings are fixed. Adding a single exception can resolve multiple warnings.

Fixing Disk Full Errors

If the Docker cached state disks are full, increase the disk sizes in:

If the GitHub Actions disks are full, follow these steps until the errors are fixed:

  1. Update your branch to the latest main branch, this builds with all the latest dependencies in the main branch cache
  2. Clear the GitHub Actions cache for the failing branch
  3. Clear the GitHub Actions caches for all the branches and the main branch

If the *-sprout-and-sapling-params caches are around 765 MB, they are the correct size. There is no need to clear them, the replacement cache will be the same size.

You can find a list of caches using:

gh api -H "Accept: application/vnd.github+json" repos/ZcashFoundation/Zebra/actions/caches

And delete a cache by id using:

gh api --method DELETE -H "Accept: application/vnd.github+json" /repos/ZcashFoundation/Zebra/actions/caches/<id>

These commands are from the GitHub Actions Cache API reference.