Mercurial pushlog vs CI/CD logs: correlating pushes with deployment failures

Answer

Use the pushlog’s push_id together with its push_timestamp (and the list of nodes) to pinpoint the changeset that triggered a CI build; the build’s start time (or the time it fetched the source) should match a pushlog entry’s timestamp, and the push_id removes ambiguity when multiple pushes occur in the same second.

Confirmed facts

• The pushlog extension stores each push with a unique push_id, a push_timestamp, the pushing user, and the nodes (changeset hashes) transmitted.
• Changesets in draft or secret phases are not visible to a plain hg log unless the repository is pulled or the phase is advanced.
• Pushlog verbosity is controlled by pushlog.maxentries, pushlog.maxage, and the pushlog.template; debug logging can be toggled with debug = True in the [pushlog] section.

Likely explanation

If the CI system does not pull before building, it may build from an older public tip, causing the failure to appear unrelated to the most recent push. Secret/draft changesets that never become public will not appear in the CI’s log, making the pushlog the only source of truth for what was actually transmitted.

Steps to map a failure to a changeset

1. Record the CI build’s start timestamp (or the moment it executed hg pull/hg update).
2. Query the pushlog for entries whose push_timestamp is closest to but not earlier than that time: hg pushlog --template '{push_id}|{push_timestamp}|{user}|{node}\n'.
3. Match the push_id (or the timestamp if IDs are unavailable) to the build; the associated nodes are the changesets that were pushed in that operation.
4. If the build fails, inspect each nodes hash with hg log -r to see the commit message and files.
5. For secret/draft changesets, ensure the CI performs a hg pull (or hg incoming) before the build, or configure a pretxnchangegroup hook that rejects pushes containing non‑public changesets so only public revisions ever appear in pushlog.
6. To keep pushlog overhead low, set pushlog.maxentries to a reasonable limit (e.g., 1000) and pushlog.maxage to expire old entries (e.g., 30 days). Use a concise pushlog.template that omits unnecessary fields. Enable debug logging only temporarily: add debug = True under [pushlog], test, then remove it.

Missing diagnostic detail

To confirm the correlation, we need the exact timestamp when the CI system fetched the source (start of the build). If that timestamp is unavailable, the mapping may be ambiguous when multiple pushes occur within the same second.