Tree Closures and What They Mean for Developers
When you push a patch to firefox-autoland via Lando, it lands on a shared integration branch that is continuously tested. Sometimes that branch is closed — meaning new pushes are temporarily blocked. This page explains why closures happen, how to check the current status, and what you should do when the tree is closed.
Checking the Tree Status
Treestatus — the dedicated treestatus website shows the status of all trees: https://lando.services.mozilla.com/treestatus/ The autoland-specific page is at https://lando.services.mozilla.com/treestatus/firefox-autoland/
Lando — the landing page shows the current state at the top.
Test infrastructure dashboard — the red line at the top of https://tests.firefox.dev/workers.html indicates the tree is closed.
Treeherder — a red banner appears at the top when the tree is closed. The job view at https://treeherder.mozilla.org/#/jobs?repo=autoland might show the failing jobs that triggered the closure.
Historical closure logs (JSON) are available at: https://treestatus.mozilla-releng.net/trees/firefox-autoland/logs_all
Types of Closures
Sheriffs (the people who keep the tree green) close the tree for different reasons. Each closure is tagged with one of the categories below.
Test Failures (checkin_test)
A recently-landed patch caused test failures (mochitest, browser-chrome, xpcshell, web-platform-tests, etc.). Sheriffs close the tree while they identify and back out the offending patch.
What to do: Wait for the backout to land and the tree to reopen. If your patch was backed out, check Treeherder or Bugzilla for the failure logs and fix the issue before re-landing.
Waiting for Coverage (waiting_for_coverage)
A new batch of pushes has landed and too many test jobs are still pending or running. The tree is temporarily closed so that sheriffs can assess the results before allowing more patches in. This is the most frequent type of closure and is usually short (under an hour).
What to do: Just wait. This is routine.
Build Failures (checkin_compilation)
A patch broke the build on one or more platforms (compile error, SpiderMonkey build failure, l10n bustage, etc.). The tree stays closed until the bustage is backed out or fixed.
What to do: Same as test failures — wait for the fix, or investigate if you suspect your patch is the cause.
Infrastructure Issues (infra)
Something outside the code is broken: Taskcluster workers, Treeherder ingestion, Lando, hg-git sync, etc. These are rarer but can last longer.
What to do: Nothing you can do. Watch the #sheriffs Matrix channel for updates. An incident might be open for a significant issue.
Merges (merges)
The tree is closed while sheriffs perform a merge (typically merging autoland back to mozilla-central).
What to do: Wait — these are usually brief.
Planned Closures (planned)
Scheduled closures for known events such as toolchain updates or large infrastructure migrations (e.g. the Git migration).
What to do: These are announced in advance. Plan your landings around them.
Other (other)
Catch-all for unusual situations: backout requests, one-off machine issues, or ad-hoc maintenance.
What Should I Do When the Tree Is Closed?
Do use the time to run try pushes, review patches, or work on other tasks.
Watch the #sheriffs Matrix channel or the Lando treestatus page for reopening announcements.
If your patch was backed out, the sheriff will file a comment on your bug with the failure details.
For a sheriff’s perspective on how closure decisions are made, see Deciding To Close A Tree.