cmd/coordinator: run subrepo trybots against recent Go release branches

This is the coordinator half of the change to make the coordinator
test subrepos against two prior releases of Go.

The next change that's required is for the maintnerd API server to
return the name of the past two releases.

For now this change is a no-op. But once maintnerd starts returning
more data, then this change will start causing causing two more
linux-amd64 builders per subrepo trybot.

Updates golang/go#17626

Change-Id: I1cedbc2e4eee51fb003c8bcc8e072fd10717a833
Reviewed-on: https://go-review.googlesource.com/c/143538
Reviewed-by: Dmitri Shuralyov <[email protected]>

Author: bradfitz

cmd/coordinator/coordinator.go

@@ -1058,9 +1058,9 @@ type trySet struct {
 
 type trySetState struct {
 	remain       int
-	failed       []string // build names
+	failed       []string // builder names, with optional " ($branch)" suffix
 	builds       []*buildStatus
-	benchResults []string // builder names
+	benchResults []string // builder names, with optional " ($branch)" suffix
 }
 
 func (ts trySetState) clone() trySetState {
@@ -1100,33 +1100,66 @@ func newTrySet(work *apipb.GerritTryWorkItem) *trySet {
 		tryID:  "T" + randHex(9),
 		trySetState: trySetState{
 			remain: len(builders),
-			builds: make([]*buildStatus, len(builders)),
+			builds: make([]*buildStatus, 0, len(builders)),
 		},
 	}
 
-	// For now, for subrepos, we only support building one repo.
-	// TODO: Issue 17626: test subrepos against Go master and past two
-	// releases. But to save resources, we'll probably only want
-	// to do that for linux-amd64 (the Kubernetes cheap builder) to
-	// not blow up usage? Or maybe it doesn't matter.
+	// GoCommit is non-empty for x/* repos (aka "subrepos"). It
+	// is the Go revision to use to build & test the x/* repo
+	// with. The first element is the master branch. We test the
+	// master branch against all the normal builders configured to
+	// do subrepos (subTryBuilders above). Any GoCommit values past
+	// the first are for older release branches, but we use a limited
+	// subset of builders for those.
 	var goRev string
 	if len(work.GoCommit) > 0 {
 		goRev = work.GoCommit[0]
 	}
 
+	addBuilderToSet := func(bs *buildStatus, brev buildgo.BuilderRev) {
+		bs.trySet = ts
+		status[brev] = bs
+
+		idx := len(ts.builds)
+		ts.builds = append(ts.builds, bs)
+		go bs.start() // acquires statusMu itself, so in a goroutine
+		go ts.awaitTryBuild(idx, bs, brev)
+	}
+
 	go ts.notifyStarting()
-	for i, bconf := range builders {
+	for _, bconf := range builders {
 		brev := tryKeyToBuilderRev(bconf.Name, key, goRev)
 		bs, err := newBuild(brev)
 		if err != nil {
 			log.Printf("can't create build for %q: %v", brev, err)
 			continue
 		}
-		bs.trySet = ts
-		status[brev] = bs
-		ts.builds[i] = bs
-		go bs.start() // acquires statusMu itself, so in a goroutine
-		go ts.awaitTryBuild(i, bconf, bs, brev)
+		addBuilderToSet(bs, brev)
+	}
+
+	// Defensive check that the input is well-formed and each GoCommit
+	// has a GoBranch.
+	if len(work.GoBranch) < len(work.GoCommit) {
+		log.Printf("WARNING: len(GoBranch) of %d != len(GoCommit) of %d", len(work.GoBranch), len(work.GoCommit))
+		work.GoCommit = work.GoCommit[:len(work.GoBranch)]
+	}
+
+	// If there's more than one GoCommit, that means this is an x/* repo
+	// and we're testing against previous releases of Go.
+	for i, goRev := range work.GoCommit {
+		if i == 0 {
+			// Skip the i==0 element, which is handled above.
+			continue
+		}
+		branch := work.GoBranch[i]
+		brev := tryKeyToBuilderRev("linux-amd64", key, goRev)
+		bs, err := newBuild(brev)
+		if err != nil {
+			log.Printf("can't create build for %q: %v", brev, err)
+			continue
+		}
+		bs.goBranch = branch
+		addBuilderToSet(bs, brev)
 	}
 	return ts
 }
@@ -1184,7 +1217,7 @@ func (ts *trySet) notifyStarting() {
 //
 // If the build fails without getting to the end, it sleeps and
 // reschedules it, as long as it's still wanted.
-func (ts *trySet) awaitTryBuild(idx int, bconf dashboard.BuildConfig, bs *buildStatus, brev buildgo.BuilderRev) {
+func (ts *trySet) awaitTryBuild(idx int, bs *buildStatus, brev buildgo.BuilderRev) {
 	for {
 	WaitCh:
 		for {
@@ -1202,7 +1235,7 @@ func (ts *trySet) awaitTryBuild(idx int, bconf dashboard.BuildConfig, bs *buildS
 		}
 
 		if bs.hasEvent(eventDone) || bs.hasEvent(eventSkipBuildMissingDep) {
-			ts.noteBuildComplete(bconf, bs)
+			ts.noteBuildComplete(bs)
 			return
 		}
 
@@ -1241,7 +1274,7 @@ func (ts *trySet) cancelBuilds() {
 	// TODO(bradfitz): implement
 }
 
-func (ts *trySet) noteBuildComplete(bconf dashboard.BuildConfig, bs *buildStatus) {
+func (ts *trySet) noteBuildComplete(bs *buildStatus) {
 	bs.mu.Lock()
 	succeeded := bs.succeeded
 	var buildLog string
@@ -1253,12 +1286,12 @@ func (ts *trySet) noteBuildComplete(bconf dashboard.BuildConfig, bs *buildStatus
 
 	ts.mu.Lock()
 	if hasBenchResults {
-		ts.benchResults = append(ts.benchResults, bs.Name)
+		ts.benchResults = append(ts.benchResults, bs.NameAndBranch())
 	}
 	ts.remain--
 	remain := ts.remain
 	if !succeeded {
-		ts.failed = append(ts.failed, bconf.Name)
+		ts.failed = append(ts.failed, bs.NameAndBranch())
 	}
 	numFail := len(ts.failed)
 	benchResults := append([]string(nil), ts.benchResults...)
@@ -1282,7 +1315,7 @@ func (ts *trySet) noteBuildComplete(bconf dashboard.BuildConfig, bs *buildStatus
 		bs.failURL = failLogURL
 		bs.mu.Unlock()
 		ts.mu.Lock()
-		fmt.Fprintf(&ts.errMsg, "Failed on %s: %s\n", bs.Name, failLogURL)
+		fmt.Fprintf(&ts.errMsg, "Failed on %s: %s\n", bs.NameAndBranch(), failLogURL)
 		ts.mu.Unlock()
 
 		if numFail == 1 && remain > 0 {
@@ -1292,7 +1325,7 @@ func (ts *trySet) noteBuildComplete(bconf dashboard.BuildConfig, bs *buildStatus
 						"This change failed on %s:\n"+
 						"See %s\n\n"+
 						"Consult https://build.golang.org/ to see whether it's a new failure. Other builds still in progress; subsequent failure notices suppressed until final report.",
-					bs.Name, failLogURL),
+					bs.NameAndBranch(), failLogURL),
 			}); err != nil {
 				log.Printf("Failed to call Gerrit: %v", err)
 				return
@@ -3251,6 +3284,7 @@ type buildStatus struct {
 	// Immutable:
 	buildgo.BuilderRev
 	buildID   string // "B" + 9 random hex
+	goBranch  string // non-empty for subrepo trybots if not go master branch
 	conf      dashboard.BuildConfig
 	startTime time.Time // actually time of newBuild (~same thing); TODO(bradfitz): rename this createTime
 	trySet    *trySet   // or nil
@@ -3275,6 +3309,13 @@ type buildStatus struct {
 	useSnapshotMemo *bool // if non-nil, memoized result of useSnapshot
 }
 
+func (st *buildStatus) NameAndBranch() string {
+	if st.goBranch != "" {
+		return fmt.Sprintf("%s (go branch %s)", st.Name, st.goBranch)
+	}
+	return st.Name
+}
+
 func (st *buildStatus) setDone(succeeded bool) {
 	st.mu.Lock()
 	defer st.mu.Unlock()