Archived
issue 974: the checks are queued by pull request on two work-queue streams, taken after a delivery build, dropped when judged, stopped when their key moves; the reordering and the forge-asking end are gone
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@@ -0,0 +1,170 @@
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package link
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import (
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"context"
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"encoding/json"
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"errors"
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"fmt"
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"strconv"
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"strings"
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"time"
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"github.com/nats-io/nats.go"
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"github.com/nats-io/nats.go/jetstream"
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"github.com/novox/mesh-controller/internal/broker"
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)
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// A pull request's check is queued by the pull request (novox/hq ADR 0406 §3, §4, issue 974).
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// SupersededByKey is the outcome of a check that stopped because its pull request's key moved on: its head or its trunk
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// commit is no longer the one it was asked for. Said as the check's failure, as a kill is; nothing is asked of the forge.
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const SupersededByKey = "superseded: the pull request's key moved on"
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// unsafeToken is what may not stand in a subject token or a key.
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var unsafeToken = strings.NewReplacer(".", "_", "*", "_", ">", "_", " ", "_", "/", "_", "\t", "_", "\n", "_")
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// tokenOf is a name as one subject token: any dot, wildcard or space replaced by an underscore.
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func tokenOf(name string) string {
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if name == "" {
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return "_"
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}
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return unsafeToken.Replace(name)
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}
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// PullKeyOf is a pull request's key in mesh-delivery's bucket, and the last tokens of the subject its check is asked on:
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// `<owner>.<repo>.<number>`, a dot in a name made an underscore.
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func PullKeyOf(owner, repo string, number int) string {
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return tokenOf(owner) + "." + tokenOf(repo) + "." + strconv.Itoa(number)
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}
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// CheckSubjectOf is the subject a check is asked on, and whether it has one of its own: a check of a pull request on
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// the ready queue or the other, by the pull request; a delivery group's composed check by `group.<name>`; any other
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// check (a branch tried before its pull request) by its own id, so it replaces nothing.
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func CheckSubjectOf(seat string, r BuildRequest) (string, bool) {
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c := r.Check
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if seat != broker.TheBuildSeat || c == nil {
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return "", false
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}
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prefix := broker.CheckSubjectPrefix(seat, c.Ready)
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switch {
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case c.Group != "":
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return prefix + "group." + tokenOf(c.Group), true
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case c.Try || c.Number <= 0:
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return prefix + "try." + tokenOf(r.ID), true
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}
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return prefix + PullKeyOf(c.Owner, c.Repo, c.Number), true
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}
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// WorkSubjectOf is where an ask is put: a check on the build seat on its own queue, anything else on the seat's.
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func WorkSubjectOf(seat string, r BuildRequest) string {
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if subject, ok := CheckSubjectOf(seat, r); ok {
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return subject
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}
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return BuildWorkOf(seat)
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}
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// PullKey is what mesh-delivery keeps of a pull request (ADR 0406 §4): its head, the trunk commit its current check is
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// asked against, and its verdict once judged.
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type PullKey struct {
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Head string `json:"head"`
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Trunk string `json:"trunk"`
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Verdict string `json:"verdict,omitempty"`
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}
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// sameCommit says two spellings name one commit; either may be short, but not under twelve characters.
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func sameCommit(a, b string) bool {
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return a == b || SameHead(a, b)
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}
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// Moved says a key no longer holds what a check was asked for: its head or its trunk commit differs.
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func (k PullKey) Moved(head, trunk string) bool {
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return !sameCommit(k.Head, head) || (trunk != "" && k.Trunk != "" && !sameCommit(k.Trunk, trunk))
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}
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// Judged says a key holds the verdict of the check of this head against this trunk commit.
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func (k PullKey) Judged(head, trunk string) bool {
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return k.Verdict != "" && sameCommit(k.Head, head) && sameCommit(k.Trunk, trunk) && trunk != ""
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}
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// ReadPullKey reads a pull request's key from mesh-delivery's bucket: false when it has none.
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func ReadPullKey(ctx context.Context, conn *nats.Conn, owner, repo string, number int) (PullKey, bool, error) {
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api, err := jetstream.New(conn)
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if err != nil {
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return PullKey{}, false, err
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}
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kv, err := api.KeyValue(ctx, broker.PullsBucket)
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if err != nil {
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return PullKey{}, false, fmt.Errorf("the pull requests' keys: %w", err)
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}
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e, err := kv.Get(ctx, PullKeyOf(owner, repo, number))
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if errors.Is(err, jetstream.ErrKeyNotFound) {
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return PullKey{}, false, nil
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}
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if err != nil {
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return PullKey{}, false, err
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}
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var key PullKey
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if err := json.Unmarshal(e.Value(), &key); err != nil {
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return PullKey{}, false, fmt.Errorf("the key of %s/%s#%d is not a pull request's: %w", owner, repo, number, err)
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}
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return key, true, nil
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}
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// WatchPull calls moved once when the pull request's key moves on from what this check was asked for — its head or its
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// trunk commit differs — and not for a key that only gains its verdict. It hears updates, not the key as it stands: the
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// key and the request are written for one announcement by two writers, so a key found older than the request is not
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// a move. The check is then stopped by whoever asked for it, without asking the forge (novox/hq issue 726). The stop
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// ends the watch.
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func WatchPull(ctx context.Context, conn *nats.Conn, r BuildRequest, moved func(PullKey)) (stop func(), err error) {
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c := r.Check
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if c == nil || c.Group != "" || c.Try || c.Number <= 0 {
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return func() {}, nil
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}
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api, err := jetstream.New(conn)
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if err != nil {
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return nil, err
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}
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kv, err := api.KeyValue(ctx, broker.PullsBucket)
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if err != nil {
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return nil, fmt.Errorf("the pull requests' keys: %w", err)
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}
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watching, end := context.WithCancel(ctx)
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w, err := kv.Watch(watching, PullKeyOf(c.Owner, c.Repo, c.Number), jetstream.UpdatesOnly())
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if err != nil {
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end()
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return nil, err
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}
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go func() {
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defer w.Stop()
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for {
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select {
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case <-watching.Done():
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return
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case e, ok := <-w.Updates():
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if !ok {
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return
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}
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if e == nil || e.Operation() != jetstream.KeyValuePut {
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continue
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}
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var key PullKey
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if json.Unmarshal(e.Value(), &key) != nil {
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continue
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}
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if key.Moved(r.Ref, c.Trunk) {
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moved(key)
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return
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}
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}
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}
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}()
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return end, nil
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}
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// checkTakeWait is how long a taking loop waits on one queue for an ask that is not there, and takeIdleWait how long it
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// waits on the first when all three are empty.
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const (
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checkTakeWait = 30 * time.Millisecond
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takeIdleWait = time.Second
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)
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