131 lines
4.3 KiB
Go
131 lines
4.3 KiB
Go
package process
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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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"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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stdio "git.novox.be/novox/mesh-sdk/go"
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)
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// stateTimeout bounds a state call (Get, Create, Update) and an Emit (emit.go): a denied publish is
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// caught at once by Conn's own ErrorHandler (conn.go withRefusal/publishRefused), never waited out, so
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// this stays the ordinary request bound and is not exposed for a test to shrink.
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const stateTimeout = 30 * time.Second
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// State is one of this process's module's states, read and written on this connection (novox/hq ADR 0436
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// clause 4), in the bucket <module>_<name> (mesh-controller internal/broker/state.go:49) — only as the
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// account's grants allow. It satisfies go/asker's Store.
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type State struct {
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Module string
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Name string
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// kv binds this state's underlying key-value store: a live connection's own (Conn.State), or, in a
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// unit test, a fake that never reaches a bus.
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kv func(ctx context.Context) (jetstream.KeyValue, error)
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}
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// bucket is this state's name on the bus.
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func (s State) bucket() string { return s.Module + "_" + s.Name }
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// State is the named state this connection's module keeps, bound lazily to its bucket on each call so a
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// bucket the account is not granted fails at the call that needed it, naming the bucket. The bind itself
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// (js.KeyValue) is what asks $JS.API.STREAM.INFO.KV_<bucket>, so it is what withRefusal watches: a bucket
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// not granted is refused there, promptly, as nats.ErrPermissionViolation.
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func (c *Conn) State(name string) State {
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bucket := c.account.Module + "_" + name
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return State{Module: c.account.Module, Name: name, kv: func(ctx context.Context) (jetstream.KeyValue, error) {
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js, err := jetstream.New(c.nc)
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if err != nil {
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return nil, err
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}
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subject := "$JS.API.STREAM.INFO.KV_" + bucket
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ctx, stop := c.withRefusal(ctx, subject)
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defer stop()
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kv, err := js.KeyValue(ctx, bucket)
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if err != nil {
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if errors.Is(context.Cause(ctx), errPermissionRefused) {
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return nil, fmt.Errorf("%w: publishing %s", nats.ErrPermissionViolation, subject)
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}
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return nil, err
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}
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return kv, nil
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}}
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}
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func (s State) store(ctx context.Context) (jetstream.KeyValue, error) {
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kv, err := s.kv(ctx)
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if err != nil {
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return nil, fmt.Errorf("%s's state %s (bucket %s): %w", s.Module, s.Name, s.bucket(), err)
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}
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return kv, nil
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}
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// Get is a key's current value, or nil when it has none.
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func (s State) Get(key string) (*stdio.StateEntry, error) {
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ctx, cancel := context.WithTimeout(context.Background(), stateTimeout)
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defer cancel()
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kv, err := s.store(ctx)
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if err != nil {
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return nil, err
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}
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entry, err := kv.Get(ctx, key)
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if errors.Is(err, jetstream.ErrKeyNotFound) {
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return nil, nil
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}
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if err != nil {
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return nil, fmt.Errorf("%s's state %s, key %s: %w", s.Module, s.Name, key, err)
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}
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return &stdio.StateEntry{Key: key, Value: json.RawMessage(entry.Value()), Revision: entry.Revision()}, nil
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}
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// Create writes a key only when it has none, and returns the revision; a key that has one is refused as
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// stdio.ErrChanged.
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func (s State) Create(key string, value any) (uint64, error) {
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ctx, cancel := context.WithTimeout(context.Background(), stateTimeout)
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defer cancel()
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kv, err := s.store(ctx)
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if err != nil {
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return 0, err
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}
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data, err := json.Marshal(value)
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if err != nil {
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return 0, err
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}
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rev, err := kv.Create(ctx, key, data)
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if errors.Is(err, jetstream.ErrKeyExists) {
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return 0, fmt.Errorf("%s: %w", key, stdio.ErrChanged)
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}
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if err != nil {
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return 0, fmt.Errorf("%s's state %s, key %s: %w", s.Module, s.Name, key, err)
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}
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return rev, nil
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}
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// Update writes a key only when it is still at revision, and returns the new one; a key changed meanwhile
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// is refused as stdio.ErrChanged.
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func (s State) Update(key string, value any, revision uint64) (uint64, error) {
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ctx, cancel := context.WithTimeout(context.Background(), stateTimeout)
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defer cancel()
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kv, err := s.store(ctx)
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if err != nil {
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return 0, err
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}
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data, err := json.Marshal(value)
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if err != nil {
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return 0, err
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}
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rev, err := kv.Update(ctx, key, data, revision)
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if errors.Is(err, jetstream.ErrKeyRevisionMismatch) {
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return 0, fmt.Errorf("%s: %w", key, stdio.ErrChanged)
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}
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if err != nil {
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return 0, fmt.Errorf("%s's state %s, key %s: %w", s.Module, s.Name, key, err)
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}
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return rev, nil
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}
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