jschoubben
769dcf16e3
A seat's event kept apart from its family (the node-engine seat's running, kept last per subject; mesh-delivery's owed, a stream with an age and a cap) had no helper: EventHub binds only the shared events stream, and dev-G-engine and dev-G-forge each met it. process.SeatStreamName is the bus's name of a contract's Stream<E> (SEAT_<seat>_<event>), one rule for its maker and its hearers; Account.SeatEventConsumerConfig the module's durable as the maker makes it (last per subject where the event is kept so); Account.HearSeatEvents binds and pulls it, making nothing. Builds: design 47 G §260, §24, §39, §146, §153, §199 Claude-Session: https://claude.ai/code/session_01JG73KEq4zoDfM9WtYpcQgZ
61 lines
3.2 KiB
Go
61 lines
3.2 KiB
Go
package process
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import (
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"context"
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"fmt"
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"strings"
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"github.com/nats-io/nats.go/jetstream"
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)
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// A seat's event kept in a stream of its own (seatdef's `keep`: the last message of each subject, or a stream with an age
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// and a cap), not on the shared events stream (novox/hq design 47: the node-engine seat's `running.<node>.<module>`, the
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// seat mesh-delivery's `owed`). A generated contract names that stream as `<seat>.<event>` (Stream<E>, seatdef.KeptStream);
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// these are the one rule, for the part that makes the stream and its consumers (the grants part, from each module's
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// `consumes`) and for every part that hears it, of the stream's name on the bus and the module's durable on it.
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// SeatStreamPrefix starts the bus's name of every stream a seat's event is kept in apart from its family.
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const SeatStreamPrefix = "SEAT_"
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// SeatStreamName is the bus's name of the stream a contract names kept (`<seat>.<event>`): the bus takes no dot in a
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// stream's name, so `SEAT_<seat>_<event>`, each dot an underscore (`node-engine.running` is `SEAT_node-engine_running`).
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func SeatStreamName(kept string) string {
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return SeatStreamPrefix + strings.ReplaceAll(kept, ".", "_")
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}
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// SeatEventConsumerConfig is the module's durable on a seat event's own stream as its maker makes it: <node>_<module>, as
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// on the shared stream, filtered to the subjects the module consumes, acknowledged one by one; for an event kept last
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// per subject it starts from the last message of each subject, never from now, so a consumer made after a subject was
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// last said still hears it, and two parts' consumers made at different times hold the same (design 47).
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func (a Account) SeatEventConsumerConfig(subjects []string, lastPerSubject bool) jetstream.ConsumerConfig {
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cfg := jetstream.ConsumerConfig{Durable: a.EventConsumerName(), AckPolicy: jetstream.AckExplicitPolicy, FilterSubjects: subjects}
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if lastPerSubject {
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cfg.DeliverPolicy = jetstream.DeliverLastPerSubjectPolicy
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}
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return cfg
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}
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// HearSeatEvents binds the module's durable on the stream of kept (a contract's Stream<E>) and pulls it, handing each
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// message to handle, which acknowledges it; every error the bus reports while hearing is said through logf. Like
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// EventHub it makes neither the stream nor the consumer: one the bus does not hold yet is this call's error, naming
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// both, and a later call binds it. The caller stops the returned context.
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func (a Account) HearSeatEvents(ctx context.Context, js jetstream.JetStream, kept string, handle func(jetstream.Msg), logf func(string, ...any)) (jetstream.ConsumeContext, error) {
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if handle == nil {
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return nil, fmt.Errorf("hearing %s needs a handler", kept)
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}
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if logf == nil {
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logf = func(string, ...any) {}
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}
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stream := SeatStreamName(kept)
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cons, err := a.EventConsumer(ctx, js, stream)
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if err != nil {
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return nil, fmt.Errorf("the consumer %s on %s (the seat's stream %s) is not there: %w", a.EventConsumerName(), stream, kept, err)
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}
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cc, err := HearEvents(cons, handle, logf)
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if err != nil {
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return nil, fmt.Errorf("the consumer %s on %s (the seat's stream %s) is not heard: %w", a.EventConsumerName(), stream, kept, err)
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}
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logf("events: the consumer %s on %s (the seat's stream %s) is heard", a.EventConsumerName(), stream, kept)
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return cc, nil
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}
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