jschoubben
4bcb6f86a4
A seat event's stream has one bus name, seatdef.KeptStream's, which the generated contract carries as Stream<E>: HearSeatEvents takes it as it stands and refuses a dotted or unprefixed name by name, so no part makes the name a second time (SEAT_SEAT_...). Builds: design 47 G §260 Claude-Session: https://claude.ai/code/session_01JG73KEq4zoDfM9WtYpcQgZ
64 lines
3.2 KiB
Go
64 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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"git.novox.be/novox/mesh-sdk/go/seatdef"
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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`). Its name on the bus is seatdef.KeptStream's, `SEAT_<seat>_<event>`, which a generated
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// contract carries as Stream<E>: one name in one place. These are the one rule, for the part that makes the stream's
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// consumers (the grants part, from each module's `consumes`) and for every part that hears it, of the module's durable
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// on it.
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// keptStreamName is whether stream is a name seatdef.KeptStream gives: the bus's, with its prefix and no dot.
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func keptStreamName(stream string) bool {
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return strings.HasPrefix(stream, seatdef.KeptStreamPrefix) && len(stream) > len(seatdef.KeptStreamPrefix) &&
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!strings.Contains(stream, ".")
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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 (a contract's Stream<E>, as it stands) 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, stream string, handle func(jetstream.Msg), logf func(string, ...any)) (jetstream.ConsumeContext, error) {
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if !keptStreamName(stream) {
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return nil, fmt.Errorf("%q is not the bus's name of a seat event's stream: a contract's Stream<E> is %s<seat>_<event>, "+
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"with no dot (seatdef.KeptStream)", stream, seatdef.KeptStreamPrefix)
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}
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if handle == nil {
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return nil, fmt.Errorf("hearing %s needs a handler", stream)
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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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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 is not there: %w", a.EventConsumerName(), stream, 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 is not heard: %w", a.EventConsumerName(), stream, err)
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}
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logf("events: the consumer %s on %s is heard", a.EventConsumerName(), stream)
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return cc, nil
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}
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