92 lines
3.9 KiB
Go
92 lines
3.9 KiB
Go
package process
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import (
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"context"
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"errors"
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"fmt"
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"strings"
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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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)
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// What a module's own principal reaches on the bus beyond a process account's queue (novox/hq issue 1242): its
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// own credential, its own stream and its durable consumer on the shared events stream. These helpers are the one
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// place a long-running part of a module (a daemon the module's delivery runs) learns them, so no part hand-writes
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// the connection, the subject spaces or the consumer's name.
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// EventsStream is the shared stream every module's events (mesh.mod.<module>.event.>) are on; a module's consumer
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// on it is the durable <node>_<module> the controller makes (mesh-controller internal/broker/nats.go
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// consumerStream, consumerDurable).
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const EventsStream = "EVENTS"
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// BrokerFileEnv names the environment variable holding the path of the module's own broker credential.
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const BrokerFileEnv = "MESH_BROKER_FILE"
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// ReadBrokerAccount reads the module's own credential from the file BrokerFileEnv names in getenv.
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func ReadBrokerAccount(getenv func(string) string) (Account, error) {
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path := strings.TrimSpace(getenv(BrokerFileEnv))
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if path == "" {
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return Account{}, errors.New(BrokerFileEnv + " is not set, so there is no credential to hear the bus with")
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}
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return ReadAccount(path)
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}
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// DialOptions is the option list Dial connects with: named <node>.<module>, as the account's user on its own
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// inbox prefix, reconnecting without limit and retrying a first connect that fails, pinned to the account's
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// fingerprint when it carries one; opts follow, so a caller may add a handler or override one.
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func (a Account) DialOptions(opts ...nats.Option) []nats.Option {
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all := []nats.Option{
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nats.Name(a.Node + "." + a.Module),
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nats.UserInfo(a.User, a.Password),
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nats.CustomInboxPrefix(a.InboxPrefix()),
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nats.MaxReconnects(-1),
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nats.RetryOnFailedConnect(true),
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}
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if strings.TrimSpace(a.Fingerprint) != "" {
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all = append(all, nats.Secure(PinnedToFingerprint(a.Fingerprint)))
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}
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return append(all, opts...)
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}
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// Dial connects as the module's own principal and opens JetStream on the connection. The caller closes the
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// connection.
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func (a Account) Dial(opts ...nats.Option) (*nats.Conn, jetstream.JetStream, error) {
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nc, err := nats.Connect(a.URL, a.DialOptions(opts...)...)
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if err != nil {
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return nil, nil, fmt.Errorf("connecting to the bus: %w", err)
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}
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js, err := jetstream.New(nc)
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if err != nil {
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nc.Close()
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return nil, nil, err
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}
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return nc, js, nil
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}
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// EventSubject is where the module's event lands on the shared events stream: mesh.mod.<module>.event.<event>.
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func (a Account) EventSubject(event string) string { return "mesh.mod." + a.Module + ".event." + event }
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// StreamSubject is where the module's event lands on a stream of its own: mesh.stream.<module>.event.<event>
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// (mesh-controller internal/broker/modstreams.go ModuleStreamSubject).
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func (a Account) StreamSubject(event string) string {
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return "mesh.stream." + a.Module + ".event." + event
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}
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// EventConsumerName is the module's durable consumer on a stream it is granted: <node>_<module>.
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func (a Account) EventConsumerName() string { return a.Node + "_" + a.Module }
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// EventConsumer binds the module's durable consumer on stream (EventsStream, or a stream of another module it is
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// granted).
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func (a Account) EventConsumer(ctx context.Context, js jetstream.JetStream, stream string) (jetstream.Consumer, error) {
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return js.Consumer(ctx, stream, a.EventConsumerName())
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}
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// HearEvents pulls from cons, handing each message to handle, and says every error the bus reports while
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// hearing through logf ("hearing the bus: ..."). The caller stops the returned context.
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func HearEvents(cons jetstream.Consumer, handle func(jetstream.Msg), logf func(string, ...any)) (jetstream.ConsumeContext, error) {
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return cons.Consume(handle, jetstream.ConsumeErrHandler(func(_ jetstream.ConsumeContext, err error) {
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logf("hearing the bus: %v", err)
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}))
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}
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