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@@ -0,0 +1,246 @@
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+// Copyright (C) 2024 The Syncthing Authors.
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+//
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+// This Source Code Form is subject to the terms of the Mozilla Public
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+// License, v. 2.0. If a copy of the MPL was not distributed with this file,
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+// You can obtain one at https://mozilla.org/MPL/2.0/.
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+
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+package main
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+
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+import (
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+ "context"
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+ "fmt"
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+ "io"
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+
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+ amqp "github.com/rabbitmq/amqp091-go"
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+ "github.com/thejerf/suture/v4"
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+)
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+
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+type amqpReplicator struct {
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+ suture.Service
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+ broker string
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+ sender *amqpSender
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+ receiver *amqpReceiver
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+ outbox chan ReplicationRecord
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+}
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+
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+func newAMQPReplicator(broker, clientID string, db database) *amqpReplicator {
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+ svc := suture.New("amqpReplicator", suture.Spec{PassThroughPanics: true})
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+
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+ sender := &amqpSender{
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+ broker: broker,
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+ clientID: clientID,
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+ outbox: make(chan ReplicationRecord, replicationOutboxSize),
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+ }
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+ svc.Add(sender)
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+
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+ receiver := &amqpReceiver{
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+ broker: broker,
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+ clientID: clientID,
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+ db: db,
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+ }
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+ svc.Add(receiver)
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+
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+ return &amqpReplicator{
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+ Service: svc,
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+ broker: broker,
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+ sender: sender,
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+ receiver: receiver,
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+ outbox: make(chan ReplicationRecord, replicationOutboxSize),
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+ }
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+}
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+
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+func (s *amqpReplicator) send(key string, ps []DatabaseAddress, seen int64) {
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+ s.sender.send(key, ps, seen)
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+}
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+
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+type amqpSender struct {
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+ broker string
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+ clientID string
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+ outbox chan ReplicationRecord
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+}
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+
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+func (s *amqpSender) Serve(ctx context.Context) error {
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+ conn, ch, err := amqpChannel(s.broker)
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+ if err != nil {
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+ return err
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+ }
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+ defer ch.Close()
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+ defer conn.Close()
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+
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+ buf := make([]byte, 1024)
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+ for {
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+ select {
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+ case rec := <-s.outbox:
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+ size := rec.Size()
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+ if len(buf) < size {
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+ buf = make([]byte, size)
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+ }
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+
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+ n, err := rec.MarshalTo(buf)
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+ if err != nil {
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+ replicationSendsTotal.WithLabelValues("error").Inc()
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+ return fmt.Errorf("replication marshal: %w", err)
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+ }
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+
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+ err = ch.PublishWithContext(ctx,
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+ "discovery", // exchange
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+ "", // routing key
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+ false, // mandatory
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+ false, // immediate
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+ amqp.Publishing{
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+ ContentType: "application/protobuf",
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+ Body: buf[:n],
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+ AppId: s.clientID,
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+ })
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+ if err != nil {
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+ replicationSendsTotal.WithLabelValues("error").Inc()
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+ return fmt.Errorf("replication publish: %w", err)
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+ }
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+
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+ replicationSendsTotal.WithLabelValues("success").Inc()
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+
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+ case <-ctx.Done():
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+ return nil
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+ }
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+ }
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+}
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+
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+func (s *amqpSender) String() string {
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+ return fmt.Sprintf("amqpSender(%q)", s.broker)
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+}
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+
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+func (s *amqpSender) send(key string, ps []DatabaseAddress, seen int64) {
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+ item := ReplicationRecord{
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+ Key: key,
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+ Addresses: ps,
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+ Seen: seen,
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+ }
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+
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+ // The send should never block. The inbox is suitably buffered for at
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+ // least a few seconds of stalls, which shouldn't happen in practice.
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+ select {
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+ case s.outbox <- item:
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+ default:
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+ replicationSendsTotal.WithLabelValues("drop").Inc()
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+ }
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+}
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+
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+type amqpReceiver struct {
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+ broker string
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+ clientID string
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+ db database
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+}
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+
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+func (s *amqpReceiver) Serve(ctx context.Context) error {
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+ conn, ch, err := amqpChannel(s.broker)
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+ if err != nil {
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+ return err
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+ }
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+ defer ch.Close()
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+ defer conn.Close()
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+
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+ msgs, err := amqpConsume(ch)
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+ if err != nil {
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+ return err
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+ }
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+
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+ for {
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+ select {
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+ case msg, ok := <-msgs:
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+ if !ok {
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+ return fmt.Errorf("subscription closed: %w", io.EOF)
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+ }
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+
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+ // ignore messages from ourself
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+ if msg.AppId == s.clientID {
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+ continue
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+ }
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+
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+ var rec ReplicationRecord
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+ if err := rec.Unmarshal(msg.Body); err != nil {
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+ replicationRecvsTotal.WithLabelValues("error").Inc()
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+ return fmt.Errorf("replication unmarshal: %w", err)
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+ }
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+
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+ if err := s.db.merge(rec.Key, rec.Addresses, rec.Seen); err != nil {
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+ return fmt.Errorf("replication database merge: %w", err)
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+ }
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+
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+ replicationRecvsTotal.WithLabelValues("success").Inc()
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+
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+ case <-ctx.Done():
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+ return nil
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+ }
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+ }
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+}
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+
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+func (s *amqpReceiver) String() string {
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+ return fmt.Sprintf("amqpReceiver(%q)", s.broker)
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+}
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+
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+func amqpChannel(dst string) (*amqp.Connection, *amqp.Channel, error) {
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+ conn, err := amqp.Dial(dst)
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+ if err != nil {
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+ return nil, nil, fmt.Errorf("AMQP dial: %w", err)
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+ }
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+
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+ ch, err := conn.Channel()
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+ if err != nil {
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+ return nil, nil, fmt.Errorf("AMQP channel: %w", err)
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+ }
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+
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+ err = ch.ExchangeDeclare(
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+ "discovery", // name
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+ "fanout", // type
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+ false, // durable
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+ false, // auto-deleted
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+ false, // internal
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+ false, // no-wait
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+ nil, // arguments
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+ )
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+ if err != nil {
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+ return nil, nil, fmt.Errorf("AMQP declare exchange: %w", err)
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+ }
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+
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+ return conn, ch, nil
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+}
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+
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+func amqpConsume(ch *amqp.Channel) (<-chan amqp.Delivery, error) {
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+ q, err := ch.QueueDeclare(
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+ "", // name
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+ false, // durable
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+ false, // delete when unused
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+ true, // exclusive
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+ false, // no-wait
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+ nil, // arguments
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+ )
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+ if err != nil {
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+ return nil, fmt.Errorf("AMQP declare queue: %w", err)
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+ }
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+
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+ err = ch.QueueBind(
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+ q.Name, // queue name
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+ "", // routing key
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+ "discovery", // exchange
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+ false,
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+ nil,
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+ )
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+ if err != nil {
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+ return nil, fmt.Errorf("AMQP bind queue: %w", err)
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+ }
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+
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+ msgs, err := ch.Consume(
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+ q.Name, // queue
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+ "", // consumer
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+ true, // auto-ack
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+ false, // exclusive
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+ false, // no-local
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+ false, // no-wait
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+ nil, // args
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+ )
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+ if err != nil {
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+ return nil, fmt.Errorf("AMQP consume: %w", err)
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+ }
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+
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+ return msgs, nil
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+}
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Jakob Borg