81 lines
2.4 KiB
Go
81 lines
2.4 KiB
Go
// Copyright (c) Mainflux
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// SPDX-License-Identifier: Apache-2.0
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package messaging
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import "context"
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type DeliveryPolicy uint8
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const (
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// DeliverNewPolicy will only deliver new messages that are sent after the consumer is created.
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// This is the default policy.
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DeliverNewPolicy DeliveryPolicy = iota
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// DeliverAllPolicy starts delivering messages from the very beginning of a stream.
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DeliverAllPolicy
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)
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// Publisher specifies message publishing API.
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type Publisher interface {
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// Publishes message to the stream.
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Publish(ctx context.Context, topic string, msg *Message) error
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// Close gracefully closes message publisher's connection.
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Close() error
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}
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// MessageHandler represents Message handler for Subscriber.
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type MessageHandler interface {
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// Handle handles messages passed by underlying implementation.
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Handle(msg *Message) error
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// Cancel is used for cleanup during unsubscribing and it's optional.
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Cancel() error
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}
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type SubscriberConfig struct {
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ID string
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Topic string
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Handler MessageHandler
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DeliveryPolicy DeliveryPolicy
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}
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// Subscriber specifies message subscription API.
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type Subscriber interface {
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// Subscribe subscribes to the message stream and consumes messages.
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Subscribe(ctx context.Context, cfg SubscriberConfig) error
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// Unsubscribe unsubscribes from the message stream and
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// stops consuming messages.
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Unsubscribe(ctx context.Context, id, topic string) error
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// Close gracefully closes message subscriber's connection.
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Close() error
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}
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// PubSub represents aggregation interface for publisher and subscriber.
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type PubSub interface {
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Publisher
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Subscriber
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}
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// Option represents optional configuration for message broker.
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//
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// This is used to provide optional configuration parameters to the
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// underlying publisher and pubsub implementation so that it can be
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// configured to meet the specific needs.
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//
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// For example, it can be used to set the message prefix so that
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// brokers can be used for event sourcing as well as internal message broker.
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// Using value of type interface is not recommended but is the most suitable
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// for this use case as options should be compiled with respect to the
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// underlying broker which can either be RabbitMQ or NATS.
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//
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// The example below shows how to set the prefix and jetstream stream for NATS.
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//
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// Example:
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//
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// broker.NewPublisher(ctx, url, broker.Prefix(eventsPrefix), broker.JSStream(js))
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type Option func(vals interface{}) error
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