CachedMessageQueue

Inherits: MessageQueue, ICleanable

Description

The CachedMessageQueue class allows you to create message queues that cache received messages in memory, to allow peek operations that may not be supported by the undelying queue.

Important points

• This queue is used as a base implementation for other queues.

Constructors

Creates a new instance of the persistence component.

public CachedMessageQueue(string name = null, MessagingCapabilities capabilities = null)

• name: string - (optional) queue name
• capabilities: MessagingCapabilities - (optional) capabilities of the message queue

Fields

Abstract methods

SubscribeAsync

Subscribes to the message broker.

protected abstract Task SubscribeAsync(string correlationId)

• correlationId: string - (optional) transaction id used to trace execution through the call chain.

UnsubscribeAsync

Unsubscribes from the message broker.

protected abstract Task UnsubscribeAsync(string correlationId)

• correlationId: string - (optional) transaction id used to trace execution through the call chain.

Instance methods

Clear

Clears component state.

public override Task ClearAsync(string correlationId)

• correlationId: string - (optional) transaction id used to trace execution through the call chain.

Configure

Configures a component by passing its configuration parameters.

public override Configure(ConfigParams config)

• config: ConfigParams - configuration parameters to be set.

EndListen

Ends listening for incoming messages. When this method is called, listen unblocks the thread and execution continues.

public override void EndListen(string correlationId)

• correlationId: string - (optional) transaction id used to trace execution through the call chain.

ListenAsync

Listens for incoming messages and blocks the current thread until the queue is closed. See IMessageReceiver, Receive

public override Task ListenAsync(string correlationId, IMessageReceiver receiver)

• correlationId: string - (optional) transaction id used to trace execution through the call chain.
• receiver: IMessageReceiver - receiver used to receive incoming messages.

OpenAsync

Opens the component.

public override Task OpenAsync(string correlationId)

• correlationId: string - (optional) transaction id used to trace execution through the call chain.

PeekAsync

Peeks a single incoming message from the queue without removing it. If there are no messages available in the queue, it returns null.

public override Task<MessageEnvelope> PeekAsync(string correlationId)

• correlationId: string - (optional) transaction id used to trace execution through the call chain.
• returns: Task<MessageEnvelope> - peeked message or null.

PeekBatchAsync

Peeks multiple incoming messages from the queue without removing them. If there are no messages available in the queue, it returns an empty list.

Important: This method is not supported by MQTT.

public override Task<List<MessageEnvelope>> PeekBatchAsync(string correlationId, int messageCount)

• correlationId: string - (optional) transaction id used to trace execution through the call chain.
• messageCount: int - maximum number of messages to peek.
• returns: Task<List<MessageEnvelope>> - list with peeked messages.

ReadMessageCountAsync

Reads the current number of messages in the queue to be delivered.

public override Task<long> ReadMessageCountAsync()

• returns: Task<long> - number of messages in the queue.

ReceiveAsync

Receives an incoming message and removes it from the queue.

public override Task<MessageEnvelope> ReceiveAsync(string correlationId, long waitTimeout)

• correlationId: string - (optional) transaction id used to trace execution through the call chain.
• waitTimeout: long - timeout in milliseconds to wait for a message to come.
• returns: Task<MessageEnvelope> - received message or null.

See also

• MessageQueue