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(IContext context)

• context: IContext - (optional) a context to trace execution through a call chain.

UnsubscribeAsync

Unsubscribes from the message broker.

protected abstract Task UnsubscribeAsync(IContext context)

• context: IContext - (optional) a context to trace execution through a call chain.

Instance methods

Clear

Clears component state.

public override Task ClearAsync(IContext context)

• context: IContext - (optional) a context to trace execution through a 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(IContext context)

• context: IContext - (optional) a context to trace execution through a call chain.

ListenAsync

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

public override Task ListenAsync(IContext context, IMessageReceiver receiver)

• context: IContext - (optional) a context to trace execution through a call chain.
• receiver: IMessageReceiver - receiver used to receive incoming messages.

OpenAsync

Opens the component.

public override Task OpenAsync(IContext context)

• context: IContext - (optional) a context to trace execution through a 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(IContext context)

• context: IContext - (optional) a context to trace execution through a 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(IContext context, int messageCount)

• context: IContext - (optional) a context to trace execution through a 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(IContext context, long waitTimeout)

• context: IContext - (optional) a context to trace execution through a call chain.
• waitTimeout: long - timeout in milliseconds to wait for a message to come.
• returns: Task<MessageEnvelope> - received message or null.

See also

• MessageQueue