Inner workings¶
This section contains information about the inner workings of RawRabbit. It can be a useful reference guide for users who wants to extend or modify the standard behaviour of the framework.
ChannelFactory¶
The default implementation of the IChannelFactory is aptly named ChannelFactory. It has two main methods
GetChannelAsyncreturns an existing open channel that is reused by other operations in the application.CreateChannelAsyncreturn an new, open channel that the caller is responsible to close.
Avoiding ‘Pipelining’ exceptions¶
It is forbidden to perform multiple synchronous operations on the same channel. Note that synchronous and asynchronous in this section does not refer to Microsoft’s Task execution, but rahter how the call is handled by the broker. Synchronous operations include declaring queues and exchanges. It is not adviced to use GetChannelAsync and perform a synchronious operation, as you may get a Pipelining of requests forbidden exception.
Managing channel count¶
The ChannelFactory is configured with the ChannelFactoryConfiguration object. The default behaviour is to re-use the same open channel whenever GetChannelAsync is called. MaxChannelCount states the maximum amout of channels in the channel pool.
Initialize multiple channels¶
The property InitialChannelCount can be used to define the number of channels that will be initialied as the ChannelFactory is initialzed.
Dynamic scaling of channel count¶
It is possible to open and close aditional channels if the workload for the currently open channels are above the specified threshold WorkThreshold. Note that EnableScaleUp and/or EnableScaleDown needs to be set to true to have scaling enabled. ScaleInterval defines the interval for checking if scaling should be performed. If scaling down is enable, the GracefulCloseInterval is used to know how long to wait before closing the channel. It is recommended to let the graceful close interval be a couple of minutes to make sure that the channel is not in used in other classes.
Alternative implementations¶
The ThreadBasedChannelFactory uses a ThreadLocal<IModel> property to make sure that channels are only used in one thread.
ConsumerFactory¶
It is the consumer factory’s responsibility to wire up and return an IRawConsumer. The IRawConsumer has to implementations, EventingRawConsumer (default) that inherits from EventingBasicConsumer and QueueingRawConsumer that inherits from QueueingBasicConsumer.
TopologyProvider¶
The TopologyProvider has async methods for creating topology features, such as queues and exchanges. In order to prevent pipelinging exception, it uses it’s own private channel that is disposes two seconds after last usage. It keeps a list of queues and exchanges that is has declared, so that if a DeclareQueueAsync is called for a queue recently declared, it returns without doing a roundtrip to the broker.