Batched Invocation Interceptors

Batch invocation interceptors allow you to implement your own auto-flush algorithm or receive notification when an auto-flush fails.

You install an interceptor by setting the batchRequestInterceptor field of the InitializationData object you use to create your communicator. The communicator invokes the interceptor for each batch request, passing the following arguments:

• req - An object representing the batch request being queued

• count - The number of requests currently in the queue

• size - The number of bytes consumed by the requests currently in the queue

The request represented by req is not included in the count and size figures.

A batch request is not queued until the interceptor calls enqueue. The minimal interceptor implementation is therefore:

A more sophisticated implementation might use its own logic for automatically flushing queued requests:

#TODO: Python version

In this example, the implementation consults the existing Ice property Ice.BatchAutoFlushSize to determine the limit that triggers an automatic flush. If a flush is necessary, the interceptor can obtain the relevant proxy by calling getProxy on the BatchRequest object.

Specifying your own exception handler when calling ice_flushBatchRequestsAsync gives you the ability to take action if a failure occurs (Ice's default automatic flushing implementation ignores any errors). Aside from logging a message, your options are somewhat limited because it's not possible for the interceptor to force a retry.

For batch datagram proxies, we recommend using a maximum queue size that is smaller than the network MTU to minimize the risk that datagram fragmentation could cause an entire batch to be lost.