All streaming metrics are automatically collected by Finagle by setting isChunked as true on Http request or response. All metrics are traced using the binary annotations with a clnt/<clnt_name>/ prefix on the client side, and srv/ prefix on the server side.

The following metrics are added by :finagle-http-src:StreamingStatsFilter <com/twitter/finagle/http/filter/StreamingStatsFilter.scala>

http/stream/request/closed A counter of the number of closed request streams.

http/stream/request/duration_ms A histogram of the duration of the lifetime of request streams, from the time a stream is initialized until it's closed, in milliseconds.

http/stream/request/failures A counter of the number of times any failure has been observed in the middle of a request stream.

http/stream/request/failures/<exception_name> A counter of the number of times a specific exception has been thrown in the middle of a request stream.

http/stream/request/opened A counter of the number of opened request streams.

http/stream/request/pending A gauge of the number of pending request streams.

http/stream/response/closed A counter of the number of closed response streams.

http/stream/response/duration_ms A histogram of the duration of the lifetime of response streams, from the time a stream is initialized until it's closed, in milliseconds.

http/stream/response/failures A counter of the number of times any failure has been observed in the middle of a response stream.

http/stream/response/failures/<exception_name> A counter of the number of times a specific exception has been thrown in the middle of a response stream.

http/stream/response/opened A counter of the number of opened response streams.

http/stream/response/pending A gauge of the number of pending response streams.

stream/request/chunk_payload_bytes verbosity:debug A histogram of the number of bytes per chunk's payload of request streams. This is measured in :finagle-http-src:c.t.finagle.http.filter.PayloadSizeFilter <com/twitter/finagle/http/filter/PayloadSizeFilter.scala>

stream/response/chunk_payload_bytes verbosity:debug A histogram of the number of bytes per chunk's payload of response streams. This is measured in :finagle-http-src:c.t.finagle.http.filter.PayloadSizeFilter <com/twitter/finagle/http/filter/PayloadSizeFilter.scala>

You could derive the streaming success rate of:

• the total number of streams number of successful streams divided by number of total streams
• closed streams number of successful streams divided by number of closed streams Here we assume a success stream as a stream terminated without an exception or a stream that has not terminated yet.

Take request stream as an example, assuming your counters are not "latched", which means that their values are monotonically increasing:

Success rate of total number of streams:

1 - (rated_counter(stream/request/failures) / (gauge(stream/request/pending) + rated_counter(stream/request/closed)))

Success rate of number of closed streams:

1 - (rated_counter(stream/request/failures) / rated_counter(stream/request/closed))