isabella232 / varz-firehose-nozzle

Expose metrics from the Loggregator Firehose to /varz for legacy monitoring applications

(DEPRECATED) varz-firehose-nozzle

The varz nozzle is no longer actively supported.

• note that a known problem is that unit tests will fail if upgraded to go 1.5
• The recommended way to get metrics is via the firehose

Summary

Expose metrics from the Loggregator Firehose to /varz for legacy monitoring applications

slowConsumerAlert

For the most part, the varz-firehose-nozzle emits metrics from the loggregator firehose without processing them too much. A notable exception is the *.varz.nozzle.slowConsumerAlert metric. The metric is a binary value (0 or 1) indicating whether or not the nozzle consuming metrics at the same rate that it is receiving them from the firehose: 0 means the the nozzle is keeping up with the firehose, and 1 means that the nozzle is falling behind.

The nozzle determines the value of slowConsumerAlert with the following rules:

1. When the nozzle receives a TruncatingBuffer.DroppedMessages metric, it publishes the value 1. The metric indicates that Doppler determined that the client (in this case, the nozzle) could not consume messages as quickly as the firehose was sending them, so it dropped messages from its queue of messages to send.

2. When the nozzle receives a websocket Close frame with status 1011, it publishes the value 1. Traffic Controller pings clients to determine if the connections are still alive. If it does not receive a Pong response before the KeepAlive deadline, it decides that the connection is too slow (or even dead) and sends the Close frame.

3. Otherwise, the nozzle publishes 0.