Required server side metrics

[NiteshKant]

As there was no insight initially on which metrics should be provided. This comment is updated post-implementation to provide information about the available metrics.

Following metrics will be available for out of the box servo metrics plugin.

TCP

• Live Connections: The number of open connections from all clients to this server. This is a gauge.
• Inflight Connections: The number of connections that are currently being processed by this server. This is a gauge.
• Failed Connections: The number of times that connection handling failed. This is a monotonically increasing counter.
• Connection processing times: Time taken for processing a connection.
• Pending connection close: Number of connections which are requested to be closed but are not yet closed. This is a gauge.
• Failed connection close: Number of times when the connection close failed. This is a monotonically increasing counter.
• Connection close times: Time taken for closing a connection.
• Pending Writes: Writes that are pending to be written over the socket. This includes writes which are not flushed.
  This is a gauge.
• Pending Flushes: Flushes that are issued but are not over yet. This is a gauge.
• Bytes Written: Total number of bytes written. This is a monotonically increasing counter.
• Write Times: The time taken to finish a write.
• Bytes Read: The total number of bytes read. This is a monotonically increasing counter.
• Failed Writes: The total number of writes that failed. This is a monotonically increasing counter.
• Failed Flushes: The total number of flushes that failed. This is a monotonically increasing counter.
• Flush times: The time taken to finish a flush.

HTTP

HTTP contains all the metrics that are available from TCP. The following metrics are specific to HTTP:

• Request backlog: The number of requests that have been received but not started processing. This is a gauge.
• Inflight requests: The number of requests that have been started processing but not yet finished processing. This is a gauge.
• Response Write Times: Time taken to write responses, including headers and content.
• Request Read Times: Time taken to read a request.
• Processed Requests: Total number of requests processed. This is a monotonically increasing counter.
• Failed Requests: Total number of requests for which the request handling failed.
• Failed response writes: Total number of responses for which the writes failed.

UDP

UDP contains all the metrics that are available from TCP.

[NiteshKant]

Moving this to milestone 0.3.5.
Had to invest time on issue #117 which requires a release now.

[NiteshKant]

The design proposal for this can be found in issue #98