Hello Ciara, Bruce, On Thu, Dec 5, 2019 at 6:34 PM Ciara Power <ciara.po...@intel.com> wrote: > > From: Bruce Richardson <bruce.richard...@intel.com> > > This patchset proposes a new library, called "process-info" for now, to > replace the existing telemetry library in DPDK. (Name subject to change > if someone can propose a better one). > > The existing telemetry library provides useful capabilities if used: > - Creates a unix socket on the system to allow external programs > connect and gather stats about the DPDK process. > - Supports outputting the xstats for various network cards on the > system. > - Can be used to output any other information exported to the metrics > library, e.g. by applications. > - Uses JSON message format, which is widely supported by other > languages and systems. > - Is supported by a plugin to collectd. > > However, the library also has some issues and limitations that could be > improved upon: > - Has a dependency on libjansson for JSON processing, so is disabled > by default. > - Tied entirely to the metrics library for statistics. > - No support for sending non-stats data, e.g. something as simple as > DPDK version string. > - All data gathering functions are in the library itself, which also > means… > - No support for libraries or drivers to present their own > information via the library. > > We therefore propose to keep the good points of the existing library, > but change the way things work to rectify the downsides. > This leads to the following design choices in the library: > - Keep the existing idea of using a unix socket for connection (just > simplifying the connection handling). > - We would like to use JSON format, where possible, but the jansson > library dependency is problematic. However, creating JSON-encoded > data is easier than trying to parse JSON in C code, so we can keep > the JSON output format for processing by e.g. collectd and other > tools, while simplifying the input to be plain text commands: > - Commands in this RFC are designed to all start with "/" for > consistency > - Any parameters to the commands, e.g. the specific port to get > stats for, are placed after a comma "," > - Have the library only handle socket creation and input handling. > All data gathering should be provided by functions external to the > library registered by other components, e.g. have ethdev library > provide the function to query NIC xstats, etc. > - Have the library directly initialized by EAL by default, so that > unless an app explicitly does not want the support, monitoring is > available on all DPDK apps. > > The obvious question that remains to be answered here is: "why a new > library rather than just fixing the old one?" > > The answer is that we have conflicts between the final two design > choices above, which require that the library be built early in the > build as other libraries will call into it to register callbacks, and > the desire to keep backward compatibility e.g. for use with collectd > plugin, which requires the existing library code be kept around and > built - as it is now - at the end of the build process since it calls > into other DPDK libraries. We therefore cannot have one library that > meets both requirements, hence the replacement which allows us to > maintain backward compatibility by just leaving the old lib in place > until e.g. 20.11. > > This is also why the new library is called "process_info", since the > name "telemetry" is already taken. Suggestions for a better name > welcome.
The only user of the rte_telemetry api I could find is the (not yet merged [1]) dpdk collectd plugin. How will this impact it? Can we expect compatibility? 1: https://github.com/collectd/collectd/pull/3273 -- David Marchand
