On Tue, 16 Aug 2022 02:17:38 +0300
Dmitry Kozlyuk <dmitry.kozl...@gmail.com> wrote:
> When debugging a live app, useful info can be obtained from logs or traces
> that were not enabled when it was started and it is undesirable to restart.
> Furthermore, unless the app authors have considered tracing,
> rte_trace_save() is only called on exit, i.e. a shutdown is required again.
>
> What if the telemetry socket gave the missing control?
> For example:
>
> --> /eal/log/set_level,debug
> {"/eal/log/set_level": {"status": "success"}}
> --> /eal/log/set_level,pmd.net.*:debug
> {"/eal/log/set_level": {"status": "success"}}
> --> /eal/log/set_level,lib.[a-d],debug
> {"/eal/log/set_level": {"status": "success"}}
> --> /eal/log/set_level,foobar
> {"/eal/log/set_level": {"status": "fail", "message": "Invalid log level:
> foobar"}}
>
> Tracing is more complicated because it requires resource allocation.
> It could be:
>
> /eal/trace/set_mode,discard
> /eal/trace/set_mode,overwrite
> rte_trace_mode_set()
>
> /eal/trace/enable_pattern,<pattern>
> /eal/trace/enable_regex,<regex>
> /eal/trace/disable_pattern,<pattern>
> /eal/trace/disable_regex,<regex>
> rte_trace_enable_pattern()
> rte_trace_enable_regex()
>
> /eal/trace/rearm
> Clear the trace buffer.
> Apply the new settings accumulated by the previous commands.
>
> /eal/trace/save
> rte_trace_save()
>
> An open question is how to deal with multi-process.
> Only the primary process listens to the telemetry socket.
> Log and trace settings are not shared between processes.
> OTOH, when enabling some log source, it is desirable to do in all processes.
>
> In general, telemetry is not for changing the state of the app,
> but logs and traces are diagnostic information that seems to be in-scope.
> A similar suggestion was not opposed recently:
>
>
> http://inbox.dpdk.org/dev/24c49429394294cfbf0d9c506b205029bac77c8b.1657890378.git.anatoly.bura...@intel.com/
Not sure if turning telemetry into a do all control api makes sense.
This seems like a different API.
Also, the default would have to be disabled for application safety reasons.
