Re: POC: Extension for adding distributed tracing - pg_tracing

Hi!

Thanks for the improvements!
>Here's a new patch with changes from the previous discussion:
>- I'm now directly storing nanoseconds duration in the span instead of the
instr_time. Using the instr_time macros was a bit awkward as the
durations I generate don't necessarily have a starting and ending
instr_time.
>Moving to straight nanoseconds made things clearer from my point of view.
Cool. It could be easily casted to ms for the user.

>- I've added an additional sample rate pg_tracing.sample_rate (on top of
the pg_tracing.caller_sample_rate). This one will allow queries to be
sampled even without trace information propagated from the caller.
>Setting this sample rate to 1 will basically trace everything. For now,
this will only work when going through the post parse hook. I will add
support for prepared statements and cached plans for the next patch.
Cool, I've just made the same improvement and wanted to send a patch a bit
later after tests.

>- I've improved how parse spans are created. It's a bit challenging to get
the start of a parse as there's no pre parse hook or instrumentation around
parse so it's only an estimation.
I've also added a query id field to span and made a table and an sql
function that flushes spans to this table instead of returning set or
records - it is more convenient for the maintenance to query the table.

--
Regards,
Nikita Malakhov
Postgres Professional
The Russian Postgres Company
https://postgrespro.ru/