Thread: uptime() for postmaster
Hi Bruce, I started to work on the uptime() for the postmaster yesterday. A couple of questions: a) is the name uptime() OK? b) is the return-type 'Interval' OK? c) does it make sense (... fit in the scheme?) to place the code here: src/backend/utils/misc/uptime.c d) Can I piggy-back on 'BackendParameters' to get postmasters start-time to the backends? happy new year, Matthias ---------------------------------------------------------------------- Matthias Schmidt Viehtriftstr. 49 67346 Speyer Tel.: +49 6232 4867 Fax.: +49 6232 640089
Matthias Schmidt <schmidtm@mock-software.de> writes:
> a) is the name uptime() OK?
Probably should use pg_uptime(), or something else starting with pg_.
> b) is the return-type 'Interval' OK?
It might be better to return the actual postmaster start time (as
timestamptz) and let the user do whatever arithmetic he wants.
With an interval, there's immediately a question of interpretation
--- what current timestamp did you use in the computation?
I'm not dead set on this, but it feels cleaner.
> c) does it make sense (... fit in the scheme?) to place the code here:
> src/backend/utils/misc/uptime.c
No. This sort of stuff should go into utils/adt/. I'd be inclined to
drop the function into one of the existing timestamp-related files
rather than make a whole new file just for it. Someplace near the
now() function would make sense, for instance.
> d) Can I piggy-back on 'BackendParameters' to get postmasters
> start-time to the backends?
AFAICS you have no other choice.
regards, tom lane
Hi Tom, Am 31.12.2004 um 20:18 schrieb Tom Lane: > Matthias Schmidt <schmidtm@mock-software.de> writes: >> a) is the name uptime() OK? > > Probably should use pg_uptime(), or something else starting with pg_. What about 'pg_starttime()' since it is not a period but a point-in-time? > >> b) is the return-type 'Interval' OK? > > It might be better to return the actual postmaster start time (as > timestamptz) and let the user do whatever arithmetic he wants. > With an interval, there's immediately a question of interpretation > --- what current timestamp did you use in the computation? > I'm not dead set on this, but it feels cleaner. you're right. Let's go for timestamptz and let the users decide ... > >> c) does it make sense (... fit in the scheme?) to place the code here: >> src/backend/utils/misc/uptime.c > > No. This sort of stuff should go into utils/adt/. I'd be inclined to > drop the function into one of the existing timestamp-related files > rather than make a whole new file just for it. Someplace near the > now() function would make sense, for instance. yep - so the stuff goes to: utils/adt/timestamp.c, where now() and many other time-related functions are. > >> d) Can I piggy-back on 'BackendParameters' to get postmasters >> start-time to the backends? > > AFAICS you have no other choice. > > regards, tom lane > > cheers, Matthias ---------------------------------------------------------------------- Matthias Schmidt Viehtriftstr. 49 67346 Speyer Tel.: +49 6232 4867 Fax.: +49 6232 640089
Matthias Schmidt wrote: > Hi Tom, > > Am 31.12.2004 um 20:18 schrieb Tom Lane: > >> Matthias Schmidt <schmidtm@mock-software.de> writes: >> >>> a) is the name uptime() OK? >> >> >> Probably should use pg_uptime(), or something else starting with pg_. > > > What about 'pg_starttime()' since it is not a period but a point-in-time? > >> >>> b) is the return-type 'Interval' OK? >> >> >> It might be better to return the actual postmaster start time (as >> timestamptz) and let the user do whatever arithmetic he wants. >> With an interval, there's immediately a question of interpretation >> --- what current timestamp did you use in the computation? >> I'm not dead set on this, but it feels cleaner. > > > you're right. Let's go for timestamptz and let the users decide ... > Well, the unix guys have the abit to have the uptime as an interval, I'm inclined to have boths: pg_uptime ( interval ) and pg_starttime ( timestamptz ) Regards Gaetano Mendola
Gaetano Mendola <mendola@bigfoot.com> writes: > Well, the unix guys have the abit to have the uptime as an interval, I'm > inclined to have boths: pg_uptime ( interval ) and pg_starttime ( timestamptz ) Well for the OS these are not redundant values. The clock could have been adjusted at any time. So you can't just calculate uptime by subtracting the current time from the start time. I suppose this argument is true for Postgres as well. But I'm not sure Postgres can really make the distinction as easily as the kernel. To return the actual uptime without being deceived by clock changes it would need to store not the wall clock time on startup, but the system uptime. And then calculate the difference in the current system uptime. I'm not sure if there is a portable interface to get a system uptime. -- greg