2012/6/16 Tom Lane <t...@sss.pgh.pa.us>: [... cut ...] > (1) In backend_read_statsfile, make an initial attempt to read the stats > file and then read GetCurrentTimestamp after that. If the local clock > reading is less than the stats file's timestamp, we know that some sort > of clock skew or glitch has happened, so force an inquiry message to be > sent with the local timestamp. But then accept the stats file anyway, > since the skew might be small and harmless. The reason for the forced > inquiry message is to cause (2) to happen at the collector. > > (2) In pgstat_recv_inquiry, if the received inquiry_time is older than > last_statwrite, we should suspect a clock glitch (though it might just > indicate delayed message receipt). In this case, do a fresh > GetCurrentTimestamp call, and if the reading is less than > last_statwrite, we know that the collector's time went backwards. > To recover, reset these variables as we do at startup: > last_statrequest = GetCurrentTimestamp(); > last_statwrite = last_statrequest - 1; > to force an immediate write to happen with the "new" local time. > > (1) is basically free in terms of the amount of work done in non-broken > cases, though it will require a few more lines of code. (2) means > adding some GetCurrentTimestamp calls that did not occur before, but > hopefully these will be infrequent, since in the absence of clock > glitches they would only happen when a backend's demand for a new stats > file is generated before the collector starts to write a new stats file > but not received till afterwards. > > Comments? Anyone see a flaw in this design? Or want to argue that > we shouldn't do anything about such cases?
What happens when Daylight saving time ends? Or it doesn't matter in this scenario? regards -- Dickson S. Guedes mail/xmpp: gue...@guedesoft.net - skype: guediz http://guedesoft.net - http://www.postgresql.org.br -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
