Re: [Server-devel] timestamps on backups
Thanks Tom and Martin, I think I have figured it out. Sorry for any confusion. It seems the timestamps are correct on the server, it is only when displayed in the backup page (dsbackup.php) where the times are off. For example, a backup done just a few minutes ago would say it was done 4 hours ago on that page. The problem is the timezone. When I specifically set the date.timezone parameter in php.ini to UTC, the text started appearing correctly in the backup page. So it seems PHP is using a different timezone. /etc/sysconfig/clock says that the timezone of the system is America/New York which is probably the timezone PHP is using. On Wed, 2009-09-16 at 15:05 -0700, Tom Mitchell wrote: On Wed, Sep 16, 2009 at 5:37 AM, Martin Langhoff martin.langh...@gmail.com wrote: On Wed, Sep 16, 2009 at 2:28 PM, Hamilton Chua hamilton.c...@gmail.com wrote: I'm not sure if anybody has noticed this yet but after doing a backup, it seems the datestamps on the backup page are wrong. We might need more detail than that if we're to understand the situation :-) Is there something about time zones and time synchronization that we need to be aware of with regards to backups. Yes, the utc time on all machines should make sense. So do date --utc on XS and on the laptops involved to make sure all players are in the same decade. This has been tested with machines on different TZs so it should work. As long as utc agrees across machines. -- martin.langh...@gmail.com http://lists.laptop.org/listinfo/server-devel The two numbers 4 hours and 40 years are almost telling. Linux keeps time as seconds from midnight January 1, 1970 12:00:00 GMT. Today GMT (Greenwich Mean Time) has been replaced by UTS (Coordinated Universal Time) which is GMT done better with atomic clocks. Since you are using XS on 0.6d5 and Sugar on a Stick the system gets the initial time of day (date) from the local hardware clock. A unix/Linux system default sets the local hardware clock to UTS while windows sets it to local time. Depending on daylight savings time in (say) Oklahoma four hours looks like a Windows system setting the hardware time of day. Since Linux can be configured to play nice with windows and set the hardware clock to local time windows is not always the issue in possiblly confusing the offset from GMT/UTS. The 40 years is very close to the beginnig of unix time (zero seconds) and can be seen on a confused local time of day clock. NTP (network time protocol) tools can be used to set the time of day on a network connected system to the correct UTS time. Local time is computed based on UTS and an offset time zone. Since all binary time stamps are UTS different users can set different timezone values in their environment and the system will do the 'right' thing. See: date date --uts date -u (export TZ=Europe/Paris;date;date-u) # touch /tmp/now stat /tmp/now (export TZ=Europe/Paris; stat now) ___ Server-devel mailing list Server-devel@lists.laptop.org http://lists.laptop.org/listinfo/server-devel
Re: [Server-devel] timestamps on backups
On Thu, Sep 17, 2009 at 1:13 PM, Hamilton Chua hamilton.c...@gmail.com wrote: /etc/sysconfig/clock says that the timezone of the system is America/New York which is probably the timezone PHP is using. That's weird. Questions - Can you confirm date --utc is correct on the XS and on the involved XOs? - If you look at the datastore-timestamp directories - are the timestamps correctly in UTC? - If you run tzselect, change the tz to your local tz -- does it fix the problem? If it does, is the problem fixed for new backups or for all backups? The PHP code in dsbackup.php should be ignoring timezones, but something might be sneaking in. Also - the timestamp in the dirnames may be wrong. m -- martin.langh...@gmail.com mar...@laptop.org -- School Server Architect - ask interesting questions - don't get distracted with shiny stuff - working code first - http://wiki.laptop.org/go/User:Martinlanghoff ___ Server-devel mailing list Server-devel@lists.laptop.org http://lists.laptop.org/listinfo/server-devel
Re: [Server-devel] timestamps on backups
Hi Martin, My responses inline ... - Can you confirm date --utc is correct on the XS and on the involved XOs? Yes, date--utc on both XS and XO's are the same if not close to each other, the difference being a few seconds. - If you look at the datastore-timestamp directories - are the timestamps correctly in UTC? Yes, the directory name uses the UTC timestamp. - If you run tzselect, change the tz to your local tz -- does it fix the problem? If it does, is the problem fixed for new backups or for all backups? The timezone of the system has always been the local tz. The PHP code in dsbackup.php should be ignoring timezones, but something might be sneaking in. Also - the timestamp in the dirnames may be wrong. I checked the directory names and it seems they are correctly UTC. It appears that the problem is just the calculation involved that returns how long ago the backup was. It seems the time() function returns the epoch based on the local timezone instead of the epoch based on UTC. Best, Ham ___ Server-devel mailing list Server-devel@lists.laptop.org http://lists.laptop.org/listinfo/server-devel
Re: [Server-devel] timestamps on backups
On Thu, Sep 17, 2009 at 1:55 PM, Hamilton Chua hamilton.c...@gmail.com wrote: - Can you confirm date --utc is correct on the XS and on the involved XOs? Yes, date--utc on both XS and XO's are the same if not close to each other, the difference being a few seconds. thanks I checked the directory names and it seems they are correctly UTC. Thanks! It seems the time() function returns the epoch based on the local timezone instead of the epoch based on UTC. Actually - time() is doiing the right thing. It was the use of mktime() that was bogus. Replace mktime() with gmmtime(), the 3 times it appears in dsbackuplib.php and the problem is gone. thanks for the debugging! m -- martin.langh...@gmail.com mar...@laptop.org -- School Server Architect - ask interesting questions - don't get distracted with shiny stuff - working code first - http://wiki.laptop.org/go/User:Martinlanghoff ___ Server-devel mailing list Server-devel@lists.laptop.org http://lists.laptop.org/listinfo/server-devel
Re: [Server-devel] timestamps on backups
Actually - time() is doiing the right thing. It was the use of mktime() that was bogus. Replace mktime() with gmmtime(), the 3 times it appears in dsbackuplib.php and the problem is gone. Thanks Martin :-) thanks for the debugging! You're welcome. ___ Server-devel mailing list Server-devel@lists.laptop.org http://lists.laptop.org/listinfo/server-devel
[Server-devel] timestamps on backups
Hello, I'm not sure if anybody has noticed this yet but after doing a backup, it seems the datestamps on the backup page are wrong. For instance, after a recent backup the backup page in moodle says that the last backup was 4 hours ago even though monitoring the cron logs show that it has just completed a backup. Even weirder, moodle claims that some backups are 40 years old ! :-) I am using XS on 0.6d5 and Sugar on a Stick. Is there something about time zones and time synchronization that we need to be aware of with regards to backups. Thanks, Hamilton ___ Server-devel mailing list Server-devel@lists.laptop.org http://lists.laptop.org/listinfo/server-devel
Re: [Server-devel] timestamps on backups
On Wed, Sep 16, 2009 at 5:37 AM, Martin Langhoff martin.langh...@gmail.com wrote: On Wed, Sep 16, 2009 at 2:28 PM, Hamilton Chua hamilton.c...@gmail.com wrote: I'm not sure if anybody has noticed this yet but after doing a backup, it seems the datestamps on the backup page are wrong. We might need more detail than that if we're to understand the situation :-) Is there something about time zones and time synchronization that we need to be aware of with regards to backups. Yes, the utc time on all machines should make sense. So do date --utc on XS and on the laptops involved to make sure all players are in the same decade. This has been tested with machines on different TZs so it should work. As long as utc agrees across machines. -- martin.langh...@gmail.com http://lists.laptop.org/listinfo/server-devel The two numbers 4 hours and 40 years are almost telling. Linux keeps time as seconds from midnight January 1, 1970 12:00:00 GMT. Today GMT (Greenwich Mean Time) has been replaced by UTS (Coordinated Universal Time) which is GMT done better with atomic clocks. Since you are using XS on 0.6d5 and Sugar on a Stick the system gets the initial time of day (date) from the local hardware clock. A unix/Linux system default sets the local hardware clock to UTS while windows sets it to local time. Depending on daylight savings time in (say) Oklahoma four hours looks like a Windows system setting the hardware time of day. Since Linux can be configured to play nice with windows and set the hardware clock to local time windows is not always the issue in possiblly confusing the offset from GMT/UTS. The 40 years is very close to the beginnig of unix time (zero seconds) and can be seen on a confused local time of day clock. NTP (network time protocol) tools can be used to set the time of day on a network connected system to the correct UTS time. Local time is computed based on UTS and an offset time zone. Since all binary time stamps are UTS different users can set different timezone values in their environment and the system will do the 'right' thing. See: date date --uts date -u (export TZ=Europe/Paris;date;date-u) # touch /tmp/now stat /tmp/now (export TZ=Europe/Paris; stat now) -- T o m M i t c h e l l mitch-at-niftyegg-dot-com ___ Server-devel mailing list Server-devel@lists.laptop.org http://lists.laptop.org/listinfo/server-devel
