My experience is that GAE backends are horrible when it comes to the 'NTP
correct' time. I have seen servers as much as 20 minutes out. For the
last 6 months or so, they have been much better, so maybe Google got its
act together.
Since I run a MMO synchronized client (android) server (GAE) game, I need
everyone to be correct to within 1-2 seconds. The following code works
pretty well:
url = "http://www.worldtimeserver.com";
format = '%a, %d %b %Y %H:%M:%S %Z'
correction = 0
try:
orig_timestamp = time.mktime(time.gmtime(time.time()))
result = urllib2.urlopen(url)
date_string = result.headers['Date']
recv_timestamp = time.mktime(time.gmtime(time.time()))
dest_timestamp = time.mktime(time.strptime(date_string, format))
correction = int((recv_timestamp - dest_timestamp)/2%180.)
Reason for the %180 in there is the games are on a 3 minute boundary.
I rarely see more than 1-3 seconds of 'correction' needing to be applied
nowadays.
On Thursday, July 25, 2013 12:53:34 PM UTC-4, Evan Ruff wrote:
>
> Hey guys,
>
> I'm curious to hear about any strategies people have used to employ time
> synchronization among the AppEngine instances. I'm working on a project
> that is looking to have a pretty important time component and the current
> strategy I'm looking at is something long the lines of:
>
> 1. Record System.currentTimeMils()
> 2. URLFetch to an NTP server somewhere
> 3. Note return time
> 4. Correct NTP time using the start time to get request time.
>
> Is this how other people are handling it? Is there another way that might
> be simpler? I'm a little hesitant to run an URLFetch for each request,
> obviously.
>
> Thanks!
>
> E
>
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