I am writing this blog as a response to the number of issues I have seen where the PAAS VM might seem to have recycled abruptly. On a quite a number of occurrences I found that users manually doing an RDP to the VM instances and changing the machine time. Based on some blogs users are leveraging“TZUTIL” from the command prompt to accomplish this. While the changes will not persist beyond a reincarnation of the VM some enterprising users have conjured up script that can be used as part of the start-up task and hence mitigate the re-creation of the VM.
But I would strongly advice against it. The Fabric Controller maintains operating system time synchronization for the system when roles are first booted. If you utilize administrative access startup scripts to change the localization settings (including local server time), but it is not recommended you do so. Doing so will introduce instability and the fabric controller may determine your role is out of sync. You will likely end up cycling your roles as fabric attempts to bring them to goal state in such a case. A better strategy is to write your applications to be aware that they actually run with UTC and default US CultureInfo settings.
WINDOWS AZURE ROLES
While it may be very tempting to change the server time on the Azure Virtual Machines using a startup task, it is not recommended, you should rather use methods like TimeZoneInfo.ConvertTimeFromUTCTime in your code.
This is a good reference article (Coding Best Practices Using DateTime in the .NET Framework).
All the machines in PAAS (Web Role or Worker Role) should always be in UTC. Changing that will lead to unpredictable situations since the internal heartbeat, ping from load balancer all depend on time. For application requirement please use the application APIs to convert the time in the code. For example below is how a time zone conversion should be done.
In case you are using .Net applications you can use the following after fetching the myUtcDateTime from the System. Use the web.config file to manage the number of hours you want to go forward or backward, this way you can set it to zero(GMT),
positive (GMT+ like EMEA and Asia) or negative values (North and South America) as per the applications/end user required time zones.
Set the double hour using the System.Configuration.ConfigurationManager AppSetting Collection. This will let the application be configurable for different time offsets.
Then use the following code
DateTime myUtcDateTime = DateTime.Now;
DateTime myLocalDate = myUtcDateTime.AddHours(hour);
In case the application will only ever need one of the standard timezone(accuracy of 30 mins is sufficient) then .Net even caters to do that. This suits lazy people like me and is actually the main usecase.
DateTime myUtcDateTime = DateTime.Now;
DateTime myConvertedDateTime = TimeZoneInfo.ConvertTime(
myUtcDateTime,TimeZoneInfo.FindSystemTimeZoneById("Indian Standard Time"))
Regardless of the datacenter location chosen, your SQL Azure server is set to the UTC timezone. The current version of SQL Azure does not support changing the timezone. So the same programmatic technique should be used in case there is a WebRole/WorkerRole which will serve the data to the end user/applications.
In case there is none then the following blog depicts the technique on how to convert the time in the SQL query itself. http://wely-lau.net/2011/07/10/managing-timezone-in-sql-azure-2/
In case you are developing mobile application then the webroles or worker roles (WFC/OData service) should always return UTC time. The client application should convert the time based on the user location.
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