Our website is currently deployed to azure and we are writing trace logs using azure diagnostics. We then ship the logs to blob storage periodically and read them using Cerebrata’s Windows Diagnostics Manger software. I would like to know what happens when the disc holding the logs on azure is full i.e before the logs are shipped. When do the logs get purged? and is it is any different if the logs are not shipped. My concern is that the site may somehow fall over when exceptions are raised (if at all) when trying to write to a full disc.
If you are using Windows Azure Diagnostics, then it will age out the logs on disk (deleting the oldest files first). You have a quota that is specified in your wad-control-container in blob storage on an instance level basis. By default, this will be 4GB (you can change it). All of your traces, counters, and event logs needs to fit in this 4GB of disk space. You can set separate quotas here if you like per data source as well. The Diagnostics Manager takes care to manage the data sources and the quota.
Now, there was a bug in older versions of the SDK where the disk could get full and diagnostics stopped working. You will know if you might be impacted by this bug by RDP'ing into an instance and trying to navigate to C:\Resources\Directory\\Monitor directory. If you are denied access, then you are likely to hit this bug. If you can view this directory as normal admin on machine, you should not be impacted. There was a permission issue in an older SDK version where deletes to this directory failed. Unfortunately, the only symptom of this impact is that suddenly you won't get data transferred out anymore. There is no overt failure.