问题
I have enabled diagnostic logging (Error level only to file system or blob) on my azure website several times and confirmed that it is working. When I come back and check the next day it is switched off. I can't seem to find any documentation that suggest that this is by design.
回答1:
If you're logging to File System, then it does disable itself after 12 hours. You can see this if you click the help bubble:
The reason is that it could affect site performance due to excessive writing to the (slow) file system.
However, if you set it up for blob, it should never get turned off until you do it.
回答2:
If you turn on Application Logging to the File System, then yes, it will turn itself off after 12 hours. You can see this in the portal if you hover over the information icon for Application Logging (see below). This behavior is also document here for reference.
The reason why this is disabled after 12 hours has to do with the limited set of storage you have on the local file system, which will be 1GB - 250GB depending on your App Service Plan (size).
If you enable application logging to Azure Storage (blob), then you have up to 500TB of potential storage. In this scenario, your logging should not be getting disabled after 12 hours.
来源：https://stackoverflow.com/questions/36902957/does-the-diagnostic-logging-setting-turn-itself-off-by-design