如何在Windows Azure的Web.config中更改所有Web角色的日志记录设置？

Question

ASP.NET application on Windows Azure. The application is scalable and runs on 1..N Web role instances.

We have log4net write to the Windows Event log and have Windows Azure Diagnostics consolidate to Azure storage.

At the moment the log4net configuration is stored in Web.config.

For application logging we have the following requirements:

1. Ability to specify a list of one or more types of log entries to write to the log

2. Ability to specify the level at which log entries are written to the log (per log entry)

The first requirement is met by the loggers naming convention. Loggers define a hierarchy and give the programmer run-time control on which statements are printed or not.

ILog log = LogManager.GetLogger("Davanti.WMS.Core.Logic.Inventory");

The second requirement can be achieved by using the logging levels DEBUG, INFO, WARN, ERROR and FATAL.

log.Debug("Process has completed");

Current situation

We have only one log4net configuration in the Web.config file that redirects to the Windows Event log. And control what to log (see requirement 1) and the depth (level) to log (see requirement 2) in application code base on settings stored in the central database.

This approach will have a negative effect on application performance because the application itself will have to check if certain messages needs to be logged or not (synchronously) instead on the logging framework (asynchronously).

Required situation

We want to control what to log and logging level from the log4net settings. The problem is that we have to apply the log4net settings on all Windows Azure Web role instances. What is the best approach for this?

Also we would like to have a more user friendly way to enable logging (for example by a consultant). What are the possibilities?

Like for example using the Enterprise Library Configuration editor. A visual representation of the confoguration settings. http://img651.imageshack.us/img651/930/logging.jpg

Answer 1

The default configuration provider will look at the app.config or web.config in your case. However you can use the XmlConfigurator class to load configurations from a Stream

http://logging.apache.org/log4net/release/sdk/log4net.Config.XmlConfigurator.Configure_overload_7.html

In your role configuration you can specify a blob location then use a blob client object from the Azure storage SDK and load the xml from a single blob location.

Log4Net configuration: http://logging.apache.org/log4net/release/manual/configuration.html

This is similar to the Azure diagnostics configuration which uses an xml blob.

The caveat to this is that you need to do some more implementation like regular queuing for updates to the file if you want to do live changes to your logging.