Adding Information to the Web Proxy Log

Web filters often need to add information to the Forefront TMG Web proxy log. The Web proxy log includes a field called Filter Information for recording information supplied by Web filters. For more information about the log fields that can be included in Forefront TMG Web proxy log entries, see Web Proxy Log Fields.

The HTTP_FILTER_LOG structure is used to supply information to the Web proxy log. The information that is to be written in the Filter Information field of a Web proxy log entry must be stored in the pszParameters member of this structure. The Forefront TMG Web proxy includes a pointer to the HTTP_FILTER_LOG structure in the notification that it sends to Web filters when it is ready to write information to a log file. If your filter should be notified for this event, it must register to receive SF_NOTIFY_LOG notifications. For more information about the types of event notifications that are sent to Web filters, see Event Notifications.

Note that the Filter Information field has a fixed length of 128 chararcters and that Forefront TMG logging will truncate the accumulated data to fit the field.

As a best practice for the Filter Information field, a Web filter should append the value of the previous buffer for this field to the new buffer. This is required so that all information added by other filters will be retained and not totally removed.

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Build date: 6/30/2010