On Mon, 01 Nov 2004 21:32:26 +0200, John Torjo <john.lists@torjo.com> wrote:
Johan wrote:
I basically was thinking about log "messages" as data structures, consisting of least one message id (possibly consisting of facility, severity and the id itself, similar to COM hresults and VMS status codes) + insertion data. Logging a message would include creating an instance of a log item and storing it in the TSS buffer for later retrieval, formatting and writing by the worker thread. Data such as timestamps, thread id, etc is added at this point and can be selected for inclusion/exclusion in the actual writing on the back-end instead.
So basically, after a message is added, a log_item is created, and different modifiers can fill different things of this log_item itself. Then, the appender(s) will decide which information to write to the real destination(s). This is an interesting idea.
This is how most of the logging frameworks I've used in the past have worked. There's always a free-form text field for a human-readable message, but there are numerous other fields which are filled-in automatically (perhaps even down to the level of the __FILE__ and __LINE__ where they were generated - very easy to do when using macros). Take for example the ACE_Log_Msg structure from the ACE library (just the important bits): class ACE_Log_Msg { [...] // Status of last operation (user defined) int status_; // errno when this message was created int errnum_; // Line number in file_ where the message was generated int linenum_; // Name of file where message was generated char file_[MAXPATHLEN + 1]; // The message itself char msg_[ACE_MAXLOGMSGLEN + 1]; // Pointer to thread descriptor ACE_Thread_Descriptor* thr_desc_; // Priority (severity) of this message unsigned long priority_mask_; // Name of the program static const char* program_name_; // Hostname static const char* hostname_; }; No judgements of relative goodness/badness, just for informational purposes. I would also suggest that any structured log message contain a timestamp indicating when it was generated.
Is this what you're talking about, or am I totally on the wrong track?
I think you've got the gist of Johan's point (assuming I have). -- Caleb Epstein caleb.epstein@gmail.com