Tutorial: Handling Log Messages

Handling Log Messages

Logging is built into the base Object class already with the log method.

This method, by default, simply calls the log method of its parent, if there is one. In order to handle logging, you have to override the log method of the object in the hierarchy where you want to log. This is typically at the top level.

You are free to handle logging in any way you like.

HTTPServer {

    // override the "log" method
    function log(domain, level, message)
    {
        const now = new Date();
        const s = now.toLocaleString() + " [" + domain + "] " + message;

        if (level === "error" || level === "fatal")
        {
            console.error(s);
        }
        else
        {
            console.log(s);
        }
    }

    ...

}

The log method takes three parameters:

• domain: The name of the logging domain. This may be any name.
• level: The severity level of the log message.
• message: The text of the log messages.

In order to log a message, simply invoke the log method of an object.

Timer {
    interval: 500

    onTimeout: () =>
    {
        log("Timer", "info", "The timer expired.");
    }
}

Internal Logging Domains

Shellfish uses the empty string ("") as domain for internal log messages.

Some classes in the shellfish/server module also use other domains for log messages that may be of special interest:

• "HTTPServer" for messages related to the HTTP server
• "HTTP" for messages related to generic HTTP traffic
• "WWW" for messages related to Web content traffic
• "DAV" for messages related to WebDAV traffic
• "RPC" for messages related to Remote Procedure Calls
• "TokenAuth" for messages related to token-based authentication