Records

Records describe a set of log Attributes that should be available to a Formatter on every log message.

NOTE: The Attribute type is used as a way to provide lazy evaluation of log record elements.

While the DefaultRecord in Memento provides many of the keys and values needed for most logging applications, you may need to implement your own Record type. For example, if you're running a julia application on a cloud service provider like Amazon's EC2 you might want to include some general information about the resource your code is running on, which might result in a custom Record type that looks like:

# TODO: Fix this example.
type EC2Record <: Record
    date::Attribute
    level::Attribute
    levelnum::Attribute
    msg::Attribute
    name::Attribute
    pid::Attribute
    lookup::Attribute
    stacktrace::Attribute
    instance_id::Attribute
    public_ip::Attribute
    iam_user::Attribute

    function EC2Record(name::AbstractString, level::AbstractString, msg)
        time = now()
        trace = Attribute(StackTrace, get_trace)

        EC2Record(
            Attribute(DateTime, () -> round(time, Base.Dates.Second)),
            Attribute(level),
            Attribute(-1),
            Attribute(AbstractString, get_msg(msg)),
            Attribute(name),
            Attribute(myid()),
            Attribute(StackFrame, get_lookup(trace)),
            trace,
            Attribute(ENV["INSTANCE_ID"]),
            Attribute(ENV["PUBLIC_IP"]),
            Attribute(ENV["IAM_USER"]),
        )
    end
end

NOTE: The above example simply assumes that you have some relevant environment variables set on the machine, but you could also query Amazon for that information.