Is there a near-consensus guideline for log levels?

Question

I've been influenced by the log levels that I and my teams have used at my last two companies. I'll share ours here but keep in mind this bit is subjective:

• Fatal - Your app is going down.
• Error - This operation or thread is crashing and burning. The app may be able to continue.
• Warn - The current operation may be able to continue but an engineer needs to investigate something.
• Info - Explain what your operation is doing.
• Debug - Explanation of operations that may get pretty spammy (inner loops, etc).

Now, my objective question is whether there is a highly-agreed upon style defined in this regard. The answer may be no. But if there is such a standard, can you point a URL to it?

Also note that I don't really care what threshold is actually configured to log somewhere useful in a deployed / production environment. Rather, my question is restricted to guidelines that those of us who write code should use.

I'm putting a C# tag and Java tag on my question. It's possible we'd have different guidelines in these two camps but there are probably only cultural reasons that we'd differ, not conceptual reasons.

Answer 1

I'm not even sure that whether something is "highly-agreed" upon can be answered objectively.

The Log4j and Log4Net libraries certainly employ the level definitions that you've described. See this link.

Somebody might yet produce a counter-example of a library that uses a differently defined set of logging levels.

Answer 2

from SSCLI (.NET sources):

namespace System {
    ...
    [Serializable]
    internal enum LogLevel {
        Trace  = 0,
        Status = 20,
        Warning= 40,
        Error  = 50,
        Panic  = 100,
    }
    ...
}

note the [warning] values) I rely on this variant of distribution. anyway it's Microsoft)