[jeffbee]

This is a great article because everyone should understand the similarity between logging and tracing. One thing worth pondering though is the differences in cost. If I am not planning to centrally collect and index informational logs, free-form text logging is extremely cheap. Even a complex log line with formatted strings and numbers can be emitted in < 1µs on modern machines. If you are handling something like 100s or 1000s of requests per second per core, which is pretty respectable, putting a handful of informational log statements in the critical path won't hurt anyone.

Off-the-shelf tracing libraries on the other hand are pretty expensive. You have one additional mandatory read of the system clock, to establish the span duration, plus you are still paying for a clock read on every span event, if you use span events. Every span has a PRNG call, too. Distributed tracing is worthless if you don't send the spans somewhere, so you have to budget for encoding your span into json, msgpack, protobuf, or whatever. It's a completely different ball game in terms of efficiency.

[xyzzy_plugh]

I will agree that conceptually logging can be much cheaper than tracing ever can, but in practice any semi-serious attempt at structured logging ends up looking very, very close to tracing. In fact I'd go so far as to say that the two are effectively interchangeable at a point. What you do with that information, whether you index it or build a graph, is up to you -- and that is where the cost creeps in.

Adding timestamps and UUIDs and an encoding is par for the course in logging these days, I don't think that is the right angle to criticize efficiency.

Tracing can be very cheap if you "simply" (and I'm glossing over a lot here) search for all messages in a liberal window matching each "span start" message and index the result sets. Offering a way to view results as a tree is just a bonus.

Of course, in practice this ends up meaning something completely different, and far costlier. Why that is I cannot fathom.

[nithril]

It is actually simpler to conceptualize the difference, one is stateless, the other one is stateful.

Actually structured logging exists since years like in Java https://github.com/logfellow/logstash-logback-encoder

[hyperpape]

I don't generally disagree, but using json for structured logs is a growing thing as well.