bard.util.log — edu.bard/util.log 0.1.6

Logging helper macros

get-loglevel! clj

(get-loglevel!)

(get-loglevel! cls)

Retrieve the current log level

pass clj macro

(pass expr msg)

(pass expr level msg)

(pass expr level fmt fmt-args)

Convenience macro to log msg while yielding expr.

passf clj macro

(passf expr fmt-or-level & args)

Convenience macro to log (format fmt args) while yielding expr.

Acceptable forms:

(passf expr :info fmt & fmt-args)
(passf expr fmt & fmt-args)

fmt-or-level is checked for being a keyword, in which case it is treated as the log level; otherwise, a default level of :debug is assumed.

Although this breaks with the tools.logging convention of expr being last, writing it in that way is incredibly confusing. This way, even the thread-last wrapper passf-last is fairly simple.

The use case is situations where you want to essentially log that something passed through some particular place in the code without necessarily wanting to log the thing itself. For example, when resolving a user, logging the user becomes more and more ridiculous at INFO-level.

This is convenient to avoid something like this:

(def x {:thing {:somekey :some value}})
(if (contains? x :thing)
  (do (log/info blah blah blah)
      x)
  (do (log/warn some other blah blah)
      x))

That's purely convenience, and making it easier to understand what the code is doing. An example of where this is almost required:

(def x {:thing {:somekey :some value}})
(some-> x
        an-operation
        (passf :info "User %s has passed the first hurdle!" user-id)
        another-operation
        (passf :info "User has passed another hurdle!" user-id))

In the above scenario, we use some-> to short-circuit on a nil value coming back from one of the operations in the chain. Without this macro, the only way to have visibility into the process would be either to ensure that each step logs aggressively, impossible if using low-level functions, or to break the logical sequence into a series of when-somes. Although using if-some would allow for logging each step that may or may not fail, and indeed I use that idiom in many places, there are any number of situations where you want visibility in the form of 'we got here!' without breaking up the logical flow of the larger operation into something harder to read.

passf-last clj macro

(passf-last & args)

thread-last wrapper for passf. See spy-first for justification.

Args should be the same as passf, except that expr comes last.

set-loglevel! clj

(set-loglevel! level)

Update the global log level

spy-first clj macro

(spy-first expr & args)

Things I like:

1. threading macros
2. inline logging in my threading macros

Things I don't like:

(-> thing
    (some-other thing)
    (->> (log/spy :trace))
    another-thing)

That's right: this is a macro so I can use log/spy with (-> ).

spyf-first clj macro

(spyf-first expr & args)

Like spy-first, but dispatches to log/spyf, rather than log/spy.

strace clj macro

(strace expr)

No relation to the syscall tracer. Logs expr at TRACE log level, then yields expr.

Most of the time that I find myself using [[log/spy]], I'm inserting some trace-level info into a threading macro. This removes a lot of the resulting cruft and also probably takes over the role of spy-first.

Before:

(-> {:important :thing}
    some-operation
    (->> (log/spy :trace))
    another-operation)

After:

(-> {:important :thing}
    some-operation
    strace
    another-operation)

Look, this happens in more places than you'd think.