A tiny clojure library wrapping the MDC functionality in slf4j.
Provides two simple macros to set up a logging context that will be used
for all nested logging calls. The logging context is expected to be
a Map<String,String>.
(with-context {"key-a" "value-a"
"key-b" "value-b"}
...
(log/info "hello with values")
...)This will make the map available for downstream processing (eg in the case of logstash-logback-encoder add the map to the emitted JSON map, see here: https://github.com/logstash/logstash-logback-encoder#loggingevent_mdc).
For other types of appenders, configuration is required to integrate selected values into log messages (see logback documentation here: http://logback.qos.ch/manual/mdc.html).
Bonus feature: with-safe-context
This enables proper shadowing of context members, ie nested calls with
different values assigned to key-a in each nesting are scoped as would
be expected with a lexical binding. The unsafe version clears up all keys
it has set, potentially removing keys that were present in an outer context.
The drawback of with-safe-context is that currently a backup of the current
context is being held and recovered at the end of the form. These maps,
unfortunately, have to be copied every time, which might result in a quite
noticable performance overhead in some scenarios.
Bonus feature: with-weak-context
This will only add the specified keys if they're not already present in the MDC (ie shadowing properties are reversed) - cleans up keys that were set.