Steno is a lightweight, modular logging library written specifically to support Cloud Foundry.
Steno is composed of three main classes: loggers, sinks, and formatters. Loggers are the main entry point for Steno. They consume user input, create structured records, and forward said records to the configured sinks. Sinks are the ultimate destination for log records. They transform a structured record into a string via a formatter and then typically write the transformed string to another transport.
To use steno, you must configure one or more 'sinks', a 'codec' and a 'context'. If you don't provide a codec, steno will encode your logs as JSON.
config = Steno::Config.new( :sinks => [Steno::Sink::IO.new(STDOUT)], :codec => Steno::Codec::Json.new, :context => Steno::Context::ThreadLocal.new)
Alternatively, Steno can read its configuration from a YAML file in the following format:
# config.yml --- logging: file: /some/path # Optional - path a log file max_retries: 3 # Optional - number of times to retry if a file write fails. syslog: some_syslog.id # Optional - only works on *nix systems eventlog: true # Optional - only works on Windows fluentd: # Optional host: fluentd.host port: 9999 level: debug # Optional - Minimum log level that will be written. # Defaults to 'info'
Then, in your code:
config = Steno::Config.from_file("path/to/config.yml")
With this configuration method, if neither
fluentd are provided,
steno will use its stdout as its sink. Also, note that the top-level field
logging is required.
As a third option, steno can be configured using a hash with the same structure as the above
YAML file (without the top-level
config = Steno::Config.from_hash(config_hash)
Steno.init(config) logger = Steno.logger("test") logger.info("Hello world!")
LEVEL NUMERIC RANKING off 0 fatal 1 error 5 warn 10 info 15 debug 16 debug1 17 debug2 18 all 30