Logging output

Logging is a vital part of system code, enabling the analysis and detection of runtime problems.

Logging in Fabric is based on the standard Go logging package, github.com/op/go-logging. The logging mechanism provides severity-based control of logs and pretty-printing decoration of messages. The logging levels are defined in decreasing order of severity, as follows:

CRITICAL | ERROR | WARNING | NOTICE | INFO | DEBUG 

The log messages are combined from all components and written into the standard error file (stderr). Logging can be controlled by the configuration of peers and modules, as well as in the code of the chaincode.