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Logging Control

Overview

Logging in the peer application and in the shim interface to chaincodes is programmed using facilities provided by the github.com/op/go-logging package. This package supports

  • Logging control based on the severity of the message
  • Logging control based on the software module generating the message
  • Different pretty-printing options based on the severity of the message

All logs are currently directed to stderr, and the pretty-printing is currently fixed. However global and module-level control of logging by severity is provided for both users and developers. There are currently no formalized rules for the types of information provided at each severity level, however when submitting bug reports the developers may want to see full logs down to the DEBUG level.

In pretty-printed logs the logging level is indicated both by color and by a 4-character code, e.g, "ERRO" for ERROR, "DEBU" for DEBUG, etc. In the logging context a module is an arbitrary name (string) given by developers to groups of related messages. In the pretty-printed example below, the logging modules "peer", "rest" and "main" are generating logs.

16:47:09.634 [peer] GetLocalAddress -> INFO 033 Auto detected peer address: 9.3.158.178:30303
16:47:09.635 [rest] StartOpenchainRESTServer -> INFO 035 Initializing the REST service...
16:47:09.635 [main] serve -> INFO 036 Starting peer with id=name:"vp1" , network id=dev, address=9.3.158.178:30303, discovery.rootnode=, validator=true

An arbitrary number of logging modules can be created at runtime, therefore there is no "master list" of modules, and logging control constructs can not check whether logging modules actually do or will exist.

PEER

The logging level of the peer command can be controlled from the command line for each invocation using the --logging-level flag, for example

peer peer --logging-level=debug

The default logging level for each individual peer subcommand can also be set in the openchain.yaml file. For example the key logging.peer sets the default level for the peer subcommmand.

Logging severity levels are specified using case-insensitive strings chosen from

CRITICAL | ERROR | WARNING | NOTICE | INFO | DEBUG

The full logging level specification for the peer is of the form

[<module>[,<module>...]=]<level>[:[<module>[,<module>...]=]<level>...]

A logging level by itself is taken as the overall default. Otherwise, overrides for individual or groups of modules can be specified using the

<module>[,<module>...]=<level>

syntax. Examples of specifications (valid for both --logging-level and openchain.yaml settings):

info                                       - Set default to INFO
warning:main,db=debug:chaincode=info       - Default WARNING; Override for main,db,chaincode
chaincode=info:main=debug:db=debug:warning - Same as above

GO chaincodes

There is currently no generic way to control logging in GO chaincodes. The chaincode shim currently defaults to DEBUG level logging, creating large log files in the chaincode containers. The following is a suggested workaround: First, add

"github.com/op/go-logging"

to the imports of the chaincode. Also add a line like

logging.SetLevel(logging.WARNING, "")

as the first line of the chaincode main routine to suppress all but WARNING and more severe errors.