Hyperledger Composer has a functional logger that can be used for both informational and diagnostic log messages. It also permits customization for different logging 'back-ends'.
Log points are added throughout the codebase, and should be very similar to other logging systems. The following APIs match to the standard log levels of debug, verbose, info, warn, error Note that silly isn't being used.
debug(method, msg, data);
verbose(method, msg, data);
info(method, msg, data);
warn(method, msg, data);
error(method, msg, data);In addition, there are entry and exit APIs for use to indicate the entry and exit of functions - these are logged at the debug level.
entry(method, data);
entry(method, data);These methods are called on a logger object. To obtain one of these the following code at the top of the file should be used.
\\ For the businessnetworkdefinition.js file in the composer-common module
const LOG = Logger.getLog('common/BusinessNetworkDefinition');Taking the businessnetworkdefinition.js file as an example, these are some real log statements:
constructor(identifier, description, packageJson, readme) {
const method = 'constructor';
LOG.entry(method, identifier, description);
// ----
LOG.info(method, 'Created package.json' + JSON.stringify(packageJson));
// ----
LOG.debug(method, 'Found model file, loading it', file.name);
// ----
LOG.exit(method);
}All the log APIs can take a variable number of data arguments for logging. Any error object is logged will have it's stack trace located.
In commong with other node.js applications, the DEBUG environment variable is used. This takes a comma separated list of the modules that need to be logged.
Examples
DEBUG=*Logs everything from everything (not just Hyperledger-Composer)DEBUG=composer:*Logs everything from just Hyperledger-ComposerDEBUG=*,!composer:*Logs everything from everything with the exception of Hyperledger-ComposerDEBUG=composer:commonLogs everything from the Hyperledger-Composer common module (the composer-common npm module)DEBUG=composer:client,composer:commonLogs everything from the Hyperledger-Composer common module (the composer-common npm module), and the client moduleDEBUG=composer:common:businessnetworkdefinitionLogs the businessnetworkdefinition ONLY
The structure of the Hyperledger-Composer log code is that it delegates the actually logging to a back-end service. This service can swapped by using configuration (see below) but by default uses the Winston library.
There are two streams setups in the default configuration - one to write log events to a file, the other to the console.
If log is not enabled for Hyperledger-Composer no events are sent to the Console but info events are sent to the file If the log is enabled then info events are sent to the console and all level of events are sent to the file.
The file by default is written to a directory off the current working directory called logs with the name trace_<processid>.log
Configuration is handled by using the config package - a config file called default.json is unless the code has specified something else. As an example - the default configuration of the logger would be represented in this file as
$ cat ./config/default.json
{
"hyperledger-composer": {
"debug": {
"logger": "./winstonInjector.js",
"config": {
'console': {
'enabledLevel': 'info',
'alwaysLevel': 'none'
},
'file': {
'filename': 'trace_PID.log',
'enabledLevel': 'silly',
'alwaysLevel': 'info'
}
}
}
}
}
Here are two examples of how to change the back-end logger simply using Winston's changeable transport feature.
Two cloud hosted application log sites are Loggly.com and Papertrailapp.com
Create a new js file, eg winstonPapertrailInjector.js
'use strict';
const fs = require('fs-extra');
const winston = require('winston');
const sprintf = require('sprintf-js').sprintf;
//
// Requiring `winston-papertrail` will expose
// `winston.transports.Papertrail`
//
require('winston-papertrail').Papertrail;
/** The json structure that has been specified in the configuration
* @private
* @param {Object} config JSON structure with specific configuration information
* @param {Array} configElements array with the DEBUG env variables for composer
*
* @returns {Object} object that is the logger to use
*/
exports.getLogger = function (config,configElements){
let consoleLevel;
let logglyLevel;
if (configElements.debug.length === 0){
consoleLevel='error';
logglyLevel='info';
} else {
papertrailLevel=config.papertrail.enabledLevel;
consoleLevel=config.console.enabledLevel;
}
let formatterFn = function(options) {
// Return string will be passed to logger.
return sprintf('%s %-7s %-20s %s'
,options.timestamp()
,options.level.toUpperCase()
,options.message
,(JSON.stringify(options.meta,null,'') +'$')
);
};
let timestampFn = function() {
return new Date(Date.now()).toISOString();
};
// this is the key part to route to Papertrail - the host and port
let newWinstonLogger = {
transports: [
new(winston.transports.Papertrail)( {
name:'papertrail',
host: 'logs5.papertrailapp.com',
port: '34662',
timestamp: timestampFn,
formatter: formatterFn ,
level: papertrailLevel,
json:true
})
]
};
winston.loggers.add('Hyperledger-Composer',newWinstonLogger);
return winston.loggers.get('Hyperledger-Composer');
};and in a configuration file - where the logger is a reference to the code above.
{
"hyperledger-composer": {
"debug": {
"logger": "/home/matthew/github/waste-notes/winstonPapertrailInjector.js",
"config": {
"console": {
"enabledLevel": "info",
"alwaysLevel": "none"
},"papertrail": {
"enabledLevel": "silly",
"alwaysLevel": "info"
}
}
}
}
}