logops
Version:
Simple and performant nodejs JSON logger
277 lines (258 loc) • 8.51 kB
JavaScript
/**
* @license
* Copyright 2015 Telefonica Investigación y Desarrollo, S.A.U
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
const formatters = require('./formatters');
const levels = ['DEBUG', 'INFO', 'WARN', 'ERROR', 'FATAL'];
const DEFAULT_LEVEL = 'INFO';
module.exports = logops();
function noop() {};
function logops(options) {
let opts = merge({
level: process.env.LOGOPS_LEVEL || DEFAULT_LEVEL,
format: formatters[process.env.LOGOPS_FORMAT] || (process.env.NODE_ENV === 'development' ?
formatters.dev :
formatters.json
),
getContext: noop,
stream: process.stdout,
}, options);
let API = {};
/**
* Internal private function that implements a decorator to all
* the level functions.
*
* @param {String} level one of
* ['DEBUG', 'INFO', 'WARN', 'ERROR', 'FATAL']
*/
function logWrap(level) {
return function log() {
let context, message, args, trace, err;
if (arguments[0] instanceof Error) {
// log.<level>(err, ...)
context = API.getContext();
args = Array.prototype.slice.call(arguments, 1);
if (!args.length) {
// log.<level>(err)
err = arguments[0];
message = err.name + ': ' + err.message;
} else {
// log.<level>(err, "More %s", "things")
// Use the err as context information
err = arguments[0];
message = arguments[1];
args = Array.prototype.slice.call(args, 1);
}
} else if (arguments[0] == null || (typeof (arguments[0]) !== 'object' && arguments[0] !== null) ||
Array.isArray(arguments[0])) {
// log.<level>(msg, ...)
context = API.getContext();
message = arguments[0];
args = Array.prototype.slice.call(arguments, 1);
} else {
// log.<level>(fields, msg, ...)
context = merge(API.getContext(), arguments[0]);
message = arguments[1];
args = Array.prototype.slice.call(arguments, 2);
}
trace = API.format(level, context || {}, message, args, err);
API.stream.write(trace + '\n');
};
}
/**
* Sets the enabled logging level.
* All the disabled logging methods are replaced by a noop,
* so there is not any performance penalty at production using an undesired level
*
* @param {String} level
*/
function setLevel(level) {
opts.level = level;
let logLevelIndex = levels.indexOf(opts.level.toUpperCase());
levels.forEach((logLevel) => {
let fn;
if (logLevelIndex <= levels.indexOf(logLevel)) {
fn = logWrap(logLevel);
} else {
fn = noop;
}
API[logLevel.toLowerCase()] = fn;
});
}
/**
* The exported API.
* The following methods are added dynamically
* API.debug
* API.info
* API.warn
* API.error
* API.fatal
*
* @type {Object}
*/
API = {
/**
* The stream where the logger will write string traces
* Defaults to process.stdout
*/
stream: opts.stream,
setStream: (stream) => {
API.stream = stream;
},
/**
* Sets the enabled logging level.
* All the disabled logging methods are replaced by a noop,
* so there is not any performance penalty at production using an undesired level
*
* @param {String} level one of the following values
* ['DEBUG', 'INFO', 'WARN', 'ERROR', 'FATAL']
*/
setLevel: setLevel,
/**
* Gets the current log level.
*/
getLevel: () => opts.level,
/**
* Gets the context for a determinate trace. By default, this is a noop that
* you can override if you are managing your execution context with node domains
*
* This function must return an object with the following fields
* {
* corr: {String},
* trans: {String},
* op: {String}
* }
*
* If you are not using domain, you should pass the context information for
* EVERY log call
*
* Both examples will produce the same trace
*
* Example usage not using getContext:
* var logger = require('logops');
* req.context = {
* corr: 'cbefb082-3429-4f5c-aafd-26b060d6a9fc',
* trans: 'cbefb082-3429-4f5c-aafd-26b060d6a9fc',
* op: 'SendEMail'
* }
* logger.info(req.context, 'This is an example');
*
* Example using this feature:
* var logger = require('logops'),
* domain = require('domain');
*
* logger.getContext = function domainContext() {
* return domain.active.myCustomContext;
* }
* //...
*
* logger.info('This is an example');
*
* @return {Object} The context object
*/
getContext: opts.getContext,
setContextGetter: (fn) => {
API.getContext = fn;
},
/**
* Creates a string representation for a trace.
*
* It checks the `LOGOPS_FORMAT` environment variable to use the built-in
* format functions. It fallbacks to check the de-facto `NODE_ENV` env var
* to use the `formatters.dev` when the value is `development`. Otherwise, it
* will use the `formatters.pipe` (while in production, for example)
*
* Example
* NODE_ENV=development node index.js
* the logger will write traces for developers
*
* node index.js
* the logger will write traces in a pipe format (assuming NODE_ENV nor
* LOGOPS_FORMAT environment vars are defined with valid values)
*
* LOGOPS_FORMAT=json node index.js
* the logger will write json traces
*
* You can override this func and manage by yourself the formatting.
*
* @param {String} level One of the following values
* ['DEBUG', 'INFO', 'WARN', 'ERROR', 'FATAL']
* @param {Object} context Additional information to add to the trace
* @param {String} message The main message to be added to the trace
* @param {Array} args More arguments provided to the log function
*
* @return {String} The trace formatted
*/
format: opts.format,
setFormat: (format) => {
API.format = format;
},
/**
* Return an Object containing the available formatters ("dev", "pipe", "json").
*
* Example using this feature to write JSON logs.
*
* var logger = require('logops');
* logger.format = logger.formatters.json;
* logger.info('This is an example')
*
* @return {Object} The available formatters.
*/
formatters: formatters,
/**
* Creates a child logger with the this logger settings that will append the
* passed context to the parent one (if any)
* ```
* let child = logger.child({hostname: 'host.local'});
* child.info({app: 'server'}, 'Startup');
* // {"hostname":"host.local","app":"server","time":"2015-12-23T11:47:25.862Z","lvl":"INFO","msg":"Startup"}
* ```
*/
child: (localContext) => {
// the current limitation for this approach is that child
// loggers will overwrite the parent and localcontext when
// calling againg `child.setContextGetter(fn)` or assign a function
// to `child.getContext = fn`
// But as the context is specified then creating the child, we can
// considerer it a corner case and dont optimize for the use case
return logops({
level: API.getLevel(),
getContext: () => merge(API.getContext(), localContext),
format: API.format,
stream: API.stream,
});
}
};
setLevel(opts.level);
return API;
}
/**
* Merges accesible properties in two objects.
* obj2 takes precedence when common properties are found
*
* @param {Object} obj1
* @param {Object} obj2
* @returns {{}} The merged, new, object
*/
function merge(obj1, obj2) {
var res = {}, attrname;
for (attrname in obj1) {
res[attrname] = obj1[attrname];
}
for (attrname in obj2) {
res[attrname] = obj2[attrname];
}
return res;
}