A Winston JSON Formatter
npm install winston-json-formatter
``javascript
const { createLogger, transports } = require('winston');
const { configuredFormatter } = require('winston-json-formatter');
// Create Logger and configure options.
const logger = createLogger({
level: 'silly',
transports: [
new (transports.Console)(),
],
});
const options = {
service: 'test-service',
logger: 'Winston-JSON-Formatter',
version: '1.0.0',
typeFormat: 'json'
};
// set winston logger format and print logs.
logger.format = configuredFormatter(options);
// Availale log levels
logger.error('message');
logger.warn('message');
logger.info('message');
logger.verbose('message');
logger.debug('message');
logger.silly('message');
// Error Objects can be logged directly
err = new Error('Heroic BSoD')
logger.error(err)
`
|| NODE_ENV=development => options.typeFormat=console
- Otherwise, (default)| Option | Default | Type |
| -------------------- | ----------------------------- | ----------------------- |
|
options.typeFormat | Default: 'json' | Enum: 'console', 'json' |
| options.hostname | Default: os.hostname() | String |
| options.logger | Default: 'application-logger' | String |
| options.node_env | Default: ENV NODE_ENV | String |
| options.service | | String |
| options.version | | String |Test
`bash
yarn install
yarn test
yarn test:coverage
`Output
$3
javascript> const err = new Error('error message');
> const err.code = 'SOME_CODE';
> // The colon and space here are recommended due to this bug in winston (https://github.com/winstonjs/winston/issues/1634)
> logger.info('log message: ', err);
{
"service": "test-service",
"logger": "Winston-JSON-Formatter",
"hostname": "host",
"level": "info",
"msg": "log message: error message",
"meta": {
"service": {
"version": "1.0.0",
"node_env": ""
},
"logger": {
"time": "2018-11-28T02:52:06.700Z"
},
"event": {
"code": "SOME_CODE"
}
},
"err": {
// There should be a member
"name": "Error" here if it were not for winston bug (https://github.com/winstonjs/winston/issues/1635)
"stack": "THE_ERROR_STACK"
}
}> const err = new Error('error message');
> const err.code = 'SOME_CODE';
> logger.info(err, {foo: 'bar', baz: 'qux'});
{
"service": "test-service",
"logger": "Winston-JSON-Formatter",
"hostname": "host",
"level": "info",
"msg": "message: error message",
"meta": {
"service": {
"version": "1.0.0",
"node_env": ""
},
"logger": {
"time": "2018-11-28T02:52:06.700Z"
},
"event": {
"foo": "bar",
"baz": "qux",
"code": "SOME_CODE"
}
},
"err": {
"name": "Error"
"stack": "THE_ERROR_STACK"
}
}
`$3
!console log style
sh
Generally, the format is:
timestamp level message
stack_if_one_exists
{
other: 'members-if-they-exist'
}
> logger.info("log message") ------------------------------------------------------------------
2019-04-12T02:10:11.091Z info log message
----
> logger.info(new Error("error message")) ------------------------------------------------------------------
2019-04-12T02:10:11.094Z info error message
Error: error message
at Object. (/Users/houli/docs/gitrepos/amida-tech/winston-json-formatter/experiment.js:38:13)
at Module._compile (module.js:653:30)
at Object.Module._extensions..js (module.js:664:10)
at Module.load (module.js:566:32)
at tryModuleLoad (module.js:506:12)
at Function.Module._load (module.js:498:3)
at Function.Module.runMain (module.js:694:10)
at startup (bootstrap_node.js:204:16)
at bootstrap_node.js:625:3
----
> logger.info("message", new Error("error message")) ------------------------------------------------------------------
2019-04-12T02:10:11.095Z info log messageerror message
Error: error message
at Object. (/Users/houli/docs/gitrepos/amida-tech/winston-json-formatter/experiment.js:41:28)
at Module._compile (module.js:653:30)
at Object.Module._extensions..js (module.js:664:10)
at Module.load (module.js:566:32)
at tryModuleLoad (module.js:506:12)
at Function.Module._load (module.js:498:3)
at Function.Module.runMain (module.js:694:10)
at startup (bootstrap_node.js:204:16)
at bootstrap_node.js:625:3
----
> logger.info({a: "a", b: "b"}) ------------------------------------------------------------------
2019-04-12T02:10:11.095Z info
{
"a": "a",
"b": "b"
}
----
> logger.info(new Error("error message"), { a: "a", b: "b" } ) ------------------------------------------------------------------
2019-04-12T02:10:11.096Z info error message
Error: error message
at Object. (/Users/houli/docs/gitrepos/amida-tech/winston-json-formatter/experiment.js:47:13)
at Module._compile (module.js:653:30)
at Object.Module._extensions..js (module.js:664:10)
at Module.load (module.js:566:32)
at tryModuleLoad (module.js:506:12)
at Function.Module._load (module.js:498:3)
at Function.Module.runMain (module.js:694:10)
at startup (bootstrap_node.js:204:16)
at bootstrap_node.js:625:3
{
"a": "a",
"b": "b"
}
----
Logging an object that is not an Error that does have a member named stack will confuse the logger. This is unavoidable.
> logger.info({ name: "some name", stack: "some stack" }) ------------------------------------------------------------------
2019-04-12T02:10:11.096Z info
{
"name": "some name",
"stack": "some stack"
}
some stack
----
Logging an object that is not an Error that does have a member named stack will confuse the logger. This is unavoidable.
> logger.info("message", { name: "some name", stack: "some stack" }) ------------------------------------------------------------------
2019-04-12T02:10:11.096Z info message
some stack
----
> logger.info("message", { a: "a", b: "b" }) ------------------------------------------------------------------
2019-04-12T02:10:11.096Z info message
{
"a": "a",
"b": "b"
}
----
> const err = new Error("error message"); err.code = "SOME_CODE"; logger.info("message", new Error("error message")) ------------------------------------------------------------------
2019-04-12T02:10:11.097Z info messageError A
Error: Error A
at Object. (/Users/houli/docs/gitrepos/amida-tech/winston-json-formatter/experiment.js:58:14)
at Module._compile (module.js:653:30)
at Object.Module._extensions..js (module.js:664:10)
at Module.load (module.js:566:32)
at tryModuleLoad (module.js:506:12)
at Function.Module._load (module.js:498:3)
at Function.Module.runMain (module.js:694:10)
at startup (bootstrap_node.js:204:16)
at bootstrap_node.js:625:3
{
"code": "SOME_CODE"
}
----
> const err = new Error("error message"); err.code = "SOME_CODE"; logger.info(new Error("error message")) ------------------------------------------------------------------
2019-04-12T02:10:11.097Z info Error A
Error: Error A
at Object. (/Users/houli/docs/gitrepos/amida-tech/winston-json-formatter/experiment.js:58:14)
at Module._compile (module.js:653:30)
at Object.Module._extensions..js (module.js:664:10)
at Module.load (module.js:566:32)
at tryModuleLoad (module.js:506:12)
at Function.Module._load (module.js:498:3)
at Function.Module.runMain (module.js:694:10)
at startup (bootstrap_node.js:204:16)
at bootstrap_node.js:625:3
{
"code": "SOME_CODE"
}
----
> const err = new Error("error message"); err.code = "SOME_CODE"; logger.info(new Error("error message"), { a: "a", b: "b" } ) ------------------------------------------------------------------
2019-04-12T02:10:11.097Z info Error A
Error: Error A
at Object. (/Users/houli/docs/gitrepos/amida-tech/winston-json-formatter/experiment.js:58:14)
at Module._compile (module.js:653:30)
at Object.Module._extensions..js (module.js:664:10)
at Module.load (module.js:566:32)
at tryModuleLoad (module.js:506:12)
at Function.Module._load (module.js:498:3)
at Function.Module.runMain (module.js:694:10)
at startup (bootstrap_node.js:204:16)
at bootstrap_node.js:625:3
{
"a": "a",
"b": "b",
"code": "SOME_CODE"
}
`Miscellaneous Goodies
This repo also provides a function to check if a particular log level is greater than the currently configured log level.
Example useage:
js
// In some service...// config.js
module.exports = {
logLevel: 'info',
}
// FancyCustomError.js
import { initLogLevelGte } from 'winston-json-formatter'
const config = require('../config/index.js')
const logLevelGte = initLogLevelGte(config.logLevel)
class FancyCustomError extends Error {
constructor(rootErrorThatCouldHaveSecretStuffInIt, message, foo, bar) {
super()
this.message = message
if (logLevelGte('debug')) {
this.rootErrorThatCouldHaveSecretStuffInIt = rootErrorThatCouldHaveSecretStuffInIt
}
}
}
// someFile.js
logger.info(new FancyCustomError(err, 'Error creating user'))
// When the configured log level is 'info', you would see logged only 'Error creating user', but when the configured log level is 'debug', you would see all the guts and glory.
``