@financial-times/n-auto-logger
v4.1.2
Published
an opinionated [enhancer](https://github.com/Financial-Times/n-express-enhancer) to log function calls in the operation/action model > using [n-logger](https://github.com/Financial-Times/n-logger) by default, can be set to any logger instance
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n-auto-logger
an opinionated enhancer to log function calls in the operation/action model
using n-logger by default, can be set to any logger instance
Install
npm install @financial-times/n-auto-logger
Usage
log an Action
automatically log the start, success/failure state with necessary metadata including function name as action
, it can be applied to both individual action function or an action function bundle.
import { logAction, tagService, compose } from '@financial-times/n-auto-logger';
const result = logAction(someFunction)({...params, meta}); // action function
export default compose(
tagService('service-name'), // optional
logAction,
)({
methodA,
methodB,
methodC
}); // action function bundle
more details on action function
log an Operation
automatically log the start, success/failure state with necessary metadata including function name as operation
, it can be applied to both individual operation function or an operation function bundle.
import { logOperation, errorToHanlder, compose } from '@financial-times/n-auto-logger';
const operationFunction = (meta, req, res) => {}; // operation function
const someMiddleware = compose(
errorToHandler,
logOperation
)(operationFunction);
export default compose(
errorToHandler,
logOperation
)({
operationFunctionA,
operationFuncitonB
}); // operation function bundle
more details on operation function
auto log level
set auto log level in .env
with 3 options: verbose
(default) | concise
| error
.
AUTO_LOG_LEVEL=concise
verbose
would log every stage(start, success/failure) of operation and actionconcise
would log success/failure of operation and only failure of actionerror
would log only failure of operation and action
You can override the ENV_VAR with a flag value as well if you would like to switch log level in production for debugging.
mute logger fields
set key names of fields to be muted in .env to reduce log for development or filter fields in production.
LOGGER_MUTE_FIELDS=transactionId, userId
customise logger instance
import { setupLoggerInstance } from '@financial-times/n-auto-logger';
import winston from 'winston'; // you can use any instance as long as it has .info, .warn, .error method
setupLoggerInstance(winston); // set the logger instance before using the enhancer
requestId
use the requestIdMiddleware to ensure the logs are easy to thread when debugging, and this would work well with n-api-factory to pass it to up stream services.
import { requestIdMiddleware } from '@financial-times/n-auto-logger';
// you might want to exclude `__*` path from log
app.use(/^\/(?!_{2}).*$/, [
// use it before any other middleware to be logged
requestIdMiddleware,
//...other middlewares
]);
Gotcha
reserved fields
n-auto-logger
will append values to following reserved fields automatically, the values would be overriden by the key value of the same name in your args/params/meta
or error object, be cautious not to override them unintentionally.
| fields | default | convention used in | |-----------|------------------------------------------------------------------------------------|------------------------| | operation | operationFunction.name | n-auto-logger/metrics | | action | actionFunction.name | n-auto-logger/metrics | | service | tagService('service-name') | n-auto-metrics | | result | 'success''failure' | n-auto-logger | | category | 'FETCH_RESPONSE_ERROR''FETCH_NETWORK_ERROR''NODE_SYSTEM_ERROR''CUSTOM_ERROR' | n-auto-metrics/n-error | | type | specify the unique error type for debugging and error handling | n-auto-metrics/n-error | | status | recorded for service action call failure | n-error/n-api-factory | | stack | error stack trace | n-error |
ignored fields
user
, handler
, _locals
fields from error
or meta
object would not be logged by default.
sensitive personal data could be put in meta.user
and would not be logged
const meta = { ...meta, user: { id, email } };
UI but not debugger facing data could be put in error.user
and would not be logged
e.g. app error status (> API call error status), user message (> error message from API for debugging)
throw nError({ status, message }).extend({ user: { status, message } });
.handler
field would not be logged, as it is only useful for error handler
throw nError({ status: 404 }).extend({ handler: 'REDIRECT_TO_INDEX' });
_locals
field would not be logged as it is verbose and not relevant to debug
// in case you didn't clone the error object in error handler
function(err, req, res, next) {
const e = {...err}; // clone the error object to avoid mutate the input
res.render('template', e); // res.render is not a pure function, it would assign _locals to e
}
error auto parse
n-auto-logger
would parse different forms of the following error objects to logger-suitable format automatically(detail), while it still logs plain object and string message.
- Fetch Response Error
content-type
:application/json
,text/plain
,text/html
- Fetch (Network) Error
- Node native Error objects
- Custom objects extends native Error object
- NError
log auto trim
n-auto-logger
would trim any empty fields and method fields in the input meta or error objects automatically to concise log (detail), you shouldn't be concerned about passing excessive meta fields or extend Error object with methods.
mute logger in test
stub the logger instance instead of the whole module
import logger from '@financial-times/n-auto-logger'; // the underlying logger instance (`n-logger`)
// sinon sandbox
sandbox.stub(logger);
// jest
logger.info = jest.fn();
logger.warn = jest.fn();
logger.error = jest.fn();