@skutopia/logger v4.0.0
SKUtopia Logger
SKUtopia Logger enables the tracing of requests across servers and throughout applications in Express.js. It enables this correlation by consuming the X-Request-Id if one exists, or generating a request id if one does not. It then provides a context-aware logger that can be invoked throughout the call-stack, appending the request id to the log message.
It is based on Winston and express-winston libraries and uses SumoLogic's preferred severity definitions.
Usage
Full example
import {
configureAccessLoggingMiddleware,
loggingContextCreatorMiddleware,
logger
} from '@skutopia/logger';
import * as express from 'express';
const server = express();
server.use(loggingContextCreatorMiddleware);
server.use(configureAccessLoggingMiddleware({ ignoredRoutes: ['/livez', '/readyz'] }));
const doFunctionCall = () => {
logger.info('This log will have the request id attached to it');
}
server.get('/', (req, res) => {
doFunctionCall(); // No work required to attach the request id to nested log calls
res.send('Hello World!');
});
Express.js access log
configureAccessLoggingMiddleware
produces access logs from Express.js. This logging middleware must be loaded
BEFORE the route handler to capture the request-response lifecycle.
import { configureAccessLoggingMiddleware } from '@skutopia/logger';
import * as express from 'express';
const app = express();
// The logging middleware goes before the route handler.
app.use(configureAccessLoggingMiddleware({ ignoredRoutes: ['/livez', '/readyz'] }));
app.get('/', (req, res) => {
res.send('Hello World!');
// Access logs for this route include the request id.
});
app.listen(3000);
Express.js error log for uncaught exceptions from route handlers
errorLoggingMiddleware
produces contextualised error logs for uncaught errors in the route handlers from Express.js.
This logging middleware must be loaded AFTER the route handler and before any custom error handlers which are
directed with next(err)
at the final stage of the request-response lifecycle.
import { errorLoggingMiddleware } from '@skutopia/logger';
import * as express from 'express';
const app = express();
app.use(router);
// The logging middleware goes after the route handler and before the custom error handler.
app.use(errorLoggingMiddleware);
app.use(customErrorHandler);
Logging with context
loggingContextCreatorMiddleware
provides the context necessary for the context-aware logger. This logging middleware
must be loaded
BEFORE the route handler.
After the logging middleware is loaded, you can simply use logger
from the @skutopia/logger
package to log messages.
To load the middleware,
import { loggingContextCreatorMiddleware } from '@skutopia/logger';
import * as express from 'express';
const app = express();
app.use(loggingContextCreatorMiddleware);
app.use(router);
To get the context object from the request object and use the logger
import { logger } from '@skutopia/logger';
function myHandler(req: express.Request, res: express.Response) {
logger.info('info message');
logger.error('error message');
logger.fatal('fatal message');
}
Logging without context
Always use logger
even if you do not expect the log to occur during a request. logger
automatically utilises a
non-contextualised logger when a log context is not available. This ensures that code can be safely refactored and the
context aware logger will adapt accordingly.
import { logger } from 'skutopia-logger';
logger.info('info message');
logger.error('error message');
logger.fatal('fatal message');
Pretty print
By default, the output is in JSON format. To print it in a human-readable format, set this environment variable. This is not recommended for Production
PRETTY_LOG_FORMAT=true
Contribution
Test
By default, the test Express.js server listens to port 8080
. You can specify a different port by setting the
environment variable PORT
with
PORT=3000 npm run test
Commit guidelines
This repo uses husky and commitlint to enforce commit message. Please always use
npm run commit
to submit commit messages.
Publish guidelines
Go through the release process by doing the following:
npm run release
This will create a release and once merged to the main branch, publish it to NPM public repository.
API Reference
Please refer to the generated docs for the API reference.
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