@loopback/logging

This module contains a component that provides logging facilities based on
Winston and
Fluentd.

Stability: ⚠️Experimental⚠️

> Experimental packages provide early access to advanced or experimental
> functionality to get community feedback. Such modules are published to npm
> using 0.x.y versions. Their APIs and functionality may be subject to
> breaking changes in future releases.

Architecture overview

!logging-component

Installation

``sh
npm install --save @loopback/logging
`

Basic use

The component should be loaded in the constructor of your custom Application
class.

Start by importing the component class:

`ts
import {LoggingComponent} from '@loopback/logging';
`

In the constructor, add the component to your application:

`ts
this.component(LoggingComponent);
`

Now your application can add a controller as follows to leverage the logging
facilities:

`ts
import {inject} from '@loopback/core';
import {WinstonLogger, logInvocation} from '@loopback/logging';
import {get, param} from '@loopback/rest';

class MyController {
// Inject a winston logger
@inject(LoggingBindings.WINSTON_LOGGER)
private logger: WinstonLogger;

// http access is logged by a global interceptor
@get('/greet/{name}')
// log the greet method invocations
@logInvocation()
greet(@param.path.string('name') name: string) {
return Hello, ${name};
}

@get('/hello/{name}')
hello(@param.path.string('name') name: string) {
// Use the winston logger explicitly
this.logger.log('info', greeting ${name});
return Hello, ${name};
}
}
`

Configure the logging component

The logging component can be configured as follows:

`ts
app.configure(LoggingBindings.COMPONENT).to({
enableFluent: false, // default to true
enableHttpAccessLog: true, // default to true
});
`

{% include note.html content="this.configure() must be called before
this.component() to take effect." %}

- enableFluent: Enable logs to be sent to Fluentd
- enableHttpAccessLog: Enable all http requests to be logged via a global
interceptor

The component contributes bindings with keys declared under LoggingBindings
namespace as follows:

- FLUENT_SENDER - A fluent sender
- WINSTON_LOGGER - A winston logger
- WINSTON_TRANSPORT_FLUENT - A fluent transport for winston
- WINSTON_INTERCEPTOR - A local interceptor set by @logInvocation to log
method invocations
- WINSTON_HTTP_ACCESS_LOGGER - A global interceptor that logs http access with
Morgan format

The fluent sender and transport for winston can be configured against
FLUENT_SENDER:

`ts
import {LoggingBindings} from '@loopback/logging';

app.configure(LoggingBindings.FLUENT_SENDER).to({
host: process.env.FLUENTD_SERVICE_HOST ?? 'localhost',
port: +(process.env.FLUENTD_SERVICE_PORT_TCP ?? 24224),
timeout: 3.0,
reconnectInterval: 600000, // 10 minutes
});
`

The winston logger can be configured against LoggingBindings.WINSTON_LOGGER:

`ts
import {LoggingBindings} from '@loopback/logging';

ctx.configure(LoggingBindings.WINSTON_LOGGER).to({
level: 'info',
format: format.json(),
defaultMeta: {framework: 'LoopBack'},
});
`

The winston logger accepts two types of extensions to the following extension
points:

- WINSTON_TRANSPORT = 'logging.winston.transport'
- WINSTON_FORMAT = 'logging.winston.format'

`ts
import {extensionFor} from '@loopback/core';
import {format} from 'winston';
import {
WINSTON_FORMAT,
WINSTON_TRANSPORT,
WinstonFormat,
WinstonTransports,
} from '@loopback/logging';

const myFormat: WinstonFormat = format((info, opts) => {
console.log(info);
return false;
})();

ctx
.bind('logging.winston.formats.myFormat')
.to(myFormat)
.apply(extensionFor(WINSTON_FORMAT));
ctx
.bind('logging.winston.formats.colorize')
.to(format.colorize())
.apply(extensionFor(WINSTON_FORMAT));

const consoleTransport = new WinstonTransports.Console({
level: 'info',
format: format.combine(format.colorize(), format.simple()),
});
ctx
.bind('logging.winston.transports.console')
.to(consoleTransport)
.apply(extensionFor(WINSTON_TRANSPORT));
`

If no transport is contributed, the winston logger uses the
console transport.

No default format is configured for the winston logger.

The access log interceptor can also be configured to customize
Morgan format and options:

`ts
ctx
.configure(LoggingBindings.WINSTON_HTTP_ACCESS_LOGGER)
.to({format: 'combined'});
`

Contributions

- Guidelines
- Join the team

Tests

Run npm test from the root folder.

The acceptance test against fluentd is available as a separate package at
acceptance/extension-logging-fluentd`.

Contributors

See
all contributors.

License

MIT