@sift/logger
v2.0.0
Published
Sift Logger
Downloads
94
Readme
Logger
Log Levels
- CRIT - A critical error has occured, and the process has crashed.
- ERROR - An unexpected error has occured, and the process may have crashed.
- WARNING - An issue has occurred that warrants notification, but the process was allowed to continue.
- INFO - An informational message that should be displayed in production.
- DEBUG - A message that should only be displayed during development.
Logs at INFO or greater severity will be logged by default.
Retrieving a Logger
get-logger
will retrieve an existing logger if a logger has already been
created for the given module name, otherwise, a new logger with default
options will be created automatically and returned.
Example
import { getLogger } from '@sift/logger';
const logger = getLogger('modulea');
logger.info('Hello World!');
Building a Logger
build-logger
will create a new logger if no logger exists for the given
module name, otherwise the existing cached logger will be overridden.
Currently, loggers that have already been retrieved from the cache will
not be updated when build-logger
is called for an existing module.
build-logger Configuration
- moduleName (required) - The moduleName that will be used as the logger cache key. This value will also be included with all logs.
- parent (optional) - A parent logger that the new logger will inherit options from.
- options (optional) - Optional logger configuration. Any options specified will override options from the parent.
- options.level - The maximum level to log at (see Log Levels).
Example
import {
buildLogger,
Level,
} from '@sift/logger';
const parentLogger = buildLogger({
moduleName: 'parent',
options: {
level: Level.DEBUG,
}
});
const logger = buildLogger({
parent: parentLogger,
moduleName: 'logger',
});
Building a Request Logger
build-request-logger
will create a new logger middleware designed to be used
with Express. This logger is primarily for logging HTTP traffic passing through
the Express app.
build-request-logger Configuration
- logger (required) - The logger to use when logging within the middleware
- appName (required) - The name of the application, usually the name within
package.json
- logRequestImmediately (optional) - Whether or not a request should be logged immediately before the response is returned. This option makes sure requests are logged, even if the server crashes; however, the response will not be included in the log.
Structuring Loggers
It is recommended that a root logger is created for the entire application, and loggers are created for each major module in the application. The root logger will serve as the parent for each major module. Each file in the module will use the module logger.
Example
Root Logger
project/logger.ts
import { buildLogger } from '@sift/logger';
export default buildLogger({
moduleName: 'project',
});
Module Logger
project/modulea/logger.ts
import { buildLogger } from '@sift/logger';
import rootLogger from '../logger';
export default buildLogger({
parent: rootLogger,
moduleName: 'project.modulea',
});
Module File
project/modulea/file.ts
import logger from './logger';
logger.info('hello world!');
Logging
Log
import {
getLogger,
Level,
} from '@sift/logger';
const logger = getLogger('module');
logger.log(Level.INFO, 'Hello world!');
{"timestamp":"2019-04-05T15:17:39.951Z","level":"INFO","module":"module","message":"Hello world!"}
Crit
import { getLogger } from '@sift/logger';
const logger = getLogger('module');
logger.crit('Hello world!');
{"timestamp":"2019-04-05T15:14:29.384Z","level":"CRIT","module":"module","message":"Hello world!"}
Error
import { getLogger } from '@sift/logger';
const logger = getLogger('module');
logger.error('Hello world!');
{"timestamp":"2019-04-05T15:14:11.545Z","level":"ERROR","module":"module","message":"Hello world!"}
Warning
import { getLogger } from '@sift/logger';
const logger = getLogger('module');
logger.warning('Hello world!');
{"timestamp":"2019-04-05T15:13:22.852Z","level":"WARNING","module":"module","message":"Hello world!"}
Info
import { getLogger } from '@sift/logger';
const logger = getLogger('module');
logger.info('Hello world!');
{"timestamp":"2019-04-05T15:13:03.391Z","level":"INFO","module":"module","message":"Hello world!"}
Debug
import { getLogger } from '@sift/logger';
const logger = getLogger('module');
logger.debug('Hello world!');
{"timestamp":"2019-04-05T15:12:36.264Z","level":"DEBUG","module":"module","message":"Hello world!"}
Exception Logging
When an Exception
is logged, The message
will be extracted from
the Exception
, and the Exception
's stacktrace will be included
as stack
.
import { getLogger } from '@sift/logger';
const logger = getLogger('module');
logger.warning(new Error('Hello Error!'));
{"timestamp":"2019-04-05T15:07:48.291Z","level":"WARNING","module":"module","message":"Hello Error!","stack":"Error: Hello Error!\n at Object.<anonymous> (/home/tnewman/repos/Lib.Core/test.js:5:16)\n at Module._compile (module.js:653:30)\n at Object.Module._extensions..js (module.js:664:10)\n at Module.load (module.js:566:32)\n at tryModuleLoad (module.js:506:12)\n at Function.Module._load (module.js:498:3)\n at Function.Module.runMain (module.js:694:10)\n at startup (bootstrap_node.js:204:16)\n at bootstrap_node.js:625:3"}
Message Type
Includes the messageType
field in the log to make it easy to identify
standardized messages, such as requests.
import { getLogger } from '@sift/logger';
const logger = getLogger('module');
logger.info('Hello World!', { messageType: 'string' });
{"timestamp":"2019-04-05T15:06:34.642Z","level":"INFO","module":"module","messageType":"string","message":"Hello World!"}
LOG_LEVEL Environment Variable
Setting the LOG_LEVEL environment variable will override the log level for every logger.
LOG_LEVEL=debug node test.js