A synchronous logger for AsyncHooks
npm install synclogA synchronous logger for AsyncHooks.
``bash`
$ npm install synclog
`js
const asyncHooks = require('async_hooks');
const SyncLog = require('synclog');
const log = new SyncLog();
const asyncHook = asyncHooks.createHook({
init(asyncId, type, triggerAsyncId, resource) {
log.info(asyncId, type, triggerAsyncId);
},
}).enable();
`
Synclog is a synchronous logger initially made to be used to print inside AsyncHooks.
Printing to the console is an asynchronous operation using console.log() will causeconsole.log()
the AsyncHooks callbacks to be called. Using or similar asynchronous
operations inside an AsyncHooks callback function will thus cause an infinite recursion.
An easy solution to this when debugging is to use a synchronous logging operation which
will print to stdout and will not invoke AsyncHooks recursively because it is synchronous.
Synclog is such a synchronous logger.
When that is said; this logger can be used outside of AsyncHooks if you need a synchronous
logger. Just be carefull and know how bad synchronous operations in node.js can be.
Create a new SyncLog instance.
`js`
const SyncLog = require('synclog');
const log = new SyncLog(options);
An Object containing misc configuration. The following values can be provided:
* level - String - What log level to output on. Can be fatal, error, warn, info, debug or trace. Default: info.
The SyncLog instance have the following API:
* fatal([args])
* error([args])
* warn([args])
* info([args])
* debug([args])
* trace([args])
All argumens (args) is printed to console.
This module is synchronous and will block the entire process during writing. You should
not use this module in any production environment or where high performance is required.
It will degrade your performance. Use this module only for debugging purposes when
needed.
As said, its not recommended using this library in production code. Though, one might
want to add log statements to your own code without having to depend on this module.
This module is compatible with abslog making
it possible to put log statements in your AsyncHooks code and only pass in this logger
in cases where one are debugging.
Here is an example on how a class with an AsyncHook can abstract its logging away:
`js
const asyncHooks = require('async_hooks');
const abslog = require('abslog');
const MyHook = class MyHook {
constructor (logger) {
const log = abslog(logger);
const asyncHook = asyncHooks.createHook({
init(asyncId, type, triggerAsyncId, resource) {
log.info(asyncId, type, triggerAsyncId);
},
}).enable();
}
};
`
When using the above class, ex locally, one can provide this module as a logger:
`js
const MyHook = require('MyHook');
const SyncLog = require('synclog');
const hook = new MyHook(new SyncLog());
`
When not debugging, ex in production, one can use the same class without passing
in a logger at all:
`js
const MyHook = require('MyHook');
const hook = new MyHook();
``
The MIT License (MIT)
Copyright (c) 2018 - Trygve Lie - post@trygve-lie.com
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