node-winston-context
Contextual logger for Winston, here used for adding per-request context to server logs:
var WinstonContext = require('winston-context');
var logger = require('winston');
// Create a per-request child
var requestCtx = new WinstonContext(logger, '', {
requestId: (Math.random()* 1e20).toString(36)
});
requestCtx.info('server.init'); // info: server.init requestId=2yn869172v40g
// User is authenticated, so we add userId
requestCtx = requestCtx.getContext('', { userId: 42 });
requestCtx.info('auth.ok'); // info: auth.ok requestId=2yn869172v40g userId=42
// We now have to log a lot of stuff for this user in a specific place
var log = requestCtx.getContext('server.system.subsystem');
log.warn('err', { what: 'User not found' }); // warn: sever.system.subsystem.err requestId=2yn869172v40g userId=24 waht="User not found"
API
ctx = new WinstonContext(logger, [prefix, [meta]]) Creates a new contextual logger.
It mocks .log and the per-level helpers set on the original logger.
ctx.log(level, name, meta, [meta, [...,]] callback) and
ctx.{silly,debug,verbose,info,warn,error}(name, meta, callback) (or whatever
else level-names you've given Winston) behave like they use to, except the
added contextual prefix, metadata and allows handling multiple meta-objects.
ctx.getContext([prefix, [meta]]) gets a contextual logger with the
added prefix/meta-data. May be called recursively. Also of note is that it
computes the complete prefix and meta-data at instantiation and gets a direct
pointer to the parent logger (thus making long inheritance-chains performant).
WinstonContext.patchWinstonWithGetContext(winstonInstance) Monkey-patches the
given instance of Winston with a .getContext() method that hands out new
contexts as above.
Bugs
Plenty! Please report them.
License
ISC