koa-smplog

Simple request logging for koa using finboxio/smplog

Usage

var Koa = require('koa')
var Log = require('koa-smplog')

// These are default tags you want added to each log line
var defaults = { app: 'my-app' }

var app = Koa()
app.use(Log(defaults))

Features

Logging

koa-smplog will generate a pair of log lines for each received request (one for the request, one for the response) in a similar format to koajs/logger, but extended to support finboxio/smplog metadata and logging levels:

[info]   <-- GET /200 {"trace":"1474401843764ic0stbr8","event":"request-start"}
[info]   --> GET /200 200 10ms 3B {"trace":"1474401843764ic0stbr8","event":"request-end","method":"GET","url":"/200","status_code":200,"response_time_ms":10,"response_size_bytes":3}

Responses with status codes in the 4xx range will be logged at the warn level, while uncaught errors and responses with 5xx status codes will be logged at the error level.

Each logged response will include details about the response size, status, duration, path, and method.

If an error is thrown in the request context, a full JSON description of that error (including the stack trace) will be included in the metadata of the response log line.

Tracing

koa-smplog will also automatically generate a trace-id for every incoming request. Any log messages emitted within that request context will include this trace id, and is useful for filtering out individual request streams. If the x-request-trace header is included in the request, or this.smplog_trace is previously set on the context, koa-smplog will use this trace id instead of generating a new one. This is primarily to enable tracing individual requests across service boundaries.

Tagging

koa-smplog exposes a log instance to subsequent middleware as this.log. This can be used to log request details with the trace-id attached. It can also be tagged using this.log.tag({ prop: 'val', ... }). These tags will be added to the metadata of the final response message. Tags are accumulated, so you can tag multiple times from multiple middleware functions.