Merge pull request #8 from bufferapp/task/log-autoinject

Take advantage of dd-trace `autoinject` feature

Author: erickhun

README.md

@@ -23,4 +23,25 @@ If you wish to see more logs, simply set the `LOG_LEVEL` to the desired level. H
 | NOTICE | Logs that track the general flow of the application. This is the default level |   |
 | WARNING | Logs that highlight an abnormal or unexpected event in the application flow, but do not otherwise cause the application execution to stop.  |   |
 | ERROR |  Logs that highlight when the current flow of execution is stopped due to a failure. These should indicate a failure in the current activity, not an application-wide failure. |   |
-| CRITICAL  | Logs that describe an unrecoverable application or system crash, or a catastrophic failure that requires immediate attention.  |   |
+| CRITICAL  | Logs that describe an unrecoverable application or system crash, or a catastrophic failure that requires immediate attention.  |   |
+
+
+## Add traces to log
+
+A great feature of Datadog is to correlate traces and logs to make troubleshooting easier. 
+
+To take advantage of this, you will need to:
+- install the `dd-trace` package 
+- import it and init it with `logInjection:true`. 
+- BuffLog will append automatically the traces to the logs (only within a request)
+
+```js
+// make sure to put those lines at the very beginning of your service
+import tracer from "dd-trace";
+tracer.init({
+    //  will automatically append the traces to BuffLog
+    logInjection: true
+
+    // ... all other options...
+});
+```

bufflog.ts

@@ -1,9 +1,7 @@
-import tracer from "dd-trace";
-import formats from "dd-trace/ext/formats";
 
 export class BuffLog {
     pinoLogger: any;
-    defaultLevel = String.prototype.toLowerCase.apply(process.env.LOG_LEVEL) || "notice";;
+    defaultLevel = process.env.LOG_LEVEL ? String.prototype.toLowerCase.apply(process.env.LOG_LEVEL) : "notice";
 
     constructor() {
         this.pinoLogger = require('pino')({
@@ -16,19 +14,6 @@ export class BuffLog {
             // soon: remove the `v` field https://github.com/pinojs/pino/issues/620
             base: {},
 
-            mixin () {
-                // Check here if a current trace exist to inject it in the log
-                // `tracer` is a singleton, will no-op if no tracer was initialized
-                var span = tracer.scope().active()
-                if (span) {
-                    const traceInfo = {}
-                    tracer.inject(span.context(), formats.LOG, traceInfo);
-                    return traceInfo;
-                } else {
-                    return {}
-                }
-            },
-
             // notice doesn't exist in pino, let's add it
             customLevels: {
                 notice: 35

index.ts

@@ -1,10 +1,11 @@
 import tracer from "dd-trace";
 import express from 'express';
-import  bufflog from './bufflog';
+import bufflog from './bufflog';
 
 tracer.init({
     hostname: "dd-agent-hostname",
-    logInjection: false
+    //  will automatically append the traces to BuffLog
+    logInjection: true
 });
 
 bufflog.info('hello info');