Adds service name (closes #14) (#20)

* Adds service name (closes #14)

* modify environment variable

* generate docs

* update tests with lowercase env var

API.md

@@ -268,6 +268,8 @@ Construct a new tracer for internal use only.  Use [GlobalTracer#init](#globaltr
     -   `options.multiEvent` **bool?** true for multi-event mode; otherwise, single-event mode
     -   `options.debug` **bool?** true for debug; otherwise, it is disabled
     -   `options.propagators` **[object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)<[string](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String), [Propagators](#propagators)>?** optional propagators
+    -   `options.serviceName` **[string](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)?** allows the configuration of the "service" tag for the entire Tracer if not
+                                                specified here, can also be set using env variable "ctrace_service_name"
 
 ### startSpan
 

README.md

@@ -51,7 +51,8 @@ tracer.init({
         }
       }
     ]
-  }
+  },
+  serviceName: "ExampleService" // can set service name for entire tracer 
 })
 ```
 

src/tracer.js

@@ -31,6 +31,8 @@ export default class Tracer {
    * @param {bool} [options.multiEvent] - true for multi-event mode; otherwise, single-event mode
    * @param {bool} [options.debug] - true for debug; otherwise, it is disabled
    * @param {object.<string, Propagators>} [options.propagators] - optional propagators
+   * @param {string} [options.serviceName] - allows the configuration of the "service" tag for the entire Tracer if not
+   *                                         specified here, can also be set using env variable "ctrace_service_name"
    */
   constructor (options = {}) {
     this._reporter = options.reporter || new Reporter(Encoder, options.stream)
@@ -50,6 +52,8 @@ export default class Tracer {
         this._propagation[key] = (list || []).concat(props[key])
       }
     }
+    // Can specify "service" tag for the entire Tracer using options or environment variable "ctrace_service_name"
+    this.serviceName = options.serviceName || process.env.ctrace_service_name
   }
 
   // ---------------------------------------------------------------------- //
@@ -127,6 +131,11 @@ export default class Tracer {
       f.tags = options.tags
     }
 
+    if (this.serviceName) {
+      f.tags = f.tags || {}
+      f.tags["service"] = this.serviceName
+    }
+
     if (baggage) {
       f.baggage = baggage
     }

test/tracer.spec.js

@@ -210,7 +210,31 @@ describe('tracer', () => {
       }), ['timestamp'])
       debugEvent2.should.eql({ event: 'Debug Log', level: 'debug', debug: true })
     })
-
+    describe('with service name', function () {
+      const serviceName = "TestService"
+      describe('from environment variable', function () {
+        beforeEach(() => {
+          process.env.ctrace_service_name = serviceName
+          tracer.init({stream})
+        })
+        afterEach(() => { delete process.env.ctrace_service_name })
+        it('tags should include service name', function () {
+          let span = tracer.startSpan('originating')
+          let fields = span._fields
+          fields.tags.service.should.equal(serviceName)
+        })
+      })
+      describe('from tracer options', function () {
+        beforeEach(() => {
+          tracer.init({stream, serviceName})
+        })
+        it('tags should include service name', function () {
+          let span = tracer.startSpan('originating')
+          let fields = span._fields
+          fields.tags.service.should.equal("TestService")
+        })
+      })
+    })
   })
 
   describe('with custom propagators', () => {