plugin inheritance explicitly specified

src/plugins/AMQPLibPlugin.ts

@@ -44,7 +44,7 @@ class AMQPLibPlugin implements SwPlugin {
       const queue = fields.routingKey || '';
       const peer = `${this.connection.stream.remoteAddress}:${this.connection.stream.remotePort}`;
 
-      const span = ContextManager.current.newExitSpan('RabbitMQ/' + topic + '/' + queue + '/Producer', peer).start();
+      const span = ContextManager.current.newExitSpan('RabbitMQ/' + topic + '/' + queue + '/Producer', peer, Component.RABBITMQ_PRODUCER).start();
 
       try {
         span.inject().items.forEach((item) => {

src/plugins/AxiosPlugin.ts

@@ -39,7 +39,7 @@ class AxiosPlugin implements SwPlugin {
 
     defaults.adapter = (config: any) => {
       const { host, pathname: operation } = new URL(config.url);  // TODO: this may throw invalid URL
-      const span = ContextManager.current.newExitSpan(operation, host).start();
+      const span = ContextManager.current.newExitSpan(operation, host, Component.AXIOS, Component.HTTP).start();
 
       let ret: any;
 

src/plugins/ExpressPlugin.ts

@@ -49,7 +49,7 @@ class ExpressPlugin implements SwPlugin {
 
       const carrier = ContextCarrier.from(headersMap);
       const operation = (req.url || '/').replace(/\?.*/g, '');
-      const span = ContextManager.current.newEntrySpan(operation, carrier).start();
+      const span = ContextManager.current.newEntrySpan(operation, carrier, Component.HTTP_SERVER).start();
 
       let stopped = 0;
       const stopIfNotStopped = (err: Error | null) => {

src/plugins/HttpPlugin.ts

@@ -62,7 +62,7 @@ class HttpPlugin implements SwPlugin {
 
       let stopped = 0;  // compensating if request aborted right after creation 'close' is not emitted
       const stopIfNotStopped = () => !stopped++ ? span.stop() : null;  // make sure we stop only because other events may proc along with req.'close'
-      const span: ExitSpan = ContextManager.current.newExitSpan(operation, host).start() as ExitSpan;
+      const span: ExitSpan = ContextManager.current.newExitSpan(operation, host, Component.HTTP).start() as ExitSpan;
 
       try {
         if (span.depth === 1) {  // only set HTTP if this span is not overridden by a higher level one

src/plugins/MongoDBPlugin.ts

@@ -41,13 +41,11 @@ class MongoDBPlugin implements SwPlugin {
       return false;
 
     cursor.on('error', (err: any) => {
-      // span.resync();  // this may precede 'close' .resync() but its fine
       span.error(err);
       span.stop();
     });
 
     cursor.on('close', () => {
-      // span.resync();  // cursor does not .resync() until it is closed because maybe other exit spans will be opened during processing
       span.stop();
     });
 
@@ -67,8 +65,6 @@ class MongoDBPlugin implements SwPlugin {
 
       args[idx] = function(this: any, error: any, result: any) {
         if (error || !plugin.maybeHookCursor(span, result)) {
-          // span.resync();
-
           if (error)
             span.error(error);
 
@@ -242,7 +238,7 @@ class MongoDBPlugin implements SwPlugin {
         host = '???';
       }
 
-      span = ContextManager.current.newExitSpan('MongoDB/' + operation, host).start();
+      span = ContextManager.current.newExitSpan('MongoDB/' + operation, host, Component.MONGODB).start();
 
       try {
         span.component = Component.MONGODB;
@@ -268,14 +264,12 @@ class MongoDBPlugin implements SwPlugin {
           } else {
             ret = ret.then(
               (res: any) => {
-                // span.resync();
                 span.stop();
 
                 return res;
               },
 
               (err: any) => {
-                // span.resync();
                 span.error(err);
                 span.stop();
 

src/plugins/MySQLPlugin.ts

@@ -36,8 +36,6 @@ class MySQLPlugin implements SwPlugin {
     Connection.prototype.query = function(sql: any, values: any, cb: any) {
       const wrapCallback = (_cb: any) => {
         return function(this: any, error: any, results: any, fields: any) {
-          // span.resync();
-
           if (error)
             span.error(error);
 
@@ -50,7 +48,7 @@ class MySQLPlugin implements SwPlugin {
       let query: any;
 
       const host = `${this.config.host}:${this.config.port}`;
-      const span = ContextManager.current.newExitSpan('mysql/query', host).start();
+      const span = ContextManager.current.newExitSpan('mysql/query', host, Component.MYSQL).start();
 
       try {
         span.component = Component.MYSQL;
@@ -122,12 +120,10 @@ class MySQLPlugin implements SwPlugin {
 
         if (streaming) {
           query.on('error', (e: any) => {
-            // span.resync();
             span.error(e);
           });
 
           query.on('end', () => {
-            // span.resync();  // may have already been done in 'error' but safe to do multiple times
             span.stop()
           });
         }

src/plugins/PgPlugin.ts

@@ -43,8 +43,6 @@ class MySQLPlugin implements SwPlugin {
     Client.prototype.query = function(config: any, values: any, callback: any) {
       const wrapCallback = (_cb: any) => {
         return function(this: any, err: any, res: any) {
-          // span.resync();
-
           if (err)
             span.error(err);
 
@@ -57,7 +55,7 @@ class MySQLPlugin implements SwPlugin {
       let query: any;
 
       const host = `${this.host}:${this.port}`;
-      const span = ContextManager.current.newExitSpan('pg/query', host).start();
+      const span = ContextManager.current.newExitSpan('pg/query', host, Component.POSTGRESQL).start();
 
       try {
         span.component = Component.POSTGRESQL;
@@ -105,27 +103,23 @@ class MySQLPlugin implements SwPlugin {
         if (query) {
           if (Cursor && query instanceof Cursor) {
             query.on('error', (err: any) => {
-              // span.resync();  // this may precede 'end' .resync() but its fine
               span.error(err);
               span.stop();
             });
 
             query.on('end', () => {
-              // span.resync();  // cursor does not .resync() until it is closed because maybe other exit spans will be opened during processing
               span.stop();
             });
 
           } else if (typeof query.then === 'function') {  // generic Promise check
             query = query.then(
               (res: any) => {
-                // span.resync();
                 span.stop();
 
                 return res;
               },
 
               (err: any) => {
-                // span.resync();
                 span.error(err);
                 span.stop();
 

src/trace/context/Context.ts

@@ -19,16 +19,23 @@
 
 import Span from '../../trace/span/Span';
 import Segment from '../../trace/context/Segment';
+import { Component } from '../../trace/Component';
 import { ContextCarrier } from './ContextCarrier';
 
 export default interface Context {
   segment: Segment;
 
   newLocalSpan(operation: string): Span;
 
-  newEntrySpan(operation: string, carrier?: ContextCarrier): Span;
+  /* If 'inherit' is specified then if the span at the top of the stack is an Entry span of this component type then the
+     span is reused instead of a new child span being created. This is intended for situations like an express handler
+     inheriting an opened incoming http connection to present a single span. */
+  newEntrySpan(operation: string, carrier?: ContextCarrier, inherit?: Component): Span;
 
-  newExitSpan(operation: string, peer: string): Span;
+  /* if 'inherit' is specified then the span returned is marked for inheritance by an Exit span component which is
+     created later and calls this function with a matching 'component' value. For example Axios using an Http exit
+     connection will be merged into a single exit span, see those plugins for how this is done. */
+  newExitSpan(operation: string, peer: string, component: Component, inherit?: Component): Span;
 
   start(span: Span): Context;
 

src/trace/context/DummyContext.ts

@@ -21,6 +21,7 @@ import Context from '../../trace/context/Context';
 import Span from '../../trace/span/Span';
 import DummySpan from '../../trace/span/DummySpan';
 import Segment from '../../trace/context/Segment';
+import { Component } from '../../trace/Component';
 import { SpanType } from '../../proto/language-agent/Tracing_pb';
 import { ContextCarrier } from './ContextCarrier';
 
@@ -33,11 +34,11 @@ export default class DummyContext implements Context {
   segment: Segment = new Segment();
   depth = 0;
 
-  newEntrySpan(operation: string, carrier?: ContextCarrier): Span {
+  newEntrySpan(operation: string, carrier?: ContextCarrier, inherit?: Component): Span {
     return this.span;
   }
 
-  newExitSpan(operation: string, peer: string): Span {
+  newExitSpan(operation: string, peer: string, component: Component, inherit?: Component): Span {
     return this.span;
   }
 

src/trace/context/SpanContext.ts

@@ -26,6 +26,7 @@ import Segment from '../../trace/context/Segment';
 import EntrySpan from '../../trace/span/EntrySpan';
 import ExitSpan from '../../trace/span/ExitSpan';
 import LocalSpan from '../../trace/span/LocalSpan';
+import { Component } from '../../trace/Component';
 import { createLogger } from '../../logging';
 import { executionAsyncId } from 'async_hooks';
 import { ContextCarrier } from './ContextCarrier';
@@ -63,7 +64,7 @@ export default class SpanContext implements Context {
     return undefined;
   }
 
-  newEntrySpan(operation: string, carrier?: ContextCarrier): Span {
+  newEntrySpan(operation: string, carrier?: ContextCarrier, inherit?: Component): Span {
     let span = this.ignoreCheck(operation, SpanType.ENTRY);
 
     if (span)
@@ -79,7 +80,7 @@ export default class SpanContext implements Context {
       });
     }
 
-    if (parent && parent.type === SpanType.ENTRY) {
+    if (parent && parent.type === SpanType.ENTRY && inherit && inherit === parent.component) {
       span = parent;
       parent.operation = operation;
 
@@ -99,7 +100,7 @@ export default class SpanContext implements Context {
     return span;
   }
 
-  newExitSpan(operation: string, peer: string): Span {
+  newExitSpan(operation: string, peer: string, component: Component, inherit?: Component): Span {
     let span = this.ignoreCheck(operation, SpanType.EXIT);
 
     if (span)
@@ -117,7 +118,7 @@ export default class SpanContext implements Context {
       });
     }
 
-    if (parent && parent.type === SpanType.EXIT) {
+    if (parent && parent.type === SpanType.EXIT && component && component === parent.inherit) {
       span = parent;
 
     } else {
@@ -130,6 +131,9 @@ export default class SpanContext implements Context {
       });
     }
 
+    if (inherit)
+      span.inherit = inherit;
+
     return span;
   }
 

src/trace/span/Span.ts

@@ -50,6 +50,7 @@ export default abstract class Span {
   operation: string;
   layer = SpanLayer.UNKNOWN;
   component = Component.UNKNOWN;
+  inherit?: Component;
 
   readonly tags: Tag[] = [];
   readonly logs: Log[] = [];