Fix missing spans in gorillamux instrumentation

CHANGELOG.md

@@ -11,6 +11,7 @@ OpenTelemetry Go Automatic Instrumentation adheres to [Semantic Versioning](http
 ### Fixed
 
 - Fix gRPC instrumentation memory access issue on newer kernels. ([#150](https://github.com/open-telemetry/opentelemetry-go-instrumentation/pull/150))
+- Fix missing spans in gorillamux instrumentation. ([#86](https://github.com/open-telemetry/opentelemetry-go-instrumentation/pull/86))
 
 ### Changed
 

pkg/instrumentors/bpf/github.com/gin-gonic/gin/bpf/probe.bpf.c

@@ -19,7 +19,7 @@
 char __license[] SEC("license") = "Dual MIT/GPL";
 
 #define PATH_MAX_LEN 100
-#define METHOD_MAX_LEN 6 // Longer method: DELETE
+#define METHOD_MAX_LEN 7
 #define MAX_CONCURRENT 50
 
 struct http_request_t {

pkg/instrumentors/bpf/github.com/gin-gonic/gin/probe.go

@@ -46,7 +46,7 @@ import (
 type Event struct {
 	StartTime   uint64
 	EndTime     uint64
-	Method      [6]byte
+	Method      [7]byte
 	Path        [100]byte
 	SpanContext context.EBPFSpanContext
 }

pkg/instrumentors/bpf/github.com/gorilla/mux/bpf/probe.bpf.c

@@ -19,7 +19,7 @@
 char __license[] SEC("license") = "Dual MIT/GPL";
 
 #define PATH_MAX_LEN 100
-#define METHOD_MAX_LEN 6 // Longer method: DELETE
+#define METHOD_MAX_LEN 7
 #define MAX_CONCURRENT 50
 
 struct http_request_t {
@@ -91,8 +91,11 @@ int uprobe_GorillaMux_ServeHTTP(struct pt_regs *ctx) {
 
 SEC("uprobe/GorillaMux_ServeHTTP")
 int uprobe_GorillaMux_ServeHTTP_Returns(struct pt_regs *ctx) {
+    u64 request_pos = 4;
     void *goroutine = get_goroutine_address(ctx, ctx_ptr_pos);
-    void *httpReq_ptr = bpf_map_lookup_elem(&context_to_http_events, &goroutine);
+    void* req_ptr = get_argument(ctx, request_pos);
+
+    void* httpReq_ptr = bpf_map_lookup_elem(&context_to_http_events, &goroutine);
     struct http_request_t httpReq = {};
     bpf_probe_read(&httpReq, sizeof(httpReq), httpReq_ptr);
     httpReq.end_time = bpf_ktime_get_ns();

pkg/instrumentors/bpf/github.com/gorilla/mux/probe.go

@@ -45,15 +45,15 @@ import (
 type Event struct {
 	StartTime   uint64
 	EndTime     uint64
-	Method      [100]byte
+	Method      [7]byte
 	Path        [100]byte
 	SpanContext context.EBPFSpanContext
 }
 
 // Instrumentor is the gorilla/mux instrumentor.
 type Instrumentor struct {
 	bpfObjects   *bpfObjects
-	uprobe       link.Link
+	uprobes      []link.Link
 	returnProbs  []link.Link
 	eventsReader *perf.Reader
 }
@@ -113,41 +113,51 @@ func (g *Instrumentor) Load(ctx *context.InstrumentorContext) error {
 		return err
 	}
 
-	offset, err := ctx.TargetDetails.GetFunctionOffset(g.FuncNames()[0])
+	for _, funcName := range g.FuncNames() {
+		g.registerProbes(ctx, funcName)
+	}
+	rd, err := perf.NewReader(g.bpfObjects.Events, os.Getpagesize())
 	if err != nil {
 		return err
 	}
+	g.eventsReader = rd
+
+	return nil
+}
+
+func (g *Instrumentor) registerProbes(ctx *context.InstrumentorContext, funcName string) {
+	logger := log.Logger.WithName("gorilla/mux-instrumentor").WithValues("function", funcName)
+	offset, err := ctx.TargetDetails.GetFunctionOffset(funcName)
+	if err != nil {
+		logger.Error(err, "could not find function start offset. Skipping")
+		return
+	}
+	retOffsets, err := ctx.TargetDetails.GetFunctionReturns(funcName)
+	if err != nil {
+		logger.Error(err, "could not find function end offset. Skipping")
+		return
+	}
 
 	up, err := ctx.Executable.Uprobe("", g.bpfObjects.UprobeGorillaMuxServeHTTP, &link.UprobeOptions{
 		Address: offset,
 	})
 	if err != nil {
-		return err
+		logger.Error(err, "could not insert start uprobe. Skipping")
+		return
 	}
 
-	g.uprobe = up
-	retOffsets, err := ctx.TargetDetails.GetFunctionReturns(g.FuncNames()[0])
-	if err != nil {
-		return err
-	}
+	g.uprobes = append(g.uprobes, up)
 
 	for _, ret := range retOffsets {
 		retProbe, err := ctx.Executable.Uprobe("", g.bpfObjects.UprobeGorillaMuxServeHTTP_Returns, &link.UprobeOptions{
 			Address: ret,
 		})
 		if err != nil {
-			return err
+			logger.Error(err, "could not insert return uprobe. Skipping")
+			return
 		}
 		g.returnProbs = append(g.returnProbs, retProbe)
 	}
-
-	rd, err := perf.NewReader(g.bpfObjects.Events, os.Getpagesize())
-	if err != nil {
-		return err
-	}
-	g.eventsReader = rd
-
-	return nil
 }
 
 // Run runs the events processing loop.
@@ -210,8 +220,8 @@ func (g *Instrumentor) Close() {
 		g.eventsReader.Close()
 	}
 
-	if g.uprobe != nil {
-		g.uprobe.Close()
+	for _, r := range g.uprobes {
+		r.Close()
 	}
 
 	for _, r := range g.returnProbs {

pkg/instrumentors/bpf/net/http/server/bpf/probe.bpf.c

@@ -19,7 +19,7 @@
 char __license[] SEC("license") = "Dual MIT/GPL";
 
 #define PATH_MAX_LEN 100
-#define METHOD_MAX_LEN 6 // Longer method: DELETE
+#define METHOD_MAX_LEN 7
 #define MAX_CONCURRENT 50
 
 struct http_request_t

pkg/instrumentors/bpf/net/http/server/probe.go

@@ -45,7 +45,7 @@ import (
 type Event struct {
 	StartTime   uint64
 	EndTime     uint64
-	Method      [6]byte
+	Method      [7]byte
 	Path        [100]byte
 	SpanContext context.EBPFSpanContext
 }

test/e2e/gorillamux/traces.json

@@ -24,6 +24,35 @@
         ]
       },
       "scopeSpans": [
+        {
+          "scope": {
+            "name": "github.com/gorilla/mux"
+          },
+          "spans": [
+            {
+              "attributes": [
+                {
+                  "key": "http.method",
+                  "value": {
+                    "stringValue": "GET"
+                  }
+                },
+                {
+                  "key": "http.target",
+                  "value": {
+                    "stringValue": "/users/foo"
+                  }
+                }
+              ],
+              "kind": 2,
+              "name": "GET /users/foo",
+              "parentSpanId": "",
+              "spanId": "xxxxx",
+              "status": {},
+              "traceId": "xxxxx"
+            }
+          ]
+        },
         {
           "scope": {
             "name": "net/http"