example: make goroutine trace example work (#95)

src/31-goroutine/README.md

@@ -1,7 +1,33 @@
 # goroutine trace
 
-TODO: make this work and implement the documentation
+**UNFINISHED YET**: The offset of goid field is hardcoded. It was only tested on the bundled `go-server-http`. It MAY NOT WORK on other go programs.
+
+The bundled fo program was compiled using go 1.17.0. The executable and source could be found at folder `go-server-http`.
+
+This example traces the state switch of goroutines, and prints the corresponding state, goid, pid and tgid.
+
+```console
+root@mnfe-pve:~/bpf-developer-tutorial/src/31-goroutine# ecc goroutine.bpf.c goroutine.h 
+INFO [ecc_rs::bpf_compiler] Compiling bpf object...
+INFO [ecc_rs::bpf_compiler] Generating export types...
+INFO [ecc_rs::bpf_compiler] Generating package json..
+INFO [ecc_rs::bpf_compiler] Packing ebpf object and config into package.json...
+root@mnfe-pve:~/bpf-developer-tutorial/src/31-goroutine# ecli-rs run package.json 
+INFO [faerie::elf] strtab: 0x6fb symtab 0x738 relocs 0x780 sh_offset 0x780
+INFO [bpf_loader_lib::skeleton::preload::section_loader] User didn't specify custom value for variable __eunomia_dummy_goroutine_execute_data_ptr, use the default one in ELF
+TIME     STATE  GOID   PID    TGID   
+INFO [bpf_loader_lib::skeleton] Running ebpf program...
+21:00:47  DEAD(6) 0    2542844 2542844
+21:00:47  RUNNABLE(1) 0 2542844 2542844
+21:00:47  DEAD(6) 0    2542844 2542844
+21:00:47  RUNNING(2) 1 2542844 2542844
+21:00:47  DEAD(6) 0    2542844 2542844
+21:00:47  RUNNABLE(1) 0 2542844 2542844
+21:00:47  RUNNABLE(1) 1 2542844 2542844
+21:00:47  RUNNING(2) 2 2542847 2542844
+21:00:47  WAITING(4) 2 2542847 2542844
+....
+```
 
-Modify from https://github.com/deepflowio/deepflow
 
 This example is provided as GPL license

src/31-goroutine/go-server-http/main.go

@@ -0,0 +1,34 @@
+package main
+
+import (
+	"crypto/rand"
+	"fmt"
+	"log"
+	"net/http"
+	"os"
+	"strconv"
+)
+
+var http_body []byte
+
+func handler(w http.ResponseWriter, r *http.Request) {
+	w.Write(http_body)
+}
+
+func main() {
+	args := os.Args
+	if len(args) > 1 {
+		body_len, _ := strconv.ParseInt(args[1], 10, 64)
+		http_body = make([]byte, body_len)
+		rand.Read(http_body)
+		fmt.Println("Body set to", body_len, "bytes of random stuff")
+	} else {
+		http_body = []byte("Hello,World!")
+	}
+	http.HandleFunc("/", handler)
+	fmt.Println("Server started!")
+	err := http.ListenAndServe(":447", nil)
+	if err != nil {
+		log.Fatalf("Failed to start server: %v", err)
+	}
+}