chmod +x otel-go-instrumentation

traces export: failed to exit idle mode: dns resolver: missing address

import (
    ...
    "go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/attribute"
    ...
)
...

var tracer = otel.Tracer("rolldice") // 创建 Tracer

...

func (s *Server) rollDice(w http.ResponseWriter, req *http.Request) {
	ctx, span := tracer.Start(req.Context(), "roll") // 新建一个 span
	defer span.End()

	n := s.rand.Intn(6) + 1

	_, err := s.db.ExecContext(ctx, "INSERT INTO results (roll_value) VALUES (?)", n)
	if err != nil {
		panic(err)
	}

	span.SetAttributes(attribute.Int("roll.value", n)) // 添加 span attributes

	fmt.Fprintf(w, "%v", n)
}

package main
import (
    "database/sql"
    "fmt"
    "net/http"
    "os"
    _ "github.com/mattn/go-sqlite3"
    "go.uber.org/zap"
)

const (
    sqlQuery = "SELECT * FROM contacts"
    dbName   = "test.db"
    tableDefinition = `CREATE TABLE contacts (
    contact_id INTEGER PRIMARY KEY,
    first_name TEXT NOT NULL,
    last_name TEXT NOT NULL,
    email TEXT NOT NULL,
    phone TEXT NOT NULL);`

    tableInsertion = `INSERT INTO 'contacts'
    ('first_name', 'last_name', 'email', 'phone') VALUES
    ('Moshe', 'Levi', 'moshe@gmail.com', '052-1234567');`
)

type Server struct {
    db *sql.DB
}
// 初始化数据库
func CreateDb() {
    file, err := os.Create(dbName)
    if err != nil {
        panic(err)
    }
    err = file.Close()
    if err != nil {
        panic(err)
    }
}

func NewServer() *Server {
    CreateDb()
    database, err := sql.Open("sqlite3", dbName)
    if err != nil {
        panic(err)
    }
    _, err = database.Exec(tableDefinition)
    if err != nil {
        panic(err)
    }
    return &Server{
        db: database,
    }
}

func (s *Server) queryDb(w http.ResponseWriter, req *http.Request) {
    ctx := req.Context()
    conn, err := s.db.Conn(ctx)
    if err != nil {
        panic(err)
    }
    // 注意这里一定要传递 `ctx` 或者 `req.Context()`，使 HTTP 请求和数据库的操作记录可以保持在一条链路中。
    // 如果在这里没有传递请求的 context，写成了 `s.db.Exec(tableInsertion)`，就会导致链路中断，HTTP span 和 database span 出现在两条链路中！
    _, err = s.db.ExecContext(ctx, tableInsertion)
    if err != nil {
        panic(err)
    }
    rows, err := conn.QueryContext(req.Context(), sqlQuery)
    if err != nil {
        panic(err)
    }
    logger.Info("queryDb called")
    for rows.Next() {
        var id int
        var firstName string
        var lastName string
        var email string
        var phone string
        err := rows.Scan(&id, &firstName, &lastName, &email, &phone)
        if err != nil {
            panic(err)
        }
        fmt.Fprintf(w, "ID: %d, firstName: %s, lastName: %s, email: %s, phone: %s\\n", id, firstName, lastName, email, phone)
    }
}