Added support to add open-tracing on go mysql

[devlibx]

it will add opentracing in all query.sql.go method

span, ctx := opentracing.StartSpanFromContext(ctx, "MethodName")
defer span.Finish()

Let me know if I need to make more changes. I have explained it in the README.md file also (this part can be ignored in merge).

[sgielen]

@devlibx I wrote a small tool to do this based on the gendb.Querier interface generated by sqlc automatically. I run it in a Makefile automatically after running sqlc generate. The generated object then implements the gendb.Querier interface and can be used in its place.

Please feel free to do with this as you like.

package main

import (
	"bytes"
	"fmt"
	"go/ast"
	"go/format"
	"go/parser"
	"go/token"
	"go/types"
	"log"
	"os"
	"strings"
)

func main() {
	if len(os.Args) != 3 {
		fmt.Printf("Usage: %s gendb/querier.go gendb/otelwrap.go", os.Args[0])
	}

	input := os.Args[1]
	output := os.Args[2]

	fileSet := token.NewFileSet()
	file, err := parser.ParseFile(fileSet, input, nil, parser.ParseComments)
	if err != nil {
		log.Fatal(err)
	}

	var buf bytes.Buffer

	buf.WriteString(fmt.Sprintf("package %s\n\n", file.Name.Name))
	for _, importSpec := range file.Imports {
		buf.WriteString(fmt.Sprintf("import %s\n", importSpec.Path.Value))
	}
	buf.WriteString("import \"go.opentelemetry.io/otel\"\n")
	buf.WriteString("import \"go.opentelemetry.io/otel/trace\"\n\n")

	for _, decl := range file.Decls {
		iface, ok := decl.(*ast.GenDecl)
		if !ok || iface.Tok != token.TYPE {
			continue
		}

		for _, declSpec := range iface.Specs {
			typeSpec, ok := declSpec.(*ast.TypeSpec)
			if !ok {
				continue
			}

			ifaceType, ok := typeSpec.Type.(*ast.InterfaceType)
			if !ok {
				continue
			}

			typeName := typeSpec.Name.Name
			variable := strings.ToLower(typeName[:1]) + typeName[1:]
			wrapperName := typeName + "OtelWrapper"

			buf.WriteString(fmt.Sprintf("type %s struct {\n", wrapperName))
			buf.WriteString(fmt.Sprintf("\t%s %s\n", variable, typeName))
			buf.WriteString("}\n\n")

			buf.WriteString(fmt.Sprintf("func NewOtelWrapper(%s %s) %s {\n", variable, typeName, typeName))
			buf.WriteString(fmt.Sprintf("\treturn &%s{%s: %s}\n", wrapperName, variable, variable))
			buf.WriteString("}\n\n")

			buf.WriteString(fmt.Sprintf("func (w *%s) GetQuerier() Querier {\n", wrapperName))
			buf.WriteString("\treturn w.querier\n")
			buf.WriteString("}\n\n")

			for _, methodNode := range ifaceType.Methods.List {
				methodName := methodNode.Names[0].Name
				buf.WriteString(fmt.Sprintf("func (w *%s) %s(", wrapperName, methodName))

				method, ok := methodNode.Type.(*ast.FuncType)
				if !ok {
					continue
				}

				for i, param := range method.Params.List {
					if i > 0 {
						buf.WriteString(", ")
					}
					for _, paramName := range param.Names {
						buf.WriteString(fmt.Sprintf("%s %s", paramName.Name, types.ExprString(param.Type)))
					}
				}
				buf.WriteString(")")

				if method.Results != nil {
					buf.WriteString(" (")
					for i, result := range method.Results.List {
						if i > 0 {
							buf.WriteString(", ")
						}
						buf.WriteString(types.ExprString(result.Type))
					}
					buf.WriteString(")")
				}

				// Write method body with OpenTelemetry span
				buf.WriteString(" {\n")
				buf.WriteString("\tctx, span := otel.Tracer(\"db\").Start(ctx, \"" + methodName + "\", trace.WithSpanKind(trace.SpanKindClient))\n")
				buf.WriteString("\tdefer span.End()\n\n")
				buf.WriteString("\treturn w." + variable + "." + methodName + "(")

				// Write method parameters for the wrapped method call
				for i, param := range method.Params.List {
					if i > 0 {
						buf.WriteString(", ")
					}
					for _, paramName := range param.Names {
						buf.WriteString(paramName.Name)
					}
				}
				buf.WriteString(")\n")
				buf.WriteString("}\n\n")
			}
		}
	}

	gofmt, err := format.Source(buf.Bytes())
	if err != nil {
		// Write the unformatted source to file and fail afterwards
		gofmt = buf.Bytes()
		defer log.Fatal(err)
	}

	if err := os.WriteFile(output, gofmt, 0644); err != nil {
		log.Fatal(err)
	}
}

[devlibx]

I thought adding inbuilt support for open tracing will be more flexible if it is a core capability. Let me try out this tool as well..