Inject DB and Logger

This PR creates an Env struct which contains DB (*sql.DB) and Logger (*zap.SugaredLogger) which enables handler dependency injection via closures.

Handler functions moved out of `./pkg/cmd/cmd.go` and to a new directory,  `./pkg/handlers/`. Handler functions use a closure to make Env available to the handler, injecting the DB and Logger dependencies into the handler. This is an implementation of dep injection option #2b as seen [here](https://www.alexedwards.net/blog/organising-database-access#closure). Option 3 is also something to consider, but for now this is functional and moves DB and Logger out of the global scope.

A few housekeeping items are addressed as well: updating README.md and .gitignore.

Author: TGPSKI

.gitignore

@@ -1,5 +1,8 @@
 .env*
+
+# VSCODE
 .vscode
+__debug_*
 
 # Binaries for programs and plugins
 *.exe
@@ -12,4 +15,4 @@
 *.test
 
 # Output of the go coverage tool, specifically when used with LiteIDE
-*.out
+*.out

README.md

@@ -58,8 +58,13 @@ $ go run cmd/main.go
 
 ## Environment Variables
 
+### DB_DRIVER Options
+
+* mysql
+* pgx
+
 ```
-DB_DRIVER=mysql # postgres
+DB_DRIVER=mysql # pgx
 DB_HOST=127.0.0.1
 DB_PORT=32084
 DB_USER=root

cmd/gabi/main.go

@@ -1,7 +1,6 @@
 package main
 
 import (
-	"database/sql"
 	"log"
 
 	"go.uber.org/zap"
@@ -10,19 +9,15 @@ import (
 	"github.com/app-sre/gabi/pkg/cmd"
 )
 
-var DB *sql.DB // Replace with dependency injection for logger and db pool
-
 func main() {
 	logger, err := zap.NewDevelopment() // NewProduction
 	if err != nil {
 		log.Fatalf("can't initialize zap logger: %v", err)
 	}
 	defer logger.Sync()
 
-	undo := zap.ReplaceGlobals(logger)
-	defer undo()
-
-	zap.S().Info("Starting gabi server version " + gabi.Version)
+	loggerS := logger.Sugar()
+	loggerS.Info("Starting gabi server version " + gabi.Version)
 
-	cmd.Run()
+	cmd.Run(loggerS)
 }

env.template

@@ -1,7 +1,7 @@
-DB_DRIVER=postgres
-DB_HOST=localhost
-DB_PORT=3306
+DB_DRIVER=pgx
+DB_HOST=127.0.0.1
+DB_PORT=5432
 DB_USER=postgres
 DB_PASS=postgres
 DB_NAME=mydb
-DB_WRITE=false
+DB_WRITE=false

pkg/cmd/cmd.go

@@ -1,63 +1,55 @@
 package cmd
 
 import (
-	"context"
 	"database/sql"
 	"log"
 	"net/http"
 	"strconv"
-	"time"
 
-	"github.com/etherlabsio/healthcheck/v2"
 	_ "github.com/go-sql-driver/mysql"
-	"github.com/gorilla/handlers"
+	gorillaHandlers "github.com/gorilla/handlers"
 	"github.com/gorilla/mux"
 	_ "github.com/jackc/pgx/v4/stdlib"
 	"go.uber.org/zap"
 
+	gabi "github.com/app-sre/gabi/pkg"
 	"github.com/app-sre/gabi/pkg/env/db"
-	"github.com/app-sre/gabi/pkg/query"
+	"github.com/app-sre/gabi/pkg/handlers"
 )
 
-func Run() {
+func Run(logger *zap.SugaredLogger) {
 	dbe := db.Dbenv{}
 	err := dbe.Populate()
 	if err != nil {
-		log.Fatal(err)
+		logger.Fatal(err)
 	}
-	zap.S().Info("Database environment variables populated.")
 
-	DB, err := sql.Open(dbe.DB_DRIVER, dbe.ConnStr)
+	logger.Info("Database environment variables populated.")
+
+	db, err := sql.Open(dbe.DB_DRIVER, dbe.ConnStr)
 	if err != nil {
-		log.Fatal("Fatal error opening database.")
+		logger.Fatal("Fatal error opening database.")
 	}
-	defer DB.Close()
-	zap.S().Info("Database connection handle established.")
-	zap.S().Infof("Using %s database driver.", dbe.DB_DRIVER)
+	defer db.Close()
+
+	env := &gabi.Env{DB: db, Logger: logger}
+	logger.Info("Database connection handle established.")
+	logger.Infof("Using %s database driver.", dbe.DB_DRIVER)
 
 	r := mux.NewRouter()
 
-	r.Handle("/healthcheck", healthcheck.Handler(
-		healthcheck.WithTimeout(5*time.Second),
-		healthcheck.WithChecker(
-			"database", healthcheck.CheckerFunc(
-				func(ctx context.Context) error {
-					return DB.PingContext(ctx)
-				},
-			),
-		),
-	))
+	r.Handle("/healthcheck", handlers.Healthcheck(env))
+	r.HandleFunc("/query", handlers.Query(env))
 
-	r.HandleFunc("/query", query.Handler)
-	zap.S().Info("Router initialized.")
+	logger.Info("Router initialized.")
 
 	servePort := 8080
-	zap.S().Infof("HTTP server starting on port %d.", servePort)
+	logger.Infof("HTTP server starting on port %d.", servePort)
 
 	// Temp workaround for easy to access io.Writer
 	httpLogger := log.Default()
 	http.ListenAndServe(
 		":"+strconv.Itoa(servePort),
-		handlers.LoggingHandler(httpLogger.Writer(), r),
+		gorillaHandlers.LoggingHandler(httpLogger.Writer(), r),
 	)
 }

pkg/gabi.go

@@ -1,3 +1,14 @@
 package gabi
 
+import (
+	"database/sql"
+
+	"go.uber.org/zap"
+)
+
 const Version = "0.0.1"
+
+type Env struct {
+	DB     *sql.DB
+	Logger *zap.SugaredLogger
+}

pkg/handlers/healthcheck.go

@@ -0,0 +1,24 @@
+package handlers
+
+import (
+	"context"
+	"net/http"
+	"time"
+
+	"github.com/etherlabsio/healthcheck/v2"
+
+	gabi "github.com/app-sre/gabi/pkg"
+)
+
+func Healthcheck(env *gabi.Env) http.Handler {
+	return healthcheck.Handler(
+		healthcheck.WithTimeout(5*time.Second),
+		healthcheck.WithChecker(
+			"database", healthcheck.CheckerFunc(
+				func(ctx context.Context) error {
+					return env.DB.PingContext(ctx)
+				},
+			),
+		),
+	)
+}

pkg/handlers/query.go

@@ -0,0 +1,22 @@
+package handlers
+
+import (
+	"fmt"
+	"net/http"
+
+	gabi "github.com/app-sre/gabi/pkg"
+)
+
+func Query(env *gabi.Env) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		// https://stackoverflow.com/a/46021789
+		env.Logger.Info("testing")
+		fmt.Fprintf(w, "%s %s %s \n", r.Method, r.URL, r.Proto)
+		for k, v := range r.Header {
+			fmt.Fprintf(w, "Header field %q, Value %q\n", k, v)
+			env.Logger.Infof("Header field %q, Value %q", k, v)
+		}
+		fmt.Fprintf(w, "Host = %q\n", r.Host)
+		fmt.Fprintf(w, "RemoteAddr= %q\n", r.RemoteAddr)
+	}
+}