Add context to logs, update readme

README.md

@@ -10,11 +10,17 @@ import "github.com/localhots/gobelt/threadpool"
 
 ```go
 ctx := context.Background()
-pool := threadpool.New(5)
+ctx, cancel = context.WithTimeout(ctx, 30 * time.Second)
+defer cancel()
+
+pool := threadpool.New(10)
+defer pool.Close()
+for i := 0; i < 1000000; i++ {
+    i := i
     pool.Enqueue(ctx, func() {
-    fmt.Println("Hello")
+        fmt.Printf("The number is %d\n", i)
     })
-pool.Close()
+}
 ```
 
 ### File cache
@@ -26,8 +32,12 @@ import "github.com/localhots/gobelt/filecache"
 ```go
 var val int
 filecache.Load(&val, "path/to/cachefile", func() interface{} {
-    // Expensive calls here
-    return 100
+    var items []Item
+    err := conn.Query(ctx, "SELECT * FROM items").Load(&items).Error()
+    if err != nil {
+        log.Fatal("Failed to load items", log.F{"error": err})
+    }
+    return items
 })
 ```
 
@@ -38,9 +48,16 @@ import "github.com/localhots/gobelt/log"
 ```
 
 ```go
-log.Info("New user signed up", log.F{
-    "name":  u.Name,
-    "email": u.Email,
-})
-log.Errorf("Invalid database flavor: %s", flavor)
+ctx := context.Background()
+ctx = log.ContextWithFields(ctx, log.F{"email": params["email"]})
+
+user, err := signup(ctx, params)
+if err != nil {
+    log.Errorf(ctx, "Signup failed: %v", err)
+    // [ERRO] Signup failed: db: duplicate entry    email=bob@example.com
+    return
+}
+
+log.Info(ctx, "New user signed up", log.F{"id": user.ID})
+// [INFO] New user signed up    email=bob@example.com  id=14 
 ```

log/context.go

@@ -0,0 +1,27 @@
+package log
+
+import "context"
+
+type logContext byte
+
+const ctxFields logContext = iota
+
+// ContextWithFields returns a new context with given fields added.
+func ContextWithFields(ctx context.Context, f F) context.Context {
+	ctxf, ok := ctx.Value(ctxFields).(F)
+	if !ok {
+		ctxf = F{}
+	}
+	for k, v := range f {
+		ctxf[k] = v
+	}
+	return context.WithValue(ctx, ctxFields, ctxf)
+}
+
+func contextFields(ctx context.Context) F {
+	f, ok := ctx.Value(ctxFields).(F)
+	if ok {
+		return f
+	}
+	return F{}
+}

log/log.go

@@ -1,6 +1,8 @@
 package log
 
 import (
+	"context"
+
 	"github.com/lytics/logrus"
 )
 
@@ -15,58 +17,61 @@ func init() {
 }
 
 // Debug prints a debug message with given fields attached.
-func Debug(msg string, fields ...F) {
-	withFields(fields).Debug(msg)
+func Debug(ctx context.Context, msg string, fields ...F) {
+	withFields(mergeFields(ctx, fields)).Debug(msg)
 }
 
 // Debugf prints a formatted debug message.
-func Debugf(format string, args ...interface{}) {
-	logrus.Debugf(format, args...)
+func Debugf(ctx context.Context, format string, args ...interface{}) {
+	withFields(contextFields(ctx)).Debugf(format, args...)
 }
 
 // Info prints an info message with given fields attached.
-func Info(msg string, fields ...F) {
-	withFields(fields).Info(msg)
+func Info(ctx context.Context, msg string, fields ...F) {
+	withFields(mergeFields(ctx, fields)).Info(msg)
 }
 
 // Infof prints a formatted info message.
-func Infof(format string, args ...interface{}) {
-	logrus.Infof(format, args...)
+func Infof(ctx context.Context, format string, args ...interface{}) {
+	withFields(contextFields(ctx)).Infof(format, args...)
 }
 
 // Error prints an error message with given fields attached.
-func Error(msg string, fields ...F) {
-	withFields(fields).Error(msg)
+func Error(ctx context.Context, msg string, fields ...F) {
+	withFields(mergeFields(ctx, fields)).Error(msg)
 }
 
 // Errorf prints a formatted error message.
-func Errorf(format string, args ...interface{}) {
-	logrus.Errorf(format, args...)
+func Errorf(ctx context.Context, format string, args ...interface{}) {
+	withFields(contextFields(ctx)).Errorf(format, args...)
 }
 
 // Fatal prints an error message with given fields attached and then exits.
-func Fatal(msg string, fields ...F) {
-	withFields(fields).Fatal(msg)
+func Fatal(ctx context.Context, msg string, fields ...F) {
+	withFields(mergeFields(ctx, fields)).Fatal(msg)
 }
 
 // Fatalf prints a formatted error message and then exits.
-func Fatalf(format string, args ...interface{}) {
-	logrus.Fatalf(format, args...)
+func Fatalf(ctx context.Context, format string, args ...interface{}) {
+	withFields(contextFields(ctx)).Fatalf(format, args...)
 }
 
-func withFields(fields []F) *logrus.Entry {
-	switch len(fields) {
-	case 0:
-		return logrus.NewEntry(Logger)
-	case 1:
-		return logrus.WithFields(logrus.Fields(fields[0]))
-	default:
-		f := F{}
+func mergeFields(ctx context.Context, fields []F) F {
+	ctxf := contextFields(ctx)
+	if len(ctxf) == 0 && len(fields) == 0 {
+		return nil
+	}
 	for i := 0; i < len(fields); i++ {
 		for k, v := range fields[i] {
-				f[k] = v
+			ctxf[k] = v
 		}
 	}
+	return ctxf
+}
+
+func withFields(f F) *logrus.Entry {
+	if len(f) == 0 {
+		return logrus.NewEntry(Logger)
+	}
 	return logrus.WithFields(logrus.Fields(f))
 }
-}

set/internal/impl/set_test.go

@@ -3,9 +3,8 @@ package impl
 import (
 	"testing"
 
-	"github.com/google/go-cmp/cmp/cmpopts"
-
 	"github.com/google/go-cmp/cmp"
+	"github.com/google/go-cmp/cmp/cmpopts"
 )
 
 const (