Logging: Introduce API for contextual logging (#55198)

Introduces a FromContext method on the log.Logger interface that 
allows contextual key/value pairs to be attached, e.g. per request, 
so that any logger using this API will automatically get the per request 
context attached. The proposal makes the traceID available for 
contextual logger , if available, and would allow logs originating from 
a certain HTTP request to be correlated with traceID.
In addition, when tracing not enabled, skip adding
traceID=00000000000000000000000000000000
to logs.

pkg/services/sqlstore/database_wrapper.go

@@ -104,7 +104,8 @@ func (h *databaseQueryWrapper) instrument(ctx context.Context, status string, qu
 		span.AddEvents([]string{"error"}, []tracing.EventValue{{Str: err.Error()}})
 	}
 
-	h.log.Debug("query finished", "status", status, "elapsed time", elapsed, "sql", query, "error", err)
+	ctxLogger := h.log.FromContext(ctx)
+	ctxLogger.Debug("query finished", "status", status, "elapsed time", elapsed, "sql", query, "error", err)
 }
 
 // OnError will be called if any error happens

pkg/services/sqlstore/session.go

@@ -47,7 +47,8 @@ func startSessionOrUseExisting(ctx context.Context, engine *xorm.Engine, beginTr
 	sess, ok := value.(*DBSession)
 
 	if ok {
-		sessionLogger.Debug("reusing existing session", "transaction", sess.transactionOpen)
+		ctxLogger := sessionLogger.FromContext(ctx)
+		ctxLogger.Debug("reusing existing session", "transaction", sess.transactionOpen)
 		sess.Session = sess.Session.Context(ctx)
 		return sess, false, nil
 	}

pkg/services/sqlstore/transactions.go

@@ -48,8 +48,10 @@ func inTransactionWithRetryCtx(ctx context.Context, engine *xorm.Engine, bus bus
 
 	err = callback(sess)
 
+	ctxLogger := tsclogger.FromContext(ctx)
+
 	if !isNew {
-		tsclogger.Debug("skip committing the transaction because it belongs to a session created in the outer scope")
+		ctxLogger.Debug("skip committing the transaction because it belongs to a session created in the outer scope")
 		// Do not commit the transaction if the session was reused.
 		return err
 	}
@@ -62,7 +64,7 @@ func inTransactionWithRetryCtx(ctx context.Context, engine *xorm.Engine, bus bus
 		}
 
 		time.Sleep(time.Millisecond * time.Duration(10))
-		sqlog.Info("Database locked, sleeping then retrying", "error", err, "retry", retry)
+		ctxLogger.Info("Database locked, sleeping then retrying", "error", err, "retry", retry)
 		return inTransactionWithRetryCtx(ctx, engine, bus, callback, retry+1)
 	}
 
@@ -79,7 +81,7 @@ func inTransactionWithRetryCtx(ctx context.Context, engine *xorm.Engine, bus bus
 	if len(sess.events) > 0 {
 		for _, e := range sess.events {
 			if err = bus.Publish(ctx, e); err != nil {
-				tsclogger.Error("Failed to publish event after commit.", "error", err)
+				ctxLogger.Error("Failed to publish event after commit.", "error", err)
 			}
 		}
 	}