server: Use default logging configuration instead of zap production one

This fixes problem where logs json changes format of timestamp.

tests/e2e/zap_logging_test.go

@@ -0,0 +1,78 @@
+// Copyright 2022 The etcd Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build !cov
+// +build !cov
+
+package e2e
+
+import (
+	"encoding/json"
+	"testing"
+	"time"
+
+	"go.etcd.io/etcd/tests/v3/framework/e2e"
+)
+
+func TestServerJsonLogging(t *testing.T) {
+	e2e.BeforeTest(t)
+
+	epc, err := e2e.NewEtcdProcessCluster(t, &e2e.EtcdProcessClusterConfig{
+		ClusterSize:  1,
+		InitialToken: "new",
+		LogLevel:     "debug",
+	})
+	if err != nil {
+		t.Fatalf("could not start etcd process cluster (%v)", err)
+	}
+	logs := epc.Procs[0].Logs()
+	time.Sleep(time.Second)
+	if err = epc.Close(); err != nil {
+		t.Fatalf("error closing etcd processes (%v)", err)
+	}
+	var entry logEntry
+	lines := logs.Lines()
+	if len(lines) == 0 {
+		t.Errorf("Expected at least one log line")
+	}
+	for _, line := range lines {
+		err := json.Unmarshal([]byte(line), &entry)
+		if err != nil {
+			t.Errorf("Failed to parse log line as json, err: %q, line: %s", err, line)
+			continue
+		}
+		if entry.Level == "" {
+			t.Errorf(`Missing "level" key, line: %s`, line)
+		}
+		if entry.Timestamp == "" {
+			t.Errorf(`Missing "ts" key, line: %s`, line)
+		}
+		if _, err := time.Parse("2006-01-02T15:04:05.000Z0700", entry.Timestamp); entry.Timestamp != "" && err != nil {
+			t.Errorf(`Unexpected "ts" key format, err: %s`, err)
+		}
+		if entry.Caller == "" {
+			t.Errorf(`Missing "caller" key, line: %s`, line)
+		}
+		if entry.Message == "" {
+			t.Errorf(`Missing "message" key, line: %s`, line)
+		}
+	}
+}
+
+type logEntry struct {
+	Level     string `json:"level"`
+	Timestamp string `json:"ts"`
+	Caller    string `json:"caller"`
+	Message   string `json:"msg"`
+}