fix(logging): revise automatic resource detection for ingested logs (#…

…6022)

align resource detection with heuristics in logging libraries for other languages:
- use /sys/class/dmi/id/product_name to read a product name of the resource on Linux
- change resource detection heuristics in a way that the order of validation is not important
- reduce timeout and retrying logic when querying metadata server
- demand active metadata server for detecting GCP resources (for GCE, GAE, GKE, CR and CF)
- add test to validate resource detection heuristics

logging/internal/environment.go

@@ -0,0 +1,75 @@
+// Copyright 2022 Google LLC
+//
+// 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
+//
+//      https://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.
+
+package internal
+
+import (
+	"io/ioutil"
+	"net"
+	"net/http"
+	"os"
+	"strings"
+	"time"
+
+	"cloud.google.com/go/compute/metadata"
+)
+
+// ResourceAtttributesGetter abstracts environment lookup methods to query for environment variables, metadata attributes and file content.
+type ResourceAtttributesGetter interface {
+	EnvVar(name string) string
+	Metadata(path string) string
+	ReadAll(path string) string
+}
+
+var getter ResourceAtttributesGetter = &defaultResourceGetter{
+	metaClient: metadata.NewClient(&http.Client{
+		Transport: &http.Transport{
+			Dial: (&net.Dialer{
+				Timeout:   1 * time.Second,
+				KeepAlive: 10 * time.Second,
+			}).Dial,
+		},
+	})}
+
+// ResourceAttributes provides read-only access to the ResourceAtttributesGetter interface implementation.
+func ResourceAttributes() ResourceAtttributesGetter {
+	return getter
+}
+
+type defaultResourceGetter struct {
+	metaClient *metadata.Client
+}
+
+// EnvVar uses os.LookupEnv() to lookup for environment variable by name.
+func (g *defaultResourceGetter) EnvVar(name string) string {
+	return os.Getenv(name)
+}
+
+// Metadata uses metadata package Client.Get() to lookup for metadata attributes by path.
+func (g *defaultResourceGetter) Metadata(path string) string {
+	val, err := g.metaClient.Get(path)
+	if err != nil {
+		return ""
+	}
+	return strings.TrimSpace(val)
+}
+
+// ReadAll reads all content of the file as a string.
+func (g *defaultResourceGetter) ReadAll(path string) string {
+	bytes, err := ioutil.ReadFile(path)
+	if err != nil {
+		return ""
+	}
+	return string(bytes)
+}