Add a binary to parse GKE log

api/internal/crawl/cmd/log-parser/README.md

@@ -0,0 +1,8 @@
+This binary takes as its input a json file including GKE logs (which can be
+[exported](https://cloud.google.com/logging/docs/export/configure_export_v2) into 
+[Cloud Storage](https://cloud.google.com/storage/docs/)), 
+and extracts the `textPayload` field of each log entry.
+
+Here is an log entry example:
+
+{"insertId":"1sxuh4jg5lw6w10","labels":{"compute.googleapis.com/resource_name":"gke-crawler2-default-pool-5e55ea05-gzgv","container.googleapis.com/namespace_name":"default","container.googleapis.com/pod_name":"kustomize-stats-5bczg","container.googleapis.com/stream":"stdout"},"logName":"projects/haiyanmeng-gke-dev/logs/kustomize-stats","receiveTimestamp":"2020-01-06T23:33:07.012831742Z","resource":{"labels":{"cluster_name":"crawler2","container_name":"kustomize-stats","instance_id":"8183086081854184383","namespace_id":"default","pod_id":"kustomize-stats-5bczg","project_id":"haiyanmeng-gke-dev","zone":"us-central1-a"},"type":"container"},"severity":"INFO","textPayload":"The kustomize index already exists\n","timestamp":"2020-01-06T23:32:46.628930547Z"}

api/internal/crawl/cmd/log-parser/main.go

@@ -0,0 +1,48 @@
+package main
+
+import (
+	"bufio"
+	"encoding/json"
+	"fmt"
+	"log"
+	"os"
+)
+
+func main() {
+	if len(os.Args) != 2 {
+		log.Fatalf("The usage of the command is: \n\t%s <log-file.json>", os.Args[0])
+	}
+
+	file, err := os.Open(os.Args[1])
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	closeFile := func(file *os.File) {
+		if err := file.Close(); err != nil {
+			log.Fatal(err)
+		}
+	}
+	defer closeFile(file)
+
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		line := scanner.Text()
+
+		var entry interface{}
+		if err := json.Unmarshal([]byte(line), &entry); err != nil {
+			log.Printf("failed to unmarshal a log entry: %s\n", line)
+		}
+
+		m := entry.(map[string]interface{})
+		if payload, ok := m["textPayload"]; ok {
+			fmt.Printf("%s", payload)
+		} else {
+			log.Printf("the log entry does not have the `textPayload` field: %s\n", line)
+		}
+	}
+
+	if err := scanner.Err(); err != nil {
+		log.Fatal(err)
+	}
+}