Added the jaeger-query service that visualizes traces stored in Elast…

…icsearch

The jaeger-query service uses a custom image containing a wait script wrapping the jaeger-query binary.

The wait script is a workaround for ensuring elastic search is ready before starting the query service. Docker does not support this natively.

TODO: figure out a way to download the jaeger-query binary in the Dockerfile, instead of saving the binary in the repo.

docker-compose.dev.yml

@@ -60,6 +60,20 @@ services:
       # receiving port of Query & UI
       QUERY_PORT: 16686
 
+  jaeger-query:
+    build: jaeger-query
+    environment:
+      SPAN_STORAGE_TYPE: elasticsearch
+      ES_SERVER_URLS: http://elasticsearch:9200
+    ports:
+      - "16686:16686" # provides UI
+      - "16687:16687" # healthcheck
+    networks:
+      - aparnet
+    command: wait.sh http://elasticsearch:9200 5 20 "jaeger-query"
+    depends_on:
+      - elasticsearch
+
   elasticsearch:
     image: elasticsearch:5.6-alpine
     ports:

jaeger-query/Dockerfile

@@ -0,0 +1,8 @@
+FROM alpine:3.9.3
+
+# required by wait script
+RUN apk add --no-cache bash curl
+
+COPY jaeger-query wait.sh /usr/local/bin/
+
+RUN chmod +x /usr/local/bin/wait.sh

jaeger-query/wait.sh

@@ -0,0 +1,36 @@
+#!/bin/bash
+
+# Requires a container with Bash and Curl installed.
+
+is_healthy () {
+	retryInterval=${2:-5}
+	maxAttempts=${3:-1000000}
+
+	i=0
+	while [ $i -lt $maxAttempts ]
+	do
+		status=$(curl -s -L -o /dev/null -w %{http_code} $1)
+
+		# stop trying if we get a success response
+		if [ $status -ge 200 ] && [ $status -lt 300 ]
+		then
+			return 0
+		fi
+
+		((i++))
+		echo "Attempt $i of $maxAttempts: Endpoint $1 returned code $status. Retrying in $retryInterval seconds."
+		sleep $retryInterval
+	done
+
+	return 1
+}
+
+# args: endpoint, retryInterval (secs), maxAttempts, command
+if is_healthy $1 $2 $3
+then
+	echo "Running command: $4"
+	# vulnerable to input-injection attacts (but I don't care :)
+	eval "$4"
+else
+	echo "Exiting: Cannot run command because health-check failed."
+fi