Table of Contents
This repo has a simple Java EE application that publishes a REST endpoint at /resources/employees. The resource returns a list of employees by querying a database.
The Java EE application is deployed as a JAR built using WildFly Swarm. MySQL is used as the backend database.
The application also publishes Prometheus-style metrics at /metrics.
Build Docker image
mvn -f employees/pom.xml clean package -Pdocker
Docker image used in this application, arungupta/docker-javaee:dockerconeu17, is already published at Docker Hub.
docker stack deploy --compose-file=docker-compose.yml webapp
Verify:
$ docker stack ls
NAME SERVICES
webapp 2
$ docker stack services webapp
ID NAME MODE REPLICAS IMAGE PORTS
9tuwp1o2sz4j webapp_web replicated 1/1 arungupta/docker-javaee:dockerconeu17 *:8080->8080/tcp,*:9990->9990/tcp
jy6qyaxv5e01 webapp_db replicated 1/1 mysql:8 *:3306->3306/tcp
$ docker stack ps webapp
ID NAME IMAGE NODE DESIRED STATE CURRENT STATE ERROR PORTS
lbnyvncsnfad webapp_web.1 arungupta/docker-javaee:dockerconeu17 moby Running Running 7 seconds ago
r7j0q1nx1y1q webapp_db.1 mysql:8 moby Running Running 9 seconds agoThe application is available as Kubernetes Helm chart in the app directory. Install Helm client and server, and then the application.
Install Helm client and server:
brew install kubernetes-helm helm init
Install Helm chart:
helm install --name app app
Verify:
$ kubectl get deployments
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
mysql-deployment 1 1 1 1 1m
webapp-deployment 1 1 1 1 1m
$ kubectl get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
db ClusterIP 100.65.195.189 <none> 3306/TCP 1m
kubernetes ClusterIP 100.64.0.1 <none> 443/TCP 1h
webapp ClusterIP 100.71.21.2 <none> 8080/TCP 1m
$ kubectl get pods
NAME READY STATUS RESTARTS AGE
mysql-deployment-1668503186-9h7lz 1/1 Running 0 1m
webapp-deployment-372583675-hlcbg 1/1 Running 0 1mAccess the application:
curl http://localhost:8080/resources/employees
The output is shown as:
<?xml version="1.0" encoding="UTF-8" standalone="yes"?><collection><employee><id>1</id><name>Penny</name></employee><employee><id>2</id><name>Sheldon</name></employee><employee><id>3</id><name>Amy</name></employee><employee><id>4</id><name>Leonard</name></employee><employee><id>5</id><name>Bernadette</name></employee><employee><id>6</id><name>Raj</name></employee><employee><id>7</id><name>Howard</name></employee><employee><id>8</id><name>Priya</name></employee></collection>
JSON output can be obtained as:
curl -H"Accept: application/json" http://localhost:8080/resources/employees
The output is shown as:
[{"id":1,"name":"Penny"},{"id":2,"name":"Sheldon"},{"id":3,"name":"Amy"},{"id":4,"name":"Leonard"},{"id":5,"name":"Bernadette"},{"id":6,"name":"Raj"},{"id":7,"name":"Howard"},{"id":8,"name":"Priya"}]
Get application metrics as:
$ curl http://localhost:8080/metrics
# HELP jvm_threads_current Current thread count of a JVM
# TYPE jvm_threads_current gauge
jvm_threads_current 105.0
# HELP jvm_threads_daemon Daemon thread count of a JVM
# TYPE jvm_threads_daemon gauge
jvm_threads_daemon 12.0
# HELP jvm_threads_peak Peak thread count of a JVM
# TYPE jvm_threads_peak gauge
jvm_threads_peak 105.0
# HELP jvm_threads_started_total Started thread count of a JVM
# TYPE jvm_threads_started_total counter
jvm_threads_started_total 138.0
# HELP jvm_threads_deadlocked Cycles of JVM-threads that are in deadlock waiting to acquire object monitors or ownable synchronizers
# TYPE jvm_threads_deadlocked gauge
jvm_threads_deadlocked 0.0
# HELP jvm_threads_deadlocked_monitor Cycles of JVM-threads that are in deadlock waiting to acquire object monitors
# TYPE jvm_threads_deadlocked_monitor gauge
jvm_threads_deadlocked_monitor 0.0
# HELP requests_get_one Total GET /{id} requests.
# TYPE requests_get_one counter
requests_get_one 7.0
# HELP requests_get_all Total GET / requests.
# TYPE requests_get_all counter
requests_get_all 14.0
# HELP jvm_memory_bytes_used Used bytes of a given JVM memory area.
# TYPE jvm_memory_bytes_used gauge
jvm_memory_bytes_used{area="heap",} 1.01012128E8
jvm_memory_bytes_used{area="nonheap",} 1.00972688E8
# HELP jvm_memory_bytes_committed Committed (bytes) of a given JVM memory area.
# TYPE jvm_memory_bytes_committed gauge
jvm_memory_bytes_committed{area="heap",} 2.87309824E8
jvm_memory_bytes_committed{area="nonheap",} 1.08756992E8
# HELP jvm_memory_bytes_max Max (bytes) of a given JVM memory area.
# TYPE jvm_memory_bytes_max gauge
jvm_memory_bytes_max{area="heap",} 4.66092032E8
jvm_memory_bytes_max{area="nonheap",} -1.0
# HELP jvm_memory_pool_bytes_used Used bytes of a given JVM memory pool.
# TYPE jvm_memory_pool_bytes_used gauge
jvm_memory_pool_bytes_used{pool="Code Cache",} 1.7550848E7
jvm_memory_pool_bytes_used{pool="Metaspace",} 7.3989384E7
jvm_memory_pool_bytes_used{pool="Compressed Class Space",} 9432456.0
jvm_memory_pool_bytes_used{pool="PS Eden Space",} 3191200.0
jvm_memory_pool_bytes_used{pool="PS Survivor Space",} 2408464.0
jvm_memory_pool_bytes_used{pool="PS Old Gen",} 9.5412464E7
# HELP jvm_memory_pool_bytes_committed Committed bytes of a given JVM memory pool.
# TYPE jvm_memory_pool_bytes_committed gauge
jvm_memory_pool_bytes_committed{pool="Code Cache",} 1.769472E7
jvm_memory_pool_bytes_committed{pool="Metaspace",} 7.9740928E7
jvm_memory_pool_bytes_committed{pool="Compressed Class Space",} 1.1321344E7
jvm_memory_pool_bytes_committed{pool="PS Eden Space",} 7.602176E7
jvm_memory_pool_bytes_committed{pool="PS Survivor Space",} 4.8234496E7
jvm_memory_pool_bytes_committed{pool="PS Old Gen",} 1.63053568E8
# HELP jvm_memory_pool_bytes_max Max bytes of a given JVM memory pool.
# TYPE jvm_memory_pool_bytes_max gauge
jvm_memory_pool_bytes_max{pool="Code Cache",} 2.5165824E8
jvm_memory_pool_bytes_max{pool="Metaspace",} -1.0
jvm_memory_pool_bytes_max{pool="Compressed Class Space",} 1.073741824E9
jvm_memory_pool_bytes_max{pool="PS Eden Space",} 7.8118912E7
jvm_memory_pool_bytes_max{pool="PS Survivor Space",} 4.8234496E7
jvm_memory_pool_bytes_max{pool="PS Old Gen",} 3.49700096E8
# HELP jvm_classes_loaded The number of classes that are currently loaded in the JVM
# TYPE jvm_classes_loaded gauge
jvm_classes_loaded 13797.0
# HELP jvm_classes_loaded_total The total number of classes that have been loaded since the JVM has started execution
# TYPE jvm_classes_loaded_total counter
jvm_classes_loaded_total 13797.0
# HELP jvm_classes_unloaded_total The total number of classes that have been unloaded since the JVM has started execution
# TYPE jvm_classes_unloaded_total counter
jvm_classes_unloaded_total 0.0
# HELP jvm_info JVM version info
# TYPE jvm_info gauge
jvm_info{version="1.8.0_141-8u141-b15-1~deb9u1-b15",vendor="Oracle Corporation",} 1.0
# HELP app_metrics The time taken fulfilling servlet requests
# TYPE app_metrics histogram
app_metrics_bucket{path="/resources",method="GET",le="0.005",} 13.0
app_metrics_bucket{path="/resources",method="GET",le="0.01",} 17.0
app_metrics_bucket{path="/resources",method="GET",le="0.025",} 20.0
app_metrics_bucket{path="/resources",method="GET",le="0.05",} 20.0
app_metrics_bucket{path="/resources",method="GET",le="0.075",} 20.0
app_metrics_bucket{path="/resources",method="GET",le="0.1",} 20.0
app_metrics_bucket{path="/resources",method="GET",le="0.25",} 21.0
app_metrics_bucket{path="/resources",method="GET",le="0.5",} 21.0
app_metrics_bucket{path="/resources",method="GET",le="0.75",} 21.0
app_metrics_bucket{path="/resources",method="GET",le="1.0",} 21.0
app_metrics_bucket{path="/resources",method="GET",le="2.5",} 21.0
app_metrics_bucket{path="/resources",method="GET",le="5.0",} 21.0
app_metrics_bucket{path="/resources",method="GET",le="7.5",} 21.0
app_metrics_bucket{path="/resources",method="GET",le="10.0",} 21.0
app_metrics_bucket{path="/resources",method="GET",le="+Inf",} 21.0
app_metrics_count{path="/resources",method="GET",} 21.0
app_metrics_sum{path="/resources",method="GET",} 0.3544065799999999
# HELP process_cpu_seconds_total Total user and system CPU time spent in seconds.
# TYPE process_cpu_seconds_total counter
process_cpu_seconds_total 44.43
# HELP process_start_time_seconds Start time of the process since unix epoch in seconds.
# TYPE process_start_time_seconds gauge
process_start_time_seconds 1.508062328635E9
# HELP process_open_fds Number of open file descriptors.
# TYPE process_open_fds gauge
process_open_fds 500.0
# HELP process_max_fds Maximum number of open file descriptors.
# TYPE process_max_fds gauge
process_max_fds 1048576.0
# HELP process_virtual_memory_bytes Virtual memory size in bytes.
# TYPE process_virtual_memory_bytes gauge
process_virtual_memory_bytes 4.289380352E9
# HELP process_resident_memory_bytes Resident memory size in bytes.
# TYPE process_resident_memory_bytes gauge
process_resident_memory_bytes 5.36694784E8
# HELP jvm_gc_collection_seconds Time spent in a given JVM garbage collector in seconds.
# TYPE jvm_gc_collection_seconds summary
jvm_gc_collection_seconds_count{gc="PS Scavenge",} 28.0
jvm_gc_collection_seconds_sum{gc="PS Scavenge",} 0.373
jvm_gc_collection_seconds_count{gc="PS MarkSweep",} 6.0
jvm_gc_collection_seconds_sum{gc="PS MarkSweep",} 0.565The application traces all requests to Jaeger (https://uber.github.io/jaeger/) and the result can be viewed on http://127.0.0.1:8090.
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