Is it to be expected that the client will discover each node twice for the Hazelcast sidecar caching pattern? - spring-boot

Question

I'm pretty new to using Hazelcast for its interesting feature of auto-sync with other cache instances. My queries are bottom of the description.
Here was my initial goal:
Design an environment following Hazelcast sidecar caching pattern.
There will be no cache on the application container side. Basically, I don't want to use "near-cache" just to avoid my JVM being heavy and reduce GC time.
Application Container in each Node will communicate with its own sidecar cache container via localhost IP.
Hazelcast management center will be a separate node that communicates with all the nodes containing Hazelcast sidecar cache container.
Here is the target design:
I prepared Hazelcast configuration [hazelcast.yaml] for Hazelcast container,
hazelcast:
cluster-name: dev
network:
port:
auto-increment: false
port-count: 3
port: 5701
I also prepared another hazelcast.yaml for my application container,
hazelcast:
map:
default:
backup-count: 0
async-backup-count: 1
read-backup-data: true
network:
reuse-address: true
port:
auto-increment: true
port: 5701
join:
multicast:
enabled: true
kubernetes:
enabled: false
tcp-ip:
enabled: false
interaface: 127.0.0.1
member-list:
- 127.0.0.1:5701
Here is the client part, I used SpringBoot for it.
#Component
public class CacheClient {
private static final String ITEMS = "items";
private HazelcastInstance client;
CacheClient() throws IOException {
ClientConfig config = new YamlClientConfigBuilder("hazelcast.yaml").build();
config.setInstanceName(UUID.randomUUID().toString());
client = HazelcastClient.getOrCreateHazelcastClient(config);
}
public Item put(String number, Item item){
IMap<String, Item> map = client.getMap(ITEMS);
return map.putIfAbsent(number, item);
}
public Item get(String key){
IMap<String, Item> map = client.getMap(ITEMS);
return map.get(key);
}
}
Here is the dockerfile, I used to build my application container image,
FROM adoptopenjdk/openjdk11:jdk-11.0.5_10-alpine-slim
# Expose port 8081 to Docker host
EXPOSE 8081
WORKDIR /opt
COPY /build/libs/hazelcast-client-0.0.1-SNAPSHOT.jar /opt/app.jar
COPY /src/main/resources/hazelcast.yaml /opt/hazelcast.yaml
COPY /src/main/resources/application.properties /opt/application.properties
ENTRYPOINT ["java","-Dhazelcast.socket.server.bind.any=false","-Dhazelcast.initial.min.cluster.size=1","-Dhazelcast.socket.bind.any=false","-Dhazelcast.socket.server.bind.any=false","-Dhazelcast.socket.client.bind=false","-Dhazelcast.socket.client.bind.any=false","-Dhazelcast.logging.type=slf4j","-jar","app.jar"]
Here is the deployment script I used,
apiVersion: v1 # Kubernetes API version
kind: Service # Kubernetes resource kind we are creating
metadata: # Metadata of the resource kind we are creating
name: spring-hazelcast-service
spec:
selector:
app: spring-hazelcast-app
ports:
- protocol: "TCP"
name: http-app
port: 8081 # The port that the service is running on in the cluster
targetPort: 8081 # The port exposed by the service
type: LoadBalancer # type of the service. LoadBalancer indicates that our service will be external.
---
apiVersion: apps/v1
kind: Deployment # Kubernetes resource kind we are creating
metadata:
name: spring-hazelcast-app
spec:
selector:
matchLabels:
app: spring-hazelcast-app
replicas: 1 # Number of replicas that will be created for this deployment
template:
metadata:
labels:
app: spring-hazelcast-app
spec:
containers:
- name: hazelcast
image: hazelcast/hazelcast:4.0.2
workingDir: /opt
ports:
- name: hazelcast
containerPort: 5701
env:
- name: HZ_CLUSTERNAME
value: dev
- name: JAVA_OPTS
value: -Dhazelcast.config=/opt/config/hazelcast.yml
volumeMounts:
- mountPath: "/opt/config/"
name: allconf
- name: spring-hazelcast-app
image: spring-hazelcast:1.0.3
imagePullPolicy: Never #IfNotPresent
ports:
- containerPort: 8081 # The port that the container is running on in the cluster
volumes:
- name: allconf
hostPath:
path: /opt/config/ # directory location on host
type: Directory # this field is optional
---
apiVersion: v1 # Kubernetes API version
kind: Service # Kubernetes resource kind we are creating
metadata: # Metadata of the resource kind we are creating
name: hazelcast-mc-service
spec:
selector:
app: hazelcast-mc
ports:
- protocol: "TCP"
name: mc-app
port: 8080 # The port that the service is running on in the cluster
targetPort: 8080 # The port exposed by the service
type: LoadBalancer # type of the
loadBalancerIP: "127.0.0.1"
---
apiVersion: apps/v1
kind: Deployment # Kubernetes resource kind we are creating
metadata:
name: hazelcast-mc
spec:
selector:
matchLabels:
app: hazelcast-mc
replicas: 1 # Number of replicas that will be created for this deployment
template:
metadata:
labels:
app: hazelcast-mc
spec:
containers:
- name: hazelcast-mc
image: hazelcast/management-center
ports:
- containerPort: 8080 # The port that the container is running on in the cluster
Here is my application logs,
. ____ _ __ _ _
/\\ / ___'_ __ _ _(_)_ __ __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
\\/ ___)| |_)| | | | | || (_| | ) ) ) )
' |____| .__|_| |_|_| |_\__, | / / / /
=========|_|==============|___/=/_/_/_/
:: Spring Boot :: (v2.5.4)
2021-09-27 06:42:51.274 INFO 1 --- [ main] com.caching.Application : Starting Application using Java 11.0.5 on spring-hazelcast-app-7bdc8b7f7-bqdlt with PID 1 (/opt/app.jar started by root in /opt)
2021-09-27 06:42:51.278 INFO 1 --- [ main] com.caching.Application : No active profile set, falling back to default profiles: default
2021-09-27 06:42:55.986 INFO 1 --- [ main] c.h.c.impl.spi.ClientInvocationService : b1bdd9bb-2879-4161-95fd-2b6e321ad30a [dev] [4.0.2] Running with 2 response threads, dynamic=true
2021-09-27 06:42:56.199 INFO 1 --- [ main] com.hazelcast.core.LifecycleService : b1bdd9bb-2879-4161-95fd-2b6e321ad30a [dev] [4.0.2] HazelcastClient 4.0.2 (20200702 - 2de3027) is STARTING
2021-09-27 06:42:56.202 INFO 1 --- [ main] com.hazelcast.core.LifecycleService : b1bdd9bb-2879-4161-95fd-2b6e321ad30a [dev] [4.0.2] HazelcastClient 4.0.2 (20200702 - 2de3027) is STARTED
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by com.hazelcast.internal.networking.nio.SelectorOptimizer (jar:file:/opt/app.jar!/BOOT-INF/lib/hazelcast-all-4.0.2.jar!/) to field sun.nio.ch.SelectorImpl.selectedKeys
WARNING: Please consider reporting this to the maintainers of com.hazelcast.internal.networking.nio.SelectorOptimizer
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
2021-09-27 06:42:56.277 INFO 1 --- [ main] c.h.c.i.c.ClientConnectionManager : b1bdd9bb-2879-4161-95fd-2b6e321ad30a [dev] [4.0.2] Trying to connect to cluster: dev
2021-09-27 06:42:56.302 INFO 1 --- [ main] c.h.c.i.c.ClientConnectionManager : b1bdd9bb-2879-4161-95fd-2b6e321ad30a [dev] [4.0.2] Trying to connect to [127.0.0.1]:5701
2021-09-27 06:42:56.429 INFO 1 --- [ main] com.hazelcast.core.LifecycleService : b1bdd9bb-2879-4161-95fd-2b6e321ad30a [dev] [4.0.2] HazelcastClient 4.0.2 (20200702 - 2de3027) is CLIENT_CONNECTED
2021-09-27 06:42:56.429 INFO 1 --- [ main] c.h.c.i.c.ClientConnectionManager : b1bdd9bb-2879-4161-95fd-2b6e321ad30a [dev] [4.0.2] Authenticated with server [172.17.0.3]:5701:c967f642-a7aa-4deb-a530-b56fb8f68c78, server version: 4.0.2, local address: /127.0.0.1:54373
2021-09-27 06:42:56.436 INFO 1 --- [ main] c.h.internal.diagnostics.Diagnostics : b1bdd9bb-2879-4161-95fd-2b6e321ad30a [dev] [4.0.2] Diagnostics disabled. To enable add -Dhazelcast.diagnostics.enabled=true to the JVM arguments.
2021-09-27 06:42:56.461 INFO 1 --- [21ad30a.event-4] c.h.c.impl.spi.ClientClusterService : b1bdd9bb-2879-4161-95fd-2b6e321ad30a [dev] [4.0.2]
Members [1] {
Member [172.17.0.3]:5701 - c967f642-a7aa-4deb-a530-b56fb8f68c78
}
2021-09-27 06:42:56.803 INFO 1 --- [ main] c.h.c.i.s.ClientStatisticsService : Client statistics is enabled with period 5 seconds.
2021-09-27 06:42:57.878 INFO 1 --- [ main] c.h.i.config.AbstractConfigLocator : Loading 'hazelcast.yaml' from the working directory.
2021-09-27 06:42:57.934 WARN 1 --- [ main] c.h.i.impl.HazelcastInstanceFactory : Hazelcast is starting in a Java modular environment (Java 9 and newer) but without proper access to required Java packages. Use additional Java arguments to provide Hazelcast access to Java internal API. The internal API access is used to get the best performance results. Arguments to be used:
--add-modules java.se --add-exports java.base/jdk.internal.ref=ALL-UNNAMED --add-opens java.base/java.lang=ALL-UNNAMED --add-opens java.base/java.nio=ALL-UNNAMED --add-opens java.base/sun.nio.ch=ALL-UNNAMED --add-opens java.management/sun.management=ALL-UNNAMED --add-opens jdk.management/com.sun.management.internal=ALL-UNNAMED
2021-09-27 06:42:57.976 INFO 1 --- [ main] com.hazelcast.instance.AddressPicker : [LOCAL] [dev] [4.0.2] Prefer IPv4 stack is true, prefer IPv6 addresses is false
2021-09-27 06:42:57.987 INFO 1 --- [ main] com.hazelcast.instance.AddressPicker : [LOCAL] [dev] [4.0.2] Picked [172.17.0.3]:5702, using socket ServerSocket[addr=/172.17.0.3,localport=5702], bind any local is false
2021-09-27 06:42:58.004 INFO 1 --- [ main] com.hazelcast.system : [172.17.0.3]:5702 [dev] [4.0.2] Hazelcast 4.0.2 (20200702 - 2de3027) starting at [172.17.0.3]:5702
2021-09-27 06:42:58.005 INFO 1 --- [ main] com.hazelcast.system : [172.17.0.3]:5702 [dev] [4.0.2] Copyright (c) 2008-2020, Hazelcast, Inc. All Rights Reserved.
2021-09-27 06:42:58.047 INFO 1 --- [ main] c.h.s.i.o.impl.BackpressureRegulator : [172.17.0.3]:5702 [dev] [4.0.2] Backpressure is disabled
2021-09-27 06:42:58.373 INFO 1 --- [ main] com.hazelcast.instance.impl.Node : [172.17.0.3]:5702 [dev] [4.0.2] Creating MulticastJoiner
2021-09-27 06:42:58.380 WARN 1 --- [ main] com.hazelcast.cp.CPSubsystem : [172.17.0.3]:5702 [dev] [4.0.2] CP Subsystem is not enabled. CP data structures will operate in UNSAFE mode! Please note that UNSAFE mode will not provide strong consistency guarantees.
2021-09-27 06:42:58.676 INFO 1 --- [ main] c.h.s.i.o.impl.OperationExecutorImpl : [172.17.0.3]:5702 [dev] [4.0.2] Starting 2 partition threads and 3 generic threads (1 dedicated for priority tasks)
2021-09-27 06:42:58.682 INFO 1 --- [ main] c.h.internal.diagnostics.Diagnostics : [172.17.0.3]:5702 [dev] [4.0.2] Diagnostics disabled. To enable add -Dhazelcast.diagnostics.enabled=true to the JVM arguments.
2021-09-27 06:42:58.687 INFO 1 --- [ main] com.hazelcast.core.LifecycleService : [172.17.0.3]:5702 [dev] [4.0.2] [172.17.0.3]:5702 is STARTING
2021-09-27 06:42:58.923 INFO 1 --- [ main] c.h.i.cluster.impl.MulticastJoiner : [172.17.0.3]:5702 [dev] [4.0.2] Trying to join to discovered node: [172.17.0.3]:5701
2021-09-27 06:42:58.932 INFO 1 --- [cached.thread-3] c.h.internal.nio.tcp.TcpIpConnector : [172.17.0.3]:5702 [dev] [4.0.2] Connecting to /172.17.0.3:5701, timeout: 10000, bind-any: false
2021-09-27 06:42:58.955 INFO 1 --- [.IO.thread-in-0] c.h.internal.nio.tcp.TcpIpConnection : [172.17.0.3]:5702 [dev] [4.0.2] Initialized new cluster connection between /172.17.0.3:40242 and /172.17.0.3:5701
2021-09-27 06:43:04.948 INFO 1 --- [21ad30a.event-3] c.h.c.impl.spi.ClientClusterService : b1bdd9bb-2879-4161-95fd-2b6e321ad30a [dev] [4.0.2]
Members [2] {
Member [172.17.0.3]:5701 - c967f642-a7aa-4deb-a530-b56fb8f68c78
Member [172.17.0.3]:5702 - 08dfe633-46b2-4581-94c7-81b6d0bc3ce3
}
2021-09-27 06:43:04.959 WARN 1 --- [ration.thread-0] c.h.c.i.operation.OnJoinCacheOperation : [172.17.0.3]:5702 [dev] [4.0.2] This member is joining a cluster whose members support JCache, however the cache-api artifact is missing from this member's classpath. In case JCache API will be used, add cache-api artifact in this member's classpath and restart the member.
2021-09-27 06:43:04.963 INFO 1 --- [ration.thread-0] c.h.internal.cluster.ClusterService : [172.17.0.3]:5702 [dev] [4.0.2]
Members {size:2, ver:2} [
Member [172.17.0.3]:5701 - c967f642-a7aa-4deb-a530-b56fb8f68c78
Member [172.17.0.3]:5702 - 08dfe633-46b2-4581-94c7-81b6d0bc3ce3 this
]
2021-09-27 06:43:05.466 INFO 1 --- [ration.thread-1] c.h.c.i.p.t.AuthenticationMessageTask : [172.17.0.3]:5702 [dev] [4.0.2] Received auth from Connection[id=2, /172.17.0.3:5702->/172.17.0.3:40773, qualifier=null, endpoint=[172.17.0.3]:40773, alive=true, connectionType=JVM], successfully authenticated, clientUuid: 8843f057-c856-4739-80ae-4bc930559bd5, client version: 4.0.2
2021-09-27 06:43:05.468 INFO 1 --- [d30a.internal-3] c.h.c.i.c.ClientConnectionManager : b1bdd9bb-2879-4161-95fd-2b6e321ad30a [dev] [4.0.2] Authenticated with server [172.17.0.3]:5702:08dfe633-46b2-4581-94c7-81b6d0bc3ce3, server version: 4.0.2, local address: /172.17.0.3:40773
2021-09-27 06:43:05.968 INFO 1 --- [ main] com.hazelcast.core.LifecycleService : [172.17.0.3]:5702 [dev] [4.0.2] [172.17.0.3]:5702 is STARTED
2021-09-27 06:43:06.237 INFO 1 --- [ main] o.s.b.web.embedded.netty.NettyWebServer : Netty started on port 8081
2021-09-27 06:43:06.251 INFO 1 --- [ main] com.caching.Application : Started Application in 17.32 seconds (JVM running for 21.02)
Here is the Hazelcast management center member list,
Finally my question is,
Why I'm seeing 2 members, where there is only one sidecar cache container deployed?
What modification I will be required to reach my initial goal?

Answer 1

According to Spring Boot documentation for Hazelcast feature:
If a client can’t be created, Spring Boot attempts to configure an embedded server.
Spring Boot starts an embedded server from your hazelcast.yaml from the application container and joins to Hazelcast container using multicast.
You should replace your hazelcast.yaml in the Spring Boot app container with hazelcast-client.yaml with the following content:
hazelcast-client:
cluster-name: "dev"
network:
cluster-members:
- "127.0.0.1:5701"
After doing that Spring Boot will autoconfigure client HazelcastInstance bean and you will be able to change your cache client like this:
#Component
public class CacheClient {
private static final String ITEMS = "items";
private final HazelcastInstance client;
public CacheClient(HazelcastInstance client) {
this.client = client;
}
public Item put(String number, Item item){
IMap<String, Item> map = client.getMap(ITEMS);
return map.putIfAbsent(number, item);
}
public Item get(String key){
IMap<String, Item> map = client.getMap(ITEMS);
return map.get(key);
}
}