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Kubernetes

Kubernetes is a container orchestration engine for automating deployment, scaling, and management of containerized applications. This page describes the details of Webswing Cluster in Kubernetes. Following guide provides examples only and actual deployments may vary depending on the requirements and infrastructure provider.

Images

Webswing Cluster Deployment examples rely on Docker images that are stored in our private Docker registry. Access to this registry is limited according to the purchased SLA. Our examples are meant for demonstration purposes only. You might need a different base image OS, Java version, ...

Base Images - Dockerfiles

In case you want to create your own base images from scratch use following Dockerfiles as an example. We are using these to create the base images.

dev.webswing.org/webswing-admin:23.1

webswing-admin-23.1-distribution.zip to be present in the same folder as Dockerfile run docker build -t dev.webswing.org/webswing-admin:23.1 .

Dockerfile:

FROM openjdk:11-jre

RUN apt-get update && apt-get install --no-install-recommends -y \
    wget \
    unzip \
    less \
    nano \
    procps \
    dos2unix

COPY *.zip /opt/webswing-admin/dist.zip

RUN unzip /opt/webswing-admin/dist.zip -d /opt/webswing-admin && \
    mv /opt/webswing-admin/webswing-admin-*/* /opt/webswing-admin && \
    rm -d /opt/webswing-admin/dist.zip /opt/webswing-admin/webswing-admin-*/

COPY *.war /opt/webswing-admin/webswing-admin-server.war

ENV WEBSWING_HOME=/opt/webswing-admin

COPY docker/docker.tgz .
RUN tar xzvf docker.tgz --strip 1 -C /usr/local/bin docker/docker && rm docker.tgz

WORKDIR $WEBSWING_HOME

RUN mkdir -p /etc/service/webswing-admin && \
    echo "#!/bin/sh\ncd $WEBSWING_HOME\nexec $JAVA_HOME/bin/java \$1 -jar $WEBSWING_HOME/server/webswing-jetty-launcher.jar -admin \$2" > /etc/service/webswing-admin/run && \
    chmod +x /etc/service/webswing-admin/run

EXPOSE 8080

CMD /etc/service/webswing-admin/run "$ADMIN_JAVA_OPTS" "$ADMIN_OPTS"

dev.webswing.org/webswing-ce-server:23.1

webswing-cluster-23.1-distribution.zip to be present in the same folder as Dockerfile run docker build -t dev.webswing.org/webswing-ce-server:23.1 .

Dockerfile:

FROM openjdk:11-jre

RUN apt-get update && apt-get install --no-install-recommends -y \
    wget \
    unzip \
    less \
    nano \
    procps

COPY *.zip /opt/webswing-cluster/dist.zip

RUN unzip /opt/webswing-cluster/dist.zip -d /opt/webswing-cluster && \
    mv /opt/webswing-cluster/webswing-cluster-*/* /opt/webswing-cluster && \
    rm -d /opt/webswing-cluster/dist.zip /opt/webswing-cluster/webswing-cluster-*/

COPY *.war /opt/webswing-cluster/webswing.war

ENV WEBSWING_HOME=/opt/webswing-cluster

WORKDIR $WEBSWING_HOME

RUN mkdir -p /etc/service/webswing-cluster && \
    echo "#!/bin/sh\ncd $WEBSWING_HOME\nexec $JAVA_HOME/bin/java \$1 -jar $WEBSWING_HOME/server/webswing-jetty-launcher.jar \$2" > /etc/service/webswing-cluster/run && \
    chmod +x /etc/service/webswing-cluster/run

EXPOSE 8080

CMD /etc/service/webswing-cluster/run "$WEBSWING_JAVA_OPTS" "$WEBSWING_OPTS"

dev.webswing.org/webswing-ce-session:23.1

webswing-cluster-23.1-distribution.zip to be present in the same folder as Dockerfile run docker build -t dev.webswing.org/webswing-ce-session:23.1 .

Dockerfile:

FROM openjdk:11-jre

RUN apt-get update && apt-get install --no-install-recommends -y \
    wget \
    unzip \
    xvfb \
    libxext6 \
    libxi6 \
    libxtst6 \
    libxrender1 \
    libpangoft2-1.0-0 \
    dos2unix \
    less \
    nano \
    procps

COPY *.zip /opt/webswing-sessionpool/dist.zip

RUN unzip /opt/webswing-sessionpool/dist.zip -d /opt/webswing-sessionpool && \
    mv /opt/webswing-sessionpool/webswing-cluster-*/* /opt/webswing-sessionpool && \
    rm -d /opt/webswing-sessionpool/dist.zip /opt/webswing-sessionpool/webswing-cluster-*/

COPY *.war /opt/webswing-sessionpool/webswing.war

ENV WEBSWING_HOME=/opt/webswing-sessionpool \
    DISPLAY=:99

WORKDIR $WEBSWING_HOME

RUN mkdir -p /etc/service/xvfb && \
    echo "#!/bin/sh\nexec Xvfb :99" > /etc/service/xvfb/run && \
    chmod +x /etc/service/xvfb/run

RUN mkdir -p /etc/service/webswing-sessionpool && \
    echo "#!/bin/sh\ncd $WEBSWING_HOME\nexec $JAVA_HOME/bin/java \$1 -jar $WEBSWING_HOME/webswing.war \$2" > /etc/service/webswing-sessionpool/run && \
    chmod +x /etc/service/webswing-sessionpool/run

COPY start.sh /opt/webswing-sessionpool/start.sh
RUN dos2unix /opt/webswing-sessionpool/start.sh
RUN chmod +x /opt/webswing-sessionpool/start.sh

CMD ./start.sh

In case of start.sh, please ensure LF line endings. CRLF endings will result in file not found. Please note the flag sessionpool.close.with.session=true. In case you do not provide environment variable WEBSWING_JAVA_OPTS it will shut down the session pool with first application that exits. This is useful in case of Pod per session and downscaling.

start.sh:

#!/bin/bash
WS_OPTS="-sessionpool"
WS_JAVA_OPTS="-Xmx128M -Djava.net.preferIPv4Stack=true"
if [ -n "$WEBSWING_OPTS" ]; then
    WS_OPTS=$WEBSWING_OPTS
fi
if [ -n "$WEBSWING_JAVA_OPTS" ]; then
    WS_JAVA_OPTS=$WEBSWING_JAVA_OPTS
fi

rm -f /tmp/.X99-lock

/etc/service/xvfb/run &
/etc/service/webswing-sessionpool/run "$WS_JAVA_OPTS" "$WS_OPTS"

Configuration

Following examples are extending the base images described above. You can merge the Dockerfiles and create the images you need.

Admin Console

run docker build -t dev.webswing.org/webswing-admin:23.1_demo .

Dockerfile:

FROM dev.webswing.org/webswing-admin:23.1

COPY ./webswing-admin.properties /opt/webswing-admin/webswing-admin.properties

CMD /etc/service/webswing-admin/run "$ADMIN_JAVA_OPTS" "$ADMIN_OPTS"

webswing-admin.properties:

# secret signing key for JWT tokens, should be at least 128 characters long string
# - change this to a random alphanumeric string in production
# - same secret must be present in webswing server's webswing.properties
webswing.connection.secret = k8s_secret_FJDBJFNSKJFNJSDNFFSDBFBDSJNCSJNDJKCHDSFJSDKFSDHJFNSDKJFSDNSDKJNCJSDNKJCNSJDNCJKDBSJFBSDJKBFJKSDBKJFBSDKBFKSDJBFBSDFBK

# public URL on which applications are accessible on public internet
webswing.server.publicUrl = http://localhost:30080

# type of websocket URL loader
# 	- propertyFile (default) - loads from this property file from webswing.server.websocketUrl property 
# 	- propertyFile_noReload - loads from this property file from webswing.server.websocketUrl property, doesn't attempt to reload the property file after start
#	- script - loads from a custom script
webswing.websocketUrlLoader.type = propertyFile
# websocket URL loader reloading interval in seconds
webswing.websocketUrlLoader.interval = 5

# use this for webswing.websocketUrlLoader.type = (propertyFile|propertyFile_noReload)
# comma-separated list of websocket URLs to webswing cluster servers
webswing.server.websocketUrl = ws://webswing-server-0.webswing-server.default.svc.cluster.local:8080,ws://webswing-server-1.webswing-server.default.svc.cluster.local:8080

# use this for webswing.websocketUrlLoader.type = script
# script that loads a comma-separated list of websocket URLs
#webswing.websocketUrlLoader.script = urls.bat

# path where admin console logs should be stored
webswing.logsDir = logs/

# path where webswing-server logs are stored, these logs will show in admin console
webswing.server.logsDir = logs/

Webswing Server

Webswing server needs to contain or reference the application web data as described here: cluster/cluster.html#web-configuration This server example extends the base image by copying the application and some configuration to the base image. It uses following folder structure, and corresponding configuration:

./apps/FlatLaf/web/index.html
./apps/FlatLaf/icon.png
./Dockerfile
./webswing.properties
./webswing-server.config

run docker build -t dev.webswing.org/webswing-ce-server:23.1_demo .

Dockerfile:

FROM dev.webswing.org/webswing-ce-server:23.1

COPY ./webswing.properties /opt/webswing-cluster/webswing.properties
COPY ./webswing-server.config /opt/webswing-cluster/webswing-server.config
COPY ./apps /opt/webswing-cluster/apps

CMD /etc/service/webswing-cluster/run "$WEBSWING_JAVA_OPTS" "$WEBSWING_OPTS"

webswing.properties:

# secret signing key for JWT tokens, should be at least 128 characters long string
# - change this to a random alphanumeric string in production
# - same secret must be present in session pool's webswing-sessionpool.properties or admin console's webswing-admin.properties
webswing.connection.secret = k8s_secret_FJDBJFNSKJFNJSDNFFSDBFBDSJNCSJNDJKCHDSFJSDKFSDHJFNSDKJFSDNSDKJNCJSDNKJCNSJDNCJKDBSJFBSDJKBFJKSDBKJFBSDKBFKSDJBFBSDFBK

# websocket URL of this server, if deployed outside embedded Jetty
#webswing.server.websocketUrl = ws://localhost:8080

webswing.logsDir = logs/

**webswing-server.config:

{
  "/" : {
    "path" : "/",
    "security" : {
      "module" : "EMBEDED",
      "config" : {
        "users" : [ {
          "username" : "admin",
          "password" : "pwd",
          "roles" : [ "admin" ]
        }, {
          "username" : "support",
          "password" : "pwd",
          "roles" : [ "support" ]
        }, {
          "username" : "user",
          "password" : "pwd"
        } ]
      },
      "classPath" : [ ]
    },
    "adminConsoleUrl" : "${webswing.admin.url}",
    "langFolder" : "${webswing.configDir}/lang",
    "homeDir" : "${user.dir}",
    "allowedCorsOrigins" : [ "*" ],
    "dataStore" : {
      "module" : "FILESYSTEM",
      "config" : {
        "threadDumpsFolder" : "${WEBSWING_DATA_STORE}/threadDumps",
        "recordingsFolder" : "${WEBSWING_DATA_STORE}/recordings",
        "transferFolder" : "${WEBSWING_DATA_STORE}/transfer"
      }
    }
  },
  "/demo" : {
    "path" : "/demo",
    "name" : "Demo",
    "webFolder" : "${webswing.configDir}/apps/FlatLaf/web",
    "security" : {
      "module" : "NONE",
      "classPath" : [ ],
      "config" : { },
      "authorizationConfig" : {
        "users" : [ ],
        "roles" : [ ]
      }
    },
    "icon" : "${webswing.configDir}/apps/FlatLaf/icon.png",
    "webHomeDir" : "/tmp",
    "langFolder" : "${webswing.configDir}/lang",
    "uploadMaxSize" : 5,
    "maxClients" : -1,
    "sessionMode" : "ALWAYS_NEW_SESSION",
    "allowStealSession" : false,
    "autoLogout" : false,
    "enabled" : true,
    "restrictedResources" : [ ],
    "monitorEdtEnabled" : true,
    "loadingAnimationDelay" : 2,
    "dataStore" : {
      "module" : "INHERITED",
      "config" : { }
    },
    "recordingConsentRequired" : false,
    "mirroringConsentRequired" : false,
    "goodbyeUrl" : ""
  }
}

Webswing Session Pool - Static cluster

Webswing Session Pool is responsible for launchiong the Java Application. It needs to contain or reference the applications jar files as described here: cluster/cluster.html#app-configuration This sesion pool example extends the base image by copying the application and some configuration to the base image. It uses following folder structure, and corresponding configuration:

./apps/FlatLaf/flatlaf-demo-1.1.2.jar
./Dockerfile
./webswing-session.properties
./webswing-app.config

run docker build -t dev.webswing.org/webswing-ce-session:23.1_demo .

Dockerfile:

FROM dev.webswing.org/webswing-ce-session:23.1

COPY ./webswing-app.config /opt/webswing-sessionpool/webswing-app.config
COPY ./webswing-session.properties /opt/webswing-sessionpool/webswing-sessionpool.properties
COPY ./FlatLaf /opt/webswing-sessionpool/apps/FlatLaf

CMD ./start.sh

webswing-session.properties:

# secret signing key for JWT tokens, should be at least 128 characters long string
# - change this to a random alphanumeric string in production
# - same secret must be present in cluster server's webswing.properties
webswing.connection.secret = k8s_secret_FJDBJFNSKJFNJSDNFFSDBFBDSJNCSJNDJKCHDSFJSDKFSDHJFNSDKJFSDNSDKJNCJSDNKJCNSJDNCJKDBSJFBSDJKBFJKSDBKJFBSDKBFKSDJBFBSDFBK

# session pool id is generated if not provided
#sessionpool.id = session-pool-0

# higher number means higher priority, you can use this value in load balancer algorithm
sessionpool.priority = 1

# maximum pool size, set -1 for infinite
sessionpool.instances.max = 10

# reconnect policy (omit to disable reconnecting, session pool will shutdown with no active ws connection)
#	- use interval, retries or both
#	- session pool will try to reconnect as many as webswing.server.reconnect.retries times
#	- session pool will try to reconnect for the duration of webswing.server.reconnect.interval interval
# reconnect interval - try to reconnect on connection loss for given amount of seconds
# 	- use -1 for infinite interval
sessionpool.reconnect.interval = -1
# reconnect retries - try to reconnect on connection loss for given amount of seconds
#sessionpool.reconnect.retries = 5
# delay between reconnects, in milliseconds
sessionpool.reconnect.delay = 3000

# type of websocket URL loader
# 	- propertyFile (default) - loads from this property file from webswing.server.websocketUrl property 
# 	- propertyFile_noReload - loads from this property file from webswing.server.websocketUrl property, doesn't attempt to reload the property file after start
#	- script - loads from a custom script
webswing.websocketUrlLoader.type = propertyFile
# websocket URL loader reloading interval in seconds
webswing.websocketUrlLoader.interval = 5

# use this for webswing.websocketUrlLoader.type = (propertyFile|propertyFile_noReload)
# comma-separated list of websocket URLs to webswing cluster servers
webswing.server.websocketUrl = ws://webswing-server-0.webswing-server.default.svc.cluster.local:8080,ws://webswing-server-1.webswing-server.default.svc.cluster.local:8080

# use this for webswing.websocketUrlLoader.type = script
# script that loads a comma-separated list of websocket URLs
#webswing.websocketUrlLoader.script = urls.bat

webswing.logsDir = logs/

webswing-app.config:

{
  "/demo" : {
    "jreExecutable" : "${java.home}/bin/java",
    "javaVersion" : "${java.version}",
    "vmArgs" : "-Xmx128m -DauthorizedUser=${user}",
    "classPathEntries" : [ "/opt/webswing-sessionpool/apps/FlatLaf/*.jar" ],
    "theme" : "Murrine",
    "fontConfig" : { },
    "swingSessionTimeout" : 60,
    "isolatedFs" : true,
    "debug" : true,
    "javaFx" : false,
    "javaFxClassPathEntries" : [  ],
    "directdraw" : true,
    "compositingWinManager" : true,
    "allowDelete" : true,
    "allowDownload" : true,
    "allowAutoDownload" : true,
    "allowUpload" : true,
    "allowJsLink" : true,
    "jsLinkWhiteList" : [ "org.webswing.demo.jslink.JsLinkDemo.*" ],
    "launcherType" : "Desktop",
    "launcherConfig" : {
      "mainClass" : "com.formdev.flatlaf.demo.FlatLafDemo"
    },
    "userDir" : "${user}",
    "homeDir" : "/opt/webswing-sessionpool/apps/FlatLaf",
    "transparentFileSave" : true,
    "clearTransferDir" : true,
    "transparentFileOpen" : true,
    "transferDir" : "${user}/upload",
    "timeoutIfInactive" : false,
    "sessionLogging" : false,
    "jsLinkWhitelist" : [ "*" ],
    "allowLocalClipboard" : true,
    "allowServerPrinting" : false,
    "dockMode" : "ALL",
    "allowStatisticsLogging" : true,
    "testMode" : false
  }
}

Webswing Session Pool - Autoscaling Experimental

For the autoscaling we need to change the maximum number of the instances per session pool to 1. All the rest remains the same. The difference is in starting the session pools which is handled by a scaling algorithm.

webswing-session.properties

sessionpool.instances.max = 1

Webswing Scaler - Autoscaling Experimental

Webswing scaler is an example on how to manage Kubernetes pods and sessions. Due to statefulness of the JVM application and different longevity of the sessions, each session is served by a dedicated POD. Once the application finishes the POD can be terminated. Some free PODs are desirable in order to ensure quick start and good user experience. run docker build -t dev.webswing.org/webswing-scaler:23.1_demo . Dockerfile:

FROM python:3.6-alpine

RUN pip install kubernetes
WORKDIR /app
COPY scaler.py scaler.py

CMD [ "python", "/app/scaler.py"]

Deployment

Admin Console

Admin Console is configured mainly by the webswing-admin.properties that is provided in the image.

webswing-admin.yaml

kind: Service
apiVersion: v1
metadata:
  name: webswing-admin
spec:
  type: NodePort
  ports:
    - port: 8090
      targetPort: 8090
      nodePort: 30090
  selector:
    app: webswing-admin
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: webswing-admin
spec:
  replicas: 1
  selector:
    matchLabels:
      app: webswing-admin
  template:
    metadata:
      labels:
        app: webswing-admin
    spec:
      containers:
      - name: webswing-admin
        image: dev.webswing.org/webswing-admin:23.1_demo
        imagePullPolicy: IfNotPresent
        ports:
          - name: web
            containerPort: 8090
          - name: ws
            containerPort: 8000
        env:
          - name: ADMIN_JAVA_OPTS
            value: "-Dwebswing.server.publicUrl=http://localhost:30080"
        env:
          - name: ADMIN_OPTS
            value: "-h 0.0.0.0 -j /opt/webswing-admin/jetty.properties"

Server

webswing-server.yaml:

kind: Service
apiVersion: v1
metadata:
  name: webswing-server
spec:
  type: NodePort
  ports:
    - port: 8080
      targetPort: 8080
      nodePort: 30080
  selector:
    app: webswing-server
---
apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: webswing-server
spec:
  replicas: 2
  selector:
    matchLabels:
      app: webswing-server
  serviceName: "webswing-server"
  template:
    metadata:
      labels:
        app: webswing-server
    spec:
      containers:
      - name: webswing-server
        image: dev.webswing.org/webswing-ce-server:23.1_demo
        imagePullPolicy: IfNotPresent
        ports:
          - name: web
            containerPort: 8080
        env:
          - name: WEBSWING_JAVA_OPTS
            value: "-Xmx256M -Djava.net.preferIPv4Stack=true -Dwebswing.admin.url=http://localhost:30090"
          - name: WEBSWING_OPTS
            value: "-h 0.0.0.0 -j /opt/webswing-cluster/jetty.properties"

Session Pool - Static Session Pools

webswing-sessionpool.yaml:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: webswing-sessionpool
spec:
  replicas: 2
  selector:
    matchLabels:
      app: webswing-sessionpool
  serviceName: "webswing-sessionpool"
  template:
    metadata:
      labels:
        app: webswing-sessionpool
    spec:
      containers:
      - name: webswing-sessionpool
        image: dev.webswing.org/webswing-ce-session:23.1_demo
        imagePullPolicy: IfNotPresent
        ports:
          - name: web
            containerPort: 8080
          - name: ws
            containerPort: 8000
        env:
          - name: WEBSWING_JAVA_OPTS
            value: "-Xmx128M -Djava.net.preferIPv4Stack=true"

Scaler - Dynamic Session Creation

Scaling feature has been reimplemented in the Admin Console. Following part is for reference only.

In case of kubernetes example with autoscaling the Session lifecycle is managed by the scaling script. In the scaler deployment descriptor we tell the scaler what is the desired buffer (MIN_FREE_PODS) and what session image to create.

webswing-scaler.yaml:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: webswing-scaler
spec:
  selector:
    matchLabels:
      app: webswing-scaler
  template:
    metadata:
      labels:
        app: webswing-scaler
    spec:
      containers:
      - name: webswing-scaler
        image: dev.webswing.org/webswing-ce-scaler:23.1_demo
        imagePullPolicy: IfNotPresent
        env:
        - name: PYTHONUNBUFFERED
          value: "0"
        - name: WEBSWING_IMAGE
          value: "dev.webswing.org/webswing-ce-session:23.1_demo"
        - name: MIN_FREE_PODS
          value: "2"
        - name: MAX_PENDING_PODS
          value: "2"