Add an example of running Cloud Native Cassandra on k8s.

examples/cassandra/cassandra-controller.yaml

+id: cassandra
+kind: ReplicationController
+apiVersion: v1beta1
+desiredState:
+  replicas: 1
+  replicaSelector:
+    name: cassandra
+  podTemplate:
+    desiredState:
+      manifest:
+        version: v1beta1
+        id: cassandra
+        containers:
+          - name: cassandra
+            image: kubernetes/cassandra
+            command:
+              - /run.sh
+            cpu: 1000
+            ports:
+              - name: cql
+                containerPort: 9042
+              - name: thrift
+                containerPort: 9160
+            env:
+              - key: MAX_HEAP_SIZE
+                value: 512M
+              - key: HEAP_NEWSIZE
+                value: 100M
+    labels:
+      name: cassandra

examples/cassandra/cassandra-service.yaml

+id: cassandra
+kind: Service
+apiVersion: v1beta1
+port: 9042
+containerPort: 9042
+selector:
+  name: cassandra

examples/cassandra/cassandra.yaml

+id: cassandra
+kind: Pod
+apiVersion: v1beta1
+desiredState:
+  manifest:
+    version: v1beta1
+    id: cassandra
+    containers:
+      - name: cassandra
+        image: kubernetes/cassandra
+        command:
+          - /run.sh
+        cpu: 1000
+        ports:
+          - name: cql
+            containerPort: 9042
+          - name: thrift
+            containerPort: 9160
+        env:
+          - key: MAX_HEAP_SIZE
+            value: 512M
+          - key: HEAP_NEWSIZE
+            value: 100M
+          - key: KUBERNETES_API_PROTOCOL
+            value: http
+labels:
+  name: cassandra
+
+    

examples/cassandra/image/Dockerfile

+FROM google/debian:wheezy
+
+COPY cassandra.list /etc/apt/sources.list.d/cassandra.list
+
+RUN gpg --keyserver pgp.mit.edu --recv-keys F758CE318D77295D
+RUN gpg --export --armor F758CE318D77295D | apt-key add -
+
+RUN gpg --keyserver pgp.mit.edu --recv-keys 2B5C1B00
+RUN gpg --export --armor 2B5C1B00 | apt-key add -
+
+RUN gpg --keyserver pgp.mit.edu --recv-keys 0353B12C
+RUN gpg --export --armor 0353B12C | apt-key add -
+
+RUN apt-get update
+RUN apt-get -qq -y install cassandra
+
+COPY cassandra.yaml /etc/cassandra/cassandra.yaml
+COPY run.sh /run.sh
+COPY kubernetes-cassandra.jar /kubernetes-cassandra.jar
+
+CMD /run.sh

examples/cassandra/image/cassandra.list

+deb http://www.apache.org/dist/cassandra/debian 21x main
+deb-src http://www.apache.org/dist/cassandra/debian 21x main
+

examples/cassandra/image/run.sh

+#!/bin/bash
+
+# Copyright 2014 Google Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+perl -pi -e "s/%%ip%%/$(hostname -I)/g" /etc/cassandra/cassandra.yaml
+export CLASSPATH=/kubernetes-cassandra.jar
+cassandra -f

examples/cassandra/java/io/k8s/cassandra/KubernetesSeedProvider.java

+package io.k8s.cassandra;
+
+import java.io.IOException;
+import java.net.InetAddress;
+import java.net.UnknownHostException;
+import java.net.URL;
+import java.net.URLConnection;
+import java.security.KeyManagementException;
+import java.security.NoSuchAlgorithmException;
+import java.security.SecureRandom;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import org.codehaus.jackson.JsonNode;
+import org.codehaus.jackson.annotate.JsonIgnoreProperties;
+import org.codehaus.jackson.map.ObjectMapper;
+import org.apache.cassandra.locator.SeedProvider;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class KubernetesSeedProvider implements SeedProvider {
+    @JsonIgnoreProperties(ignoreUnknown = true)
+    static class Endpoints {
+        public String[] endpoints;
+    }
+    
+    private static String getEnvOrDefault(String var, String def) {
+        String val = System.getenv(var);
+        if (val == null) {
+	    val = def;
+        }
+        return val;
+    }
+
+    private static final Logger logger = LoggerFactory.getLogger(KubernetesSeedProvider.class);
+
+    private List defaultSeeds;
+   
+    public KubernetesSeedProvider(Map<String, String> params) {
+        // Taken from SimpleSeedProvider.java
+        // These are used as a fallback, if we get nothing from k8s.
+        String[] hosts = params.get("seeds").split(",", -1);
+        defaultSeeds = new ArrayList<InetAddress>(hosts.length);
+        for (String host : hosts)
+	    {
+		try {
+		    defaultSeeds.add(InetAddress.getByName(host.trim()));
+		}
+		catch (UnknownHostException ex)
+		    {
+			// not fatal... DD will bark if there end up being zero seeds.
+			logger.warn("Seed provider couldn't lookup host " + host);
+		    }
+	    }
+    } 
+
+    public List<InetAddress> getSeeds() {
+        List<InetAddress> list = new ArrayList<InetAddress>();
+        String protocol = getEnvOrDefault("KUBERNETES_API_PROTOCOL", "http");
+        String hostName = getEnvOrDefault("KUBERNETES_RO_SERVICE_HOST", "localhost");
+        String hostPort = getEnvOrDefault("KUBERNETES_RO_SERVICE_PORT", "8080");
+
+        String host = protocol + "://" + hostName + ":" + hostPort;
+        String serviceName = getEnvOrDefault("CASSANDRA_SERVICE", "cassandra");
+        String path = "/api/v1beta1/endpoints/";
+        try {
+	    URL url = new URL(host + path + serviceName);
+	    ObjectMapper mapper = new ObjectMapper();
+	    Endpoints endpoints = mapper.readValue(url, Endpoints.class);
+	    if (endpoints != null) {
+		for (String endpoint : endpoints.endpoints) {
+		    String[] parts = endpoint.split(":");
+		    list.add(InetAddress.getByName(parts[0]));
+		}
+	    }
+        } catch (IOException ex) {
+	    logger.warn("Request to kubernetes apiserver failed"); 
+        }
+        if (list.size() == 0) {
+	    // If we got nothing, we might be the first instance, in that case
+	    // fall back on the seeds that were passed in cassandra.yaml.
+	    return defaultSeeds;
+        }
+        return list;
+    }
+
+    // Simple main to test the implementation
+    public static void main(String[] args) {
+        SeedProvider provider = new KubernetesSeedProvider(new HashMap<String, String>());
+        System.out.println(provider.getSeeds());
+    }
+}