Refactor health checking logic separate objects.

health/src/main/java/services/HealthResource.java

@@ -6,6 +6,9 @@
 import org.xbill.DNS.SRVRecord;
 import org.xbill.DNS.SimpleResolver;
 import org.xbill.DNS.Type;
+import services.doctor.Doctor;
+import services.doctor.EnvironmentHealth;
+import services.registry.ServiceRegistry;
 
 import javax.ws.rs.GET;
 import javax.ws.rs.Path;
@@ -16,31 +19,24 @@
 
 @Path("/health")
 public class HealthResource {
-    private final String dnsHost;
+    private final ServiceRegistry registry;
+    private final Doctor doctor;
 
-    public HealthResource(String dnsHost) {
-        this.dnsHost = dnsHost;
+    public HealthResource(ServiceRegistry registry, Doctor doctor) {
+        this.registry = registry;
+        this.doctor = doctor;
     }
 
     @Path("/{environment}")
     @GET
-    public Response services(@PathParam("environment") String environment) throws Exception {
-        Lookup lookup = new Lookup(environment + ".skydns.local", Type.SRV);
-        lookup.setResolver(new SimpleResolver(dnsHost));
-        Record[] records = lookup.run();
+    public Response services(@PathParam("environment") String environmentName) throws Exception {
+        ServiceRegistry.Environment environment = registry.resolve(environmentName);
+        EnvironmentHealth health = doctor.check(environment);
 
-
-        if(records == null) {
-            return Response.status(200).type("application/json").entity(new EnvironmentHealth(environment)).build();
-        } else {
-            List<Health> services = new ArrayList<Health>();
-            for(Record record : records) {
-                int port = ((SRVRecord) record).getPort();
-                String host = ((SRVRecord) record).getTarget().toString();
-                boolean ok = true;
-                services.add(new Health(host, port, ok));
-            }
-            return Response.status(200).type("application/json").entity(Optional.of(new EnvironmentHealth(environment, services))).build();
-        }
+        return Response
+                .status(200)
+                .type("application/json")
+                .entity(health)
+                .build();
     }
 }

health/src/main/java/services/HealthService.java

@@ -2,6 +2,8 @@
 
 import com.yammer.dropwizard.config.Bootstrap;
 import com.yammer.dropwizard.config.Environment;
+import services.doctor.Doctor;
+import services.registry.ServiceRegistry;
 
 import static org.quartz.JobBuilder.newJob;
 
@@ -19,6 +21,9 @@ public void initialize(Bootstrap<SkyDnsServiceConfiguration> bootstrap) {
 
     @Override
     public void run(SkyDnsServiceConfiguration configuration, final Environment environment) {
-        environment.addResource(new HealthResource(configuration.getSkyDnsHost()));
+        ServiceRegistry registry = new ServiceRegistry(configuration.getSkyDnsHost(), ".skydns.local");
+        Doctor doctor = new Doctor();
+
+        environment.addResource(new HealthResource(registry, doctor));
     }
 }

health/src/main/java/services/doctor/Doctor.java

@@ -0,0 +1,17 @@
+package services.doctor;
+
+import services.Health;
+import services.registry.ServiceRegistry;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class Doctor {
+    public EnvironmentHealth check(ServiceRegistry.Environment environment) {
+        List<Health> health = new ArrayList<Health>();
+        for (ServiceRegistry.Service service : environment.getServices()) {
+            health.add(new Health(service.getDomain(), service.getPort(), true));
+        }
+        return new EnvironmentHealth(environment.getEnvironment(), health);
+    }
+}

health/src/main/java/services/EnvironmentHealth.java → health/src/main/java/services/doctor/EnvironmentHealth.java

@@ -1,7 +1,8 @@
-package services;
+package services.doctor;
 
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.google.common.collect.ImmutableList;
+import services.Health;
 
 import java.util.List;
 

health/src/main/java/services/registry/ServiceRegistry.java

@@ -0,0 +1,84 @@
+package services.registry;
+
+import com.google.common.collect.ImmutableList;
+import org.xbill.DNS.Lookup;
+import org.xbill.DNS.Record;
+import org.xbill.DNS.SRVRecord;
+import org.xbill.DNS.SimpleResolver;
+import org.xbill.DNS.Type;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class ServiceRegistry {
+    public static class Service {
+        private final String domain;
+        private final int port;
+
+        public Service(String domain, int port) {
+            this.domain = domain;
+            this.port = port;
+        }
+
+        public String getDomain() {
+            return domain;
+        }
+
+        public int getPort() {
+            return port;
+        }
+    }
+
+    public static class Environment {
+        private final String environment;
+        private final List<Service> services;
+
+        public Environment(String environment, List<Service> services) {
+            this.environment = environment;
+            this.services = services;
+        }
+
+        public Environment(String environment) {
+            this(environment, ImmutableList.<Service>of());
+        }
+
+        public String getEnvironment() {
+            return environment;
+        }
+
+        public List<Service> getServices() {
+            return services;
+        }
+    }
+
+    private final String domain;
+    private final String dns;
+
+    public ServiceRegistry(String dns, String domain) {
+        this.dns = dns;
+        this.domain = domain;
+    }
+
+    public Environment resolve(String environment) {
+        Record[] records = null;
+        try {
+            Lookup lookup = new Lookup(environment + domain, Type.SRV);
+            lookup.setResolver(new SimpleResolver(dns));
+            records = lookup.run();
+        } catch (Exception e) {
+            throw new RuntimeException(e);
+        }
+
+        if (records == null) {
+            return new Environment(environment);
+        } else {
+            List<Service> services = new ArrayList<Service>();
+            for (Record record : records) {
+                int port = ((SRVRecord) record).getPort();
+                String host = ((SRVRecord) record).getTarget().toString();
+                services.add(new Service(host, port));
+            }
+            return new Environment(environment, services);
+        }
+    }
+}