Merge branch 'master' into gossip-gc

7 files changed, 331 insertions, 253 deletions

diff --git a/src/main/java/pl/edu/mimuw/cloudatlas/agent/Agent.java b/src/main/java/pl/edu/mimuw/cloudatlas/agent/Agent.java
index 58b55da..0cbda2d 100644
--- a/src/main/java/pl/edu/mimuw/cloudatlas/agent/Agent.java
+++ b/src/main/java/pl/edu/mimuw/cloudatlas/agent/Agent.java
@@ -1,280 +1,55 @@
 package pl.edu.mimuw.cloudatlas.agent;
 
-import java.net.Inet4Address;
-import java.net.InetAddress;
-import java.net.SocketException;
-import java.net.UnknownHostException;
-import java.rmi.registry.LocateRegistry;
-import java.rmi.registry.Registry;
-import java.rmi.server.UnicastRemoteObject;
-import java.util.List;
-import java.util.ArrayList;
-import java.util.HashMap;
-import java.util.HashSet;
-import java.util.Iterator;
-import java.util.Map;
-import java.util.Random;
-import java.util.Set;
-import java.util.concurrent.CompletableFuture;
-import java.util.function.Supplier;
-
-import pl.edu.mimuw.cloudatlas.agent.NewApiImplementation;
-import pl.edu.mimuw.cloudatlas.agent.messages.*;
-import pl.edu.mimuw.cloudatlas.agent.modules.*;
-import pl.edu.mimuw.cloudatlas.agent.modules.Module;
-import pl.edu.mimuw.cloudatlas.api.Api;
+import pl.edu.mimuw.cloudatlas.agent.messages.UpdateAttributesMessage;
 import pl.edu.mimuw.cloudatlas.interpreter.Main;
 import pl.edu.mimuw.cloudatlas.model.PathName;
-import pl.edu.mimuw.cloudatlas.model.Value;
-import pl.edu.mimuw.cloudatlas.model.ValueContact;
-import pl.edu.mimuw.cloudatlas.model.ValueSet;
 import pl.edu.mimuw.cloudatlas.model.ZMI;
 
 public class Agent {
-    private static EventBus eventBus;
-    private static GossipGirlStrategies.ZoneSelectionStrategy zoneSelectionStrategy;
-    private static GossipGirlStrategies gossipGirlStrategies;
-    private static Random random = new Random();
 
-    public static void runRegistry() {
+    private static void addZoneAndChildren(ZMI zmi, PathName pathName, EventBus eventBus) {
         try {
-            NewApiImplementation api = new NewApiImplementation(eventBus);
-            Api apiStub =
-                    (Api) UnicastRemoteObject.exportObject(api, 0);
-            Registry registry = LocateRegistry.getRegistry();
-            registry.rebind("Api", apiStub);
-            System.out.println("Agent: api bound");
+            UpdateAttributesMessage message = new UpdateAttributesMessage("", 0, pathName.toString(), zmi.getAttributes());
+            eventBus.addMessage(message);
+            for (ZMI son : zmi.getSons()) {
+                addZoneAndChildren(son, pathName.levelDown(son.getAttributes().getOrNull("name").toString()), eventBus);
+            }
         } catch (Exception e) {
-            System.err.println("Agent registry initialization exception:");
-            e.printStackTrace();
-        }
-    }
-
-    public static HashMap<ModuleType, Module> initializeModules() throws UnknownHostException, SocketException, NullPointerException {
-        HashMap<ModuleType, Module> modules = new HashMap<ModuleType, Module>();
-        modules.put(ModuleType.TIMER_SCHEDULER, new TimerScheduler(ModuleType.TIMER_SCHEDULER));
-        modules.put(ModuleType.RMI, new Remik());
-        Long freshnessPeriod = Long.getLong("freshness_period");
-        modules.put(ModuleType.STATE, new Stanik(freshnessPeriod));
-        modules.put(ModuleType.QUERY, new Qurnik());
-        modules.put(ModuleType.GOSSIP, new GossipGirl());
-
-        Integer port = Integer.getInteger("UDUPServer.port");
-        Integer timeout = Integer.getInteger("UDUPServer.timeout");
-        Integer bufsize = Integer.getInteger("UDUPServer.bufsize");
-        UDUPServer server = new UDUPServer(InetAddress.getByName("127.0.0.1"), port, bufsize);
-        modules.put(ModuleType.UDP, new UDUP(port, timeout, bufsize, server));
-        return modules;
-    }
-
-    public static HashMap<ModuleType, Executor> initializeExecutors(
-            HashMap<ModuleType, Module> modules) {
-        HashMap<ModuleType, Executor> executors = new HashMap<ModuleType, Executor>();
-
-        for (Map.Entry<ModuleType, Module> moduleEntry : modules.entrySet()) {
-            Module module = moduleEntry.getValue();
-            Executor executor = new Executor(module);
-            executors.put(moduleEntry.getKey(), executor);
-        }
-
-        return executors;
-    }
-
-    public static ArrayList<Thread>  initializeExecutorThreads(HashMap<ModuleType, Executor> executors) {
-        ArrayList<Thread> executorThreads = new ArrayList<Thread>();
-
-        for (Map.Entry<ModuleType, Executor> executorEntry : executors.entrySet()) {
-            Thread thread = new Thread(executorEntry.getValue());
-            thread.setDaemon(true);
-            System.out.println("Initializing executor " + executorEntry.getKey());
-            thread.start();
-            executorThreads.add(thread);
-        }
-
-        return executorThreads;
-    }
-
-    public static void closeExecutors(ArrayList<Thread> executorThreads) {
-        for (Thread executorThread : executorThreads) {
-            executorThread.interrupt();
-        }
-    }
-
-    public static void runModulesAsThreads() {
-        HashMap<ModuleType, Module> modules = null;
-
-        try {
-            modules = initializeModules();
-        } catch (UnknownHostException | SocketException e) {
-            System.out.println("Module initialization failed");
-            e.printStackTrace();
-            return;
+            System.out.println("ERROR: failed to add zone");
         }
-
-        HashMap<ModuleType, Executor> executors = initializeExecutors(modules);
-        ArrayList<Thread> executorThreads = initializeExecutorThreads(executors);
-        eventBus = new EventBus(executors);
-        Thread UDUPServerThread = new Thread(((UDUP) modules.get(ModuleType.UDP)).getServer());
-        Thread eventBusThread = new Thread(eventBus);
-        System.out.println("Initializing event bus");
-        eventBusThread.start();
-        UDUPServerThread.start();
     }
 
-    private static void initZones() {
+    public static void initZones(EventBus eventBus) {
         try {
             ZMI root = Main.createTestHierarchy2();
-            addZoneAndChildren(root, new PathName(""));
+            addZoneAndChildren(root, new PathName(""), eventBus);
             System.out.println("Initialized with test hierarchy");
         } catch (Exception e) {
             System.out.println("ERROR: failed to create test hierarchy");
         }
     }
 
-    private static void startQueries(long queriesPeriod) {
-        Supplier<TimerScheduledTask> taskSupplier = () ->
-            new TimerScheduledTask() {
-                public void run() {
-                    try {
-                        sendMessage(new RunQueriesMessage("", 0));
-                    } catch (InterruptedException e) {
-                        System.out.println("Interrupted while triggering queries");
-                    }
-                }
-            };
-
-        startRecursiveTask(taskSupplier, queriesPeriod);
-    }
-
-    private static void startGossip(long gossipPeriod) {
-        Supplier<TimerScheduledTask> taskSupplier = () ->
-            new TimerScheduledTask() {
-                public void run() {
-                    try {
-                        System.out.println("INFO: initiating gossip");
-                        PathName gossipLevel = gossipGirlStrategies.selectStrategy(zoneSelectionStrategy);
-                        ValueContact contact = selectContactFromLevel(gossipLevel);
-                        if (contact != null) {
-                            System.out.println("INFO: found a contact " + contact.toString());
-                            InitiateGossipMessage message = new InitiateGossipMessage("", 0, new PathName("/uw/violet07"), contact);
-                            sendMessage(message);
-                        } else {
-                            System.out.println("DEBUG: couldn't find contact for gossip");
-                        }
-                    } catch (InterruptedException e) {
-                        System.out.println("Interrupted while initiating gossip");
-                    } catch (Exception e) {
-                        System.out.println("ERROR: something happened " + e.toString());
-                    }
-                }
-            };
-
-        startRecursiveTask(taskSupplier, gossipPeriod);
-    }
-
-    private static ValueContact selectContactFromLevel(PathName path) throws Exception {
-        CompletableFuture<ResponseMessage> responseFuture = new CompletableFuture();
-        eventBus.addMessage(new RequestStateMessage("", 0, responseFuture));
-        StateMessage response = (StateMessage) responseFuture.get();
-        ZMI root = response.getZMI();
-        List<ZMI> siblings = getSiblings(root, path);
-        filterEmptyContacts(siblings);
-        if (siblings.isEmpty()) {
-            return selectFallbackContact();
-        }
-        ZMI zmi = selectZMI(siblings);
-        ValueSet contactsValue = (ValueSet) zmi.getAttributes().getOrNull("contacts");
-        Set<Value> valueSet = contactsValue.getValue();
-        return selectContactFromSet(valueSet);
-    }
-
-    private static ValueContact selectFallbackContact() throws Exception {
-        return null;
-    }
-
-    private static ZMI selectZMI(List<ZMI> zmis) throws Exception {
-        int i = random.nextInt(zmis.size());
-        for (ZMI zmi : zmis) {
-            if (i == 0) {
-                return zmi;
-            }
-            i--;
-        }
-        System.out.println("ERROR: empty list passed to selectZMI");
-        throw new Exception("empty list passed to selectZMI");
-    }
-
-    private static ValueContact selectContactFromSet(Set<Value> contacts) throws Exception {
-        int i = random.nextInt(contacts.size());
-        for (Value contact : contacts) {
-            if (i == 0) {
-                return (ValueContact) contact;
-            }
-            i--;
-        }
-        System.out.println("ERROR: empty list passed to selectContactFromSet");
-        throw new Exception("empty list passed to selectContactFromSet");
-    }
-
-    private static List<ZMI> getSiblings(ZMI root, PathName path) {
-        try {
-            List<ZMI> siblingsAndI = root.findDescendant(path).getFather().getSons();
-            List<ZMI> siblings = new ArrayList();
-            for (ZMI siblingOrI : siblingsAndI) {
-                if (!siblingOrI.getPathName().equals(path)) {
-                    siblings.add(siblingOrI);
-                }
-            }
-            return siblings;
-        } catch (ZMI.NoSuchZoneException e) {
-            System.out.println("ERROR: didn't find path when looking for siblings");
-            return new ArrayList();
-        }
-    }
-
-    private static void filterEmptyContacts(List<ZMI> zmis) {
-        Iterator<ZMI> iterator = zmis.iterator();
-        while (iterator.hasNext()) {
-            ZMI zmi = iterator.next();
-            ValueSet contacts = (ValueSet) zmi.getAttributes().getOrNull("contacts");
-            if (contacts == null || contacts.isNull() || contacts.isEmpty()) {
-                iterator.remove();
-            }
-        }
-    }
+    public static void main(String[] args) {
+        AgentConfig agentConfig = new AgentConfig();
 
-    private static void startRecursiveTask(Supplier<TimerScheduledTask> taskSupplier, long period) {
-        TimerScheduledTask timerTask = new RecursiveScheduledTask(period, taskSupplier);
+        agentConfig.runModulesAsThreads();
 
-        try {
-            eventBus.addMessage(new TimerSchedulerMessage("", 0, "", period, 0, timerTask));
-        } catch (InterruptedException e) {
-            System.out.println("Interrupted while starting queries");
-        }
-    }
+        EventBus eventBus = new EventBus(agentConfig.getExecutors());
+        agentConfig.runRegistry(eventBus);
+        agentConfig.startNonModuleThreads(eventBus);
 
-    private static void addZoneAndChildren(ZMI zmi, PathName pathName) {
-        try {
-            UpdateAttributesMessage message = new UpdateAttributesMessage("", 0, pathName.toString(), zmi.getAttributes());
-            eventBus.addMessage(message);
-            for (ZMI son : zmi.getSons()) {
-                addZoneAndChildren(son, pathName.levelDown(son.getAttributes().getOrNull("name").toString()));
-            }
-        } catch (Exception e) {
-            System.out.println("ERROR: failed to add zone");
-        }
-    }
+        // initZones(eventBus);
 
-    public static void main(String[] args) {
-        zoneSelectionStrategy = GossipGirlStrategies.ZoneSelectionStrategy.ROUND_ROBIN_SAME_FREQ;
-        gossipGirlStrategies = new GossipGirlStrategies(new PathName("/uw/violet07"));
-        runModulesAsThreads();
-        runRegistry();
-        initZones();
         // TODO: make query period confiurable with config file and from tests
+
+        // TODO config setup
+        String zonePath = System.getProperty("zone_path");
+        String selectionStrategy = System.getProperty("Gossip.zone_strategy");
         Long queryPeriod = Long.getLong("query_period");
-        startQueries(queryPeriod);
         Long gossipPeriod = Long.getLong("gossip_period");
-        startGossip(gossipPeriod);
+
+        HierarchyConfig hierarchyConfig = new HierarchyConfig(eventBus, zonePath, selectionStrategy);
+        hierarchyConfig.startQueries(queryPeriod);
+        hierarchyConfig.startGossip(gossipPeriod);
     }
 }
diff --git a/src/main/java/pl/edu/mimuw/cloudatlas/agent/AgentConfig.java b/src/main/java/pl/edu/mimuw/cloudatlas/agent/AgentConfig.java
new file mode 100644
index 0000000..38d764a
--- /dev/null
+++ b/src/main/java/pl/edu/mimuw/cloudatlas/agent/AgentConfig.java
@@ -0,0 +1,112 @@
+package pl.edu.mimuw.cloudatlas.agent;
+
+import pl.edu.mimuw.cloudatlas.agent.modules.*;
+import pl.edu.mimuw.cloudatlas.agent.modules.Module;
+import pl.edu.mimuw.cloudatlas.api.Api;
+
+import java.net.InetAddress;
+import java.net.SocketException;
+import java.net.UnknownHostException;
+import java.rmi.registry.LocateRegistry;
+import java.rmi.registry.Registry;
+import java.rmi.server.UnicastRemoteObject;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.Map;
+
+public class AgentConfig {
+    private HashMap<ModuleType, Executor> executors;
+    HashMap<ModuleType, Module> modules;
+
+    public HashMap<ModuleType, Executor> getExecutors() {
+        return executors;
+    }
+
+    public void runRegistry(EventBus eventBus) {
+        try {
+            NewApiImplementation api = new NewApiImplementation(eventBus);
+            Api apiStub =
+                    (Api) UnicastRemoteObject.exportObject(api, 0);
+            Registry registry = LocateRegistry.getRegistry();
+            registry.rebind("Api", apiStub);
+            System.out.println("Agent: api bound");
+        } catch (Exception e) {
+            System.err.println("Agent registry initialization exception:");
+            e.printStackTrace();
+        }
+    }
+
+    private HashMap<ModuleType, Module> initializeModules() throws UnknownHostException, SocketException, NullPointerException {
+        // TODO config setup
+        Long freshnessPeriod = Long.getLong("freshness_period");
+        Integer port = Integer.getInteger("UDUPServer.port");
+        Integer timeout = Integer.getInteger("UDUPServer.timeout");
+        Integer bufsize = Integer.getInteger("UDUPServer.bufsize");
+        InetAddress serverAddr = InetAddress.getByName(System.getProperty("UDUPServer.hostname"));
+
+        HashMap<ModuleType, Module> modules = new HashMap<ModuleType, Module>();
+        modules.put(ModuleType.TIMER_SCHEDULER, new TimerScheduler(ModuleType.TIMER_SCHEDULER));
+        modules.put(ModuleType.RMI, new Remik());
+        modules.put(ModuleType.STATE, new Stanik(freshnessPeriod));
+        modules.put(ModuleType.QUERY, new Qurnik());
+        modules.put(ModuleType.GOSSIP, new GossipGirl());
+
+        UDUPServer server = new UDUPServer(serverAddr, port, bufsize);
+        modules.put(ModuleType.UDP, new UDUP(port, timeout, bufsize, server));
+        return modules;
+    }
+
+    public static HashMap<ModuleType, Executor> initializeExecutors(
+            HashMap<ModuleType, Module> modules) {
+        HashMap<ModuleType, Executor> executors = new HashMap<ModuleType, Executor>();
+
+        for (Map.Entry<ModuleType, Module> moduleEntry : modules.entrySet()) {
+            Module module = moduleEntry.getValue();
+            Executor executor = new Executor(module);
+            executors.put(moduleEntry.getKey(), executor);
+        }
+
+        return executors;
+    }
+
+    public static ArrayList<Thread> initializeExecutorThreads(HashMap<ModuleType, Executor> executors) {
+        ArrayList<Thread> executorThreads = new ArrayList<Thread>();
+
+        for (Map.Entry<ModuleType, Executor> executorEntry : executors.entrySet()) {
+            Thread thread = new Thread(executorEntry.getValue());
+            thread.setDaemon(true);
+            System.out.println("Initializing executor " + executorEntry.getKey());
+            thread.start();
+            executorThreads.add(thread);
+        }
+
+        return executorThreads;
+    }
+
+    public void closeExecutors(ArrayList<Thread> executorThreads) {
+        for (Thread executorThread : executorThreads) {
+            executorThread.interrupt();
+        }
+    }
+
+    public void runModulesAsThreads() {
+        try {
+            modules = initializeModules();
+        } catch (UnknownHostException | SocketException e) {
+            System.out.println("Module initialization failed");
+            e.printStackTrace();
+            return;
+        }
+
+        executors = initializeExecutors(modules);
+        ArrayList<Thread> executorThreads = initializeExecutorThreads(executors);
+    }
+
+    void startNonModuleThreads(EventBus eventBus) {
+        Thread UDUPServerThread = new Thread(((UDUP) modules.get(ModuleType.UDP)).getServer());
+        Thread eventBusThread = new Thread(eventBus);
+        System.out.println("Initializing event bus");
+        eventBusThread.start();
+        UDUPServerThread.start();
+    }
+}
diff --git a/src/main/java/pl/edu/mimuw/cloudatlas/agent/AgentUtils.java b/src/main/java/pl/edu/mimuw/cloudatlas/agent/AgentUtils.java
new file mode 100644
index 0000000..62d4bcd
--- /dev/null
+++ b/src/main/java/pl/edu/mimuw/cloudatlas/agent/AgentUtils.java
@@ -0,0 +1,19 @@
+package pl.edu.mimuw.cloudatlas.agent;
+
+import pl.edu.mimuw.cloudatlas.agent.messages.TimerSchedulerMessage;
+import pl.edu.mimuw.cloudatlas.agent.modules.RecursiveScheduledTask;
+import pl.edu.mimuw.cloudatlas.agent.modules.TimerScheduledTask;
+
+import java.util.function.Supplier;
+
+public class AgentUtils {
+
+    public static void startRecursiveTask(Supplier<TimerScheduledTask> taskSupplier, long period, EventBus eventBus) {
+        TimerScheduledTask timerTask = new RecursiveScheduledTask(period, taskSupplier);
+        try {
+            eventBus.addMessage(new TimerSchedulerMessage("", 0, "", period, 0, timerTask));
+        } catch (InterruptedException e) {
+            System.out.println("Interrupted while starting queries");
+        }
+    }
+}
diff --git a/src/main/java/pl/edu/mimuw/cloudatlas/agent/EventBus.java b/src/main/java/pl/edu/mimuw/cloudatlas/agent/EventBus.java
index a6d3b2d..0e972f4 100644
--- a/src/main/java/pl/edu/mimuw/cloudatlas/agent/EventBus.java
+++ b/src/main/java/pl/edu/mimuw/cloudatlas/agent/EventBus.java
@@ -22,6 +22,7 @@ public class EventBus implements Runnable {
 
     // Allows for testing with a mock EventBus
     protected EventBus() {
+        this.events = new LinkedBlockingQueue<AgentMessage>();
     }
 
     EventBus(HashMap<ModuleType, Executor> executors) {
@@ -30,6 +31,10 @@ public class EventBus implements Runnable {
         this.events = new LinkedBlockingQueue<AgentMessage>();
     }
 
+    public void setEvents(LinkedBlockingQueue<AgentMessage> events) {
+        this.events = events;
+    }
+
     public void run() {
         System.out.println("Event bus running");
         while (!Thread.currentThread().interrupted()) {
@@ -49,6 +54,7 @@ public class EventBus implements Runnable {
     }
 
     public void addMessage(AgentMessage msg) throws InterruptedException {
+        System.out.println("INFO: message added for " + msg.getDestinationModule().toString());
         this.events.put(msg);
     }
 }
diff --git a/src/main/java/pl/edu/mimuw/cloudatlas/agent/HierarchyConfig.java b/src/main/java/pl/edu/mimuw/cloudatlas/agent/HierarchyConfig.java
new file mode 100644
index 0000000..dc5241d
--- /dev/null
+++ b/src/main/java/pl/edu/mimuw/cloudatlas/agent/HierarchyConfig.java
@@ -0,0 +1,156 @@
+package pl.edu.mimuw.cloudatlas.agent;
+
+import pl.edu.mimuw.cloudatlas.agent.messages.*;
+import pl.edu.mimuw.cloudatlas.agent.modules.GossipGirlStrategies;
+import pl.edu.mimuw.cloudatlas.agent.modules.TimerScheduledTask;
+import pl.edu.mimuw.cloudatlas.model.*;
+
+import java.lang.reflect.UndeclaredThrowableException;
+import java.util.*;
+import java.util.concurrent.CompletableFuture;
+import java.util.function.Supplier;
+
+public class HierarchyConfig {
+    private GossipGirlStrategies gossipGirlStrategies;
+    private GossipGirlStrategies.ZoneSelectionStrategy zoneSelectionStrategy;
+    private Random random = new Random();
+    private EventBus eventBus;
+
+    HierarchyConfig(EventBus eventBus, String zonePath, String zoneStrategy) {
+        zoneSelectionStrategy = parseStrategy(zoneStrategy);
+        gossipGirlStrategies = new GossipGirlStrategies(new PathName(zonePath));
+        this.eventBus = eventBus;
+    }
+
+    private GossipGirlStrategies.ZoneSelectionStrategy parseStrategy(String selectionStrategy) {
+        switch (selectionStrategy) {
+            case "RoundRobinExp":
+                return GossipGirlStrategies.ZoneSelectionStrategy.ROUND_ROBIN_EXP_FREQ;
+            case "RoundRobinUniform":
+                return GossipGirlStrategies.ZoneSelectionStrategy.ROUND_ROBIN_SAME_FREQ;
+            case "RandomExp":
+                return GossipGirlStrategies.ZoneSelectionStrategy.RANDOM_DECR_EXP;
+            case "RandomUniform":
+                return GossipGirlStrategies.ZoneSelectionStrategy.RANDOM_UNFIORM;
+            default:
+                throw new UnsupportedOperationException("Selection strategy doesnt exist");
+        }
+    }
+
+    public void startGossip(long gossipPeriod) {
+        Supplier<TimerScheduledTask> taskSupplier = () ->
+                new TimerScheduledTask() {
+                    public void run() {
+                        try {
+                            System.out.println("INFO: initiating gossip");
+                            PathName gossipLevel = gossipGirlStrategies.selectStrategy(zoneSelectionStrategy);
+                            ValueContact contact = selectContactFromLevel(gossipLevel);
+                            if (contact != null) {
+                                System.out.println("INFO: found a contact " + contact.toString());
+                                InitiateGossipMessage message = new InitiateGossipMessage("", 0, new PathName("/uw/violet07"), contact);
+                                sendMessage(message);
+                            } else {
+                                System.out.println("DEBUG: couldn't find contact for gossip");
+                            }
+                        } catch (InterruptedException e) {
+                            System.out.println("Interrupted while initiating gossip");
+                        } catch (Exception e) {
+                            System.out.println("ERROR: something happened " + e.toString());
+                        }
+                    }
+                };
+
+        AgentUtils.startRecursiveTask(taskSupplier, gossipPeriod, eventBus);
+    }
+
+    private ValueContact selectContactFromLevel(PathName path) throws Exception {
+        CompletableFuture<ResponseMessage> responseFuture = new CompletableFuture();
+        this.eventBus.addMessage(new RequestStateMessage("", 0, responseFuture));
+        StateMessage response = (StateMessage) responseFuture.get();
+        ZMI root = response.getZMI();
+        List<ZMI> siblings = getSiblings(root, path);
+        filterEmptyContacts(siblings);
+        if (siblings.isEmpty()) {
+            return selectFallbackContact(response.getContacts());
+        }
+        ZMI zmi = selectZMI(siblings);
+        ValueSet contactsValue = (ValueSet) zmi.getAttributes().getOrNull("contacts");
+        Set<Value> valueSet = contactsValue.getValue();
+        return selectContactFromSet(valueSet);
+    }
+
+    // TODO
+    private ValueContact selectFallbackContact(Set<ValueContact> contacts) throws Exception {
+        if (contacts.isEmpty()) {
+            return null;
+        } else {
+            return selectContactFromSet(contacts);
+        }
+    }
+
+    private ZMI selectZMI(List<ZMI> zmis) throws Exception {
+        int i = random.nextInt(zmis.size());
+        for (ZMI zmi : zmis) {
+            if (i == 0) {
+                return zmi;
+            }
+            i--;
+        }
+        System.out.println("ERROR: empty list passed to selectZMI");
+        throw new Exception("empty list passed to selectZMI");
+    }
+
+    private <T> ValueContact selectContactFromSet(Set<T> contacts) throws Exception {
+        int i = random.nextInt(contacts.size());
+        for (T contact : contacts) {
+            if (i == 0) {
+                return (ValueContact) contact;
+            }
+            i--;
+        }
+        System.out.println("ERROR: empty list passed to selectContactFromSet");
+        throw new Exception("empty list passed to selectContactFromSet");
+    }
+
+    private List<ZMI> getSiblings(ZMI root, PathName path) {
+        try {
+            List<ZMI> siblingsAndI = root.findDescendant(path).getFather().getSons();
+            List<ZMI> siblings = new ArrayList();
+            for (ZMI siblingOrI : siblingsAndI) {
+                if (!siblingOrI.getPathName().equals(path)) {
+                    siblings.add(siblingOrI);
+                }
+            }
+            return siblings;
+        } catch (ZMI.NoSuchZoneException e) {
+            System.out.println("ERROR: didn't find path when looking for siblings");
+            return new ArrayList();
+        }
+    }
+
+    private void filterEmptyContacts(List<ZMI> zmis) {
+        Iterator<ZMI> iterator = zmis.iterator();
+        while (iterator.hasNext()) {
+            ZMI zmi = iterator.next();
+            ValueSet contacts = (ValueSet) zmi.getAttributes().getOrNull("contacts");
+            if (contacts == null || contacts.isNull() || contacts.isEmpty()) {
+                iterator.remove();
+            }
+        }
+    }
+
+    public void startQueries(long queriesPeriod) {
+        Supplier<TimerScheduledTask> taskSupplier = () ->
+                new TimerScheduledTask() {
+                    public void run() {
+                        try {
+                            sendMessage(new RunQueriesMessage("", 0));
+                        } catch (InterruptedException e) {
+                            System.out.println("Interrupted while triggering queries");
+                        }
+                    }
+                };
+
+        AgentUtils.startRecursiveTask(taskSupplier, queriesPeriod, eventBus);
+    }
+}
diff --git a/src/main/java/pl/edu/mimuw/cloudatlas/agent/messages/StateMessage.java b/src/main/java/pl/edu/mimuw/cloudatlas/agent/messages/StateMessage.java
index 759723b..806d41f 100644
--- a/src/main/java/pl/edu/mimuw/cloudatlas/agent/messages/StateMessage.java
+++ b/src/main/java/pl/edu/mimuw/cloudatlas/agent/messages/StateMessage.java
@@ -2,9 +2,11 @@ package pl.edu.mimuw.cloudatlas.agent.messages;
 
 import java.util.Map;
 import java.util.Map.Entry;
+import java.util.Set;
 
 import pl.edu.mimuw.cloudatlas.agent.modules.ModuleType;
 import pl.edu.mimuw.cloudatlas.model.Attribute;
+import pl.edu.mimuw.cloudatlas.model.ValueContact;
 import pl.edu.mimuw.cloudatlas.model.ValueQuery;
 import pl.edu.mimuw.cloudatlas.model.ValueTime;
 import pl.edu.mimuw.cloudatlas.model.ZMI;
@@ -12,11 +14,13 @@ import pl.edu.mimuw.cloudatlas.model.ZMI;
 public class StateMessage extends ResponseMessage {
     private ZMI zmi;
     private Map<Attribute, Entry<ValueQuery, ValueTime>> queries;
+    private Set<ValueContact> contacts;
 
-    public StateMessage(String messageId, ModuleType destinationModule, long timestamp, long requestId, ZMI zmi, Map<Attribute, Entry<ValueQuery, ValueTime>> queries) {
+    public StateMessage(String messageId, ModuleType destinationModule, long timestamp, long requestId, ZMI zmi, Map<Attribute, Entry<ValueQuery, ValueTime>> queries, Set<ValueContact> contacts) {
         super(messageId, destinationModule, timestamp, Type.STATE, requestId);
         this.zmi = zmi;
         this.queries = queries;
+        this.contacts = contacts;
     }
 
     public StateMessage() {}
@@ -28,4 +32,8 @@ public class StateMessage extends ResponseMessage {
     public Map<Attribute, Entry<ValueQuery, ValueTime>> getQueries() {
         return queries;
     }
+
+    public Set<ValueContact> getContacts() {
+        return contacts;
+    }
 }
diff --git a/src/main/java/pl/edu/mimuw/cloudatlas/agent/modules/Stanik.java b/src/main/java/pl/edu/mimuw/cloudatlas/agent/modules/Stanik.java
index c713827..999c193 100644
--- a/src/main/java/pl/edu/mimuw/cloudatlas/agent/modules/Stanik.java
+++ b/src/main/java/pl/edu/mimuw/cloudatlas/agent/modules/Stanik.java
@@ -53,8 +53,9 @@ public class Stanik extends Module {
                 break;
             case UPDATE_CONTACTS:
                 handleUpdateContacts((UpdateContactsMessage) message);
+                break;
             default:
-                throw new InvalidMessageType("This type of message cannot be handled by Stanik");
+                throw new InvalidMessageType("This type of message cannot be handled by Stanik" + message.getType().toString());
         }
     }
 
@@ -66,7 +67,8 @@ public class Stanik extends Module {
             0,
             message.getRequestId(),
             hierarchy.clone(),
-            (HashMap<Attribute, Entry<ValueQuery, ValueTime>>) queries.clone()
+            (HashMap<Attribute, Entry<ValueQuery, ValueTime>>) queries.clone(),
+            contacts
         );
         sendMessage(response);
     }