From 651c2b76ff3db39cefd1542d6f4c19d8686dfb85 Mon Sep 17 00:00:00 2001
From: Martin <marcin.j.chrzanowski@gmail.com>
Date: Sun, 22 Dec 2019 17:29:25 +0100
Subject: Implement executor (#65)

---
 .../pl/edu/mimuw/cloudatlas/agent/EventBus.java    |  7 +++
 .../pl/edu/mimuw/cloudatlas/agent/Executor.java    | 35 ++++++++++++++
 .../java/pl/edu/mimuw/cloudatlas/agent/Module.java | 10 ++++
 .../edu/mimuw/cloudatlas/agent/ExecutorTest.java   | 54 ++++++++++++++++++++++
 4 files changed, 106 insertions(+)
 create mode 100644 src/main/java/pl/edu/mimuw/cloudatlas/agent/EventBus.java
 create mode 100644 src/main/java/pl/edu/mimuw/cloudatlas/agent/Executor.java
 create mode 100644 src/main/java/pl/edu/mimuw/cloudatlas/agent/Module.java
 create mode 100644 src/test/java/pl/edu/mimuw/cloudatlas/agent/ExecutorTest.java

(limited to 'src')

diff --git a/src/main/java/pl/edu/mimuw/cloudatlas/agent/EventBus.java b/src/main/java/pl/edu/mimuw/cloudatlas/agent/EventBus.java
new file mode 100644
index 0000000..47cb1ff
--- /dev/null
+++ b/src/main/java/pl/edu/mimuw/cloudatlas/agent/EventBus.java
@@ -0,0 +1,7 @@
+package pl.edu.mimuw.cloudatlas.agent;
+
+/*
+ * The EventBus routes messages sent between Modules.
+ */
+public class EventBus {
+}
diff --git a/src/main/java/pl/edu/mimuw/cloudatlas/agent/Executor.java b/src/main/java/pl/edu/mimuw/cloudatlas/agent/Executor.java
new file mode 100644
index 0000000..0651a9b
--- /dev/null
+++ b/src/main/java/pl/edu/mimuw/cloudatlas/agent/Executor.java
@@ -0,0 +1,35 @@
+package pl.edu.mimuw.cloudatlas.agent;
+
+import java.util.concurrent.LinkedBlockingQueue;
+
+import pl.edu.mimuw.cloudatlas.agent.message.AgentMessage;
+
+/*
+ * Queues messages sent to a particular module and ensures they are eventually
+ * handled.
+ */
+public class Executor implements Runnable {
+    private Module module;
+    private LinkedBlockingQueue<AgentMessage> events;
+
+    public Executor(Module module) {
+        this.module = module;
+        this.events = new LinkedBlockingQueue<AgentMessage>();
+    }
+
+    public void run() {
+        while (!Thread.currentThread().interrupted()) {
+            try {
+                AgentMessage event = events.take();
+                module.handle(event);
+            } catch (InterruptedException e) {
+                System.out.println("Executor interrupted. Exiting loop.");
+                break;
+            }
+        }
+    }
+
+    public void addMessage(AgentMessage event) throws InterruptedException {
+        events.put(event);
+    }
+}
diff --git a/src/main/java/pl/edu/mimuw/cloudatlas/agent/Module.java b/src/main/java/pl/edu/mimuw/cloudatlas/agent/Module.java
new file mode 100644
index 0000000..46df31b
--- /dev/null
+++ b/src/main/java/pl/edu/mimuw/cloudatlas/agent/Module.java
@@ -0,0 +1,10 @@
+package pl.edu.mimuw.cloudatlas.agent;
+
+import pl.edu.mimuw.cloudatlas.agent.message.AgentMessage;
+
+/*
+ * A Module is a (potentially stateful) event handler.
+ */
+public abstract class Module {
+    public abstract void handle(AgentMessage event);
+}
diff --git a/src/test/java/pl/edu/mimuw/cloudatlas/agent/ExecutorTest.java b/src/test/java/pl/edu/mimuw/cloudatlas/agent/ExecutorTest.java
new file mode 100644
index 0000000..445a5b4
--- /dev/null
+++ b/src/test/java/pl/edu/mimuw/cloudatlas/agent/ExecutorTest.java
@@ -0,0 +1,54 @@
+package pl.edu.mimuw.cloudatlas.agent;
+
+import org.junit.Test;
+import static org.junit.Assert.*;
+
+import pl.edu.mimuw.cloudatlas.agent.message.AgentMessage;
+import pl.edu.mimuw.cloudatlas.agent.message.AgentMessage.AgentModule;
+
+public class ExecutorTest {
+    public class MessageCounterModule extends Module {
+        public int counter = 0;
+        public void handle(AgentMessage m) {
+            counter++;
+        }
+    }
+
+    @Test
+    public void testDoesntExecuteWhenNoMessages() throws Exception {
+        MessageCounterModule module = new MessageCounterModule();
+        Executor executor = new Executor(module);
+        Thread thread = new Thread(executor);
+        thread.start();
+        Thread.sleep(100);
+        thread.interrupt();
+        assertEquals(0, module.counter);
+    }
+
+    @Test
+    public void testExecutesHandlerOnce() throws Exception {
+        MessageCounterModule module = new MessageCounterModule();
+        Executor executor = new Executor(module);
+        executor.addMessage(new AgentMessage("", AgentModule.UDP, 0) {});
+        Thread thread = new Thread(executor);
+        thread.start();
+        Thread.sleep(100);
+        thread.interrupt();
+        assertEquals(1, module.counter);
+    }
+
+    @Test
+    public void testExecutesHandlerMultipleTimes() throws Exception {
+        MessageCounterModule module = new MessageCounterModule();
+        Executor executor = new Executor(module);
+        executor.addMessage(new AgentMessage("", AgentModule.UDP, 0) {});
+        executor.addMessage(new AgentMessage("", AgentModule.UDP, 0) {});
+        Thread thread = new Thread(executor);
+        thread.start();
+        Thread.sleep(100);
+        executor.addMessage(new AgentMessage("", AgentModule.UDP, 0) {});
+        Thread.sleep(100);
+        thread.interrupt();
+        assertEquals(3, module.counter);
+    }
+}
-- 
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