logging - file appender

README.md

@@ -2,6 +2,7 @@
 
 *topics*
 * [Logback vs SLF4J vs Log4J2 - what is the difference?](https://www.youtube.com/watch?v=SWHYrCXIL38&ab_channel=JavaBrains)
+* [SLF4J Logback Tutorial](https://mkyong.com/logging/slf4j-logback-tutorial/)
 * Introduction to Service Registry & Service Discovery
 * Implement Service Registry with Zookeeper
 * Integrate into our leader-worker architecture 
\ No newline at end of file

logs/app.log

+2024-01-16 10:35:09,211 INFO Registration_Discovery.Application [main] Connected
+2024-01-16 10:35:19,177 DEBUG Registration_Discovery.Application [main-EventThread] Successfully connected to Zookeeper
+2024-01-16 10:35:19,277 INFO Registration_Discovery.LeaderElection [main] I'm a leader
+2024-01-16 10:35:19,296 INFO Registration_Discovery.ServiceRegistry [main] The cluster addresses are: []

src/main/java/Application.java → src/main/java/Registration_Discovery/Application.java

+package Registration_Discovery;
+
 import org.apache.zookeeper.KeeperException;
 import org.apache.zookeeper.WatchedEvent;
 import org.apache.zookeeper.Watcher;
@@ -9,6 +11,8 @@ import java.io.IOException;
 
 public class Application implements Watcher {
 
+    private static final Logger logger = LoggerFactory.getLogger(Application.class);
+
     private static final String address = "172.29.3.101:2181";
     private static final int SESSION_TIMEOUT = 3000; //dead client
     private static final int DEFAULT_PORT = 8080;
@@ -20,6 +24,8 @@ public class Application implements Watcher {
         Application application = new Application();
         ZooKeeper zooKeeper = application.connectToZookeeper();
 
+        logger.info("Connected");
+
         ServiceRegistry serviceRegistry = new ServiceRegistry(zooKeeper);
 
         OnElectionAction onElectionAction = new OnElectionAction(serviceRegistry, currentServerPort);
@@ -31,6 +37,7 @@ public class Application implements Watcher {
         application.run();
         application.close();
 
+
     }
 
     public ZooKeeper connectToZookeeper() throws IOException {
@@ -53,14 +60,17 @@ public class Application implements Watcher {
         switch (watchedEvent.getType()) {
             case None:
                 if (watchedEvent.getState() == Event.KeeperState.SyncConnected) {
-                    System.out.println("Successfully connected to Zookeeper");
+//                    System.out.println("Successfully connected to Zookeeper");
+                    logger.debug("Successfully connected to Zookeeper");
                 } else if (watchedEvent.getState() == Event.KeeperState.Disconnected) {
                     synchronized (zooKeeper) {
-                        System.out.println("Disconnected from Zookeeper");
+//                        System.out.println("Disconnected from Zookeeper");
+                        logger.debug("Disconnected from Zookeeper");
                         zooKeeper.notifyAll();
                     }
                 } else if (watchedEvent.getState() == Event.KeeperState.Closed) {
-                    System.out.println("Closed Successfully");
+//                    System.out.println("Closed Successfully");
+                    logger.debug("Closed Successfully");
                 }
                 break;
         }

src/main/java/LeaderElection.java → src/main/java/Registration_Discovery/LeaderElection.java

+package Registration_Discovery;
+
 import org.apache.zookeeper.*;
 import org.apache.zookeeper.data.Stat;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import java.util.Collections;
 import java.util.List;
 
 public class LeaderElection implements Watcher {
 
+    private static final Logger logger = LoggerFactory.getLogger(LeaderElection.class);
     private static final String ELECTION_NAMESPACE = "/election";
 
     private String currentZnodeName;
@@ -38,19 +43,22 @@ public class LeaderElection implements Watcher {
 
             String smallestChild = children.get(0); //the first element
             if (smallestChild.equals(currentZnodeName)) {
-                System.out.println("I'm a leader");
+//                System.out.println("I'm a leader");
+                logger.info("I'm a leader");
                 onElectionCallback.onElectedToBeLeader();
 
                 return;
             } else {
                 System.out.println("I'm not a leader");
+                logger.info("I'm not a leader");
                 int predecessorIndex = children.indexOf(currentZnodeName) - 1;
                 predecessorName = children.get(predecessorIndex);
                 predecessorStat = zooKeeper.exists(ELECTION_NAMESPACE + "/" + predecessorName, this);
             }
         }
         onElectionCallback.onWorker();
-        System.out.println("Watching znode " + predecessorName);
+//        System.out.println("Watching znode " + predecessorName);
+        logger.info("Watching znode {}", predecessorName);
         System.out.println();
 
     }

src/main/java/OnElectionAction.java → src/main/java/Registration_Discovery/OnElectionAction.java

+package Registration_Discovery;
+
 import org.apache.zookeeper.KeeperException;
 
 import java.net.InetAddress;

src/main/java/OnElectionCallback.java → src/main/java/Registration_Discovery/OnElectionCallback.java

+package Registration_Discovery;
+
 public interface OnElectionCallback {
 
     void onElectedToBeLeader();

src/main/java/ServiceRegistry.java → src/main/java/Registration_Discovery/ServiceRegistry.java

+package Registration_Discovery;
+
 import org.apache.zookeeper.*;
 import org.apache.zookeeper.data.Stat;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 
 public class ServiceRegistry implements Watcher {
+
+    private static final Logger logger = LoggerFactory.getLogger(ServiceRegistry.class);
+
     private static final String REGISTRY_ZNODE = "/service_registry";
     private final ZooKeeper zooKeeper;
 
@@ -31,12 +38,14 @@ public class ServiceRegistry implements Watcher {
 
     public void registerToCluster(String metadata) throws KeeperException, InterruptedException {
         if (this.currentZnode != null) {
-            System.out.println("Already registered to service registry");
+//            System.out.println("Already registered to service registry");
+            logger.debug("Already registered to service registry");
             return;
         }
         this.currentZnode = zooKeeper.create(REGISTRY_ZNODE + "/n_", metadata.getBytes(),
                 ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);
-        System.out.println("Registered to service registry");
+//        System.out.println("Registered to service registry");
+        logger.debug("Registered to service registry");
     }
 
     public void registerForUpdates() {
@@ -79,7 +88,8 @@ public class ServiceRegistry implements Watcher {
         }
 
         this.allServiceAddresses = Collections.unmodifiableList(addresses);
-        System.out.println("The cluster addresses are: " + this.allServiceAddresses);
+//        System.out.println("The cluster addresses are: " + this.allServiceAddresses);
+        logger.info("The cluster addresses are: {}",this.allServiceAddresses);
     }
 
     @Override

src/main/resources/logback.xml

 <?xml version="1.0" encoding="UTF-8"?>
-<Configuration status="WARN">
-    <Appenders>
-        <Console name="Console" target="SYSTEM_OUT">
-            <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n"/>
-        </Console>
-    </Appenders>
-    <Loggers>
-        <Root level="WARN">
-            <AppenderRef ref="Console"/>
-        </Root>
-    </Loggers>
-</Configuration>
\ No newline at end of file
+<configuration>
+    <property name="HOME_LOG" value="logs/app.log"/>
+    <appender name="CONSOLE" class="ch.qos.logback.core.ConsoleAppender">
+        <layout class="ch.qos.logback.classic.PatternLayout">
+            <Pattern>
+                %d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n
+            </Pattern>
+        </layout>
+    </appender>
+
+    <appender name="FILE" class="ch.qos.logback.core.FileAppender">
+        <file>${HOME_LOG}</file>
+        <append>true</append>
+        <immediateFlush>true</immediateFlush>
+        <encoder>
+            <pattern>%d %p %c{1.} [%t] %m%n</pattern>
+        </encoder>
+    </appender>
+
+    <!-- Log Level: ERROR, WARN, INFO, DEBUG, TRACE-->
+    <logger name="Registration_Discovery" level="DEBUG" additivity="false">
+        <appender-ref ref="CONSOLE"/>
+        <appender-ref ref="FILE"/>
+    </logger>
+
+    <root level="error">
+        <appender-ref ref="CONSOLE"/>
+    </root>
+
+</configuration>