#176: Fix issue with empty log files

core/src/main/java/org/seamcat/model/Simulation.java

@@ -6,6 +6,7 @@ import java.util.TimeZone;
 import org.apache.logging.log4j.Level;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
+import org.apache.logging.log4j.core.Appender;
 import org.apache.logging.log4j.core.LoggerContext;
 import org.apache.logging.log4j.core.appender.FileAppender;
 import org.apache.logging.log4j.core.config.Configuration;
@@ -68,17 +69,41 @@ public class Simulation {
                 + "." + cal.get(Calendar.MINUTE) + ".log");
 
         LoggerContext lc = (LoggerContext) LogManager.getContext(false);
-        FileAppender fa =
-            FileAppender.newBuilder()
-                .withName("DEBUG")
-                .withAppend(true)
-                .withFileName(logfile.toString())
-                .withLayout(PatternLayout.newBuilder().withPattern("%d{HH:mm:ss.SSS} %F %5p: %msg%n").build())
-                .setConfiguration(lc.getConfiguration())
-                .build();
-        fa.start();
-        lc.getConfiguration().addAppender(fa);
-        lc.getRootLogger().addAppender(lc.getConfiguration().getAppender(fa.getName()));
+        FileAppender fa = (FileAppender) lc.getConfiguration().getAppender("DEBUG");
+
+        if (fa != null) {
+            // Stop the old appender
+            fa.stop();
+
+            // Reconfigure the appender with the new file path (and possibly other parameters if needed)
+            FileAppender newAppender = FileAppender.newBuilder()
+                                           .setConfiguration(lc.getConfiguration())
+                                           .withName("DEBUG")
+                                           .withAppend(true)
+                                           .withFileName(logfile.toString())
+                                           .withLayout(fa.getLayout())
+                                           .build();
+
+            // Start the new appender
+            newAppender.start();
+
+            // Replace old appender with the new one in the configuration and logger
+            lc.getConfiguration().getAppenders().put("DEBUG", newAppender);
+            lc.getRootLogger().removeAppender(fa);
+            lc.getRootLogger().addAppender(newAppender);
+        } else {
+            fa = FileAppender.newBuilder()
+                     .withName("DEBUG")
+                     .withAppend(true)
+                     .withFileName(logfile.toString())
+                     .withLayout(PatternLayout.newBuilder().withPattern("%d{HH:mm:ss.SSS} %F %5p: %msg%n").build())
+                     .setConfiguration(lc.getConfiguration())
+                     .build();
+            fa.start();
+            lc.getConfiguration().addAppender(fa);
+            lc.getRootLogger().addAppender(lc.getConfiguration().getAppender(fa.getName()));
+        }
+
         Configuration config = lc.getConfiguration();
         LoggerConfig loggerConfig = config.getRootLogger();
         loggerConfig.setLevel(Level.DEBUG);
@@ -93,9 +118,6 @@ public class Simulation {
     public void removeDebugLog() {
         LOG.debug("Removing debug logger");
         LoggerContext lc = (LoggerContext) LogManager.getContext(false);
-        FileAppender debug = lc.getConfiguration().getAppender("DEBUG");
-        debug.stop();
-        lc.getRootLogger().removeAppender(debug);
         Configuration config = lc.getConfiguration();
         LoggerConfig loggerConfig = config.getRootLogger();
         loggerConfig.setLevel(Level.INFO);