safer monitoring and cleanup

src/main/java/org/cobbzilla/util/io/multi/MultiUnderflowHandler.java

@@ -11,6 +11,7 @@ import java.io.IOException;
 import java.util.Iterator;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.atomic.AtomicBoolean;
 
 import static java.util.UUID.randomUUID;
 import static java.util.concurrent.TimeUnit.SECONDS;
@@ -29,11 +30,20 @@ public class MultiUnderflowHandler extends SimpleDaemon {
     @Override protected long getSleepTime() { return checkInterval; }
 
     @Override protected void process() {
+        if (log.isTraceEnabled()) log.trace("process: examining "+handlers.size()+" underflow handlers");
         for (Iterator<MultiUnderflowHandler> iter = handlers.values().iterator(); iter.hasNext(); ) {
             final MultiUnderflowHandler underflow = iter.next();
-            if (now() - underflow.getLastRead() > underflow.getUnderflowTimeout()) {
-                log.error("process: underflow timed out, terminating: name="+underflow.getHandlerName()+" thread="+underflow.getThread());
+            if (underflow.closed()) {
+                if (log.isDebugEnabled()) log.debug("process: removing closed handler: name="+underflow.getHandlerName()+" thread="+underflow.getThread());
                 iter.remove();
+
+            } else if (underflow.getLastRead() > 0 && !underflow.getThread().isAlive()) {
+                if (log.isDebugEnabled()) log.debug("process: removing dead thread: name="+underflow.getHandlerName()+" thread="+underflow.getThread());
+                iter.remove();
+
+            } else if (now() - underflow.getLastRead() > underflow.getUnderflowTimeout()) {
+                iter.remove();
+                if (log.isErrorEnabled()) log.error("process: underflow timed out, terminating: name="+underflow.getHandlerName()+" thread="+underflow.getThread());
                 terminate(underflow.getThread(), TERMINATE_TIMEOUT);
             }
         }
@@ -48,15 +58,18 @@ public class MultiUnderflowHandler extends SimpleDaemon {
 
     @Getter @Setter private long maxUnderflowSleep = 500;
 
-    @Getter @Setter private long lastRead = now();
+    @Getter @Setter private long lastRead = 0;
     @Getter @Setter private long firstUnderflow = 0;
     @Getter @Setter private long underflowTimeout = SECONDS.toMillis(60);
     private long underflowSleep = minUnderflowSleep;
     @Getter private Thread thread;
+    private final AtomicBoolean closed = new AtomicBoolean(false);
+    public boolean closed () { return closed.get(); }
 
     public void handleUnderflow() throws IOException {
         if (thread == null) {
             thread = Thread.currentThread();
+            lastRead = now();
             handlers.put(id, this);
         }
         if (firstUnderflow == 0) {
@@ -73,16 +86,21 @@ public class MultiUnderflowHandler extends SimpleDaemon {
     }
 
     public void handleSuccessfulRead() {
+        lastRead = now();
         if (thread == null) {
             thread = Thread.currentThread();
             handlers.put(id, this);
         }
         firstUnderflow = 0;
-        lastRead = now();
         underflowSleep = minUnderflowSleep;
     }
 
     public void close() {
-
+        if (!closed()) {
+            closed.set(true);
+            if (log.isDebugEnabled()) log.debug(handlerName + ": closing");
+            handlers.remove(id);
+        }
     }
+
 }