allow monitor to call a function to determine if thread should be terminated

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

@@ -101,7 +101,8 @@ public class MultiStream extends InputStream {
     }
 
     @Override public void close() throws IOException {
-        if (log.isTraceEnabled()) log.trace("close: closing current stream ("+(currentStream == null ? "null" : currentStream.getClass().getSimpleName())+"). this="+this);
+        if (log.isInfoEnabled()) log.info("close: closing current stream ("+(currentStream == null ? "null" : currentStream.getClass().getSimpleName())+"). name="+underflow.getHandlerName());
+        if (log.isTraceEnabled()) log.trace("close: closing current stream ("+(currentStream == null ? "null" : currentStream.getClass().getSimpleName())+"). name="+underflow.getHandlerName());
         if (currentStream != null) currentStream.close();
         underflow.close();
     }

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

@@ -8,6 +8,7 @@ import org.cobbzilla.util.daemon.SimpleDaemon;
 import java.util.Iterator;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
+import java.util.function.Function;
 
 import static java.util.concurrent.TimeUnit.SECONDS;
 import static org.cobbzilla.util.daemon.ZillaRuntime.now;
@@ -20,9 +21,11 @@ public class MultiUnderflowHandlerMonitor extends SimpleDaemon {
 
     private final Map<String, MultiUnderflowHandler> handlers = new ConcurrentHashMap<>();
 
-    @Getter @Setter private static long checkInterval = SECONDS.toMillis(20);
+    @Getter @Setter private long checkInterval = SECONDS.toMillis(20);
     private static final long TERMINATE_TIMEOUT = SECONDS.toMillis(2);
 
+    @Getter @Setter private Function<Thread, Boolean> terminateThreadFunc = null;
+
     @Override protected long getSleepTime() { return checkInterval; }
 
     @Override protected void process() {
@@ -39,8 +42,12 @@ public class MultiUnderflowHandlerMonitor extends SimpleDaemon {
 
             } 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);
+                if (terminateThreadFunc == null || terminateThreadFunc.apply(underflow.getThread())) {
+                    if (log.isErrorEnabled()) log.error("process: underflow timed out, terminating: name=" + underflow.getHandlerName() + " thread=" + underflow.getThread());
+                    terminate(underflow.getThread(), TERMINATE_TIMEOUT);
+                } else {
+                    if (log.isErrorEnabled()) log.error("process: underflow timed out, removing but NOT terminating: name=" + underflow.getHandlerName() + " thread=" + underflow.getThread());
+                }
             }
         }
     }

src/test/java/org/cobbzilla/util/io/regex/RegexFilterReaderTest.java

@@ -5,7 +5,6 @@ import org.apache.commons.io.IOUtils;
 import org.cobbzilla.util.io.BlockedInputStream;
 import org.cobbzilla.util.io.multi.MultiReader;
 import org.cobbzilla.util.io.multi.MultiStream;
-import org.cobbzilla.util.io.multi.MultiUnderflowHandlerMonitor;
 import org.junit.Test;
 
 import java.io.*;
@@ -13,6 +12,7 @@ import java.util.concurrent.atomic.AtomicReference;
 
 import static org.cobbzilla.util.daemon.ZillaRuntime.background;
 import static org.cobbzilla.util.daemon.ZillaRuntime.die;
+import static org.cobbzilla.util.io.multi.MultiUnderflowHandlerMonitor.DEFAULT_UNDERFLOW_MONITOR;
 import static org.cobbzilla.util.io.regex.RegexReplacementFilter.DEFAULT_PREFIX_REPLACEMENT_WITH_MATCH;
 import static org.cobbzilla.util.system.Sleep.sleep;
 import static org.junit.Assert.*;
@@ -192,7 +192,7 @@ public class RegexFilterReaderTest {
         final InputStream stream2 = new ByteArrayInputStream("some test data2 ".repeat(1000).getBytes());
         final InputStream stream3 = new BlockedInputStream();
 
-        MultiUnderflowHandlerMonitor.setCheckInterval(1000);
+        DEFAULT_UNDERFLOW_MONITOR.setCheckInterval(1000);
         final MultiStream multiStream = new MultiStream(stream1);
         multiStream.getUnderflow()
                 .setMinUnderflowSleep(1000)