[ZEPPELIN-6561] Restore default SIGINT handler so python paragraph cancel works under daemon launch

python/src/main/resources/python/zeppelin_python.py

@@ -15,13 +15,20 @@
 # limitations under the License.
 #
 
-import os, sys, traceback, json, re
+import os, signal, sys, traceback, json, re
 
 from py4j.java_gateway import java_import, JavaGateway, GatewayClient
 from py4j.protocol import Py4JJavaError
 
 import ast
 
+# When Zeppelin is started via zeppelin-daemon.sh (nohup ... &), this process
+# inherits SIGINT=SIG_IGN and CPython keeps it ignored instead of installing the
+# KeyboardInterrupt handler, so PythonInterpreter.cancel()'s SIGINT would be a
+# no-op. Restore the default handler to keep paragraph cancellation working.
+if signal.getsignal(signal.SIGINT) == signal.SIG_IGN:
+  signal.signal(signal.SIGINT, signal.default_int_handler)
+
 class Logger(object):
   def __init__(self):
     pass

python/src/test/java/org/apache/zeppelin/python/PythonInterpreterTest.java

@@ -24,6 +24,7 @@
 import org.apache.zeppelin.interpreter.InterpreterException;
 import org.apache.zeppelin.interpreter.InterpreterGroup;
 import org.apache.zeppelin.interpreter.InterpreterResult;
+import org.apache.zeppelin.interpreter.InterpreterResultMessage;
 import org.apache.zeppelin.interpreter.LazyOpenInterpreter;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
@@ -35,8 +36,12 @@
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.junit.jupiter.api.Assertions.fail;
 
+import java.io.File;
 import java.io.IOException;
+import java.nio.file.Files;
+import java.util.Arrays;
 import java.util.LinkedList;
+import java.util.List;
 import java.util.Properties;
 import java.util.concurrent.TimeoutException;
 import java.util.regex.Matcher;
@@ -174,4 +179,42 @@ public void testFailtoLaunchPythonProcess() throws InterpreterException {
       assertTrue(stacktrace.contains("No such file or directory"), stacktrace);
     }
   }
+
+  @Test
+  public void testSigintDefaultHandlerRestoredWhenInheritedIgnored()
+      throws IOException, InterpreterException {
+    tearDown();
+
+    File wrapper = File.createTempFile("python-sigint-wrapper", ".sh");
+    wrapper.deleteOnExit();
+    Files.write(wrapper.toPath(), Arrays.asList(
+        "#!/bin/sh",
+        "trap '' INT",
+        "exec python \"$@\""));
+    wrapper.setExecutable(true);
+
+    intpGroup = new InterpreterGroup();
+
+    Properties properties = new Properties();
+    properties.setProperty("zeppelin.python", wrapper.getAbsolutePath());
+    properties.setProperty("zeppelin.python.useIPython", "false");
+    properties.setProperty("zeppelin.python.gatewayserver_address", "127.0.0.1");
+
+    interpreter = new LazyOpenInterpreter(new PythonInterpreter(properties));
+
+    intpGroup.put("note", new LinkedList<Interpreter>());
+    intpGroup.get("note").add(interpreter);
+    interpreter.setInterpreterGroup(intpGroup);
+
+    InterpreterContext.set(getInterpreterContext());
+
+    InterpreterContext context = getInterpreterContext();
+    InterpreterResult result = interpreter.interpret(
+        "import signal\nprint(signal.getsignal(signal.SIGINT))", context);
+    assertEquals(InterpreterResult.Code.SUCCESS, result.code());
+    List<InterpreterResultMessage> interpreterResultMessages =
+        context.out.toInterpreterResultMessage();
+    String output = interpreterResultMessages.get(0).getData();
+    assertTrue(output.contains("default_int_handler"), output);
+  }
 }