Adding optional list handling to the exc_handler option in Worker.

Adding command line --exception_handler option (with multiple entries allowed) to `rq worker`
Added tests for command line options.

rq/cli/cli.py

@@ -132,10 +132,11 @@ def info(url, path, interval, raw, only_queues, only_workers, by_queue, queues):
 @click.option('--verbose', '-v', is_flag=True, help='Show more output')
 @click.option('--quiet', '-q', is_flag=True, help='Show less output')
 @click.option('--sentry-dsn', envvar='SENTRY_DSN', help='Report exceptions to this Sentry DSN')
+@click.option('--exception-handler', help='Exception handler(s) to use', multiple=True)
 @click.option('--pid', help='Write the process ID number to a file at the specified path')
 @click.argument('queues', nargs=-1)
 def worker(url, config, burst, name, worker_class, job_class, queue_class, path, results_ttl, worker_ttl,
-           verbose, quiet, sentry_dsn, pid, queues):
+           verbose, quiet, sentry_dsn, exception_handler, pid, queues):
     """Starts an RQ worker."""
 
     if path:
@@ -157,6 +158,9 @@ def worker(url, config, burst, name, worker_class, job_class, queue_class, path,
     cleanup_ghosts(conn)
     worker_class = import_attribute(worker_class)
     queue_class = import_attribute(queue_class)
+    exc_handler = []
+    for h in exception_handler:
+        exc_handler.append(import_attribute(h))
 
     try:
         queues = [queue_class(queue, connection=conn) for queue in queues]
@@ -165,7 +169,8 @@ def worker(url, config, burst, name, worker_class, job_class, queue_class, path,
                          connection=conn,
                          default_worker_ttl=worker_ttl,
                          default_result_ttl=results_ttl,
-                         job_class=job_class)
+                         job_class=job_class,
+                         exc_handler=exc_handler)
 
         # Should we configure Sentry?
         if sentry_dsn:

rq/worker.py

@@ -140,7 +140,10 @@ class Worker(object):
         # By default, push the "move-to-failed-queue" exception handler onto
         # the stack
         self.push_exc_handler(self.move_to_failed_queue)
-        if exc_handler is not None:
+        if isinstance(exc_handler, list):
+            for h in exc_handler:
+                self.push_exc_handler(h)
+        elif exc_handler is not None:
             self.push_exc_handler(exc_handler)
 
         if job_class is not None:

tests/fixtures.py

@@ -87,3 +87,7 @@ with Connection():
 
 def long_running_job():
     time.sleep(10)
+
+def black_hole(job, *exc_info):
+    # Don't fall through to default behaviour (moving to failed queue)
+    return False

tests/test_cli.py

@@ -3,7 +3,7 @@ from __future__ import (absolute_import, division, print_function,
                         unicode_literals)
 
 from click.testing import CliRunner
-from rq import get_failed_queue
+from rq import get_failed_queue, Queue
 from rq.compat import is_python_version
 from rq.job import Job
 from rq.cli import main
@@ -63,3 +63,27 @@ class TestRQCli(RQTestCase):
         runner = CliRunner()
         result = runner.invoke(main, ['worker', '-u', self.redis_url, '-b'])
         self.assertEqual(result.exit_code, 0)
+
+    def test_exc_handler(self):
+        """rq worker -u <url> -b --exception-handler <handler>"""
+        q = Queue()
+        failed_q = get_failed_queue()
+        failed_q.empty()
+        # Preconditions
+        self.assertEquals(failed_q.count, 0)
+        self.assertEquals(q.count, 0)
+
+        # Action
+        job = q.enqueue(div_by_zero)
+        self.assertEquals(q.count, 1)
+
+        runner = CliRunner()
+        result = runner.invoke(main, ['worker', '-u', self.redis_url, '-b', '--exception-handler', 'tests.fixtures.black_hole'])
+        self.assertEqual(result.exit_code, 0)
+        # Postconditions
+        self.assertEquals(q.count, 0)
+        self.assertEquals(failed_q.count, 0)
+
+        # Check the job
+        job = Job.fetch(job.id)
+        self.assertEquals(job.is_failed, True)