diff --git a/lib/galaxy/jobs/runners/slurm.py b/lib/galaxy/jobs/runners/slurm.py
index 333fd55d563..ec2ce131d45 100644
--- a/lib/galaxy/jobs/runners/slurm.py
+++ b/lib/galaxy/jobs/runners/slurm.py
@@ -28,13 +28,9 @@ SLURM_MEMORY_LIMIT_EXCEEDED_MSG = 'slurmstepd: error: Exceeded job memory limit'
 SLURM_MEMORY_LIMIT_EXCEEDED_PARTIAL_WARNINGS = [': Exceeded job memory limit at some point.',
                                                 ': Exceeded step memory limit at some point.']
 SLURM_MEMORY_LIMIT_SCAN_SIZE = 16 * 1024 * 1024  # 16MB
-SLURM_UNABLE_TO_ADD_TASK_TO_MEMORY_CG_MSG_RE = re.compile(r"""slurmstepd: error: task/cgroup: unable to add task\[pid=\d+\] to memory cg '\(null\)'$""")
-SLURM_UNABLE_TO_CREATE_CGROUP_MSG_RE = re.compile(r"""slurmstepd: error: xcgroup_instantiate: unable to create cgroup '[^']+' : No space left on device$""")
-SLURM_UNABLE_TO_INSTANCIATE_CGROUP_MSG_RE = re.compile(r"""slurmstepd: error: jobacct_gather/cgroup: unable to instanciate (job|user) \d+ memory cgroup$""")
+SLURM_CGROUP_RE = re.compile(r"""slurmstepd: .*cgroup.*$""")
 SLURM_TOP_WARNING_RES = (
-    SLURM_UNABLE_TO_ADD_TASK_TO_MEMORY_CG_MSG_RE,
-    SLURM_UNABLE_TO_CREATE_CGROUP_MSG_RE,
-    SLURM_UNABLE_TO_INSTANCIATE_CGROUP_MSG_RE
+    SLURM_CGROUP_RE,
 )
 
 # These messages are returned to the user
diff --git a/lib/galaxy/objectstore/s3_multipart_upload.py b/lib/galaxy/objectstore/s3_multipart_upload.py
index f564c1f8524..64b15ce76f9 100644
--- a/lib/galaxy/objectstore/s3_multipart_upload.py
+++ b/lib/galaxy/objectstore/s3_multipart_upload.py
@@ -5,13 +5,10 @@ This parallelizes the task over available cores using multiprocessing.
 Code mostly taken form CloudBioLinux.
 """
 
-import contextlib
-import functools
 import glob
-import multiprocessing
 import os
 import subprocess
-from multiprocessing.pool import IMapIterator
+import threading
 
 try:
     import boto
@@ -20,13 +17,6 @@ except ImportError:
     boto = None
 
 
-def map_wrap(f):
-    @functools.wraps(f)
-    def wrapper(args):
-        return f(*args)
-    return wrapper
-
-
 def mp_from_ids(s3server, mp_id, mp_keyname, mp_bucketname):
     """Get the multipart upload from the bucket and multipart IDs.
 
@@ -51,7 +41,6 @@ def mp_from_ids(s3server, mp_id, mp_keyname, mp_bucketname):
     return mp
 
 
-@map_wrap
 def transfer_part(s3server, mp_id, mp_keyname, mp_bucketname, i, part):
     """Transfer a part of a multipart upload. Designed to be run in parallel.
     """
@@ -64,8 +53,6 @@ def transfer_part(s3server, mp_id, mp_keyname, mp_bucketname, i, part):
 def multipart_upload(s3server, bucket, s3_key_name, tarball, mb_size):
     """Upload large files using Amazon's multipart upload functionality.
     """
-    cores = multiprocessing.cpu_count()
-
     def split_file(in_file, mb_size, split_num=5):
         prefix = os.path.join(os.path.dirname(in_file),
                               "%sS3PART" % (os.path.basename(s3_key_name)))
@@ -80,29 +67,11 @@ def multipart_upload(s3server, bucket, s3_key_name, tarball, mb_size):
     mp = bucket.initiate_multipart_upload(s3_key_name,
                                           reduced_redundancy=s3server['use_rr'])
 
-    with multimap(cores) as pmap:
-        for _ in pmap(transfer_part, ((s3server, mp.id, mp.key_name, mp.bucket_name, i, part)
-                                      for (i, part) in
-                                      enumerate(split_file(tarball, mb_size, cores)))):
-            pass
+    for (i, part) in enumerate(split_file(tarball, mb_size)):
+        t = threading.Thread(
+            target=transfer_part,
+            args=(s3server, mp.id, mp.key_name, mp.bucket_name, i, part))
+        t.start()
+        t.join()
+
     mp.complete_upload()
-
-
-@contextlib.contextmanager
-def multimap(cores=None):
-    """Provide multiprocessing imap like function.
-
-    The context manager handles setting up the pool, worked around interrupt issues
-    and terminating the pool on completion.
-    """
-    if cores is None:
-        cores = max(multiprocessing.cpu_count() - 1, 1)
-
-    def wrapper(func):
-        def wrap(self, timeout=None):
-            return func(self, timeout=timeout if timeout is not None else 1e100)
-        return wrap
-    IMapIterator.next = wrapper(IMapIterator.next)
-    pool = multiprocessing.Pool(cores)
-    yield pool.imap
-    pool.terminate()
diff --git a/lib/galaxy/web/stack/handlers.py b/lib/galaxy/web/stack/handlers.py
index 124cf91d7fc..d52509b9a23 100644
--- a/lib/galaxy/web/stack/handlers.py
+++ b/lib/galaxy/web/stack/handlers.py
@@ -62,7 +62,8 @@ class ConfiguresHandlers(object):
                         handler_id,
                         [x.strip() for x in handler.get('tags', self.DEFAULT_HANDLER_TAG).split(',')]
                     )
-            self.default_handler_id = self._get_default(self.app.config, config_element, list(self.handlers.keys()))
+            self.default_handler_id = self._get_default(
+                self.app.config, config_element, list(self.handlers.keys()), required=False)
 
     def _init_handler_assignment_methods(self, config_element=None):
         self.__is_handler = None
@@ -116,7 +117,7 @@ class ConfiguresHandlers(object):
     def _parse_handler(self, handler_id, handler_def):
         pass
 
-    def _get_default(self, config, parent, names, auto=False):
+    def _get_default(self, config, parent, names, auto=False, required=True):
         """
         Returns the default attribute set in a parent tag like <handlers> or
         <destinations>, or return the ID of the child, if there is no explicit
@@ -128,6 +129,8 @@ class ConfiguresHandlers(object):
         :type names: list of str
         :param auto: Automatically set a default if there is no default in the parent tag and there is only one child.
         :type auto: bool
+        :param required: Require a default to be set or determined automatically, else raise Exception
+        :type required: bool
 
         :returns: str -- id or tag representing the default.
         """
@@ -142,12 +145,14 @@ class ConfiguresHandlers(object):
 
         if rval is not None:
             # If the parent element has a 'default' attribute, use the id or tag in that attribute
-            if self.deterministic_handler_assignment and rval not in names:
+            if required and rval not in names:
                 raise Exception("<%s> default attribute '%s' does not match a defined id or tag in a child element" % (parent.tag, rval))
             log.debug("<%s> default set to child with id or tag '%s'" % (parent.tag, rval))
         elif auto and len(names) == 1:
             log.info("Setting <%s> default to child with id '%s'" % (parent.tag, names[0]))
             rval = names[0]
+        elif required:
+            raise Exception("No <%s> default specified, please specify a valid id or tag with the 'default' attribute" % parent.tag)
         return rval
 
     def _findall_with_required(self, parent, match, attribs=None):
@@ -181,7 +186,7 @@ class ConfiguresHandlers(object):
 
     @property
     def deterministic_handler_assignment(self):
-        return self.handler_assignment_methods and all(
+        return self.handler_assignment_methods and any(
             filter(lambda x: x in (
                 HANDLER_ASSIGNMENT_METHODS.UWSGI_MULE_MESSAGE,
                 HANDLER_ASSIGNMENT_METHODS.DB_PREASSIGN,