diff --git a/confluent_server/confluent/discovery/core.py b/confluent_server/confluent/discovery/core.py
index 3f66d95d..148cdac3 100644
--- a/confluent_server/confluent/discovery/core.py
+++ b/confluent_server/confluent/discovery/core.py
@@ -78,6 +78,7 @@ import confluent.util as util
 import traceback
 
 import eventlet
+import eventlet.greenpool
 import eventlet.semaphore
 
 class nesteddict(dict):
@@ -106,6 +107,9 @@ servicebyname = {
     'lenovo-xcc': 'service:management-hardware.Lenovo:lenovo-xclarity-controller',
     'lenovo-imm2': 'service:management-hardware.IBM:integrated-management-module2',
 }
+
+discopool = eventlet.greenpool.GreenPool(500)
+runningevals = {}
 # Passive-only auto-detection protocols:
 # PXE
 
@@ -141,7 +145,6 @@ known_uuids = nesteddict()
 known_nodes = nesteddict()
 unknown_info = {}
 pending_nodes = {}
-blockrecheck = False
 
 
 def enrich_pxe_info(info):
@@ -386,8 +389,14 @@ def detected_models():
 
 
 def _recheck_nodes(nodeattribs, configmanager):
-    if blockrecheck:
+    if rechecklock.locked():
+        # if already in progress, don't run again
+        # it may make sense to schedule a repeat, but will try the easier and less redundant way first
         return
+    with rechecklock:
+        return _recheck_nodes_backend(nodeattribs, configmanager)
+
+def _recheck_nodes_backend(nodeattribs, configmanager):
     global rechecker
     _map_unique_ids(nodeattribs)
     # for the nodes whose attributes have changed, consider them as potential
@@ -410,7 +419,7 @@ def _recheck_nodes(nodeattribs, configmanager):
         info = pending_nodes[nodename]
         try:
             handler = info['handler'].NodeHandler(info, configmanager)
-            eventlet.spawn_n(eval_node, configmanager, handler, info, nodename)
+            discopool.spawn_n(eval_node, configmanager, handler, info, nodename)
         except Exception:
             traceback.print_exc()
             log.log({'error': 'Unexpected error during discovery of {0}, check debug '
@@ -466,25 +475,29 @@ def _recheck_single_unknown(configmanager, mac):
                 known_nodes[nodename][info['hwaddr']] = info
                 info['discostatus'] = 'discovered'
                 return  # already known, no need for more
-        eventlet.spawn_n(eval_node, configmanager, handler, info, nodename)
+        discopool.spawn_n(eval_node, configmanager, handler, info, nodename)
 
 
 def safe_detected(info):
-    eventlet.spawn_n(eval_detected, info)
+    if 'hwaddr' not in info:
+        return
+    if info['hwaddr'] in runningevals:
+        # Do not evaluate the same mac multiple times at once
+        return
+    runningevals[info['hwaddr']] = discopool.spawn(eval_detected, info)
 
 
 def eval_detected(info):
     try:
-        return detected(info)
+        detected(info)
     except Exception as e:
         traceback.print_exc()
+    del runningevals[info['hwaddr']]
 
 
 def detected(info):
     global rechecker
     global rechecktime
-    if 'hwaddr' not in info:
-        return  # For now, require hwaddr field to proceed
     # later, manual and CMM discovery may act on SN and/or UUID
     for service in info['services']:
         if nodehandlers.get(service, None):
@@ -696,7 +709,6 @@ def eval_node(cfg, handler, info, nodename, manual=False):
 
 
 def discover_node(cfg, handler, info, nodename, manual):
-    global blockrecheck
     known_nodes[nodename][info['hwaddr']] = info
     if info['hwaddr'] in unknown_info:
         del unknown_info[info['hwaddr']]
@@ -753,9 +765,7 @@ def discover_node(cfg, handler, info, nodename, manual):
                 newnodeattribs['pubkeys.tls_hardwaremanager'] = \
                     util.get_fingerprint(handler.https_cert)
             if newnodeattribs:
-                blockrecheck = True
                 cfg.set_node_attributes({nodename: newnodeattribs})
-                blockrecheck = False
             log.log({'info': 'Discovered {0} ({1})'.format(nodename,
                                                           handler.devname)})
         info['discostatus'] = 'discovered'
@@ -771,7 +781,6 @@ def do_pxe_discovery(cfg, handler, info, manual, nodename, policies):
     # use uuid based scheme in lieu of tls cert, ideally only
     # for stateless 'discovery' targets like pxe, where data does not
     # change
-    global blockrecheck
     uuidinfo = cfg.get_node_attributes(nodename, ['id.uuid', 'id.serial', 'id.model', 'net*.bootable'])
     if manual or policies & set(('open', 'pxe')):
         enrich_pxe_info(info)
@@ -791,9 +800,7 @@ def do_pxe_discovery(cfg, handler, info, manual, nodename, policies):
                 newattrname = attrname[:-8] + 'hwaddr'
                 attribs[newattrname] = info['hwaddr']
         if attribs:
-            blockrecheck = True
             cfg.set_node_attributes({nodename: attribs})
-            blockrecheck = False
     if info['uuid'] in known_pxe_uuids:
         return True
     known_pxe_uuids[info['uuid']] = nodename
@@ -843,21 +850,18 @@ def _periodic_recheck(configmanager):
     global rechecker
     global rechecktime
     rechecker = None
-    # There shouldn't be anything causing this to double up, but just in case
-    # use a semaphore to absolutely guarantee this doesn't multiply
-    with rechecklock:
-        try:
-            _recheck_nodes((), configmanager)
-        except Exception:
-            traceback.print_exc()
-            log.log({'error': 'Unexpected error during discovery, check debug '
-                              'logs'})
-        # if rechecker is set, it means that an accelerated schedule
-        # for rechecker was requested in the course of recheck_nodes
-        if rechecker is None:
-            rechecktime = util.monotonic_time() + 900
-            rechecker = eventlet.spawn_after(900, _periodic_recheck,
-                                             configmanager)
+    try:
+        _recheck_nodes((), configmanager)
+    except Exception:
+        traceback.print_exc()
+        log.log({'error': 'Unexpected error during discovery, check debug '
+                          'logs'})
+    # if rechecker is set, it means that an accelerated schedule
+    # for rechecker was requested in the course of recheck_nodes
+    if rechecker is None:
+        rechecktime = util.monotonic_time() + 900
+        rechecker = eventlet.spawn_after(900, _periodic_recheck,
+                                         configmanager)
 
 
 def rescan():