diff --git a/include/scscfsproutlet.h b/include/scscfsproutlet.h
index a8b5c808f..ff8e31e77 100644
--- a/include/scscfsproutlet.h
+++ b/include/scscfsproutlet.h
@@ -147,7 +147,7 @@ class SCSCFSproutlet : public Sproutlet
   /// Record the time an INVITE took to reach ringing state.
   ///
   /// @param ringing_us Time spent until a 180 Ringing, in microseconds.
-  void track_session_setup_time(uint64_t tsx_start_time_usec, bool video_call);
+  uint64_t track_session_setup_time(uint64_t tsx_start_time_usec, bool video_call);
 
   /// Translate RequestURI using ENUM service if appropriate.
   void translate_request_uri(pjsip_msg* req, pj_pool_t* pool, SAS::TrailId trail);
diff --git a/modules/cpp-common b/modules/cpp-common
index 92f87b637..78dd50deb 160000
--- a/modules/cpp-common
+++ b/modules/cpp-common
@@ -1 +1 @@
-Subproject commit 92f87b6377fe22a052b1c0e73c6b9b4f4e15bfa6
+Subproject commit 78dd50deb55cbb4e59f3e3ab75edbb2d03cdeb04
diff --git a/src/Makefile b/src/Makefile
index dc2293aff..a52c65341 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -9,6 +9,7 @@ SPROUT_COMMON_SOURCES := logger.cpp \
                          stack.cpp \
                          dnsparser.cpp \
                          dnscachedresolver.cpp \
+                         static_dns_cache.cpp \
                          baseresolver.cpp \
                          sipresolver.cpp \
                          bono.cpp \
diff --git a/src/authenticationsproutlet.cpp b/src/authenticationsproutlet.cpp
index dcb6c348c..205a9f4d0 100644
--- a/src/authenticationsproutlet.cpp
+++ b/src/authenticationsproutlet.cpp
@@ -871,7 +871,7 @@ void AuthenticationSproutletTsx::create_challenge(pjsip_digest_credential* crede
       // We've failed to store the nonce in memcached, so we have no hope of
       // successfully authenticating any repsonse to a 401 Unauthorized.  Send
       // a 500 Server Internal Error instead.
-      TRC_DEBUG("Failed to store nonce in memcached");
+      TRC_ERROR("Failed to store nonce in memcached, for impi %s", impi.c_str());
       rsp->line.status.code = PJSIP_SC_INTERNAL_SERVER_ERROR;
       rsp->line.status.reason = *pjsip_get_status_text(PJSIP_SC_INTERNAL_SERVER_ERROR);
 
@@ -902,7 +902,7 @@ void AuthenticationSproutletTsx::create_challenge(pjsip_digest_credential* crede
     // a 4xx error to the client.
     if (av_source_unavailable)
     {
-      TRC_DEBUG("Downstream node is overloaded or unresponsive, unable to get Authentication vector");
+      TRC_ERROR("Downstream node is overloaded or unresponsive, unable to get Authentication vector");
       rsp->line.status.code = PJSIP_SC_SERVER_TIMEOUT;
       rsp->line.status.reason = *pjsip_get_status_text(PJSIP_SC_SERVER_TIMEOUT);
       SAS::Event event(trail(), SASEvent::AUTHENTICATION_FAILED_OVERLOAD, 0);
diff --git a/src/compositesproutlet.cpp b/src/compositesproutlet.cpp
index 758220e14..1fbdf5eff 100644
--- a/src/compositesproutlet.cpp
+++ b/src/compositesproutlet.cpp
@@ -1,5 +1,5 @@
 /**
- * @file compositesproutlet.h
+ * @file compositesproutlet.cpp
  *
  * Copyright (C) Metaswitch Networks 2017
  * If license terms are provided to you in a COPYING file in the root directory
diff --git a/src/dnsresolver.cpp b/src/dnsresolver.cpp
index 0ebccf86d..b55164886 100644
--- a/src/dnsresolver.cpp
+++ b/src/dnsresolver.cpp
@@ -1,5 +1,5 @@
 /**
- * @file enumservice.cpp class implementation for an ENUM service provider
+ * @file dnsresolver.cpp class implementation for a DNS resolver
  *
  * Copyright (C) Metaswitch Networks 2015
  * If license terms are provided to you in a COPYING file in the root directory
diff --git a/src/enumservice.cpp b/src/enumservice.cpp
index a61c3960d..62e0cf911 100644
--- a/src/enumservice.cpp
+++ b/src/enumservice.cpp
@@ -1,5 +1,5 @@
 /**
- * @file dnsresolver.cpp class implementation for a DNS resolver
+ * @file enumservice.cpp class implementation for an ENUM service provider
  *
  * Copyright (C) Metaswitch Networks 2017
  * If license terms are provided to you in a COPYING file in the root directory
diff --git a/src/hss_sip_mapping.cpp b/src/hss_sip_mapping.cpp
index 98a9fcce3..a6e26dd62 100644
--- a/src/hss_sip_mapping.cpp
+++ b/src/hss_sip_mapping.cpp
@@ -60,6 +60,15 @@ pjsip_status_code determine_hss_sip_response(HTTPCode http_code,
         break;
 
       case HTTP_SERVER_UNAVAILABLE:
+        // The HSS is unavailable - the client should retry on timeout but no
+        // other Clearwater nodes should (as Sprout will already have retried on
+        // timeout). Reject with a 504 (503 is used for overload).
+        TRC_ERROR("Rejecting %s request as unable to contact HSS: %d",
+                  sip_msg_type, http_code);
+
+        st_code = (pjsip_status_code)554;
+        break;
+
       case HTTP_GATEWAY_TIMEOUT:
         // The HSS is unavailable - the client should retry on timeout but no
         // other Clearwater nodes should (as Sprout will already have retried on
diff --git a/src/icscfrouter.cpp b/src/icscfrouter.cpp
index 53a297fc2..c71ccff1c 100644
--- a/src/icscfrouter.cpp
+++ b/src/icscfrouter.cpp
@@ -374,6 +374,7 @@ int ICSCFUARouter::hss_query()
   {
     // HSS failed to respond or responded with invalid data, so reject the
     // request with a 480.
+    TRC_ERROR("I-CSCF UAR got %d HTTP response from Homestead", rc);
     status_code = PJSIP_SC_TEMPORARILY_UNAVAILABLE;
   }
   else
@@ -447,6 +448,7 @@ int ICSCFLIRouter::hss_query()
     // HSS failed to respond or responded with invalid data, so reject the
     // request with a 480.
     // LCOV_EXCL_START
+    TRC_ERROR("I-CSCF UAR got %d HTTP response from Homestead", rc);
     status_code = PJSIP_SC_TEMPORARILY_UNAVAILABLE;
     // LCOV_EXCL_STOP
   }
diff --git a/src/icscfsproutlet.cpp b/src/icscfsproutlet.cpp
index 91156657a..1a957b748 100644
--- a/src/icscfsproutlet.cpp
+++ b/src/icscfsproutlet.cpp
@@ -403,6 +403,7 @@ void ICSCFSproutletRegTsx::on_rx_response(pjsip_msg* rsp, int fork_id)
         // capabilitires, or the HSS is temporarily unavailable). There was at
         // least one valid S-CSCF (as this is retry processing). The I-CSCF
         // must return 504 (TS 24.229, 5.3.1.3) in this case.
+        TRC_ERROR("I-CSCF can't select an S-CSCF for REGISTER request");
         rsp->line.status.code = PJSIP_SC_SERVER_TIMEOUT;
         rsp->line.status.reason =
           *pjsip_get_status_text(rsp->line.status.code);
diff --git a/src/main.cpp b/src/main.cpp
index d42b39a6e..d5809d8c7 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -87,6 +87,7 @@ extern "C" {
 #include "sprout_alarmdefinition.h"
 #include "sproutlet_options.h"
 #include "astaire_impistore.h"
+#include "updater.h"
 
 enum OptionTypes
 {
@@ -2003,7 +2004,15 @@ int main(int argc, char* argv[])
                                            hc);
 
   // Create a DNS resolver and a SIP specific resolver.
-  dns_resolver = new DnsCachedResolver(opt.dns_servers, opt.dns_timeout);
+  dns_resolver = new DnsCachedResolver(opt.dns_servers,
+                                       opt.dns_timeout,
+                                       "/etc/clearwater/dns.json");
+
+  // Reload dns.json on SIGHUP
+  Updater<void, DnsCachedResolver>* dns_updater =
+         new Updater<void, DnsCachedResolver>(dns_resolver,
+                                              std::mem_fun(&DnsCachedResolver::reload_static_records));
+
   if (opt.pcscf_enabled)
   {
     sip_resolver = new SIPResolver(dns_resolver, opt.sip_blacklist_duration, 0);
@@ -2562,6 +2571,7 @@ int main(int argc, char* argv[])
   delete enum_service;
   delete scscf_acr_factory;
 
+  delete dns_updater;
   delete sip_resolver;
   delete http_resolver;
   delete astaire_resolver;
diff --git a/src/registrarsproutlet.cpp b/src/registrarsproutlet.cpp
index 94a1e4db2..827720903 100644
--- a/src/registrarsproutlet.cpp
+++ b/src/registrarsproutlet.cpp
@@ -529,6 +529,7 @@ void RegistrarSproutletTsx::process_register_request(pjsip_msg *req)
     // Failed to connect to the local store.  Reject the register with a 500
     // response.
     // LCOV_EXCL_START - the can't fail to connect to the store we use for UT
+    TRC_ERROR("Failed to connect to local store, private_id= %s", private_id.c_str());
     st_code = PJSIP_SC_INTERNAL_SERVER_ERROR;
 
     SAS::Event event(trail(), SASEvent::REGISTER_FAILED_REGSTORE, 0);
@@ -604,7 +605,7 @@ void RegistrarSproutletTsx::process_register_request(pjsip_msg *req)
   if (gen_hdr == NULL)
   {
     // LCOV_EXCL_START - can't see how this could ever happen
-    TRC_ERROR("Failed to add RFC 5626 headers");
+    TRC_ERROR("Failed to add RFC 5626 headers to reply");
 
     SAS::Event event(trail(), SASEvent::REGISTER_FAILED_5636, 0);
     event.add_var_param(public_id);
diff --git a/src/rphservice.cpp b/src/rphservice.cpp
index 30ec375ac..219aca984 100644
--- a/src/rphservice.cpp
+++ b/src/rphservice.cpp
@@ -221,9 +221,9 @@ SIPEventPriorityLevel RPHService::lookup_priority(std::string rph_value,
     // We received a message with an unknown RPH value. This could be because:
     //  - It is not defined in the IANA namespace.
     //  - It is not assigned a priority value in the rph.json file.
-    TRC_WARNING("An unknown RPH value \"%s\" was received on an incoming message."
-                " This message will be handled, but will not be prioritized.",
-                rph_value.c_str());
+    TRC_DEBUG("An unknown RPH value \"%s\" was received on an incoming message."
+              " This message will be handled, but will not be prioritized.",
+              rph_value.c_str());
     SAS::Event event(trail, SASEvent::RPH_VALUE_UNKNOWN, 0);
     event.add_var_param(rph_value);
     SAS::report_event(event);
diff --git a/src/scscfsproutlet.cpp b/src/scscfsproutlet.cpp
index c3769e0b8..e08cd8bd2 100644
--- a/src/scscfsproutlet.cpp
+++ b/src/scscfsproutlet.cpp
@@ -378,7 +378,7 @@ void SCSCFSproutlet::track_app_serv_comm_success(const std::string& uri,
   }
 }
 
-void SCSCFSproutlet::track_session_setup_time(uint64_t tsx_start_time_usec,
+uint64_t SCSCFSproutlet::track_session_setup_time(uint64_t tsx_start_time_usec,
                                               bool video_call)
 {
   // Calculate how long it has taken to setup the session.
@@ -394,6 +394,8 @@ void SCSCFSproutlet::track_session_setup_time(uint64_t tsx_start_time_usec,
   {
     _audio_session_setup_time_tbl->accumulate(ringing_usec);
   }
+
+  return ringing_usec;
 }
 
 SCSCFSproutletTsx::SCSCFSproutletTsx(SCSCFSproutlet* scscf,
@@ -884,7 +886,15 @@ void SCSCFSproutletTsx::on_tx_response(pjsip_msg* rsp)
       ((st_code == PJSIP_SC_RINGING) ||
        PJSIP_IS_STATUS_IN_CLASS(st_code, 200)))
   {
-    _scscf->track_session_setup_time(_tsx_start_time_usec, _video_call);
+    uint64_t setup_time = _scscf->track_session_setup_time(_tsx_start_time_usec, _video_call);
+    if (setup_time > 2000000)
+    {
+      pjsip_cid_hdr* cid = PJSIP_MSG_CID_HDR(rsp);
+      TRC_WARNING("Call setup time exceeded 2 seconds for Call-ID %.*s (was %lu us)",
+                  cid->id.slen,
+                  cid->id.ptr,
+                  setup_time);
+    }
     _record_session_setup_time = false;
   }
 }
@@ -1137,6 +1147,7 @@ pjsip_status_code SCSCFSproutletTsx::determine_served_user(pjsip_msg* req)
           if ((http_code == HTTP_SERVER_UNAVAILABLE) || (http_code == HTTP_GATEWAY_TIMEOUT))
           {
             // Send a SIP 504 response if we got a 500/503 HTTP response.
+            TRC_ERROR("AS retargeting failed to lookup IFCs for served user");
             status_code = PJSIP_SC_SERVER_TIMEOUT;
           }
           else
@@ -1248,7 +1259,7 @@ pjsip_status_code SCSCFSproutletTsx::determine_served_user(pjsip_msg* req)
       }
       else
       {
-        TRC_DEBUG("Failed to retrieve ServiceProfile for %s", served_user.c_str());
+        TRC_ERROR("Failed to retrieve ServiceProfile for %s", served_user.c_str());
 
         if ((http_code == HTTP_SERVER_UNAVAILABLE) || (http_code == HTTP_GATEWAY_TIMEOUT))
         {
diff --git a/src/subscriptionsproutlet.cpp b/src/subscriptionsproutlet.cpp
index 91cc21c77..35896cf8c 100644
--- a/src/subscriptionsproutlet.cpp
+++ b/src/subscriptionsproutlet.cpp
@@ -342,6 +342,8 @@ void SubscriptionSproutletTsx::process_subscription_request(pjsip_msg* req)
   std::string aor;
   if (!irs_info._associated_uris.get_default_impu(aor, false))
   {
+    TRC_ERROR("SUBSCRIBE for public ID %s uses AOR %s", public_id.c_str(), aor.c_str());
+    TRC_ERROR("Could not determine default URI, Subscribe is being rejected with 403");
     pjsip_msg* rsp = create_response(req, PJSIP_SC_FORBIDDEN);
     send_response(rsp);
     free_msg(req);
@@ -349,7 +351,6 @@ void SubscriptionSproutletTsx::process_subscription_request(pjsip_msg* req)
     return;
   }
 
-  TRC_DEBUG("aor = %s", aor.c_str());
   TRC_DEBUG("SUBSCRIBE for public ID %s uses AOR %s", public_id.c_str(), aor.c_str());
 
   // Create a subscription object from the request that we can pass down to
@@ -406,6 +407,7 @@ void SubscriptionSproutletTsx::process_subscription_request(pjsip_msg* req)
   {
     // Failed to connect to the local store.  Reject the subscribe with a 500
     // response.
+    TRC_ERROR("Failed to connect to local store for SUBSCRIBE, aor=%s", aor.c_str());
     st_code = PJSIP_SC_INTERNAL_SERVER_ERROR;
 
     // Build and send the reply.
diff --git a/src/thread_dispatcher.cpp b/src/thread_dispatcher.cpp
index 8be128f38..b925b2e67 100644
--- a/src/thread_dispatcher.cpp
+++ b/src/thread_dispatcher.cpp
@@ -257,7 +257,7 @@ bool process_queue_element()
             if ((rdata->msg_info.msg->type == PJSIP_REQUEST_MSG) &&
                (rdata->msg_info.msg->line.req.method.id != PJSIP_ACK_METHOD))
             {
-              TRC_DEBUG("Returning 500 response following exception");
+              TRC_ERROR("Returning 500 response following exception");
               reject_with_retry_header(rdata, PJSIP_SC_INTERNAL_SERVER_ERROR);
             }
 
@@ -523,7 +523,7 @@ static void reject_rx_msg_overload(pjsip_rx_data* rdata, SAS::TrailId trail)
 {
   // Respond statelessly with a 503 Service Unavailable, including a
   // Retry-After header with a zero length timeout.
-  TRC_DEBUG("Rejected request due to overload");
+  TRC_WARNING("Rejected request due to overload");
 
   SAS::Marker start_marker(trail, MARKER_ID_START, 1u);
   SAS::report_marker(start_marker);