diff --git a/lib/resty/healthcheck.lua b/lib/resty/healthcheck.lua
index 89d1284a..9be05cd6 100644
--- a/lib/resty/healthcheck.lua
+++ b/lib/resty/healthcheck.lua
@@ -31,6 +31,7 @@ local ngx_log = ngx.log
 local tostring = tostring
 local ipairs = ipairs
 local cjson = require("cjson.safe").new()
+local table_insert = table.insert
 local table_remove = table.remove
 local worker_events = require("resty.worker.events")
 local resty_lock = require ("resty.lock")
@@ -281,6 +282,7 @@ end
 function checker:add_target(ip, port, hostname, is_healthy, hostheader)
   ip = tostring(assert(ip, "no ip address provided"))
   port = assert(tonumber(port), "no port number provided")
+  hostname = hostname or ip
   if is_healthy == nil then
     is_healthy = true
   end
@@ -288,13 +290,17 @@ function checker:add_target(ip, port, hostname, is_healthy, hostheader)
   local internal_health = is_healthy and "healthy" or "unhealthy"
 
   local ok, err = locking_target_list(self, function(target_list)
+  local found = false
 
     -- check whether we already have this target
     for _, target in ipairs(target_list) do
       if target.ip == ip and target.port == port and target.hostname == hostname then
         self:log(DEBUG, "adding an existing target: ", hostname or "", " ", ip,
                 ":", port, " (ignoring)")
-        return false
+        target.purge_time = nil
+        found = true
+        internal_health = self:get_target_status(ip, port, hostname) and
+                          "healthy" or "unhealthy"
       end
     end
 
@@ -308,12 +314,14 @@ function checker:add_target(ip, port, hostname, is_healthy, hostheader)
     end
 
     -- target does not exist, go add it
-    target_list[#target_list + 1] = {
-      ip = ip,
-      port = port,
-      hostname = hostname,
-      hostheader = hostheader,
-    }
+    if not found then
+      target_list[#target_list + 1] = {
+        ip = ip,
+        port = port,
+        hostname = hostname,
+        hostheader = hostheader,
+      }
+    end
     target_list = serialize(target_list)
 
     ok, err = self.shm:set(self.TARGET_LIST, target_list)
@@ -433,6 +441,28 @@ function checker:clear()
 end
 
 
+function checker:delayed_clear(delay)
+  assert(tonumber(delay), "no delay provided")
+
+  return locking_target_list(self, function(target_list)
+    local purge_time = ngx_now() + delay
+
+    -- add purge time to all targets
+    for _, target in ipairs(target_list) do
+      target.purge_time = purge_time
+    end
+
+    target_list = serialize(target_list)
+    local ok, err = self.shm:set(self.TARGET_LIST, target_list)
+    if not ok then
+      return nil, "failed to store target_list in shm: " .. err
+    end
+
+    return true
+  end)
+end
+
+
 --- Get the current status of the target.
 -- @param ip IP address of the target being checked.
 -- @param port the port being checked against.
@@ -629,7 +659,7 @@ function checker:report_failure(ip, port, hostname, check)
     ctr_type = CTR_HTTP
   end
 
-  return incr_counter(self, "unhealthy", ip, port, hostname, limit, ctr_type)
+  return incr_counter(self, "unhealthy", ip, port, hostname or ip, limit, ctr_type)
 
 end
 
@@ -648,7 +678,7 @@ function checker:report_success(ip, port, hostname, check)
 
   local limit = self.checks[check or "passive"].healthy.successes
 
-  return incr_counter(self, "healthy", ip, port, hostname, limit, CTR_SUCCESS)
+  return incr_counter(self, "healthy", ip, port, hostname or ip, limit, CTR_SUCCESS)
 
 end
 
@@ -686,7 +716,7 @@ function checker:report_http_status(ip, port, hostname, http_status, check)
     return
   end
 
-  return incr_counter(self, status_type, ip, port, hostname, limit, ctr)
+  return incr_counter(self, status_type, ip, port, hostname or ip, limit, ctr)
 
 end
 
@@ -708,7 +738,7 @@ function checker:report_tcp_failure(ip, port, hostname, operation, check)
   local limit = self.checks[check or "passive"].unhealthy.tcp_failures
 
   -- TODO what do we do with the `operation` information
-  return incr_counter(self, "unhealthy", ip, port, hostname, limit, CTR_TCP)
+  return incr_counter(self, "unhealthy", ip, port, hostname or ip, limit, CTR_TCP)
 
 end
 
@@ -725,7 +755,7 @@ function checker:report_timeout(ip, port, hostname, check)
 
   local limit = self.checks[check or "passive"].unhealthy.timeouts
 
-  return incr_counter(self, "unhealthy", ip, port, hostname, limit, CTR_TIMEOUT)
+  return incr_counter(self, "unhealthy", ip, port, hostname or ip, limit, CTR_TIMEOUT)
 
 end
 
@@ -766,6 +796,7 @@ end
 function checker:set_target_status(ip, port, hostname, is_healthy)
   ip   = tostring(assert(ip, "no ip address provided"))
   port = assert(tonumber(port), "no port number provided")
+  hostname = hostname or ip
   assert(type(is_healthy) == "boolean")
 
   local health_report = is_healthy and "healthy" or "unhealthy"
@@ -1085,7 +1116,7 @@ function checker:event_handler(event_name, ip, port, hostname)
          then
     if not target_found then
       -- it is a new target, must add it first
-      target_found = { ip = ip, port = port, hostname = hostname }
+      target_found = { ip = ip, port = port, hostname = hostname or ip }
       self.targets[target_found.ip] = self.targets[target_found.ip] or {}
       self.targets[target_found.ip][target_found.port] = self.targets[target_found.ip][target_found.port] or {}
       self.targets[target_found.ip][target_found.port][target_found.hostname or ip] = target_found
@@ -1126,7 +1157,7 @@ end
 
 -- Raises an event for a target status change.
 function checker:raise_event(event_name, ip, port, hostname)
-  local target = { ip = ip, port = port, hostname = hostname }
+  local target = { ip = ip, port = port, hostname = hostname or ip}
   worker_events.post(self.EVENT_SOURCE, event_name, target)
 end
 
@@ -1451,9 +1482,8 @@ function _M.new(opts)
     return nil, err
   end
 
-  -- if active checker is needed and not running, start it
-  if (self.checks.active.healthy.active or self.checks.active.unhealthy.active)
-    and active_check_timer == nil then
+  -- if active checker is not running, start it
+  if active_check_timer == nil then
 
     self:log(DEBUG, "worker ", ngx_worker_id(), " (pid: ", ngx_worker_pid(), ") ",
       "starting active check timer")
@@ -1475,6 +1505,29 @@ function _M.new(opts)
 
         local cur_time = ngx_now()
         for _, checker_obj in ipairs(hcs) do
+          -- clear targets marked for delayed removal
+          locking_target_list(checker_obj, function(target_list)
+            local removed_targets = {}
+            for i, target in ipairs(target_list) do
+              if target.purge_time and target.purge_time <= cur_time then
+                table_insert(removed_targets, target)
+                table_remove(target_list, i)
+              end
+            end
+
+            target_list = serialize(target_list)
+
+            local ok, err = shm:set(checker_obj.TARGET_LIST, target_list)
+            if not ok then
+              return nil, "failed to store target_list in shm: " .. err
+            end
+
+            for _, target in ipairs(removed_targets) do
+              clear_target_data_from_shm(checker_obj, target.ip, target.port, target.hostname)
+              checker_obj:raise_event(checker_obj.events.remove, target.ip, target.port, target.hostname)
+            end
+          end)
+
           if checker_obj.checks.active.healthy.active and
             (checker_obj.checks.active.healthy.last_run +
               checker_obj.checks.active.healthy.interval <= cur_time)
diff --git a/t/04-report_success.t b/t/04-report_success.t
index 8fb5fb6e..084d02da 100644
--- a/t/04-report_success.t
+++ b/t/04-report_success.t
@@ -84,14 +84,14 @@ GET /t
 true
 true
 --- error_log
-healthy SUCCESS increment (1/3) for '(127.0.0.1:2116)'
-healthy SUCCESS increment (2/3) for '(127.0.0.1:2116)'
-healthy SUCCESS increment (3/3) for '(127.0.0.1:2116)'
-event: target status '(127.0.0.1:2116)' from 'false' to 'true'
-healthy SUCCESS increment (1/3) for '(127.0.0.1:2116)'
-healthy SUCCESS increment (2/3) for '(127.0.0.1:2116)'
-healthy SUCCESS increment (3/3) for '(127.0.0.1:2116)'
-event: target status '(127.0.0.1:2118)' from 'false' to 'true'
+healthy SUCCESS increment (1/3) for '127.0.0.1(127.0.0.1:2116)'
+healthy SUCCESS increment (2/3) for '127.0.0.1(127.0.0.1:2116)'
+healthy SUCCESS increment (3/3) for '127.0.0.1(127.0.0.1:2116)'
+event: target status '127.0.0.1(127.0.0.1:2116)' from 'false' to 'true'
+healthy SUCCESS increment (1/3) for '127.0.0.1(127.0.0.1:2116)'
+healthy SUCCESS increment (2/3) for '127.0.0.1(127.0.0.1:2116)'
+healthy SUCCESS increment (3/3) for '127.0.0.1(127.0.0.1:2116)'
+event: target status '127.0.0.1(127.0.0.1:2118)' from 'false' to 'true'
 
 
 === TEST 2: report_success() recovers TCP active = passive
@@ -159,14 +159,14 @@ GET /t
 true
 true
 --- error_log
-healthy SUCCESS increment (1/3) for '(127.0.0.1:2116)'
-healthy SUCCESS increment (2/3) for '(127.0.0.1:2116)'
-healthy SUCCESS increment (3/3) for '(127.0.0.1:2116)'
-event: target status '(127.0.0.1:2116)' from 'false' to 'true'
-healthy SUCCESS increment (1/3) for '(127.0.0.1:2116)'
-healthy SUCCESS increment (2/3) for '(127.0.0.1:2116)'
-healthy SUCCESS increment (3/3) for '(127.0.0.1:2116)'
-event: target status '(127.0.0.1:2118)' from 'false' to 'true'
+healthy SUCCESS increment (1/3) for '127.0.0.1(127.0.0.1:2116)'
+healthy SUCCESS increment (2/3) for '127.0.0.1(127.0.0.1:2116)'
+healthy SUCCESS increment (3/3) for '127.0.0.1(127.0.0.1:2116)'
+event: target status '127.0.0.1(127.0.0.1:2116)' from 'false' to 'true'
+healthy SUCCESS increment (1/3) for '127.0.0.1(127.0.0.1:2116)'
+healthy SUCCESS increment (2/3) for '127.0.0.1(127.0.0.1:2116)'
+healthy SUCCESS increment (3/3) for '127.0.0.1(127.0.0.1:2116)'
+event: target status '127.0.0.1(127.0.0.1:2118)' from 'false' to 'true'
 
 === TEST 3: report_success() is a nop when active.healthy.sucesses == 0
 --- http_config eval
@@ -292,4 +292,4 @@ GET /t
 false
 --- no_error_log
 healthy SUCCESS increment
-event: target status '(127.0.0.1:2118)' from 'false' to 'true'
+event: target status '127.0.0.1(127.0.0.1:2118)' from 'false' to 'true'
diff --git a/t/05-report_failure.t b/t/05-report_failure.t
index 47f8c7e9..05eefa25 100644
--- a/t/05-report_failure.t
+++ b/t/05-report_failure.t
@@ -84,14 +84,14 @@ GET /t
 false
 false
 --- error_log
-unhealthy HTTP increment (1/3) for '(127.0.0.1:2117)'
-unhealthy HTTP increment (2/3) for '(127.0.0.1:2117)'
-unhealthy HTTP increment (3/3) for '(127.0.0.1:2117)'
-event: target status '(127.0.0.1:2117)' from 'true' to 'false'
-unhealthy HTTP increment (1/3) for '(127.0.0.1:2113)'
-unhealthy HTTP increment (2/3) for '(127.0.0.1:2113)'
-unhealthy HTTP increment (3/3) for '(127.0.0.1:2113)'
-event: target status '(127.0.0.1:2113)' from 'true' to 'false'
+unhealthy HTTP increment (1/3) for '127.0.0.1(127.0.0.1:2117)'
+unhealthy HTTP increment (2/3) for '127.0.0.1(127.0.0.1:2117)'
+unhealthy HTTP increment (3/3) for '127.0.0.1(127.0.0.1:2117)'
+event: target status '127.0.0.1(127.0.0.1:2117)' from 'true' to 'false'
+unhealthy HTTP increment (1/3) for '127.0.0.1(127.0.0.1:2113)'
+unhealthy HTTP increment (2/3) for '127.0.0.1(127.0.0.1:2113)'
+unhealthy HTTP increment (3/3) for '127.0.0.1(127.0.0.1:2113)'
+event: target status '127.0.0.1(127.0.0.1:2113)' from 'true' to 'false'
 
 
 === TEST 2: report_failure() fails TCP active + passive
@@ -159,12 +159,12 @@ GET /t
 false
 false
 --- error_log
-unhealthy TCP increment (1/2) for '(127.0.0.1:2117)'
-unhealthy TCP increment (2/2) for '(127.0.0.1:2117)'
-event: target status '(127.0.0.1:2117)' from 'true' to 'false'
-unhealthy TCP increment (1/2) for '(127.0.0.1:2113)'
-unhealthy TCP increment (2/2) for '(127.0.0.1:2113)'
-event: target status '(127.0.0.1:2113)' from 'true' to 'false'
+unhealthy TCP increment (1/2) for '127.0.0.1(127.0.0.1:2117)'
+unhealthy TCP increment (2/2) for '127.0.0.1(127.0.0.1:2117)'
+event: target status '127.0.0.1(127.0.0.1:2117)' from 'true' to 'false'
+unhealthy TCP increment (1/2) for '127.0.0.1(127.0.0.1:2113)'
+unhealthy TCP increment (2/2) for '127.0.0.1(127.0.0.1:2113)'
+event: target status '127.0.0.1(127.0.0.1:2113)' from 'true' to 'false'
 
 
 === TEST 3: report_failure() is a nop when failure counters == 0
@@ -232,9 +232,9 @@ GET /t
 true
 true
 --- no_error_log
-unhealthy TCP increment (1/2) for '(127.0.0.1:2117)'
-unhealthy TCP increment (2/2) for '(127.0.0.1:2117)'
-event: target status '(127.0.0.1:2117)' from 'true' to 'false'
-unhealthy TCP increment (1/2) for '(127.0.0.1:2113)'
-unhealthy TCP increment (2/2) for '(127.0.0.1:2113)'
-event: target status '(127.0.0.1:2113)' from 'true' to 'false'
+unhealthy TCP increment (1/2) for '127.0.0.1(127.0.0.1:2117)'
+unhealthy TCP increment (2/2) for '127.0.0.1(127.0.0.1:2117)'
+event: target status '127.0.0.1(127.0.0.1:2117)' from 'true' to 'false'
+unhealthy TCP increment (1/2) for '127.0.0.1(127.0.0.1:2113)'
+unhealthy TCP increment (2/2) for '127.0.0.1(127.0.0.1:2113)'
+event: target status '127.0.0.1(127.0.0.1:2113)' from 'true' to 'false'
diff --git a/t/06-report_http_status.t b/t/06-report_http_status.t
index 0d2c1cdd..5d694832 100644
--- a/t/06-report_http_status.t
+++ b/t/06-report_http_status.t
@@ -84,14 +84,14 @@ GET /t
 false
 false
 --- error_log
-unhealthy HTTP increment (1/3) for '(127.0.0.1:2119)'
-unhealthy HTTP increment (2/3) for '(127.0.0.1:2119)'
-unhealthy HTTP increment (3/3) for '(127.0.0.1:2119)'
-event: target status '(127.0.0.1:2119)' from 'true' to 'false'
-unhealthy HTTP increment (1/3) for '(127.0.0.1:2113)'
-unhealthy HTTP increment (2/3) for '(127.0.0.1:2113)'
-unhealthy HTTP increment (3/3) for '(127.0.0.1:2113)'
-event: target status '(127.0.0.1:2113)' from 'true' to 'false'
+unhealthy HTTP increment (1/3) for '127.0.0.1(127.0.0.1:2119)'
+unhealthy HTTP increment (2/3) for '127.0.0.1(127.0.0.1:2119)'
+unhealthy HTTP increment (3/3) for '127.0.0.1(127.0.0.1:2119)'
+event: target status '127.0.0.1(127.0.0.1:2119)' from 'true' to 'false'
+unhealthy HTTP increment (1/3) for '127.0.0.1(127.0.0.1:2113)'
+unhealthy HTTP increment (2/3) for '127.0.0.1(127.0.0.1:2113)'
+unhealthy HTTP increment (3/3) for '127.0.0.1(127.0.0.1:2113)'
+event: target status '127.0.0.1(127.0.0.1:2113)' from 'true' to 'false'
 
 
 
@@ -162,16 +162,16 @@ GET /t
 true
 true
 --- error_log
-healthy SUCCESS increment (1/4) for '(127.0.0.1:2119)'
-healthy SUCCESS increment (2/4) for '(127.0.0.1:2119)'
-healthy SUCCESS increment (3/4) for '(127.0.0.1:2119)'
-healthy SUCCESS increment (4/4) for '(127.0.0.1:2119)'
-event: target status '(127.0.0.1:2119)' from 'false' to 'true'
-healthy SUCCESS increment (1/4) for '(127.0.0.1:2113)'
-healthy SUCCESS increment (2/4) for '(127.0.0.1:2113)'
-healthy SUCCESS increment (3/4) for '(127.0.0.1:2113)'
-healthy SUCCESS increment (4/4) for '(127.0.0.1:2113)'
-event: target status '(127.0.0.1:2113)' from 'false' to 'true'
+healthy SUCCESS increment (1/4) for '127.0.0.1(127.0.0.1:2119)'
+healthy SUCCESS increment (2/4) for '127.0.0.1(127.0.0.1:2119)'
+healthy SUCCESS increment (3/4) for '127.0.0.1(127.0.0.1:2119)'
+healthy SUCCESS increment (4/4) for '127.0.0.1(127.0.0.1:2119)'
+event: target status '127.0.0.1(127.0.0.1:2119)' from 'false' to 'true'
+healthy SUCCESS increment (1/4) for '127.0.0.1(127.0.0.1:2113)'
+healthy SUCCESS increment (2/4) for '127.0.0.1(127.0.0.1:2113)'
+healthy SUCCESS increment (3/4) for '127.0.0.1(127.0.0.1:2113)'
+healthy SUCCESS increment (4/4) for '127.0.0.1(127.0.0.1:2113)'
+event: target status '127.0.0.1(127.0.0.1:2113)' from 'false' to 'true'
 
 
 === TEST 3: report_http_status() with success is a nop when passive.healthy.successes == 0
@@ -427,7 +427,7 @@ GET /t
 true
 --- no_error_log
 unhealthy HTTP increment
-event: target status '(127.0.0.1:2119)' from 'true' to 'false'
+event: target status '127.0.0.1(127.0.0.1:2119)' from 'true' to 'false'
 
 
 === TEST 5: report_http_status() must work in log phase
diff --git a/t/07-report_tcp_failure.t b/t/07-report_tcp_failure.t
index 9e4e0e7c..f2355e96 100644
--- a/t/07-report_tcp_failure.t
+++ b/t/07-report_tcp_failure.t
@@ -84,14 +84,14 @@ GET /t
 false
 false
 --- error_log
-unhealthy TCP increment (1/3) for '(127.0.0.1:2120)'
-unhealthy TCP increment (2/3) for '(127.0.0.1:2120)'
-unhealthy TCP increment (3/3) for '(127.0.0.1:2120)'
-event: target status '(127.0.0.1:2120)' from 'true' to 'false'
-unhealthy TCP increment (1/3) for '(127.0.0.1:2113)'
-unhealthy TCP increment (2/3) for '(127.0.0.1:2113)'
-unhealthy TCP increment (3/3) for '(127.0.0.1:2113)'
-event: target status '(127.0.0.1:2113)' from 'true' to 'false'
+unhealthy TCP increment (1/3) for '127.0.0.1(127.0.0.1:2120)'
+unhealthy TCP increment (2/3) for '127.0.0.1(127.0.0.1:2120)'
+unhealthy TCP increment (3/3) for '127.0.0.1(127.0.0.1:2120)'
+event: target status '127.0.0.1(127.0.0.1:2120)' from 'true' to 'false'
+unhealthy TCP increment (1/3) for '127.0.0.1(127.0.0.1:2113)'
+unhealthy TCP increment (2/3) for '127.0.0.1(127.0.0.1:2113)'
+unhealthy TCP increment (3/3) for '127.0.0.1(127.0.0.1:2113)'
+event: target status '127.0.0.1(127.0.0.1:2113)' from 'true' to 'false'
 
 
 === TEST 2: report_tcp_failure() for active is a nop when active.unhealthy.tcp_failures == 0
@@ -154,7 +154,7 @@ GET /t
 true
 --- no_error_log
 unhealthy TCP increment
-event: target status '(127.0.0.1:2120)' from 'true' to 'false'
+event: target status '127.0.0.1(127.0.0.1:2120)' from 'true' to 'false'
 
 
 
@@ -218,4 +218,4 @@ GET /t
 true
 --- no_error_log
 unhealthy TCP increment
-event: target status '(127.0.0.1:2120)' from 'true' to 'false'
+event: target status '127.0.0.1(127.0.0.1:2120)' from 'true' to 'false'
diff --git a/t/08-report_timeout.t b/t/08-report_timeout.t
index fb61ea18..1dd01358 100644
--- a/t/08-report_timeout.t
+++ b/t/08-report_timeout.t
@@ -84,12 +84,12 @@ GET /t
 false
 false
 --- error_log
-unhealthy TIMEOUT increment (1/2) for '(127.0.0.1:2122)'
-unhealthy TIMEOUT increment (2/2) for '(127.0.0.1:2122)'
-event: target status '(127.0.0.1:2122)' from 'true' to 'false'
-unhealthy TIMEOUT increment (1/2) for '(127.0.0.1:2113)'
-unhealthy TIMEOUT increment (2/2) for '(127.0.0.1:2113)'
-event: target status '(127.0.0.1:2113)' from 'true' to 'false'
+unhealthy TIMEOUT increment (1/2) for '127.0.0.1(127.0.0.1:2122)'
+unhealthy TIMEOUT increment (2/2) for '127.0.0.1(127.0.0.1:2122)'
+event: target status '127.0.0.1(127.0.0.1:2122)' from 'true' to 'false'
+unhealthy TIMEOUT increment (1/2) for '127.0.0.1(127.0.0.1:2113)'
+unhealthy TIMEOUT increment (2/2) for '127.0.0.1(127.0.0.1:2113)'
+event: target status '127.0.0.1(127.0.0.1:2113)' from 'true' to 'false'
 
 
 === TEST 2: report_timeout() for active is a nop when active.unhealthy.timeouts == 0
@@ -154,7 +154,7 @@ GET /t
 true
 --- no_error_log
 unhealthy TCP increment
-event: target status '(127.0.0.1:2122)' from 'true' to 'false'
+event: target status '127.0.0.1(127.0.0.1:2122)' from 'true' to 'false'
 
 
 
@@ -220,4 +220,4 @@ GET /t
 true
 --- no_error_log
 unhealthy TCP increment
-event: target status '(127.0.0.1:2122)' from 'true' to 'false'
+event: target status '127.0.0.1(127.0.0.1:2122)' from 'true' to 'false'
diff --git a/t/09-active_probes.t b/t/09-active_probes.t
index 86c523cd..dd68faf4 100644
--- a/t/09-active_probes.t
+++ b/t/09-active_probes.t
@@ -67,10 +67,10 @@ GET /t
 false
 --- error_log
 checking unhealthy targets: nothing to do
-unhealthy HTTP increment (1/3) for '(127.0.0.1:2114)'
-unhealthy HTTP increment (2/3) for '(127.0.0.1:2114)'
-unhealthy HTTP increment (3/3) for '(127.0.0.1:2114)'
-event: target status '(127.0.0.1:2114)' from 'true' to 'false'
+unhealthy HTTP increment (1/3) for '127.0.0.1(127.0.0.1:2114)'
+unhealthy HTTP increment (2/3) for '127.0.0.1(127.0.0.1:2114)'
+unhealthy HTTP increment (3/3) for '127.0.0.1(127.0.0.1:2114)'
+event: target status '127.0.0.1(127.0.0.1:2114)' from 'true' to 'false'
 checking healthy targets: nothing to do
 
 
@@ -123,10 +123,10 @@ GET /t
 true
 --- error_log
 checking healthy targets: nothing to do
-healthy SUCCESS increment (1/3) for '(127.0.0.1:2114)'
-healthy SUCCESS increment (2/3) for '(127.0.0.1:2114)'
-healthy SUCCESS increment (3/3) for '(127.0.0.1:2114)'
-event: target status '(127.0.0.1:2114)' from 'false' to 'true'
+healthy SUCCESS increment (1/3) for '127.0.0.1(127.0.0.1:2114)'
+healthy SUCCESS increment (2/3) for '127.0.0.1(127.0.0.1:2114)'
+healthy SUCCESS increment (3/3) for '127.0.0.1(127.0.0.1:2114)'
+event: target status '127.0.0.1(127.0.0.1:2114)' from 'false' to 'true'
 checking unhealthy targets: nothing to do
 
 === TEST 3: active probes, custom http status (regression test for pre-filled defaults)
@@ -179,10 +179,10 @@ true
 checking unhealthy targets: nothing to do
 --- no_error_log
 checking healthy targets: nothing to do
-unhealthy HTTP increment (1/3) for '(127.0.0.1:2114)'
-unhealthy HTTP increment (2/3) for '(127.0.0.1:2114)'
-unhealthy HTTP increment (3/3) for '(127.0.0.1:2114)'
-event: target status '(127.0.0.1:2114)' from 'true' to 'false'
+unhealthy HTTP increment (1/3) for '127.0.0.1(127.0.0.1:2114)'
+unhealthy HTTP increment (2/3) for '127.0.0.1(127.0.0.1:2114)'
+unhealthy HTTP increment (3/3) for '127.0.0.1(127.0.0.1:2114)'
+event: target status '127.0.0.1(127.0.0.1:2114)' from 'true' to 'false'
 
 
 === TEST 4: active probes, custom http status, node failing
@@ -234,10 +234,10 @@ GET /t
 false
 --- error_log
 checking unhealthy targets: nothing to do
-unhealthy HTTP increment (1/3) for '(127.0.0.1:2114)'
-unhealthy HTTP increment (2/3) for '(127.0.0.1:2114)'
-unhealthy HTTP increment (3/3) for '(127.0.0.1:2114)'
-event: target status '(127.0.0.1:2114)' from 'true' to 'false'
+unhealthy HTTP increment (1/3) for '127.0.0.1(127.0.0.1:2114)'
+unhealthy HTTP increment (2/3) for '127.0.0.1(127.0.0.1:2114)'
+unhealthy HTTP increment (3/3) for '127.0.0.1(127.0.0.1:2114)'
+event: target status '127.0.0.1(127.0.0.1:2114)' from 'true' to 'false'
 checking healthy targets: nothing to do
 
 
@@ -340,10 +340,10 @@ GET /t
 false
 --- error_log
 checking unhealthy targets: nothing to do
-unhealthy TCP increment (1/3) for '(127.0.0.1:2114)'
-unhealthy TCP increment (2/3) for '(127.0.0.1:2114)'
-unhealthy TCP increment (3/3) for '(127.0.0.1:2114)'
-event: target status '(127.0.0.1:2114)' from 'true' to 'false'
+unhealthy TCP increment (1/3) for '127.0.0.1(127.0.0.1:2114)'
+unhealthy TCP increment (2/3) for '127.0.0.1(127.0.0.1:2114)'
+unhealthy TCP increment (3/3) for '127.0.0.1(127.0.0.1:2114)'
+event: target status '127.0.0.1(127.0.0.1:2114)' from 'true' to 'false'
 checking healthy targets: nothing to do
 
 
@@ -396,10 +396,10 @@ GET /t
 true
 --- error_log
 checking healthy targets: nothing to do
-healthy SUCCESS increment (1/3) for '(127.0.0.1:2114)'
-healthy SUCCESS increment (2/3) for '(127.0.0.1:2114)'
-healthy SUCCESS increment (3/3) for '(127.0.0.1:2114)'
-event: target status '(127.0.0.1:2114)' from 'false' to 'true'
+healthy SUCCESS increment (1/3) for '127.0.0.1(127.0.0.1:2114)'
+healthy SUCCESS increment (2/3) for '127.0.0.1(127.0.0.1:2114)'
+healthy SUCCESS increment (3/3) for '127.0.0.1(127.0.0.1:2114)'
+event: target status '127.0.0.1(127.0.0.1:2114)' from 'false' to 'true'
 checking unhealthy targets: nothing to do
 
 
diff --git a/t/11-clear.t b/t/11-clear.t
index d3a9ebd7..7eb33375 100644
--- a/t/11-clear.t
+++ b/t/11-clear.t
@@ -3,7 +3,7 @@ use Cwd qw(cwd);
 
 workers(1);
 
-plan tests => repeat_each() * 23;
+plan tests => repeat_each() * 27;
 
 my $pwd = cwd();
 
@@ -164,7 +164,119 @@ GET /t
 true
 
 --- error_log
-unhealthy HTTP increment (1/3) for '(127.0.0.1:21120)'
-unhealthy HTTP increment (2/3) for '(127.0.0.1:21120)'
+unhealthy HTTP increment (1/3) for '127.0.0.1(127.0.0.1:21120)'
+unhealthy HTTP increment (2/3) for '127.0.0.1(127.0.0.1:21120)'
 --- no_error_log
-unhealthy HTTP increment (3/3) for '(127.0.0.1:21120)'
+unhealthy HTTP increment (3/3) for '127.0.0.1(127.0.0.1:21120)'
+
+
+=== TEST 4: delayed_clear() clears the list, after interval new checkers don't see it
+--- http_config eval: $::HttpConfig
+--- config
+    location = /t {
+        content_by_lua_block {
+            local we = require "resty.worker.events"
+            assert(we.configure{ shm = "my_worker_events", interval = 0.1 })
+            local healthcheck = require("resty.healthcheck")
+            local config = {
+                name = "testing",
+                shm_name = "test_shm",
+                checks = {
+                    active = {
+                        healthy  = {
+                            interval = 0.1
+                        },
+                        unhealthy  = {
+                            interval = 0.1
+                        }
+                    }
+                }
+            }
+            local checker1 = healthcheck.new(config)
+            for i = 1, 10 do
+                checker1:add_target("127.0.0.1", 10000 + i, nil, false)
+            end
+            ngx.sleep(0.2) -- wait twice the interval
+            ngx.say(checker1:get_target_status("127.0.0.1", 10001))
+            checker1:delayed_clear(0.2)
+
+            local checker2 = healthcheck.new(config)
+            ngx.say(checker2:get_target_status("127.0.0.1", 10001))
+            ngx.sleep(0.4) -- wait while the targets are cleared
+            local status, err = checker2:get_target_status("127.0.0.1", 10001)
+            if status ~= nil then
+                ngx.say(status)
+            else
+                ngx.say(err)
+            end
+        }
+    }
+--- request
+GET /t
+--- response_body
+false
+false
+target not found
+
+=== TEST 5: delayed_clear() would clear tgt list, but adding again keeps the previous status
+--- http_config eval: $::HttpConfig
+--- config
+    location = /t {
+        content_by_lua_block {
+            local we = require "resty.worker.events"
+            assert(we.configure{ shm = "my_worker_events", interval = 0.1 })
+            local healthcheck = require("resty.healthcheck")
+            local config = {
+                name = "testing",
+                shm_name = "test_shm",
+                checks = {
+                    active = {
+                        healthy  = {
+                            interval = 0.1
+                        },
+                        unhealthy  = {
+                            interval = 0.1
+                        }
+                    }
+                }
+            }
+            local checker1 = healthcheck.new(config)
+            checker1:add_target("127.0.0.1", 10001, nil, false)
+            checker1:add_target("127.0.0.1", 10002, nil, false)
+            checker1:add_target("127.0.0.1", 10003, nil, false)
+            ngx.sleep(0.2) -- wait twice the interval
+            ngx.say(checker1:get_target_status("127.0.0.1", 10002))
+            checker1:delayed_clear(0.2)
+
+            local checker2 = healthcheck.new(config)
+            checker2:add_target("127.0.0.1", 10002, nil, true)
+            ngx.say(checker2:get_target_status("127.0.0.1", 10002))
+            ngx.sleep(0.4) -- wait while the targets would be cleared
+            local status, err = checker2:get_target_status("127.0.0.1", 10001)
+            if status ~= nil then
+                ngx.say(status)
+            else
+                ngx.say(err)
+            end
+            status, err = checker2:get_target_status("127.0.0.1", 10002)
+            if status ~= nil then
+                ngx.say(status)
+            else
+                ngx.say(err)
+            end
+            status, err = checker2:get_target_status("127.0.0.1", 10003)
+            if status ~= nil then
+                ngx.say(status)
+            else
+                ngx.say(err)
+            end
+        }
+    }
+--- request
+GET /t
+--- response_body
+false
+false
+target not found
+false
+target not found
diff --git a/t/15-get_virtualhost_target_status.t b/t/15-get_virtualhost_target_status.t
index 9bfbc92c..2a3f5fce 100644
--- a/t/15-get_virtualhost_target_status.t
+++ b/t/15-get_virtualhost_target_status.t
@@ -147,8 +147,8 @@ true
 true
 false
 --- error_log
-unhealthy HTTP increment (1/1) for '(127.0.0.1:2116)'
-event: target status '(127.0.0.1:2116)' from 'true' to 'false'
+unhealthy HTTP increment (1/1) for '127.0.0.1(127.0.0.1:2116)'
+event: target status '127.0.0.1(127.0.0.1:2116)' from 'true' to 'false'
 
 
 
@@ -293,7 +293,7 @@ false
 false
 false
 --- error_log
-unhealthy HTTP increment (1/1) for '(127.0.0.1:2118)'
-event: target status '(127.0.0.1:2118)' from 'true' to 'false'
+unhealthy HTTP increment (1/1) for '127.0.0.1(127.0.0.1:2118)'
+event: target status '127.0.0.1(127.0.0.1:2118)' from 'true' to 'false'
 unhealthy HTTP increment (1/1) for '127.0.0.1(127.0.0.1:2119)'
 event: target status '127.0.0.1(127.0.0.1:2119)' from 'true' to 'false'