diff --git a/.idea/workspace.xml b/.idea/workspace.xml
index 8938665..40417eb 100644
--- a/.idea/workspace.xml
+++ b/.idea/workspace.xml
@@ -2,8 +2,6 @@
 <project version="4">
   <component name="ChangeListManager">
     <list default="true" id="a609a0a0-94e8-451b-a70b-2605da1cae25" name="Default Changelist" comment="">
-      <change beforePath="$PROJECT_DIR$/.idea/workspace.xml" beforeDir="false" afterPath="$PROJECT_DIR$/.idea/workspace.xml" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/pom.xml" beforeDir="false" afterPath="$PROJECT_DIR$/pom.xml" afterDir="false" />
       <change beforePath="$PROJECT_DIR$/src/main/java/com/doodream/robustdns/RobustDnsResolver.java" beforeDir="false" afterPath="$PROJECT_DIR$/src/main/java/com/doodream/robustdns/RobustDnsResolver.java" afterDir="false" />
     </list>
     <ignored path="$PROJECT_DIR$/out/" />
@@ -22,8 +20,8 @@
       <file pinned="false" current-in-tab="false">
         <entry file="file://$PROJECT_DIR$/pom.xml">
           <provider selected="true" editor-type-id="text-editor">
-            <state relative-caret-position="425">
-              <caret line="25" column="28" selection-start-line="25" selection-start-column="28" selection-end-line="25" selection-end-column="28" />
+            <state relative-caret-position="144">
+              <caret line="8" column="18" selection-start-line="8" selection-start-column="18" selection-end-line="8" selection-end-column="18" />
             </state>
           </provider>
         </entry>
@@ -31,8 +29,8 @@
       <file pinned="false" current-in-tab="false">
         <entry file="file://$PROJECT_DIR$/src/test/java/com/doodream/robustdns/DnsAgingTest.java">
           <provider selected="true" editor-type-id="text-editor">
-            <state relative-caret-position="374">
-              <caret line="30" column="30" selection-start-line="30" selection-start-column="30" selection-end-line="30" selection-end-column="30" />
+            <state relative-caret-position="220">
+              <caret line="30" column="31" lean-forward="true" selection-start-line="30" selection-start-column="31" selection-end-line="30" selection-end-column="31" />
               <folding>
                 <element signature="imports" expanded="true" />
               </folding>
@@ -43,11 +41,8 @@
       <file pinned="false" current-in-tab="true">
         <entry file="file://$PROJECT_DIR$/src/main/java/com/doodream/robustdns/RobustDnsResolver.java">
           <provider selected="true" editor-type-id="text-editor">
-            <state relative-caret-position="362">
-              <caret line="192" column="48" selection-start-line="192" selection-start-column="48" selection-end-line="192" selection-end-column="48" />
-              <folding>
-                <element signature="imports" expanded="true" />
-              </folding>
+            <state relative-caret-position="184">
+              <caret line="119" column="32" selection-start-line="119" selection-start-column="32" selection-end-line="119" selection-end-column="32" />
             </state>
           </provider>
         </entry>
@@ -56,8 +51,8 @@
         <entry file="file://$PROJECT_DIR$/README.md">
           <provider selected="true" editor-type-id="split-provider[text-editor;markdown-preview-editor]">
             <state split_layout="SPLIT">
-              <first_editor relative-caret-position="204">
-                <caret line="12" column="10" selection-start-line="12" selection-start-column="10" selection-end-line="12" selection-end-column="10" />
+              <first_editor relative-caret-position="118">
+                <caret line="61" column="11" selection-start-line="61" selection-start-column="11" selection-end-line="61" selection-end-column="11" />
               </first_editor>
               <second_editor />
             </state>
@@ -108,45 +103,66 @@
       <foldersAlwaysOnTop value="true" />
     </navigator>
     <panes>
+      <pane id="Scope" />
       <pane id="PackagesPane" />
       <pane id="ProjectPane">
         <subPane>
           <expand>
             <path>
-              <item name="robust-dns" type="b2602c69:ProjectViewProjectNode" />
-              <item name="robust-dns" type="462c0819:PsiDirectoryNode" />
+              <item name="dns_robust" type="b2602c69:ProjectViewProjectNode" />
+              <item name="dns_robust" type="462c0819:PsiDirectoryNode" />
             </path>
             <path>
-              <item name="robust-dns" type="b2602c69:ProjectViewProjectNode" />
-              <item name="robust-dns" type="462c0819:PsiDirectoryNode" />
+              <item name="dns_robust" type="b2602c69:ProjectViewProjectNode" />
+              <item name="dns_robust" type="462c0819:PsiDirectoryNode" />
               <item name="src" type="462c0819:PsiDirectoryNode" />
             </path>
             <path>
-              <item name="robust-dns" type="b2602c69:ProjectViewProjectNode" />
-              <item name="robust-dns" type="462c0819:PsiDirectoryNode" />
+              <item name="dns_robust" type="b2602c69:ProjectViewProjectNode" />
+              <item name="dns_robust" type="462c0819:PsiDirectoryNode" />
               <item name="src" type="462c0819:PsiDirectoryNode" />
               <item name="main" type="462c0819:PsiDirectoryNode" />
             </path>
             <path>
-              <item name="robust-dns" type="b2602c69:ProjectViewProjectNode" />
-              <item name="robust-dns" type="462c0819:PsiDirectoryNode" />
+              <item name="dns_robust" type="b2602c69:ProjectViewProjectNode" />
+              <item name="dns_robust" type="462c0819:PsiDirectoryNode" />
               <item name="src" type="462c0819:PsiDirectoryNode" />
               <item name="main" type="462c0819:PsiDirectoryNode" />
               <item name="java" type="462c0819:PsiDirectoryNode" />
             </path>
             <path>
-              <item name="robust-dns" type="b2602c69:ProjectViewProjectNode" />
-              <item name="robust-dns" type="462c0819:PsiDirectoryNode" />
+              <item name="dns_robust" type="b2602c69:ProjectViewProjectNode" />
+              <item name="dns_robust" type="462c0819:PsiDirectoryNode" />
               <item name="src" type="462c0819:PsiDirectoryNode" />
               <item name="main" type="462c0819:PsiDirectoryNode" />
               <item name="java" type="462c0819:PsiDirectoryNode" />
               <item name="robustdns" type="462c0819:PsiDirectoryNode" />
             </path>
+            <path>
+              <item name="dns_robust" type="b2602c69:ProjectViewProjectNode" />
+              <item name="dns_robust" type="462c0819:PsiDirectoryNode" />
+              <item name="src" type="462c0819:PsiDirectoryNode" />
+              <item name="test" type="462c0819:PsiDirectoryNode" />
+            </path>
+            <path>
+              <item name="dns_robust" type="b2602c69:ProjectViewProjectNode" />
+              <item name="dns_robust" type="462c0819:PsiDirectoryNode" />
+              <item name="src" type="462c0819:PsiDirectoryNode" />
+              <item name="test" type="462c0819:PsiDirectoryNode" />
+              <item name="java" type="462c0819:PsiDirectoryNode" />
+            </path>
+            <path>
+              <item name="dns_robust" type="b2602c69:ProjectViewProjectNode" />
+              <item name="dns_robust" type="462c0819:PsiDirectoryNode" />
+              <item name="src" type="462c0819:PsiDirectoryNode" />
+              <item name="test" type="462c0819:PsiDirectoryNode" />
+              <item name="java" type="462c0819:PsiDirectoryNode" />
+              <item name="robustdns" type="462c0819:PsiDirectoryNode" />
+            </path>
           </expand>
           <select />
         </subPane>
       </pane>
-      <pane id="Scope" />
     </panes>
   </component>
   <component name="PropertiesComponent">
@@ -230,12 +246,13 @@
     <servers />
   </component>
   <component name="TimeTrackingManager">
-    <option name="totallyTimeSpent" value="31698000" />
+    <option name="totallyTimeSpent" value="31861000" />
   </component>
   <component name="ToolWindowManager">
-    <frame x="1920" y="-2" width="1920" height="1082" extended-state="6" />
+    <frame x="1667" y="25" width="1853" height="1055" extended-state="6" />
+    <editor active="true" />
     <layout>
-      <window_info content_ui="combo" id="Project" order="0" visible="true" weight="0.26093918" />
+      <window_info active="true" content_ui="combo" id="Project" order="0" visible="true" weight="0.14016621" />
       <window_info id="Structure" order="1" side_tool="true" weight="0.25" />
       <window_info id="Designer" order="2" />
       <window_info id="Image Layers" order="3" />
@@ -249,7 +266,7 @@
       <window_info anchor="bottom" id="Cvs" order="4" weight="0.25" />
       <window_info anchor="bottom" id="Inspection" order="5" weight="0.4" />
       <window_info anchor="bottom" id="TODO" order="6" />
-      <window_info active="true" anchor="bottom" id="Terminal" order="7" visible="true" weight="0.31794333" />
+      <window_info anchor="bottom" id="Terminal" order="7" visible="true" weight="0.39459458" />
       <window_info anchor="bottom" id="Docker" order="8" show_stripe_button="false" />
       <window_info anchor="bottom" id="Event Log" order="9" side_tool="true" />
       <window_info anchor="bottom" id="Database Changes" order="10" />
@@ -315,13 +332,6 @@
         </state>
       </provider>
     </entry>
-    <entry file="jar://$MAVEN_REPOSITORY$/dnsjava/dnsjava/2.1.8/dnsjava-2.1.8.jar!/org/xbill/DNS/ResolveThread.class">
-      <provider selected="true" editor-type-id="text-editor">
-        <state relative-caret-position="281">
-          <caret line="22" selection-start-line="22" selection-end-line="22" />
-        </state>
-      </provider>
-    </entry>
     <entry file="jar://$MAVEN_REPOSITORY$/dnsjava/dnsjava/2.1.8/dnsjava-2.1.8.jar!/org/xbill/DNS/Resolver.class">
       <provider selected="true" editor-type-id="text-editor">
         <state relative-caret-position="357">
@@ -331,41 +341,45 @@
     </entry>
     <entry file="file://$PROJECT_DIR$/pom.xml">
       <provider selected="true" editor-type-id="text-editor">
-        <state relative-caret-position="425">
-          <caret line="25" column="28" selection-start-line="25" selection-start-column="28" selection-end-line="25" selection-end-column="28" />
-        </state>
-      </provider>
-    </entry>
-    <entry file="file://$PROJECT_DIR$/src/test/java/com/doodream/robustdns/DnsAgingTest.java">
-      <provider selected="true" editor-type-id="text-editor">
-        <state relative-caret-position="374">
-          <caret line="30" column="30" selection-start-line="30" selection-start-column="30" selection-end-line="30" selection-end-column="30" />
-          <folding>
-            <element signature="imports" expanded="true" />
-          </folding>
+        <state relative-caret-position="144">
+          <caret line="8" column="18" selection-start-line="8" selection-start-column="18" selection-end-line="8" selection-end-column="18" />
         </state>
       </provider>
     </entry>
     <entry file="file://$PROJECT_DIR$/README.md">
       <provider selected="true" editor-type-id="split-provider[text-editor;markdown-preview-editor]">
         <state split_layout="SPLIT">
-          <first_editor relative-caret-position="204">
-            <caret line="12" column="10" selection-start-line="12" selection-start-column="10" selection-end-line="12" selection-end-column="10" />
+          <first_editor relative-caret-position="118">
+            <caret line="61" column="11" selection-start-line="61" selection-start-column="11" selection-end-line="61" selection-end-column="11" />
           </first_editor>
           <second_editor />
         </state>
       </provider>
     </entry>
-    <entry file="file://$PROJECT_DIR$/src/main/java/com/doodream/robustdns/RobustDnsResolver.java">
+    <entry file="jar://$MAVEN_REPOSITORY$/dnsjava/dnsjava/2.1.8/dnsjava-2.1.8.jar!/org/xbill/DNS/ResolveThread.class">
       <provider selected="true" editor-type-id="text-editor">
-        <state relative-caret-position="362">
-          <caret line="192" column="48" selection-start-line="192" selection-start-column="48" selection-end-line="192" selection-end-column="48" />
+        <state relative-caret-position="281">
+          <caret line="22" selection-start-line="22" selection-end-line="22" />
+        </state>
+      </provider>
+    </entry>
+    <entry file="file://$PROJECT_DIR$/src/test/java/com/doodream/robustdns/DnsAgingTest.java">
+      <provider selected="true" editor-type-id="text-editor">
+        <state relative-caret-position="220">
+          <caret line="30" column="31" lean-forward="true" selection-start-line="30" selection-start-column="31" selection-end-line="30" selection-end-column="31" />
           <folding>
             <element signature="imports" expanded="true" />
           </folding>
         </state>
       </provider>
     </entry>
+    <entry file="file://$PROJECT_DIR$/src/main/java/com/doodream/robustdns/RobustDnsResolver.java">
+      <provider selected="true" editor-type-id="text-editor">
+        <state relative-caret-position="184">
+          <caret line="119" column="32" selection-start-line="119" selection-start-column="32" selection-end-line="119" selection-end-column="32" />
+        </state>
+      </provider>
+    </entry>
   </component>
   <component name="masterDetails">
     <states>
diff --git a/src/main/java/com/doodream/robustdns/RobustDnsResolver.java b/src/main/java/com/doodream/robustdns/RobustDnsResolver.java
index 0ec792b..afcf1aa 100644
--- a/src/main/java/com/doodream/robustdns/RobustDnsResolver.java
+++ b/src/main/java/com/doodream/robustdns/RobustDnsResolver.java
@@ -117,7 +117,8 @@ private RobustDnsResolver() {
     public Single<InetAddress> resolve(String name) {
         if(cache.containsKey(name)) {
             final DnsRecord record = cache.get(name);
-            if(record.expireAt > System.currentTimeMillis()) {
+            if(record.expireAt < System.currentTimeMillis()) {
+                System.out.println("cache miss");
                 cache.remove(name);
                 if(updateOnExpire) {
                     resolve(name).subscribe();