[WIP] Implement certificate refreshes asynchronously (#137)

* Add new CloudSqlInstance Class for managing instance info.

* Add updateInstanceMetadata for fetching InstanceMetadata.

* Added updateEphemeralCerificate.

* Add createSocket and updateSslContext.

* Update CloudSQLInstance methods to use async.

* Fix checkstyle errors.

* Added getPrefferedIpType.

* Use callbacks over in method future updates.

* Add RateLimiting for immediateSslContextUpdate().

* Correct 'connect' to be static.

* Use new class in createSSLSocket.

* Remove older code.

* Add generic whenComplete function.

* Refactor 3 seperate tasks into a single operation.

* Fixed scheduling for next refresh.

* Update to Futures.getDone instead of .get

* Clean up some error handling.

* Clean up commenting.

* Update from blocked call to nested ListenableFutures.

* Improve future handling of scheduleRefresh.

* Remove blocking from forcedRefresh.

* Fix error propegation to cause.

* Fix miscellanous Javadoc comments.

* Fix miscellaneous style and best practice issues.

* Inline blockInstanceDataOnNext into forceRefresh.

* Move listener to performRefresh.

* Misc updates.

* Move the rest of scheduledRefresh into performRefresh.

* Update tests.

* Style fix in fetchMetadata.

* Switch whenAllComplete to whenAllSucceed.

* Updates based on review feedback.

* Additional feedback updates.

* Remove unncessary annotation.

* Remove nullcheck for nextInstanceData.

* Update tests to use error.hasMessageThat.

Author: kurtisvg

connector-j-5/src/main/java/com/google/cloud/sql/mysql/SocketFactory.java

@@ -33,8 +33,7 @@ public class SocketFactory implements com.mysql.jdbc.SocketFactory {
 
   @Override
   public Socket connect(String hostname, int portNumber, Properties props) throws IOException {
-    socket =
-        CoreSocketFactory.getInstance().connect(props, CoreSocketFactory.MYSQL_SOCKET_FILE_FORMAT);
+    socket = CoreSocketFactory.connect(props, CoreSocketFactory.MYSQL_SOCKET_FILE_FORMAT);
     return socket;
   }
 

connector-j-6/src/main/java/com/google/cloud/sql/mysql/SocketFactory.java

@@ -34,8 +34,7 @@ public class SocketFactory implements com.mysql.cj.api.io.SocketFactory {
   @Override
   public Socket connect(String host, int portNumber, Properties props, int loginTimeout)
       throws IOException {
-    socket =
-        CoreSocketFactory.getInstance().connect(props, CoreSocketFactory.MYSQL_SOCKET_FILE_FORMAT);
+    socket = CoreSocketFactory.connect(props, CoreSocketFactory.MYSQL_SOCKET_FILE_FORMAT);
     return socket;
   }
 

connector-j-8/src/main/java/com/google/cloud/sql/mysql/SocketFactory.java

@@ -45,10 +45,7 @@ public <T extends Closeable> T connect(
   public <T extends Closeable> T connect(
       String host, int portNumber, Properties props, int loginTimeout) throws IOException {
     @SuppressWarnings("unchecked")
-    T socket =
-        (T)
-            CoreSocketFactory.getInstance()
-                .connect(props, CoreSocketFactory.MYSQL_SOCKET_FILE_FORMAT);
+    T socket = (T) CoreSocketFactory.connect(props, CoreSocketFactory.MYSQL_SOCKET_FILE_FORMAT);
     return socket;
   }
 
@@ -67,5 +64,4 @@ public <T extends Closeable> T performTlsHandshake(
 
   @Override
   public void afterHandshake() {}
-
 }