added counting semaphore to fix a potential time skew issue (JSDK-301)

build.gradle

@@ -35,7 +35,7 @@ plugins {
 
 allprojects {
     group = 'com.spectralogic.ds3'
-    version = '3.5.5'
+    version = '3.5.6'
 }
 
 subprojects {

ds3-sdk/src/main/java/com/spectralogic/ds3client/networking/NetworkClientImpl.java

@@ -62,6 +62,7 @@
 import java.security.cert.CertificateException;
 import java.security.cert.X509Certificate;
 import java.util.Map;
+import java.util.concurrent.Semaphore;
 
 import static com.spectralogic.ds3client.utils.Signature.canonicalizeAmzHeaders;
 import static com.spectralogic.ds3client.utils.Signature.canonicalizeResource;
@@ -88,6 +89,7 @@ public class NetworkClientImpl implements NetworkClient {
 
     final private CloseableHttpClient client;
     final private HttpHost host;
+    final private Semaphore clientLock;
 
     public NetworkClientImpl(final ConnectionDetails connectionDetails) {
         this(connectionDetails, createDefaultClient(connectionDetails));
@@ -100,6 +102,7 @@ public NetworkClientImpl(final ConnectionDetails connectionDetails, final Closea
             this.connectionDetails = connectionDetails;
             this.host = buildHost(connectionDetails);
             this.client = client;
+            this.clientLock = new Semaphore(MAX_CONNECTION_PER_ROUTE);
         } catch (final MalformedURLException e) {
             throw new RuntimeException(e);
         }
@@ -236,11 +239,16 @@ public CloseableHttpResponse execute() throws IOException {
             }
 
             final HttpRequest httpRequest = this.buildHttpRequest();
-            this.addHeaders(httpRequest);
+            clientLock.acquireUninterruptibly();
             try {
-                return client.execute(this.host, httpRequest, this.getContext());
-            } catch (final javax.net.ssl.SSLHandshakeException e) {
-                throw new InvalidCertificate("The certificate on black pearl is not a strong certificate and the request is being aborted.  Configure with the insecure option to perform the request.", e);
+                this.addHeaders(httpRequest);
+                try {
+                    return client.execute(this.host, httpRequest, this.getContext());
+                } catch (final javax.net.ssl.SSLHandshakeException e) {
+                    throw new InvalidCertificate("The certificate on black pearl is not a strong certificate and the request is being aborted.  Configure with the insecure option to perform the request.", e);
+                }
+            } finally {
+                clientLock.release();
             }
         }