Support session cookies.

If set in response headers, allow setting a cookie named "session"
to enable session persistence in load balancer routing.

Author: connelly38

driver/src/main/java/oracle/nosql/driver/http/Client.java

@@ -24,6 +24,7 @@
 import static oracle.nosql.driver.util.HttpConstants.CONNECTION;
 import static oracle.nosql.driver.util.HttpConstants.CONTENT_LENGTH;
 import static oracle.nosql.driver.util.HttpConstants.CONTENT_TYPE;
+import static oracle.nosql.driver.util.HttpConstants.COOKIE;
 import static oracle.nosql.driver.util.HttpConstants.NOSQL_DATA_PATH;
 import static oracle.nosql.driver.util.HttpConstants.REQUEST_ID_HEADER;
 import static oracle.nosql.driver.util.HttpConstants.USER_AGENT;
@@ -172,6 +173,14 @@ public class Client {
      */
     private StatsControlImpl statsControl;
 
+    /*
+     * for session persistence, if used. This has the
+     * full "session=xxxxx" key/value pair.
+     */
+    private volatile String sessionCookie;
+    /* note this must end with '=' */
+    private final String SESSION_COOKIE_FIELD = "session=";
+
     public Client(Logger logger,
                   NoSQLHandleConfig httpConfig) {
 
@@ -546,6 +555,9 @@ public Result execute(Request kvRequest) {
                 headers.add(HttpHeaderNames.HOST, host)
                     .add(REQUEST_ID_HEADER, requestId)
                     .setInt(CONTENT_LENGTH, contentLength);
+                if (sessionCookie != null) {
+                    headers.add(COOKIE, sessionCookie);
+                }
 
                 authProvider.setRequiredHeaders(authString, kvRequest, headers);
 
@@ -569,6 +581,7 @@ public Result execute(Request kvRequest) {
 
                 ByteBuf wireContent = responseHandler.getContent();
                 Result res = processResponse(responseHandler.getStatus(),
+                                       responseHandler.getHeaders(),
                                        wireContent,
                                        kvRequest);
                 int resSize = wireContent.readerIndex();
@@ -955,6 +968,7 @@ private short writeContent(ByteBuf content, Request kvRequest)
      * @return the programmatic response object
      */
     final Result processResponse(HttpResponseStatus status,
+                                 HttpHeaders headers,
                                  ByteBuf content,
                                  Request kvRequest) {
 
@@ -966,6 +980,8 @@ final Result processResponse(HttpResponseStatus status,
                                             status);
         }
 
+        setSessionCookie(headers);
+
         try (ByteInputStream bis = new NettyByteInputStream(content)) {
             return processOKResponse(bis, kvRequest);
         }
@@ -1037,6 +1053,38 @@ private void processNotOKResponse(HttpResponseStatus status,
                                  ", reason = " + status.reasonPhrase());
     }
 
+    /* set session cookie, if set in response headers */
+    private void setSessionCookie(HttpHeaders headers) {
+        if (headers == null) {
+            return;
+        }
+        /*
+         * NOTE: this code assumes there will always be at most
+         * one Set-Cookie header in the response. If the load balancer
+         * settings change, or the proxy changes to add Set-Cookie
+         * headers, this code may need to be changed to look for
+         * multiple Set-Cookie headers.
+         */
+        String v = headers.get("Set-Cookie");
+        /* note SESSION_COOKIE_FIELD has appended '=' */
+        if (v == null || v.startsWith(SESSION_COOKIE_FIELD) == false) {
+            return;
+        }
+        int semi = v.indexOf(";");
+        if (semi < 0) {
+            setSessionCookieValue(v);
+        } else {
+            setSessionCookieValue(v.substring(0, semi));
+        }
+        if (isLoggable(logger, Level.FINE)) {
+            logTrace(logger, "Set session cookie to \"" + sessionCookie + "\"");
+        }
+    }
+
+    private synchronized void setSessionCookieValue(String pVal) {
+        sessionCookie = pVal;
+    }
+
     /**
      * Return true if table needs limits refresh.
      */

driver/src/main/java/oracle/nosql/driver/util/HttpConstants.java

@@ -63,6 +63,11 @@ public class HttpConstants {
      */
     public static final String CONTENT_LENGTH = "Content-Length";
 
+    /**
+     * The name of the cookie header
+     */
+    public static final String COOKIE = "Cookie";
+
     /**
      * The name of the date header
      */