Read rate limiter delay from response headers. (#34)

* Read rate limiter delay from response headers.

* Renamed rate limiting delay header
Added @SInCE to javadoc

Author: connelly38

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

@@ -25,6 +25,7 @@
 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;
+import static oracle.nosql.driver.util.HttpConstants.X_RATELIMIT_DELAY;
 import static oracle.nosql.driver.util.LogUtil.isLoggable;
 import static oracle.nosql.driver.util.LogUtil.logFine;
 import static oracle.nosql.driver.util.LogUtil.logInfo;
@@ -644,6 +645,8 @@ public Result execute(Request kvRequest) {
                                        responseHandler.getHeaders(),
                                        wireContent,
                                        kvRequest);
+                rateDelayedMs += getRateDelayedFromHeader(
+                                       responseHandler.getHeaders());
                 int resSize = wireContent.readerIndex();
                 networkLatency = System.currentTimeMillis() - networkLatency;
 
@@ -1620,4 +1623,25 @@ private SerializerFactory chooseFactory(Request rq) {
     private String getSerdeVersion(Request rq) {
         return chooseFactory(rq).getSerdeVersionString();
     }
+
+    /*
+     * If the response has a header indicating the amount of time the
+     * server side delayed the request due to rate limiting, return that
+     * value (in milliseconds).
+     */
+    private int getRateDelayedFromHeader(HttpHeaders headers) {
+        if (headers == null) {
+            return 0;
+        }
+        String v = headers.get(X_RATELIMIT_DELAY);
+        if (v == null || v.isEmpty()) {
+            return 0;
+        }
+        try {
+            return Integer.parseInt(v);
+        } catch (Exception e) {
+        }
+
+        return 0;
+    }
 }

driver/src/main/java/oracle/nosql/driver/ops/Request.java

@@ -423,6 +423,16 @@ public void setRateLimitDelayedMs(int rateLimitDelayedMs) {
         this.rateLimitDelayedMs = rateLimitDelayedMs;
     }
 
+    /**
+     * Get the time the operation was delayed due to rate limiting.
+     * Cloud only.
+     * If rate limiting is in place, this value will represent the number of
+     * milliseconds that the operation was delayed due to rate limiting.
+     * If the value is zero, rate limiting did not apply or the operation
+     * did not need to wait for rate limiting.
+     * @return delay time in milliseconds
+     * @since 5.2.25
+     */
     public int getRateLimitDelayedMs() {
         return rateLimitDelayedMs;
     }

driver/src/main/java/oracle/nosql/driver/ops/Result.java

@@ -79,6 +79,7 @@ public int getWriteUnitsInternal() {
      * If the value is zero, rate limiting did not apply or the operation
      * did not need to wait for rate limiting.
      * @return delay time in milliseconds
+     * @since 5.2.25
      */
     public int getRateLimitDelayedMs() {
         return rateLimitDelayedMs;

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

@@ -128,6 +128,12 @@ public class HttpConstants {
 
     public static final String userAgent = makeUserAgent();
 
+    /*
+     * If present, the amount of time the request was delayed due to
+     * rate limiting (in milliseconds).
+     */
+    public static final String X_RATELIMIT_DELAY = "X-Nosql-RL-Delay-Ms";
+
     /*
      * Path Components
      */