APIClient: Adding cache support to the APIClient

Some operations are not changing frequently and are called multiple time
during a nodetool execution.

This patch adds the ability to cache results for a define period of time
(typically it will be for a few seconds) so that during the same
nodetool command call, the results will be retrieved from the cache.

It is currently only implemented for string values, other commands will
be added when needed.

Signed-off-by: Amnon Heiman <amnon@cloudius-systems.com>

src/main/java/com/cloudius/urchin/api/APIClient.java

@@ -22,6 +22,7 @@ import javax.json.JsonReaderFactory;
 import javax.json.JsonString;
 import javax.management.openmbean.TabularData;
 import javax.management.openmbean.TabularDataSupport;
+import javax.ws.rs.core.MediaType;
 import javax.ws.rs.core.MultivaluedMap;
 import javax.ws.rs.core.UriBuilder;
 
@@ -33,9 +34,29 @@ import com.sun.jersey.api.client.config.ClientConfig;
 import com.sun.jersey.api.client.config.DefaultClientConfig;
 import com.yammer.metrics.core.HistogramValues;
 
-import javax.ws.rs.core.MediaType;
-
 public class APIClient {
+    Map<String, CacheEntry> cache = new HashMap<String, CacheEntry>();
+    String getCacheKey(String key, MultivaluedMap<String, String> param, long duration) {
+        if (duration <= 0) {
+            return null;
+        }
+        if (param != null) {
+            StringBuilder sb = new StringBuilder(key);
+            sb.append("?");
+            for (String k : param.keySet()) {
+                sb.append(k).append('=').append(param.get(k)).append('&');
+            }
+            return sb.toString();
+        }
+        return key;
+    }
+    String getFromCache(String key, long duration) {
+        if (key == null) {
+            return null;
+        }
+        CacheEntry value = cache.get(key);
+        return (value!= null && value.valid(duration))? value.value : null;
+    }
     JsonReaderFactory factory = Json.createReaderFactory(null);
     private static final java.util.logging.Logger logger = java.util.logging.Logger
             .getLogger(APIClient.class.getName());
@@ -105,15 +126,34 @@ public class APIClient {
     }
 
     public String getRawValue(String string,
-            MultivaluedMap<String, String> queryParams) {
-        if (!string.equals("")) {
-            return get(string, queryParams).get(String.class);
+            MultivaluedMap<String, String> queryParams, long duration) {
+        if (string.equals("")) {
+            return "";
         }
-        return "";
+        String key = getCacheKey(string, queryParams, duration);
+        String res = getFromCache(key, duration);
+        if (res != null) {
+            return res;
+        }
+
+        res = get(string, queryParams).get(String.class);
+        if (duration > 0) {
+            cache.put(key, new CacheEntry(res));
+        }
+        return res;
+    }
+
+    public String getRawValue(String string,
+            MultivaluedMap<String, String> queryParams) {
+        return getRawValue(string, queryParams, 0);
+    }
+
+    public String getRawValue(String string, long duration) {
+        return getRawValue(string, null, duration);
     }
 
     public String getRawValue(String string) {
-        return getRawValue(string, null);
+        return getRawValue(string, null, 0);
     }
 
     public String getStringValue(String string, MultivaluedMap<String, String> queryParams) {
@@ -121,6 +161,11 @@ public class APIClient {
                 queryParams).replaceAll("^\"|\"$", "");
     }
 
+    public String getStringValue(String string, MultivaluedMap<String, String> queryParams, long duration) {
+        return getRawValue(string,
+                queryParams, duration).replaceAll("^\"|\"$", "");
+    }
+
     public String getStringValue(String string) {
         return getStringValue(string, null);
     }