public int getMetricsServiceCacheTimeout() {
    return Integer.parseInt(getProperty(METRIC_RETRIEVAL_SERVICE_CACHE_TIMEOUT));
  }
Gets the number of minutes that data cached by the
{@link MetricsRetrievalService} is kept. The longer this value is, the
older the data will be when a user first logs in. After that first login,
data will be updated by the {@link MetricsRetrievalService} as long as
incoming REST requests are made.
<p/>
It is recommended that this value be longer rather than shorter since the
performance benefit of the cache greatly outweighs the data loaded after
first login.

@return the number of minutes, defaulting to 30 if not specified.
ambari-server/src/main/java/org/apache/ambari/server/configuration/Configuration.java