public String getMetricsCacheManagerHeapPercent() {
    String percent = getProperty(TIMELINE_METRICS_CACHE_HEAP_PERCENT);
    return percent.trim().endsWith("%") ? percent.trim() : percent.trim() + "%";
  }
Percentage of total heap allocated to metrics cache, default is 15%.
Default heap setting for the server is 2 GB so max allocated heap size
for this cache is 300 MB.
ambari-server/src/main/java/org/apache/ambari/server/configuration/Configuration.java