private static Location getLocationFromServer(ServerStats server) {
String availabilityZone = null;
if (server.getServerInstance() instanceof EurekaServerInstance) {
EurekaServerInstance instance = (EurekaServerInstance) server.getServerInstance();
EuerkaServiceDataCenterInfo dataCenterInfo = instance.getInstanceInfo().getDataCenterInfo();
if (dataCenterInfo instanceof EurekaServiceAmazonDataCenterInfo) {
EurekaServiceAmazonDataCenterInfo amazonInfo =
(EurekaServiceAmazonDataCenterInfo) dataCenterInfo;
availabilityZone = amazonInfo.getMetadata().get("availability-zone");
}
}
if (availabilityZone == null) {
availabilityZone = DEFAULT;
}
return new Location(availabilityZone);
}
/**
* @param availableServerStats the server instances to choose from
* @return the nearest, less loaded server instance
* @see {@link LoadBalancer#choose(java.util.List)}
*/
@Override
public ServerStats choose(List<ServerStats> availableServerStats) {
// cache properties to speed up loop
double maxRequestsPerSecond = propMaxRequestsPerSecond.get();
double escapeAreaThreshold = propEscapeAreaThreshold.get();
double escapeRegionThreshold = propEscapeRegionThreshold.get();
double escapeAvailabilityThreshold = propEscapeAvailabilityThreshold.get();
// find the best available server
MetaData max = null;
for (ServerStats stat : availableServerStats) {
ServerStats s = (ServerStats) stat;
ServerInstance instance = s.getServerInstance();
MetaData meta = new MetaData();
meta.location = locations.getUnchecked(s);
meta.server = s;
meta.load = s.getSentMessagesPerSecond() / maxRequestsPerSecond;
meta.sessionCount = s.getOpenSessionsCount();
meta.locationBits = 0;
if (myLocation.getAvailabilityZone().equals(meta.location.getAvailabilityZone())) {
// same availability zone
meta.locationBits = 7;
} else if (myLocation.getRegion().equals(meta.location.getRegion())) {
// same region
meta.locationBits = 3;
} else if (myLocation.getArea().equals(meta.location.getArea())) {
// same area
meta.locationBits = 1;
}
// keep the best server instance
if (max == null) {
max = meta;
} else if (meta.isBetterThan(
max, escapeAreaThreshold, escapeRegionThreshold, escapeAvailabilityThreshold)) {
max = meta;
}
}
if (max != null) {
if (metricRegistry != null) {
Counter counter = availabilityZoneToCounter.get(max.location.getAvailabilityZone());
if (counter == null) {
counter =
metricRegistry.counter(
name(serviceName, "az-requests", max.location.getAvailabilityZone()));
Counter prevCount =
availabilityZoneToCounter.putIfAbsent(max.location.getAvailabilityZone(), counter);
if (prevCount != null) {
// another thread snuck in their counter during a race condition so use it instead.
counter = prevCount;
}
}
counter.inc();
}
return max.server;
} else {
return null;
}
}