public static List getServiceUrlsFromDNS()

in eureka-client/src/main/java/com/netflix/discovery/endpoint/EndpointUtils.java [95:180]
78 lines of code
18 McCabe index (conditional complexity)

    public static List<String> getServiceUrlsFromDNS(EurekaClientConfig clientConfig, String instanceZone, boolean preferSameZone, ServiceUrlRandomizer randomizer) {
        String region = getRegion(clientConfig);
        // Get zone-specific DNS names for the given region so that we can get a
        // list of available zones
        Map<String, List<String>> zoneDnsNamesMap = getZoneBasedDiscoveryUrlsFromRegion(clientConfig, region);
        Set<String> availableZones = zoneDnsNamesMap.keySet();
        List<String> zones = new ArrayList<>(availableZones);
        if (zones.isEmpty()) {
            throw new RuntimeException("No available zones configured for the instanceZone " + instanceZone);
        }
        int zoneIndex = 0;
        boolean zoneFound = false;
        for (String zone : zones) {
            logger.debug("Checking if the instance zone {} is the same as the zone from DNS {}", instanceZone, zone);
            if (preferSameZone) {
                if (instanceZone.equalsIgnoreCase(zone)) {
                    zoneFound = true;
                }
            } else {
                if (!instanceZone.equalsIgnoreCase(zone)) {
                    zoneFound = true;
                }
            }
            if (zoneFound) {
                logger.debug("The zone index from the list {} that matches the instance zone {} is {}",
                        zones, instanceZone, zoneIndex);
                break;
            }
            zoneIndex++;
        }
        if (zoneIndex >= zones.size()) {
            if (logger.isWarnEnabled()) {
                logger.warn("No match for the zone {} in the list of available zones {}",
                        instanceZone, zones.toArray());
            }
        } else {
            // Rearrange the zones with the instance zone first
            for (int i = 0; i < zoneIndex; i++) {
                String zone = zones.remove(0);
                zones.add(zone);
            }
        }

        // Now get the eureka urls for all the zones in the order and return it
        List<String> serviceUrls = new ArrayList<>();
        for (String zone : zones) {
            for (String zoneCname : zoneDnsNamesMap.get(zone)) {
                List<String> ec2Urls = new ArrayList<>(getEC2DiscoveryUrlsFromZone(zoneCname, DiscoveryUrlType.CNAME));
                // Rearrange the list to distribute the load in case of multiple servers
                if (ec2Urls.size() > 1) {
                    randomizer.randomize(ec2Urls);
                }
                for (String ec2Url : ec2Urls) {
                    StringBuilder sb = new StringBuilder()
                            .append("http://")
                            .append(ec2Url)
                            .append(":")
                            .append(clientConfig.getEurekaServerPort());
                    if (clientConfig.getEurekaServerURLContext() != null) {
                        if (!clientConfig.getEurekaServerURLContext().startsWith("/")) {
                            sb.append("/");
                        }
                        sb.append(clientConfig.getEurekaServerURLContext());
                        if (!clientConfig.getEurekaServerURLContext().endsWith("/")) {
                            sb.append("/");
                        }
                    } else {
                        sb.append("/");
                    }
                    String serviceUrl = sb.toString();
                    logger.debug("The EC2 url is {}", serviceUrl);
                    serviceUrls.add(serviceUrl);
                }
            }
        }
        // Rearrange the fail over server list to distribute the load
        String primaryServiceUrl = serviceUrls.remove(0);
        randomizer.randomize(serviceUrls);
        serviceUrls.add(0, primaryServiceUrl);

        if (logger.isDebugEnabled()) {
            logger.debug("This client will talk to the following serviceUrls in order : {} ",
                    (Object) serviceUrls.toArray());
        }
        return serviceUrls;
    }