Example usage for com.amazonaws.services.elasticloadbalancing.model Policies getLBCookieStickinessPolicies

List of usage examples for com.amazonaws.services.elasticloadbalancing.model Policies getLBCookieStickinessPolicies

Introduction

In this page you can find the example usage for com.amazonaws.services.elasticloadbalancing.model Policies getLBCookieStickinessPolicies.

Prototype


public java.util.List<LBCookieStickinessPolicy> getLBCookieStickinessPolicies() 

Source Link

Document

The stickiness policies created using CreateLBCookieStickinessPolicy.

Usage

From source file:fr.xebia.demo.amazon.aws.PetclinicInfrastructureEnforcer.java

License:Apache License

/**
 * //from   w w  w .j  a  v a 2  s. c o  m
 * @param healthCheckUri
 *            start with slash. E.g. "/myapp/healthcheck.jsp
 * @param applicationIdentifier
 *            used to name the load balancer and to filter the instances on
 *            their "Role" tag.
 * @return created load balancer description
 */
@Nonnull
public LoadBalancerDescription createOrUpdateElasticLoadBalancer(@Nonnull String healthCheckUri,
        @Nonnull String applicationIdentifier) {
    LOGGER.info("ENFORCE LOAD BALANCER");

    DescribeInstancesRequest describeInstancesWithRoleRequest = new DescribeInstancesRequest(). //
            withFilters(new Filter("tag:Role", Arrays.asList(applicationIdentifier)));
    DescribeInstancesResult describeInstancesResult = ec2.describeInstances(describeInstancesWithRoleRequest);

    Iterable<Instance> expectedEc2Instances = toEc2Instances(describeInstancesResult.getReservations());

    Set<String> expectedAvailabilityZones = Sets
            .newHashSet(Iterables.transform(expectedEc2Instances, EC2_INSTANCE_TO_AVAILABILITY_ZONE));
    Listener expectedListener = new Listener("HTTP", 80, 8080);

    String loadBalancerName = applicationIdentifier;

    LoadBalancerDescription actualLoadBalancerDescription;
    try {
        DescribeLoadBalancersResult describeLoadBalancers = elb
                .describeLoadBalancers(new DescribeLoadBalancersRequest(Arrays.asList(loadBalancerName)));
        if (describeLoadBalancers.getLoadBalancerDescriptions().isEmpty()) {
            // unexpected, this should have been a
            // LoadBalancerNotFoundException
            actualLoadBalancerDescription = null;
        } else {
            // re-query to get updated config

            actualLoadBalancerDescription = Iterables
                    .getFirst(describeLoadBalancers.getLoadBalancerDescriptions(), null);
        }
    } catch (LoadBalancerNotFoundException e) {
        actualLoadBalancerDescription = null;
    }

    Set<String> actualAvailabilityZones;
    Set<String> actualInstanceIds;
    Policies actualPolicies;
    HealthCheck actualHealthCheck;
    ListenerDescription actualListenerDescription = null;
    if (actualLoadBalancerDescription == null) {
        CreateLoadBalancerRequest createLoadBalancerRequest = new CreateLoadBalancerRequest() //
                .withLoadBalancerName(loadBalancerName) //
                .withAvailabilityZones(expectedAvailabilityZones) //
                .withListeners(expectedListener);
        elb.createLoadBalancer(createLoadBalancerRequest);

        actualListenerDescription = new ListenerDescription().withListener(expectedListener);
        actualAvailabilityZones = expectedAvailabilityZones;
        actualInstanceIds = Collections.emptySet();
        actualHealthCheck = new HealthCheck();
        actualPolicies = new Policies();
    } else {
        // check listeners
        List<ListenerDescription> actualListenerDescriptions = actualLoadBalancerDescription
                .getListenerDescriptions();
        boolean loadBalancerMustBeRecreated;

        if (actualListenerDescriptions.size() == 1) {
            actualListenerDescription = Iterables.getOnlyElement(actualListenerDescriptions);
            Listener actualListener = actualListenerDescription.getListener();
            if (ObjectUtils.equals(expectedListener.getProtocol(), actualListener.getProtocol()) && //
                    ObjectUtils.equals(expectedListener.getLoadBalancerPort(),
                            actualListener.getLoadBalancerPort())
                    && //
                    ObjectUtils.equals(expectedListener.getInstancePort(), actualListener.getInstancePort())) {
                loadBalancerMustBeRecreated = false;
            } else {
                loadBalancerMustBeRecreated = true;
            }
        } else {
            loadBalancerMustBeRecreated = true;
        }

        if (loadBalancerMustBeRecreated) {
            LOGGER.info("Recreate miss configured load balancer actualListeners:{}, expectedListener:{}",
                    actualListenerDescriptions, expectedListener);
            elb.deleteLoadBalancer(new DeleteLoadBalancerRequest(loadBalancerName));
            return createOrUpdateElasticLoadBalancer(healthCheckUri, applicationIdentifier);
        }

        //
        actualAvailabilityZones = Sets.newHashSet(actualLoadBalancerDescription.getAvailabilityZones());
        actualInstanceIds = Sets.newHashSet(
                Iterables.transform(actualLoadBalancerDescription.getInstances(), ELB_INSTANCE_TO_INSTANCE_ID));

        actualHealthCheck = actualLoadBalancerDescription.getHealthCheck();

        actualPolicies = actualLoadBalancerDescription.getPolicies();
    }

    // HEALTH CHECK
    if (!healthCheckUri.startsWith("/")) {
        healthCheckUri = "/" + healthCheckUri;
    }

    HealthCheck expectedHealthCheck = new HealthCheck() //
            .withTarget("HTTP:8080" + healthCheckUri) //
            .withHealthyThreshold(2) //
            .withUnhealthyThreshold(2) //
            .withInterval(30) //
            .withTimeout(2);
    if (Objects.equal(expectedHealthCheck.getTarget(), actualHealthCheck.getTarget()) && //
            Objects.equal(expectedHealthCheck.getHealthyThreshold(), actualHealthCheck.getHealthyThreshold()) && //
            Objects.equal(expectedHealthCheck.getInterval(), actualHealthCheck.getInterval()) && //
            Objects.equal(expectedHealthCheck.getTimeout(), actualHealthCheck.getTimeout()) && //
            Objects.equal(expectedHealthCheck.getUnhealthyThreshold(),
                    actualHealthCheck.getHealthyThreshold())) {
        // health check is ok
    } else {
        LOGGER.info("Set Healthcheck: {}", expectedHealthCheck);
        elb.configureHealthCheck(new ConfigureHealthCheckRequest(loadBalancerName, expectedHealthCheck));
    }

    // AVAILABILITY ZONES
    // enable
    Iterable<String> availabilityZonesToEnable = Sets.difference(expectedAvailabilityZones,
            actualAvailabilityZones);
    LOGGER.info("Enable availability zones: {}", availabilityZonesToEnable);
    if (!Iterables.isEmpty(availabilityZonesToEnable)) {
        elb.enableAvailabilityZonesForLoadBalancer(new EnableAvailabilityZonesForLoadBalancerRequest(
                loadBalancerName, Lists.newArrayList(availabilityZonesToEnable)));
    }

    // disable
    Iterable<String> availabilityZonesToDisable = Sets.difference(actualAvailabilityZones,
            expectedAvailabilityZones);
    LOGGER.info("Disable availability zones: {}", availabilityZonesToDisable);
    if (!Iterables.isEmpty(availabilityZonesToDisable)) {
        elb.disableAvailabilityZonesForLoadBalancer(new DisableAvailabilityZonesForLoadBalancerRequest(
                loadBalancerName, Lists.newArrayList(availabilityZonesToDisable)));
    }

    // STICKINESS
    List<AppCookieStickinessPolicy> appCookieStickinessPoliciesToDelete = actualPolicies
            .getAppCookieStickinessPolicies();
    LOGGER.info("Delete app cookie stickiness policies: {}", appCookieStickinessPoliciesToDelete);
    for (AppCookieStickinessPolicy appCookieStickinessPolicyToDelete : appCookieStickinessPoliciesToDelete) {
        elb.deleteLoadBalancerPolicy(new DeleteLoadBalancerPolicyRequest(loadBalancerName,
                appCookieStickinessPolicyToDelete.getPolicyName()));
    }

    final LBCookieStickinessPolicy expectedLbCookieStickinessPolicy = new LBCookieStickinessPolicy(
            applicationIdentifier + "-stickiness-policy", null);
    Predicate<LBCookieStickinessPolicy> isExpectedPolicyPredicate = new Predicate<LBCookieStickinessPolicy>() {
        @Override
        public boolean apply(LBCookieStickinessPolicy lbCookieStickinessPolicy) {
            return Objects.equal(expectedLbCookieStickinessPolicy.getPolicyName(),
                    lbCookieStickinessPolicy.getPolicyName()) && //
            Objects.equal(expectedLbCookieStickinessPolicy.getCookieExpirationPeriod(),
                    lbCookieStickinessPolicy.getCookieExpirationPeriod());
        }
    };
    Collection<LBCookieStickinessPolicy> lbCookieStickinessPoliciesToDelete = Collections2
            .filter(actualPolicies.getLBCookieStickinessPolicies(), Predicates.not(isExpectedPolicyPredicate));
    LOGGER.info("Delete lb cookie stickiness policies: {}", lbCookieStickinessPoliciesToDelete);
    for (LBCookieStickinessPolicy lbCookieStickinessPolicy : lbCookieStickinessPoliciesToDelete) {
        elb.deleteLoadBalancerPolicy(new DeleteLoadBalancerPolicyRequest(loadBalancerName,
                lbCookieStickinessPolicy.getPolicyName()));
    }

    Collection<LBCookieStickinessPolicy> matchingLbCookieStyckinessPolicy = Collections2
            .filter(actualPolicies.getLBCookieStickinessPolicies(), isExpectedPolicyPredicate);
    if (matchingLbCookieStyckinessPolicy.isEmpty()) {
        // COOKIE STICKINESS
        CreateLBCookieStickinessPolicyRequest createLbCookieStickinessPolicy = new CreateLBCookieStickinessPolicyRequest() //
                .withLoadBalancerName(loadBalancerName) //
                .withPolicyName(expectedLbCookieStickinessPolicy.getPolicyName())
                //
                .withCookieExpirationPeriod(expectedLbCookieStickinessPolicy.getCookieExpirationPeriod());
        LOGGER.info("Create LBCookieStickinessPolicy: {}", createLbCookieStickinessPolicy);
        elb.createLBCookieStickinessPolicy(createLbCookieStickinessPolicy);

    } else {
        // what ?
    }

    // TODO verify load balancer policy is associated with the listener
    List<String> expectedListenerDescriptionPolicyNames = Lists
            .newArrayList(expectedLbCookieStickinessPolicy.getPolicyName());

    boolean mustOverWriteListenerPolicy = !ObjectUtils.equals(expectedListenerDescriptionPolicyNames,
            actualListenerDescription.getPolicyNames());

    if (mustOverWriteListenerPolicy) {

        SetLoadBalancerPoliciesOfListenerRequest setLoadBalancerPoliciesOfListenerRequest = new SetLoadBalancerPoliciesOfListenerRequest() //
                .withLoadBalancerName(loadBalancerName) //
                .withLoadBalancerPort(expectedListener.getLoadBalancerPort()) //
                .withPolicyNames(expectedLbCookieStickinessPolicy.getPolicyName());
        LOGGER.debug("setLoadBalancerPoliciesOfListener: {}", setLoadBalancerPoliciesOfListenerRequest);
        elb.setLoadBalancerPoliciesOfListener(setLoadBalancerPoliciesOfListenerRequest);
    }

    // INSTANCES
    Set<String> expectedEc2InstanceIds = Sets
            .newHashSet(Iterables.transform(expectedEc2Instances, EC2_INSTANCE_TO_INSTANCE_ID));
    // register
    Iterable<String> instanceIdsToRegister = Sets.difference(expectedEc2InstanceIds, actualInstanceIds);
    LOGGER.info("Register {} instances: {}", applicationIdentifier, instanceIdsToRegister);
    if (!Iterables.isEmpty(instanceIdsToRegister)) {
        elb.registerInstancesWithLoadBalancer(new RegisterInstancesWithLoadBalancerRequest(loadBalancerName,
                Lists.newArrayList(Iterables.transform(instanceIdsToRegister, INSTANCE_ID_TO_ELB_INSTANCE))));
    }

    // deregister
    Iterable<String> instanceIdsToDeregister = Sets.difference(actualInstanceIds, expectedEc2InstanceIds);
    LOGGER.info("Deregister {} instances: {}", applicationIdentifier, instanceIdsToDeregister);
    if (!Iterables.isEmpty(instanceIdsToDeregister)) {
        elb.deregisterInstancesFromLoadBalancer(new DeregisterInstancesFromLoadBalancerRequest(loadBalancerName,
                Lists.newArrayList(Iterables.transform(instanceIdsToDeregister, INSTANCE_ID_TO_ELB_INSTANCE))));
    }

    // QUERY TO GET UP TO DATE LOAD BALANCER DESCRIPTION
    LoadBalancerDescription elasticLoadBalancerDescription = Iterables.getOnlyElement(
            elb.describeLoadBalancers(new DescribeLoadBalancersRequest(Arrays.asList(loadBalancerName)))
                    .getLoadBalancerDescriptions());

    return elasticLoadBalancerDescription;
}

From source file:fr.xebia.workshop.infrastructureascode.AmazonAwsPetclinicInfrastructureEnforcer.java

License:Apache License

/**
 * /*from   www .  j av a2 s .com*/
 * @param healthCheckUri
 *            start with slash. E.g. "/myapp/healthcheck.jsp
 * @param applicationIdentifier
 *            used to name the load balancer and to filter the instances on
 *            their "Role" tag.
 * @return created load balancer description
 */
@Nonnull
public LoadBalancerDescription createOrUpdateElasticLoadBalancer(@Nonnull String healthCheckUri,
        @Nonnull String applicationIdentifier) {
    logger.info("ENFORCE LOAD BALANCER");

    DescribeInstancesRequest describeInstancesWithRoleRequest = new DescribeInstancesRequest(). //
            withFilters(new Filter("tag:Role", Arrays.asList(applicationIdentifier)));
    DescribeInstancesResult describeInstancesResult = ec2.describeInstances(describeInstancesWithRoleRequest);

    Iterable<Instance> expectedEc2Instances = toEc2Instances(describeInstancesResult.getReservations());

    Set<String> expectedAvailabilityZones = Sets
            .newHashSet(Iterables.transform(expectedEc2Instances, EC2_INSTANCE_TO_AVAILABILITY_ZONE));
    Listener expectedListener = new Listener("HTTP", 80, 8080);

    String loadBalancerName = applicationIdentifier;

    LoadBalancerDescription actualLoadBalancerDescription;
    try {
        DescribeLoadBalancersResult describeLoadBalancers = elb
                .describeLoadBalancers(new DescribeLoadBalancersRequest(Arrays.asList(loadBalancerName)));
        if (describeLoadBalancers.getLoadBalancerDescriptions().isEmpty()) {
            // unexpected, this should have been a
            // LoadBalancerNotFoundException
            actualLoadBalancerDescription = null;
        } else {
            // re-query to get updated config

            actualLoadBalancerDescription = Iterables
                    .getFirst(describeLoadBalancers.getLoadBalancerDescriptions(), null);
        }
    } catch (LoadBalancerNotFoundException e) {
        actualLoadBalancerDescription = null;
    }

    Set<String> actualAvailabilityZones;
    Set<String> actualInstanceIds;
    Policies actualPolicies;
    HealthCheck actualHealthCheck;
    ListenerDescription actualListenerDescription = null;
    if (actualLoadBalancerDescription == null) {
        CreateLoadBalancerRequest createLoadBalancerRequest = new CreateLoadBalancerRequest() //
                .withLoadBalancerName(loadBalancerName) //
                .withAvailabilityZones(expectedAvailabilityZones) //
                .withListeners(expectedListener);
        elb.createLoadBalancer(createLoadBalancerRequest);

        actualListenerDescription = new ListenerDescription().withListener(expectedListener);
        actualAvailabilityZones = expectedAvailabilityZones;
        actualInstanceIds = Collections.emptySet();
        actualHealthCheck = new HealthCheck();
        actualPolicies = new Policies();
    } else {
        // check listeners
        List<ListenerDescription> actualListenerDescriptions = actualLoadBalancerDescription
                .getListenerDescriptions();
        boolean loadBalancerMustBeRecreated;

        if (actualListenerDescriptions.size() == 1) {
            actualListenerDescription = Iterables.getOnlyElement(actualListenerDescriptions);
            Listener actualListener = actualListenerDescription.getListener();
            if (ObjectUtils.equals(expectedListener.getProtocol(), actualListener.getProtocol()) && //
                    ObjectUtils.equals(expectedListener.getLoadBalancerPort(),
                            actualListener.getLoadBalancerPort())
                    && //
                    ObjectUtils.equals(expectedListener.getInstancePort(), actualListener.getInstancePort())) {
                loadBalancerMustBeRecreated = false;
            } else {
                loadBalancerMustBeRecreated = true;
            }
        } else {
            loadBalancerMustBeRecreated = true;
        }

        if (loadBalancerMustBeRecreated) {
            logger.info("Recreate miss configured load balancer actualListeners:{}, expectedListener:{}",
                    actualListenerDescriptions, expectedListener);
            elb.deleteLoadBalancer(new DeleteLoadBalancerRequest(loadBalancerName));
            return createOrUpdateElasticLoadBalancer(healthCheckUri, applicationIdentifier);
        }

        //
        actualAvailabilityZones = Sets.newHashSet(actualLoadBalancerDescription.getAvailabilityZones());
        actualInstanceIds = Sets.newHashSet(
                Iterables.transform(actualLoadBalancerDescription.getInstances(), ELB_INSTANCE_TO_INSTANCE_ID));

        actualHealthCheck = actualLoadBalancerDescription.getHealthCheck();

        actualPolicies = actualLoadBalancerDescription.getPolicies();
    }

    // HEALTH CHECK
    if (!healthCheckUri.startsWith("/")) {
        healthCheckUri = "/" + healthCheckUri;
    }

    HealthCheck expectedHealthCheck = new HealthCheck() //
            .withTarget("HTTP:8080" + healthCheckUri) //
            .withHealthyThreshold(2) //
            .withUnhealthyThreshold(2) //
            .withInterval(30) //
            .withTimeout(2);
    if (Objects.equal(expectedHealthCheck.getTarget(), actualHealthCheck.getTarget()) && //
            Objects.equal(expectedHealthCheck.getHealthyThreshold(), actualHealthCheck.getHealthyThreshold()) && //
            Objects.equal(expectedHealthCheck.getInterval(), actualHealthCheck.getInterval()) && //
            Objects.equal(expectedHealthCheck.getTimeout(), actualHealthCheck.getTimeout()) && //
            Objects.equal(expectedHealthCheck.getUnhealthyThreshold(),
                    actualHealthCheck.getHealthyThreshold())) {
        // health check is ok
    } else {
        logger.info("Set Healthcheck: " + expectedHealthCheck);
        elb.configureHealthCheck(new ConfigureHealthCheckRequest(loadBalancerName, expectedHealthCheck));
    }

    // AVAILABILITY ZONES
    // enable
    Iterable<String> availabilityZonesToEnable = Sets.difference(expectedAvailabilityZones,
            actualAvailabilityZones);
    logger.info("Enable availability zones: " + availabilityZonesToEnable);
    if (!Iterables.isEmpty(availabilityZonesToEnable)) {
        elb.enableAvailabilityZonesForLoadBalancer(new EnableAvailabilityZonesForLoadBalancerRequest(
                loadBalancerName, Lists.newArrayList(availabilityZonesToEnable)));
    }

    // disable
    Iterable<String> availabilityZonesToDisable = Sets.difference(actualAvailabilityZones,
            expectedAvailabilityZones);
    logger.info("Disable availability zones: " + availabilityZonesToDisable);
    if (!Iterables.isEmpty(availabilityZonesToDisable)) {
        elb.disableAvailabilityZonesForLoadBalancer(new DisableAvailabilityZonesForLoadBalancerRequest(
                loadBalancerName, Lists.newArrayList(availabilityZonesToDisable)));
    }

    // STICKINESS
    List<AppCookieStickinessPolicy> appCookieStickinessPoliciesToDelete = actualPolicies
            .getAppCookieStickinessPolicies();
    logger.info("Delete app cookie stickiness policies:" + appCookieStickinessPoliciesToDelete);
    for (AppCookieStickinessPolicy appCookieStickinessPolicyToDelete : appCookieStickinessPoliciesToDelete) {
        elb.deleteLoadBalancerPolicy(new DeleteLoadBalancerPolicyRequest(loadBalancerName,
                appCookieStickinessPolicyToDelete.getPolicyName()));
    }

    final LBCookieStickinessPolicy expectedLbCookieStickinessPolicy = new LBCookieStickinessPolicy(
            applicationIdentifier + "-stickiness-policy", null);
    Predicate<LBCookieStickinessPolicy> isExpectedPolicyPredicate = new Predicate<LBCookieStickinessPolicy>() {
        @Override
        public boolean apply(LBCookieStickinessPolicy lbCookieStickinessPolicy) {
            return Objects.equal(expectedLbCookieStickinessPolicy.getPolicyName(),
                    lbCookieStickinessPolicy.getPolicyName()) && //
            Objects.equal(expectedLbCookieStickinessPolicy.getCookieExpirationPeriod(),
                    lbCookieStickinessPolicy.getCookieExpirationPeriod());
        }
    };
    Collection<LBCookieStickinessPolicy> lbCookieStickinessPoliciesToDelete = Collections2
            .filter(actualPolicies.getLBCookieStickinessPolicies(), Predicates.not(isExpectedPolicyPredicate));
    logger.info("Delete lb cookie stickiness policies: " + lbCookieStickinessPoliciesToDelete);
    for (LBCookieStickinessPolicy lbCookieStickinessPolicy : lbCookieStickinessPoliciesToDelete) {
        elb.deleteLoadBalancerPolicy(new DeleteLoadBalancerPolicyRequest(loadBalancerName,
                lbCookieStickinessPolicy.getPolicyName()));
    }

    Collection<LBCookieStickinessPolicy> matchingLbCookieStyckinessPolicy = Collections2
            .filter(actualPolicies.getLBCookieStickinessPolicies(), isExpectedPolicyPredicate);
    if (matchingLbCookieStyckinessPolicy.isEmpty()) {
        // COOKIE STICKINESS
        CreateLBCookieStickinessPolicyRequest createLbCookieStickinessPolicy = new CreateLBCookieStickinessPolicyRequest() //
                .withLoadBalancerName(loadBalancerName) //
                .withPolicyName(expectedLbCookieStickinessPolicy.getPolicyName()) //
                .withCookieExpirationPeriod(expectedLbCookieStickinessPolicy.getCookieExpirationPeriod());
        logger.info("Create LBCookieStickinessPolicy: " + createLbCookieStickinessPolicy);
        elb.createLBCookieStickinessPolicy(createLbCookieStickinessPolicy);

    } else {
        // what ?
    }

    // TODO verify load balancer policy is associated with the listener
    List<String> expectedListenerDescriptionPolicyNames = Lists
            .newArrayList(expectedLbCookieStickinessPolicy.getPolicyName());

    boolean mustOverWriteListenerPolicy = !ObjectUtils.equals(expectedListenerDescriptionPolicyNames,
            actualListenerDescription.getPolicyNames());

    if (mustOverWriteListenerPolicy) {

        SetLoadBalancerPoliciesOfListenerRequest setLoadBalancerPoliciesOfListenerRequest = new SetLoadBalancerPoliciesOfListenerRequest() //
                .withLoadBalancerName(loadBalancerName) //
                .withLoadBalancerPort(expectedListener.getLoadBalancerPort()) //
                .withPolicyNames(expectedLbCookieStickinessPolicy.getPolicyName());
        logger.debug("setLoadBalancerPoliciesOfListener: {}", setLoadBalancerPoliciesOfListenerRequest);
        elb.setLoadBalancerPoliciesOfListener(setLoadBalancerPoliciesOfListenerRequest);
    }

    // INSTANCES
    Set<String> expectedEc2InstanceIds = Sets
            .newHashSet(Iterables.transform(expectedEc2Instances, EC2_INSTANCE_TO_INSTANCE_ID));
    // register
    Iterable<String> instanceIdsToRegister = Sets.difference(expectedEc2InstanceIds, actualInstanceIds);
    logger.info("Register " + applicationIdentifier + " instances: " + instanceIdsToRegister);
    if (!Iterables.isEmpty(instanceIdsToRegister)) {
        elb.registerInstancesWithLoadBalancer(new RegisterInstancesWithLoadBalancerRequest(loadBalancerName,
                Lists.newArrayList(Iterables.transform(instanceIdsToRegister, INSTANCE_ID_TO_ELB_INSTANCE))));
    }

    // deregister
    Iterable<String> instanceIdsToDeregister = Sets.difference(actualInstanceIds, expectedEc2InstanceIds);
    logger.info("Deregister " + applicationIdentifier + " instances: " + instanceIdsToDeregister);
    if (!Iterables.isEmpty(instanceIdsToDeregister)) {
        elb.deregisterInstancesFromLoadBalancer(new DeregisterInstancesFromLoadBalancerRequest(loadBalancerName,
                Lists.newArrayList(Iterables.transform(instanceIdsToDeregister, INSTANCE_ID_TO_ELB_INSTANCE))));
    }

    // QUERY TO GET UP TO DATE LOAD BALANCER DESCRIPTION
    LoadBalancerDescription elasticLoadBalancerDescription = Iterables.getOnlyElement(
            elb.describeLoadBalancers(new DescribeLoadBalancersRequest(Arrays.asList(loadBalancerName)))
                    .getLoadBalancerDescriptions());

    return elasticLoadBalancerDescription;
}