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Elastic Load Balancing (Classic, v1)

Protocol: Query (XML), form POST or SigV4-signed GET at http://localhost:4566/ with Action= and Version=2012-06-01.

Classic Elastic Load Balancing is the 2012-06-01 API behind aws elb and Terraform's aws_elb resource. It is a different API from ELB v2 (ALB/NLB, 2015-12-01), even though both are served from the same endpoint host and signed with the same elasticloadbalancing credential scope.

How Floci tells the two apart

Every Query-protocol request carries the API version it is speaking as the Version request parameter, and that is what Floci routes on:

Version Answered by
2012-06-01 Classic (this page)
2015-12-01 ELB v2

Responses are emitted in the matching namespace — http://elasticloadbalancing.amazonaws.com/doc/2012-06-01/ for Classic. A Classic CreateLoadBalancer returns DNSName and nothing else; Classic load balancers have no ARN and are addressed by LoadBalancerName for their whole life.

If a hand-rolled client omits Version, Floci falls back to the request shape: an action unique to one API decides, and for the action names both APIs define (CreateLoadBalancer, DescribeLoadBalancers, AddTags, …) the presence of LoadBalancerName or LoadBalancerNames selects Classic. With neither present the request goes to ELB v2.

Supported Actions

Action Description
CreateLoadBalancer Creates a Classic load balancer with listeners, subnets or AZs, security groups, scheme, and tags. Returns DNSName.
DescribeLoadBalancers Returns LoadBalancerDescription records, optionally filtered by LoadBalancerNames.
DeleteLoadBalancer Deletes a load balancer; deleting one that does not exist succeeds.
CreateLoadBalancerListeners Adds listeners. A conflicting listener on a port already in use is rejected with DuplicateListener.
DeleteLoadBalancerListeners Removes listeners by LoadBalancerPorts.
ConfigureHealthCheck Replaces the health check and re-arms Floci's checker.
RegisterInstancesWithLoadBalancer Registers EC2 instances and returns the full registered set.
DeregisterInstancesFromLoadBalancer Removes instances and returns the remaining set.
DescribeInstanceHealth Returns InstanceStates for the named instances, or for every registered instance.
ModifyLoadBalancerAttributes Updates cross-zone, access log, connection draining, connection settings, and additional attributes. Unsent members keep their current value.
DescribeLoadBalancerAttributes Returns the full attribute structure.
ApplySecurityGroupsToLoadBalancer Replaces the security groups.
AttachLoadBalancerToSubnets / DetachLoadBalancerFromSubnets Adds or removes subnets and recomputes the availability zones and VPC.
EnableAvailabilityZonesForLoadBalancer / DisableAvailabilityZonesForLoadBalancer Adds or removes availability zones.
AddTags / RemoveTags / DescribeTags Tagging, keyed by LoadBalancerNames.
DescribeAccountLimits Returns standard default Classic limits.

Not implemented

These Classic operations return UnsupportedOperation in the 2012-06-01 namespace rather than a fabricated result:

CreateAppCookieStickinessPolicy, CreateLBCookieStickinessPolicy, CreateLoadBalancerPolicy, DeleteLoadBalancerPolicy, DescribeLoadBalancerPolicies, DescribeLoadBalancerPolicyTypes, SetLoadBalancerPoliciesForBackendServer, SetLoadBalancerPoliciesOfListener, SetLoadBalancerListenerSSLCertificate.

Floci also does not run a Classic data plane: listener ports are recorded but no socket is opened and no traffic is forwarded. Only the control plane and health checking are emulated.

Behavior Notes

  • An omitted InstanceProtocol defaults to HTTP for HTTP/HTTPS listeners and TCP for TCP/SSL listeners. Explicit backend protocols remain unchanged. Creation, listener additions, persisted readback and identical listener retries use the same effective value.
  • Load balancer state is persisted through Floci storage, and on startup health checking is restarted for the load balancers of every account.
  • A new load balancer gets AWS's default health check (TCP:80, interval 30, timeout 5, unhealthy 2, healthy 10) and AWS's default attributes (cross-zone off, access log off, connection draining off with a 300 second timeout, 60 second idle timeout).
  • Health checks probe the instance's reachable local address. HTTP:/HTTPS: targets are probed with an HTTP request to the target's path and any 2xx/3xx is healthy; TCP:/SSL: targets are probed by connecting. TLS is not terminated — an HTTPS: target is probed over plain HTTP on the same port.
  • Between registration and the first successful check an instance reports OutOfService with reason code ELB, as it does on AWS.
  • Health is tracked per account, so two accounts can each have a load balancer with the same name without either one changing the instance health the other reports.
  • An Auto Scaling group that names Classic load balancers in LoadBalancerNames has its instances registered and deregistered automatically, so a Terraform min_elb_capacity wait can be satisfied.
  • A listener's SSLCertificateId must name an existing certificate: an IAM server certificate ARN or an ACM certificate ARN. CreateLoadBalancer and CreateLoadBalancerListeners reject a missing one with CertificateNotFound, and a blank one on an HTTPS or SSL listener; an HTTP or TCP listener may carry a blank one, as Terraform sends. A certificate a listener references cannot be deleted until the listener is removed: DeleteServerCertificate returns DeleteConflict, and ACM's DeleteCertificate returns ResourceInUseException and lists the load balancer under InUseBy.

Configuration

Environment variable Default Description
FLOCI_SERVICES_ELB_ENABLED true Enable or disable the Classic ELB service
FLOCI_SERVICES_ELB_MOCK false When true, never probe: a registered instance is InService immediately

Examples

export AWS_ENDPOINT_URL=http://localhost:4566

aws elb create-load-balancer \
  --load-balancer-name my-classic-elb \
  --listeners "Protocol=HTTP,LoadBalancerPort=80,InstanceProtocol=HTTP,InstancePort=8080" \
  --subnets subnet-12345678

aws elb configure-health-check \
  --load-balancer-name my-classic-elb \
  --health-check Target=HTTP:8080/,Interval=10,Timeout=3,UnhealthyThreshold=2,HealthyThreshold=2

aws elb register-instances-with-load-balancer \
  --load-balancer-name my-classic-elb \
  --instances i-1234567890abcdef0

aws elb describe-instance-health --load-balancer-name my-classic-elb

aws elb delete-load-balancer --load-balancer-name my-classic-elb