Zakaria
110 lines
5.6 KiB
Markdown
110 lines
5.6 KiB
Markdown
# Elastic Load Balancing (Classic, v1)
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**Protocol:** Query (XML) — `POST http://localhost:4566/` with `Action=` and `Version=2012-06-01`
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Classic Elastic Load Balancing is the 2012-06-01 API behind `aws elb` and Terraform's `aws_elb`
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resource. It is a **different API** from [ELB v2](elb.md) (ALB/NLB, 2015-12-01), even though both
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are served from the same endpoint host and signed with the same `elasticloadbalancing` credential
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scope.
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## How Floci tells the two apart
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Every Query-protocol request carries the API version it is speaking as the `Version` form
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parameter, and that is what Floci routes on:
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| `Version` | Answered by |
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|---|---|
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| `2012-06-01` | Classic (this page) |
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| `2015-12-01` | [ELB v2](elb.md) |
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Responses are emitted in the matching namespace —
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`http://elasticloadbalancing.amazonaws.com/doc/2012-06-01/` for Classic. A Classic
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`CreateLoadBalancer` returns `DNSName` and nothing else; Classic load balancers have no ARN and
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are addressed by `LoadBalancerName` for their whole life.
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If a hand-rolled client omits `Version`, Floci falls back to the request shape: an action unique
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to one API decides, and for the action names both APIs define (`CreateLoadBalancer`,
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`DescribeLoadBalancers`, `AddTags`, …) the presence of `LoadBalancerName` or `LoadBalancerNames`
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selects Classic. With neither present the request goes to ELB v2.
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## Supported Actions
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| Action | Description |
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|--------|-------------|
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| CreateLoadBalancer | Creates a Classic load balancer with listeners, subnets or AZs, security groups, scheme, and tags. Returns `DNSName`. |
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| DescribeLoadBalancers | Returns `LoadBalancerDescription` records, optionally filtered by `LoadBalancerNames`. |
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| DeleteLoadBalancer | Deletes a load balancer; deleting one that does not exist succeeds. |
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| CreateLoadBalancerListeners | Adds listeners. A conflicting listener on a port already in use is rejected with `DuplicateListener`. |
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| DeleteLoadBalancerListeners | Removes listeners by `LoadBalancerPorts`. |
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| ConfigureHealthCheck | Replaces the health check and re-arms Floci's checker. |
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| RegisterInstancesWithLoadBalancer | Registers EC2 instances and returns the full registered set. |
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| DeregisterInstancesFromLoadBalancer | Removes instances and returns the remaining set. |
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| DescribeInstanceHealth | Returns `InstanceStates` for the named instances, or for every registered instance. |
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| ModifyLoadBalancerAttributes | Updates cross-zone, access log, connection draining, connection settings, and additional attributes. Unsent members keep their current value. |
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| DescribeLoadBalancerAttributes | Returns the full attribute structure. |
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| ApplySecurityGroupsToLoadBalancer | Replaces the security groups. |
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| AttachLoadBalancerToSubnets / DetachLoadBalancerFromSubnets | Adds or removes subnets and recomputes the availability zones and VPC. |
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| EnableAvailabilityZonesForLoadBalancer / DisableAvailabilityZonesForLoadBalancer | Adds or removes availability zones. |
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| AddTags / RemoveTags / DescribeTags | Tagging, keyed by `LoadBalancerNames`. |
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| DescribeAccountLimits | Returns standard default Classic limits. |
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## Not implemented
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These Classic operations return `UnsupportedOperation` in the 2012-06-01 namespace rather than a
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fabricated result:
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`CreateAppCookieStickinessPolicy`, `CreateLBCookieStickinessPolicy`, `CreateLoadBalancerPolicy`,
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`DeleteLoadBalancerPolicy`, `DescribeLoadBalancerPolicies`, `DescribeLoadBalancerPolicyTypes`,
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`SetLoadBalancerPoliciesForBackendServer`, `SetLoadBalancerPoliciesOfListener`,
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`SetLoadBalancerListenerSSLCertificate`.
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Floci also does not run a Classic **data plane**: listener ports are recorded but no socket is
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opened and no traffic is forwarded. Only the control plane and health checking are emulated.
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## Behavior Notes
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- Load balancer state is persisted through Floci storage and health checking is restarted on
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startup.
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- A new load balancer gets AWS's default health check (`TCP:80`, interval 30, timeout 5,
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unhealthy 2, healthy 10) and AWS's default attributes (cross-zone off, access log off,
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connection draining off with a 300 second timeout, 60 second idle timeout).
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- Health checks probe the instance's reachable local address. `HTTP:`/`HTTPS:` targets are probed
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with an HTTP request to the target's path and any 2xx/3xx is healthy; `TCP:`/`SSL:` targets are
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probed by connecting. TLS is not terminated — an `HTTPS:` target is probed over plain HTTP on
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the same port.
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- Between registration and the first successful check an instance reports `OutOfService` with
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reason code `ELB`, as it does on AWS.
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- An Auto Scaling group that names Classic load balancers in `LoadBalancerNames` has its instances
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registered and deregistered automatically, so a Terraform `min_elb_capacity` wait can be
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satisfied.
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## Configuration
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| Environment variable | Default | Description |
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|---|---|---|
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| `FLOCI_SERVICES_ELB_ENABLED` | `true` | Enable or disable the Classic ELB service |
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| `FLOCI_SERVICES_ELB_MOCK` | `false` | When `true`, never probe: a registered instance is `InService` immediately |
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## Examples
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```bash
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export AWS_ENDPOINT_URL=http://localhost:4566
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aws elb create-load-balancer \
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--load-balancer-name my-classic-elb \
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--listeners "Protocol=HTTP,LoadBalancerPort=80,InstanceProtocol=HTTP,InstancePort=8080" \
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--subnets subnet-12345678
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aws elb configure-health-check \
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--load-balancer-name my-classic-elb \
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--health-check Target=HTTP:8080/,Interval=10,Timeout=3,UnhealthyThreshold=2,HealthyThreshold=2
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aws elb register-instances-with-load-balancer \
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--load-balancer-name my-classic-elb \
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--instances i-1234567890abcdef0
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aws elb describe-instance-health --load-balancer-name my-classic-elb
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aws elb delete-load-balancer --load-balancer-name my-classic-elb
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```
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