Load Balancer Concepts
Describes concepts associated with load balancers and their resources.
The following concepts are essential to working with Load Balancer.
- BACKEND SERVER
- An application server responsible for generating content in reply to the incoming TCP or HTTP traffic. You typically identify application servers with a unique combination of overlay (private) IPv4 address and port, for example, 10.10.10.1:8080 and 10.10.10.2:8080.
- BACKEND SET
- A logical entity defined by a list of backend servers, a load balancing policy, and a health check policy. SSL configuration is optional. The backend set determines how the load balancer directs traffic to the collection of backend servers.
- CERTIFICATES
- If you use HTTPS or SSL for your listener, you must associate an SSL server certificate (X.509) with your load balancer. A certificate enables the load balancer to terminate the connection and decrypt incoming requests before passing them to the backend servers.
- health check
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A health check is a test to confirm the availability of backend servers. A health check can be a request or a connection attempt. Based on a time interval you specify, the load balancer applies the health check policy to continuously monitor backend servers. If a server fails the health check, the load balancer takes the server temporarily out of rotation. If the server subsequently passes the health check, the load balancer returns it to the rotation.
You configure your health check policy when you create a backend set. You can configure TCP-level or HTTP-level health checks for your backend servers.
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TCP-level health checks attempt to make a TCP connection with the backend servers and validate the response based on the connection status.
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HTTP-level health checks send requests to the backend servers at a specific URI and validate the response based on the status code or entity data (body) returned.
The service provides application-specific health check capabilities to help you increase availability and reduce your application maintenance window.
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- HEALTH STATUS
- An indicator that reports the general health of your load balancers and their components.
- HOSTNAME
- A virtual server name applied to a listener to enhance request routing.
- LISTENER
- A logical entity that checks for incoming traffic on the load balancer's IP address. You configure a listener's protocol and port number, and the optional SSL settings. To handle TCP, HTTP, and HTTPS traffic, you must configure multiple listeners.
- LOAD BALANCING POLICY
- A load balancing policy tells the load balancer how to distribute incoming traffic to the backend servers. Common load balancer policies include:
- PATH ROUTE SET
- A set of path route rules to route traffic to the correct backend set without using multiple listeners or load balancers.
- REGIONS AND availability domains
- The Load Balancer service manages application traffic across availability domains within a region . A region is a localized geographic area, and an availability domain is one or more data centers located within a region. A region is composed of several availability domains.
- SESSION PERSISTENCE
- A method to direct all requests originating from a single logical client to a single backend web server.
- shape
- A template that determines the load balancer's total pre-provisioned maximum capacity (bandwidth) for ingress plus egress traffic. Available shapes include 10 Mbps, 100 Mbps, 400 Mbps, and 8000 Mbps.
- SSL
- Secure Sockets Layer (SSL) is a security technology for establishing an encrypted link between a client and a server. You can apply the following SSL configurations to your load balancer:
- subnet
- A subdivision you define in a virtual cloud network (VCN), such as 10.0.0.0/24 and 10.0.1.0/24. A subnet can span a region or exist within in a single availability domain. A subnet consists of a contiguous range of IP addresses that do not overlap with other subnets in the VCN. For each subnet, you specify the routing and security rules that apply to it.
- TAGS
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You can apply tags to your resources to help you organize them according to your business needs. You can apply tags at the time you create a resource, or you can update the resource later with the wanted tags. For general information about applying tags, see Resource Tags.
- VIRTUAL CLOUD NETWORK (VCN)
- A private network that you set up in the Oracle data centers, with firewall rules and specific types of communication gateways that you can choose to use. A VCN covers a single, contiguous IPv4 CIDR block of your choice in the allowed IP address ranges.
- VISIBILITY
- Specifies whether your load balancer is public or private.
- WORK REQUEST
- An object that reports on the current state of a Load Balancer request.