Advanced Forwarding

Forwarding rule

The following forwarding rules are supported: domain name, path, HTTP request method, HTTP header, query string, cookie, and CIDR block.

For details, see Forwarding Rule.

Action

The following actions are supported: forward to a backend server group, redirect to another listener, redirect to another URL, rewrite, write header, remove header, limit request, and return a specific response body.

• If Action is set to Forward to a backend server group, you can also select from one of the following additional forwarding actions: rewrite, write header, remove header, and limit request.
• If Action is set to Return a specific response body, you can also select the additional action Limit request.

For details, see Action Types.

Domain name

• Description

  Route requests based on the domain name. You can configure multiple domain names with each consisting of at least two labels separated by periods (.). Each domain name can contain a maximum of 63 characters per label and a maximum total length of 100 characters.

• Matching rules
  • Exact match and wildcard match: The domain name can contain only letters, digits, and special characters .-?=~_+\^*!$&|()[]. Asterisks (*) and question marks (?) can be used as wildcards. The domain name cannot start or end with a period (.) or contain two consecutive periods (..).
  • Regular expression match: The domain name can contain only letters, digits, and special characters: .-?=~_+\^*!$&|()[].

Example
Request URL: https://www.example.com/login.php?locale=en-us=#videos
Domain name in the forwarding rule: www.example.com

Path

• Description

  Route requests based on paths. You can configure multiple paths in a forwarding policy. Each path contains 1 to 128 characters, including letters, digits, and special characters: _~';@^-%#$.*+?,=!:|\/()[]{}.

• Matching rules
  • Exact match: The request path is the same as the specified path and must start with a slash (/).
  • Prefix match: The request path starts with the specified path string and must start with a slash (/).
  • Regular expression match: The URLs are matched using a regular expression.

For more information about path matching rules, see Path Matching.

Example path:
Request URL: https://www.example.com/login.php?locale=en-us#videos
Path in the forwarding rule: /login.php

Query string

Route requests based on the query string.

Example
Request URL: https://www.example.com/login.php?locale=en-us#videos
A query string needs to be configured for the forwarding rule:
Key: locale
Value: en-us

HTTP request method

Route requests based on the HTTP method.

• You can configure multiple request methods in a forwarding policy.
• The following methods are available: GET, POST, PUT, DELETE, PATCH, HEAD, and OPTIONS.

Example
GET

HTTP header

Route requests based on the HTTP header.

Example
Key: Accept-Language
Value: en-us

CIDR block

Route requests based on the source IP addresses from where requests originate.

Example
192.168.1.0/24 or 2020:50::44/127

Cookie

Route requests based on the cookie.

A cookie consists of a key and a value. You need to configure the key and value separately.

• A key can contain 1 to 100 characters and cannot start or end with a space.
• A key can have one value, which can contain 1 to 100 characters.

You can enter multiple key-value pairs. The key-value pairs can contain letters, digits, and special characters: !%'"()*+,./:=?@^-_`~

Example:
Key: cookie_name
Value: cookie_value

Forward to a backend server group

Requests are forwarded to the specified backend server group.

Redirect to another listener

Requests are redirected to another listener, which then routes the requests to its associated backend server group.

Redirect to another URL

Requests are redirected to the configured URL.

When clients access website A, the load balancer returns 302 or any other 3xx status code and automatically redirects the clients to website B. You can customize the redirection URL that will be returned to the clients.

Example
URL for redirection: http://www.example1.com/index.html?locale=en-us#videos
Protocol: HTTP
Domain name: www.example1.com
Port: 8081
Path: /index.html
Query String: locale=en-us
HTTP Status Code: 301

Return a specific response body

Load balancers return a fixed response to the clients.

You can custom the status code and response body that load balancers directly return to the clients without the need to route the requests to backend servers.

Example

text/plain

Sorry, the language is not supported.

text/css

<head><style type="text/css">div {background-color:red}#div {font-size:15px;color:red}</style></head>

text/html

<form action="/" method="post" enctype="multipart/form-data"><input type="text" name="description" value="some text"><input type="file" name="myFile"><button type="submit">Submit</button></form>

application/javascript

String.prototype.trim = function() {var reExtraSpace = /^\s*(.*?)\s+$/;return this.replace(reExtraSpace, "$1")}

application/json

{ "publicip": { "type": "5_bgp","ip_version": 4},"bandwidth": {"name": "bandwidth123","size": 10,"share_type": "PER"}}

Rewrite

Rewrites the request URL before forwarding requests to the specified backend server group.

Write header

Writes the configured header into the request before forwarding it to the specified backend server group.

You can specify the key and value of the header you want to write into the request that matches the forwarding rule. The headers you have configured will overwrite the existing headers. By default, you can configure five headers.

For details about how to write a header, see Table 5.

Remove header

Removes the configured headers from the request before forwarding it to the specified backend server group.

You can specify the value of the header you want to remove from the request that matches the forwarding rule. The headers match the ones you have configured will be removed from the requests. By default, you can configure five headers.

The key can contain only letters, digits, underscores (_), and hyphens (-).

Limit request

Limits the maximum number of queries per second if Forward to a backend server group or Return a specific response body is selected as the action.

You need to configure the following parameters:

• QPS (Total): Specifies the maximum number of queries per second (QPS). The value ranges from 1 to 100000. If the number of requests reaches the specified value, new requests will be discarded and 503 Service Unavailable will be returned to the client.
• QPS (Client IP Address): Specifies the maximum number of QPS from a source IP address. The value ranges from 1 to 100000. If both QPS (Total) and QPS (Client IP Address) are configured, the latter value must be smaller than the former. If the number of requests reaches the specified value, new requests will be discarded and 503 Service Unavailable will be returned to the client.
  NOTE:

  QPS (Client IP Address) is not available for QUIC listeners.

header1:aaa

header2:bbb

header3

Manually-defined value

ccc

header1:aaa

header2:bbb

header3:ccc

header3

System-defined value

Client port

header1:aaa

header2:bbb

header3: Client port

header3

Reference value

header1

header1:aaa

header2:bbb

header3:aaa

/elb/abc.html

Forwarding policy 01

/elb/abc.html

Prefix match

1

Backend server group 01

Forwarding policy 02

/elb

Prefix match

2

Backend server group 02

/exa/index.html

Forwarding policy 03

/exa[^\s]*

Regular expression match

3

Backend server group 03

Forwarding policy 04

/exa/index.html

Regular expression match

4

Backend server group 04

/mpl/index.html

Forwarding policy 05

/mpl/index.html

Exact match

5

Backend server group 05

Forwarding rule: path

Regular expression match

• Matching condition: /test/(.*)/(.*)/index
• Request path: /test/ELB/elb/index

Action: rewrite or redirect to another URL

Path

• Path: /$1/$2
• Extracting content

  $1: ELB

  $2: elb

• Destination path: /ELB/elb