Server Load Balancer:Request processing functions

Item

Description

Syntax

add_req_header(name, value [, append])

Feature

Adds a request header to requests before they are redirected to the origin server.

Parameter

• name: the name of the request header that you want to add. Data type: string.

• value: the value of the request header that you want to add. Data type: string.

• append: specifies whether to append the specified value if a request header with the same name already exists. Valid values: true and false. Default value: false. Data type: Boolean. If you set this parameter to false, the specified value will overwrite the value of the existing request header.

Return value

true is returned by default. If the specified request header is invalid, false is returned.

Example

add_req_header('USER-DEFINED-REQ-1', '1')
add_req_header('USER-DEFINED-REQ-1', 'x', true)
add_req_header('USER-DEFINED-REQ-2', '2')
del_req_header('USER-DEFINED-REQ-2')

Request headers:

USER-DEFINED-REQ-1: 1
USER-DEFINED-REQ-1: x

Item

Description

Syntax

del_req_header(name)

Feature

Deletes a request header from requests before they are redirected to the origin server.

Parameter

name: the name of the request header that you want to delete. Data type: string.

Return value

true is returned by default. If the specified request header is invalid, false is returned.

Example

add_req_header('USER-DEFINED-REQ-1', '1')
add_req_header('USER-DEFINED-REQ-1', 'x', true)
add_req_header('USER-DEFINED-REQ-2', '2')
del_req_header('USER-DEFINED-REQ-2')

Headers:

USER-DEFINED-REQ-1: 1
USER-DEFINED-REQ-1: x

Item

Description

Syntax

add_rsp_header(name, value [, append])

Feature

Adds a response header.

Parameter

• name: the name of the response header that you want to add. Data type: string.

• value: the value of the response header that you want to add. Data type: string.

  You can specify one of the following expressions for the value parameter to enable the value to be dynamically replaced in the response phase:

  • ${x}: replaced with the value of variable x.

  • @{y}: replaced with the value of response header y.

• append: specifies whether to append the specified value if a response header with the same name already exists. Valid values: true and false. Default value: false. Data type: Boolean. If you set this parameter to false, the specified value will overwrite the value of the existing response header.

Return value

true is returned by default. If the specified response header is invalid, false is returned.

Example

add_rsp_header('USER-DEFINED-RSP-1', '1')
add_rsp_header('USER-DEFINED-RSP-1', 'x', true)
add_rsp_header('USER-DEFINED-RSP-2', '2')
del_rsp_header('USER-DEFINED-RSP-2')

Response headers:

USER-DEFINED-RSP-1: 1
USER-DEFINED-RSP-1: x

Item

Description

Syntax

del_rsp_header(name)

Feature

Deletes a response header.

Parameter

name: the name of the response header that you want to delete. Data type: string.

Return value

true is returned by default. If the specified response header is invalid, false is returned.

Example

add_rsp_header('USER-DEFINED-RSP-1', '1')
add_rsp_header('USER-DEFINED-RSP-1', 'x', true)
add_rsp_header('USER-DEFINED-RSP-2', '2')
del_rsp_header('USER-DEFINED-RSP-2')

Response headers:

USER-DEFINED-RSP-1: 1
USER-DEFINED-RSP-1: x

Item

Description

Syntax

encode_args(d)

Feature

Converts the key-value pair in the dictionary specified by d to a URI-encoded string in the format of k1=v1&k2=v2.

Parameter

d: the dictionary that you want to convert.

Return value

A URI-encoded string.

Example

my_args = []
set(my_args, 'signature', 'da9dc4b7-87ae-4330-aaaf-e5454e2c2af1')
set(my_args, 'algo', 'private sign1')
my_args_str = encode_args(my_args)
add_rsp_header('X-AScript-ENCODE-ARGS', my_args_str)

to_args = decode_args(my_args_str)
if get(to_args, 'algo') {
    add_rsp_header('X-AScript-DECODE-ARGS-ALGO', get(to_args, 'algo'))
}
if get(to_args, 'signature') {
    add_rsp_header('X-AScript-DECODE-ARGS-SIGN', get(to_args, 'signature'))
}

Response headers:

X-AScript-ENCODE-ARGS: signature=da9dc4b7-87ae-4330-aaaf-e5454e2c2af1&algo=private%20sign1
X-AScript-DECODE-ARGS-ALGO: private sign1
X-AScript-DECODE-ARGS-SIGN: da9dc4b7-87ae-4330-aaaf-e5454e2c2af1

Item

Description

Syntax

decode_args(s)

Feature

Converts a URI-encoded string in the format of k1=v1&k2=v2 to a string of dictionary type.

Parameter

s: the string that you want to convert.

Return value

A dictionary object converted from the specified string.

Example

my_args = []
set(my_args, 'signature', 'da9dc4b7-87ae-4330-aaaf-e5454e2c2af1')
set(my_args, 'algo', 'private sign1')
my_args_str = encode_args(my_args)
add_rsp_header('X-AScript-ENCODE-ARGS', my_args_str)

to_args = decode_args(my_args_str)
if get(to_args, 'algo') {
    add_rsp_header('X-AScript-DECODE-ARGS-ALGO', get(to_args, 'algo'))
}
if get(to_args, 'signature') {
    add_rsp_header('X-AScript-DECODE-ARGS-SIGN', get(to_args, 'signature'))
}

Response headers:

X-AScript-ENCODE-ARGS: signature=da9dc4b7-87ae-4330-aaaf-e5454e2c2af1&algo=private%20sign1
X-AScript-DECODE-ARGS-ALGO: private sign1
X-AScript-DECODE-ARGS-SIGN: da9dc4b7-87ae-4330-aaaf-e5454e2c2af1

Item

Description

Syntax

rewrite(url, flag, code)

Feature

Performs a rewrite or redirect.

Parameter

• url: the URL to which the source URI is rewritten after the rewrite operation. Data type: string.

  • If you set the flag parameter to redirect or break, only the URI is rewritten. This parameter specifies the final URI after the rewrite operation.

  • If you set the flag parameter to enhance_redirect or enhance_break, both the URI and parameters are rewritten. This parameter specifies the final URI and parameters after the rewrite operation.

• flag: the rewrite mode. Data type: string.

  • redirect: rewrites only the URI. Parameters are not rewritten. By default, a 302 redirect is performed. If you specify this mode, the code parameter is configurable. Valid values for the code parameter are 301, 302 (default), 303, 307, and 308.

  • break: rewrites only the URI to a URL. Parameters are not rewritten.

  • enhance_redirect: similar to redirect. However, both the URI and parameters are rewritten.

  • enhance_break: similar to break. However, both the URI and parameters are rewritten.

• code: the HTTP status code. Data type: numeric.

  This parameter is available only when you set the flag parameter to redirect or enhance_redirect.

Return value

• true is returned by default for a rewrite operation.

• By default, no value is returned for a redirect.

Example

if and($arg_mode, eq($arg_mode, 'rewrite:enhance_break')) {
  rewrite('/a/b/c.txt?k=v', 'enhance_break')
}
#Note: The URI and parameters of requests redirected to the origin server are rewritten to /a/b/c.txt?k=v

if and($arg_mode, eq($arg_mode, 'rewrite:enhance_redirect')) {
  rewrite('/a/b/c.txt?k=v', 'enhance_redirect')
}
if and($arg_mode, eq($arg_mode, 'rewrite:enhance_redirect_301')) {
  rewrite('/a/b/c.txt?k=v', 'enhance_redirect', 301)
}
#Note: A 302 or 301 redirect to /a/b/c.txt?k=v is performed.

if and($arg_mode, eq($arg_mode, 'rewrite:break')) {
  rewrite('/a/b/c.txt', 'break')
}
#Note: The URI of requests redirected to the origin server is rewritten to /a/b/c.txt and the original parameters in the requests remain unchanged.

if and($arg_mode, eq($arg_mode, 'rewrite:redirect')) {
  rewrite('/a/b/c.txt', 'redirect')
}
if and($arg_mode, eq($arg_mode, 'rewrite:redirect_301')) {
  rewrite('/a/b/c.txt', 'redirect', 301)
}
#Note: A 302 or 301 redirect to /a/b/c.txt is performed and the original parameters remain unchanged.

Item

Description

Syntax

say(arg)

Feature

Prints a response body and appends a newline character at the end of the output.

Parameter

arg: the content of the response body. Data type: any type.

Return value

N/A

Example

say('hello')
print('byebye')
print('byebye')

Output:

hello
byebyebyebye

Item

Description

Syntax

print(arg)

Feature

Prints a response body. This function is different from the say() function. This function does not append a newline at the end of the output.

Parameter

arg: the content of the response body. Data type: any type.

Return value

N/A

Example

say('hello')
print('byebye')
print('byebye')

Output:

hello
byebyebyebye

Item

Description

Syntax

exit(code [, body])

Feature

Ends the current request with the specified HTTP status code. If you also set the body parameter, a response that includes the specified response body is returned.

Parameter

• code: the HTTP status code to return.

• body: the response body.

Return value

N/A

Example

• Example 1:

  if not($arg_key) {
      exit(403)
  }
  #Note: If a request does not include the key parameter, the request is denied and the HTTP 403 status code is returned. 
  
  if not($cookie_user) {
      exit(403, 'not cookie user')
  }
  #Note: If a request does not include cookie_user, the request is denied and a response that contains the body "not cookie user" is returned with the HTTP 403 status code.
  
  if not(0) {
      exit(403)
  }
  #Note: The not(0) function returns a value of false.
  
  if not(false) {
      exit(403)
  }
  #Note: The not(false) function returns a value of true.

• Example 2

  pcs = capture_re($request_uri,'^/([^/]+)/([^/]+)([^?]+)\?(.*)')
  sec1 = get(pcs, 1)
  sec2 = get(pcs, 2)
  sec3 = get(pcs, 3)
  if or(not(sec1), not(sec2), not(sec3)) {
     add_rsp_header('X-TENGINE-ERROR', 'auth failed - missing necessary uri set')
     exit(403)
  }
  digest = md5(concat(sec1, sec3))
  if ne(digest, sec2) {
      add_rsp_header('X-TENGINE-ERROR', 'auth failed - invalid digest')
      exit(403)
  }