This topic describes the syntax, description, parameters, and return values of request processing functions. This topic also provides examples of these functions.

add_req_header

The following table describes the details about this function.
Item Description 
Syntax add_req_header(name, value [, append])
Description 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 a request header with 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 Returns true by default and returns false if the specified request header is invalid.
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')

Note: The following request headers are added:
USER-DEFINED-REQ-1: 1
USER-DEFINED-REQ-1: x

The USER-DEFINED-REQ-2 header is added and then deleted. Therefore, the USER-DEFINED-REQ-2 request header is not included in requests that are redirected to the origin server.

del_req_header

The following table describes the details about this function.
Item Description
Syntax del_req_header(name)
Description 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 Returns true by default and returns false if the specified request header is invalid.
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')

Note: The following request headers are added:
USER-DEFINED-REQ-1: 1
USER-DEFINED-REQ-1: x

The USER-DEFINED-REQ-2 header is added and then deleted. Therefore, the USER-DEFINED-REQ-2 request header is not included in requests that are redirected to the origin server.

add_rsp_header

The following table describes the details about this function.
Item Description
Syntax add_rsp_header(name, value [, append])
Description 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 ngx.var.x.
    • @{y}: replaced with the value of response header y.
  • append: specifies whether to append a response header with 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 Returns true by default and returns false if the specified response header is invalid.
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')

Note: The following response headers are added:
USER-DEFINED-RSP-1: 1
USER-DEFINED-RSP-1: x

The USER-DEFINED-RSP-2 header is added and then deleted. Therefore, the USER-DEFINED-RSP-2 header is not included in the responses.

del_rsp_header

The following table describes the details about this function.
Item Description
Syntax del_rsp_header(name)
Description Deletes a response header.
Parameter name: the name of the response header that you want to delete. Data type: string.
Return value Returns true by default and returns false if the specified response header is invalid.
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')

The following response headers are added:
USER-DEFINED-RSP-1: 1
USER-DEFINED-RSP-1: x

The USER-DEFINED-RSP-2 header is added and then deleted. Therefore, the USER-DEFINED-RSP-2 header is not included in the responses.

encode_args

The following table describes the details about this function.
Item Description
Syntax encode_args(d)
Description Converts the k/v pairs 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 Returns 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-DSL-ENCODE-ARGS', my_args_str)

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

Output: The following response headers are added:
X-DSL-ENCODE-ARGS: signature=da9dc4b7-87ae-4330-aaaf-e5454e2c2af1&algo=private%20sign1
X-DSL-DECODE-ARGS-ALGO: private sign1
X-DSL-DECODE-ARGS-SIGN: da9dc4b7-87ae-4330-aaaf-e5454e2c2af1

decode_args

The following table describes the details about this function.
Item Description
Syntax decode_args(s)
Description 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 Returns 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-DSL-ENCODE-ARGS', my_args_str)

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

Output: The following response headers are added:
X-DSL-ENCODE-ARGS: signature=da9dc4b7-87ae-4330-aaaf-e5454e2c2af1&algo=private%20sign1
X-DSL-DECODE-ARGS-ALGO: private sign1
X-DSL-DECODE-ARGS-SIGN: da9dc4b7-87ae-4330-aaaf-e5454e2c2af1

rewrite

The following table describes the details about this function.
Item Description
Syntax rewrite(url, flag, code)
Description Performs a rewrite or redirect operation.
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 URI after the rewrite operation.
    • If you set the flag parameter to enhance_redirect or enhance_break, the URI and parameters are rewritten. This parameter specifies the 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
  • Returns true by default for a rewrite operation.
  • Does not return values by default for a redirect operation.
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? is performed.k=v

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.

say

The following table describes the details about this function.
Item Description
Syntax say(arg)
Description 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 None.
Example 
say('hello')
print('byebye')
print('byebye')

Output:
hello
byebyebyebye

print

The following table describes the details about this function.
Item Description 
Syntax print(arg)
Description 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 None.
Example 
say('hello')
print('byebye')
print('byebye')

Output:
hello
byebyebyebye

exit

The following table describes the details about this function.
Item Description
Syntax exit(code [, body])
Description Ends the current request with the specified 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 None.
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)
}