Using the Query API
From Amazon Elastic Load Balancing: 2009-05-15
Query requests are HTTP or HTTPS requests that use the HTTP verb GET or POST and a Query parameter named Action or Operation. Action is used throughout this documentation, although Operation is supported for backward compatibility with other AWS Query APIs.
Each Query request must include some common parameters to handle authentication and selection of an action. For more information, see Common Request Parameters.
![[Note]](/elb-dg-2009-05-15/note.png){kind=small}
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Note |
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Some API operations take lists of parameters. These lists are specified using the following
notation: &attribute.member.1=this
&attribute.member.2=that
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You can send Query requests over either HTTP or HTTPS. Regardless of which protocol you use, you must include a signature in every Query request. This section describes how to create the signature. The method described in the following procedure is known as signature version 2.
To create the signature
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Create the canonicalized query string that you need later in this procedure:
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Sort the UTF-8 query string components by parameter name with natural byte ordering.
The parameters can come from the GET URI or from the POST body (when
Content-Typeisapplication/x-www-form-urlencoded). -
URL encode the parameter name and values according to the following rules:
Note Currently all AWS service parameter names use unreserved characters, so you don't need to encode them. However, you might want to include code to handle parameter names that use reserved characters, for possible future use.
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Separate the encoded parameter names from their encoded values with the equals sign ( = ) (ASCII character 61), even if the parameter value is empty.
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Separate the name-value pairs with an ampersand ( & ) (ASCII code 38).
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Create the string to sign according to the following pseudo-grammar (the
"\n"represents an ASCII newline).StringToSign = HTTPVerb + "\n" + ValueOfHostHeaderInLowercase + "\n" + HTTPRequestURI + "\n" + CanonicalizedQueryString <from the preceding step>The
HTTPRequestURIcomponent is the HTTP absolute path component of the URI up to, but not including, the query string. If theHTTPRequestURIis empty, use a forward slash ( / ). -
Calculate an RFC 2104-compliant HMAC with the string you just created, your Secret Access Key as the key, and SHA256 or SHA1 as the hash algorithm.
For more information, go to http://www.ietf.org/rfc/rfc2104.txt.
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Convert the resulting value to base64.
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Use the resulting value as the value of the
Signaturerequest parameter.
![[Important]](/elb-dg-2009-05-15/important.png){kind=small}
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Important |
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The final signature you send in the request must be URL encoded as specified in RFC 3986 (for more information, go to http://www.ietf.org/rfc/rfc3986.txt). If your toolkit URL encodes your final request, then it handles the required URL encoding of the signature. If your toolkit doesn't URL encode the final request, then make sure to URL encode the signature before you include it in the request. Most importantly, make sure the signature is URL encoded only once. A common mistake is to URL encode it manually during signature formation, and then again when the toolkit URL encodes the entire request. |