You can access the Elastic Load Balancing web service using the SOAP web services messaging protocol. This interface is described by a Web Services Description Language (WSDL) document, which defines the operations and security model for the particular service. The WSDL references an XML Schema document, which strictly defines the data types that might appear in SOAP requests and responses. For more information on WSDL and SOAP, see Web Services References.

	Note
	Elastic Load Balancing supports SOAP only through HTTPS.

All schemas have a version number. The version number appears in the URL of a schema file and in a schema's target namespace. This makes upgrading easy by differentiating requests based on the version number.

Since the SOAP requests and responses in Elastic Load Balancing follow current standards, any programming language with the appropriate library support can be used. Languages known to have this support include C++, C#, Java, Perl, Python and Ruby.

Elastic Load Balancing complies with the current WS-Security standard, which requires you to hash and sign SOAP requests for integrity and non-repudiation. WS-Security defines profiles which are used to implement various levels of security. Secure SOAP messages use the BinarySecurityToken profile, consisting of an X.509 certificate with an RSA public key.

The following is the content of an insecure RunInstances operation (using EC2 as an example):

<Runinstances xmlns="http://ec2.amazonaws.com/doc/2009-05-05">
    <instancesSet>
        <item>
            <imageId>ami-60a54009</imageId>
            <minCount>1</minCount>
            <maxCount>3</maxCount>
        </item>
    </instancesSet>
    <groupSet/>
</RunInstances>

To secure the request, we add the BinarySecurityToken element.

The secure version of the request begins with the following:

<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/">
  <SOAP-ENV:Header>
    <wsse:Security xmlns:wsse="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd">
      <wsse:BinarySecurityToken
      xmlns:wsu="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd"
      EncodingType="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-soap-message-security-1.0#Base64Binary"
      ValueType="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-X.509-token-profile-1.0#X.509v3"
      wsu:Id="CertId-1064304">....many, many lines of base64 encoded
      X.509 certificate...</wsse:BinarySecurityToken>
      <ds:Signature xmlns:ds="http://www.w3.org/2000/09/xmldsig#">
        <ds:SignedInfo>
          <ds:CanonicalizationMethod Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"></ds:CanonicalizationMethod>
          <ds:SignatureMethod Algorithm="http://www.w3.org/2000/09/xmldsig#rsa-sha1"></ds:SignatureMethod>
          <ds:Reference URI="#id-17984263">
            <ds:Transforms>
              <ds:Transform Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"></ds:Transform>
            </ds:Transforms>
            <ds:DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1"></ds:DigestMethod>
            <ds:DigestValue>0pjZ1+TvgPf6uG7o+Yp3l2YdGZ4=</ds:DigestValue>
          </ds:Reference>
          <ds:Reference URI="#id-15778003">
            <ds:Transforms>
              <ds:Transform Algorithm="http://www.w3.org/2001/10/xml-exc-c14n#"></ds:Transform>
            </ds:Transforms>
            <ds:DigestMethod Algorithm="http://www.w3.org/2000/09/xmldsig#sha1"></ds:DigestMethod>
            <ds:DigestValue>HhRbxBBmc2OO348f8nLNZyo4AOM=</ds:DigestValue>
          </ds:Reference>
        </ds:SignedInfo>
        <ds:SignatureValue>bmVx24Qom4kd9QQtclxWIlgLk4QsQBPaKESi79x479xgbO9PEStXMiHZuBAi9luuKdNTcfQ8UE/d
        jjHKZKEQRCOlLVy0Dn5ZL1RlMHsv+OzJzzvIJFTq3LQKNrzJzsNe</ds:SignatureValue>
        <ds:KeyInfo Id="KeyId-17007273">
          <wsse:SecurityTokenReference
              xmlns:wsu="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd" wsu:Id="STRId-22438818">
            <wsse:Reference URI="#CertId-1064304"
                            ValueType="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-X.509-token-profile-1.0#X.509v3">
            </wsse:Reference>
          </wsse:SecurityTokenReference>
        </ds:KeyInfo>
      </ds:Signature>
      <wsu:Timestamp
          xmlns:wsu="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd" wsu:Id="id-17984263">
        <wsu:Created>2006-06-09T10:57:35Z</wsu:Created>
        <wsu:Expires>2006-06-09T11:02:35Z</wsu:Expires>
      </wsu:Timestamp>
    </wsse:Security>
  </SOAP-ENV:Header>

If you are matching this against requests generated by Elastic Load Balancing supplied libraries, or those of another vendor, the following are the most important elements.

In response to a request, the Elastic Load Balancing service returns an XML data structure that conforms to an XML schema defined as part of the Elastic Load Balancing WSDL. The structure of a XML response is specific to the associated request.

The following is an example response (using EC2 as an example):

	<RuninstancesResponse xmlns="http://ec2.amazonaws.com/doc/2009-05-05">
  <reservationId>r-47a5402e</reservationId>
  <ownerId>UYY3TLBUXIEON5NQVUUX6OMPWBZIQNFM</ownerId>
  <groupSet>
    <item>
      <groupId>default</groupId>
    </item>
  </groupSet>
  <instancesSet>
    <item>
      	<InstanceId>i-2ba64342</InstanceId>
      	<imageId>ami-60a54009</imageId>
     	 <InstanceState>
        <code>0</code>
    <name>pending</name>
      </InstanceState>
      <DNSName></DNSName>
    </item>
    <item>
      <InstanceId>i-2bc64242</InstanceId>
      <imageId>ami-60a54009</imageId>
      <InstanceState>
        <code>0</code>
    <name>pending</name>
      </InstanceState>
      <DNSName>ec2-67-202-51-176.compute-1.amazonaws.com </DNSName>
    </item>
    <item>
      <InstanceId>i-2be64332</InstanceId>
      <imageId>ami-60a54009</imageId>
      <InstanceState>
        <code>0</code>
    <name>pending</name>
      </InstanceState>
      <DNSName>ec2-67-202-51-122.compute-1.amazonaws.com</DNSName>
      <keyName>example-key-name</keyName>
      <instanceType>m1.small</instanceType>
      <launchTime>2007-08-07T11:54:42.000Z</launchTime>
    </item>
  </instancesSet>
</RunInstancesResponse>

For more information about using web services, go to any of the following resources: