DataFlex

S3 Streaming Upload with Expect: 100-continue

See more Amazon S3 (new) Examples

Demonstrates how to do an S3 streaming upload that includes an "Expect: 100-continue" request header. The purpose of sending an "Expect: 100-continue" header is to cleanly handle the case when the request fails, for whatever reason. (Failure reasons can be anything, such as a permissions problem, invalid authentication, etc.)

If no "Expect: 100-continue" header is included, and the AWS server rejects the request immediately after receiving the header, then this is what happens: The server closes the connection immediately after processing the request header. This results in a half-closed connection. Meanwhile, the client continues with sending the file data in the body of the HTTP request. Eventually, because nothing is consuming the data on the server-side, the outgoing socket buffer on the client (i.e. local machine) fills up, and an error such as "WSAECONNABORTED An established connection was aborted by the software in your host machine." is returned.

When the "Expect: 100-continue" is inclued, the server sends a response immediately after receiving the request header. A 100 response status code indicates that all is OK and the client should continue with sending the request body (i.e. file data), after which the server will respond with a final response.

DataFlex

Use ChilkatAx-win32.pkg

Procedure Test
    Boolean iSuccess
    Handle hoCrypt
    String sFileToUploadPath
    String sHashStr
    Handle hoRest
    Boolean iBTls
    Integer iPort
    Boolean iBAutoReconnect
    Variant vAuthAws
    Handle hoAuthAws
    Variant vFileStream
    Handle hoFileStream
    String sResponseStr
    String sTemp1
    Integer iTemp1
    Boolean bTemp1

    Move False To iSuccess

    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    // This first part is optional.  AWS authentication requires
    // the SHA-256 hash of the request body (i.e. the contents of the file
    // to be uploaded).  We can choose to pre-calculate the SHA-256 in a streaming fashion
    // and then provide it to the authenticator object.  This way, if the file is
    // extremely large, it never needs to completely reside in memory.
    Get Create (RefClass(cComChilkatCrypt2)) To hoCrypt
    If (Not(IsComObjectCreated(hoCrypt))) Begin
        Send CreateComObject of hoCrypt
    End
    Set ComEncodingMode Of hoCrypt To "hex"
    Set ComHashAlgorithm Of hoCrypt To "sha-256"
    Move "qa_data/xml/hamlet.xml" To sFileToUploadPath
    Get ComHashFileENC Of hoCrypt sFileToUploadPath To sHashStr

    Get Create (RefClass(cComChilkatRest)) To hoRest
    If (Not(IsComObjectCreated(hoRest))) Begin
        Send CreateComObject of hoRest
    End

    // Connect to the Amazon AWS REST server.
    Move True To iBTls
    Move 443 To iPort
    Move True To iBAutoReconnect
    Get ComConnect Of hoRest "s3.amazonaws.com" iPort iBTls iBAutoReconnect To iSuccess

    // ----------------------------------------------------------------------------
    // Important: For buckets created in regions outside us-east-1,
    // there are three important changes that need to be made.
    // See Working with S3 Buckets in Non-us-east-1 Regions for the details.
    // ----------------------------------------------------------------------------

    // Provide AWS credentials for the REST call.
    Get Create (RefClass(cComChilkatAuthAws)) To hoAuthAws
    If (Not(IsComObjectCreated(hoAuthAws))) Begin
        Send CreateComObject of hoAuthAws
    End
    Set ComAccessKey Of hoAuthAws To "AWS_ACCESS_KEY"
    Set ComSecretKey Of hoAuthAws To "AWS_SECRET_KEY"
    Set ComServiceName Of hoAuthAws To "s3"
    // Provide the pre-computed SHA-256 here:
    Set ComPrecomputedSha256 Of hoAuthAws To sHashStr

    Get pvComObject of hoAuthAws to vAuthAws
    Get ComSetAuthAws Of hoRest vAuthAws To iSuccess

    // Add an Expect: 100-continue request header
    Get ComAddHeader Of hoRest "Expect" "100-continue" To iSuccess

    // Set the bucket name via the HOST header.
    // In this case, the bucket name is "chilkat100".
    Set ComHost Of hoRest To "chilkat100.s3.amazonaws.com"

    Get Create (RefClass(cComChilkatStream)) To hoFileStream
    If (Not(IsComObjectCreated(hoFileStream))) Begin
        Send CreateComObject of hoFileStream
    End
    Set ComSourceFile Of hoFileStream To sFileToUploadPath

    // Upload to the S3 Storage service.
    // If the application provided the SHA-256 hash of the file contents (as shown above)
    // then file is streamed and never has to completely reside in memory.
    // If the application did NOT provide the SHA-256, then Chilkat will (internally) 
    // load the entire file into memory, calculate the SHA-256, and then upload.
    Get pvComObject of hoFileStream to vFileStream
    Get ComFullRequestStream Of hoRest "PUT" "/hamlet.xml" vFileStream To sResponseStr
    Get ComLastMethodSuccess Of hoRest To bTemp1
    If (bTemp1 <> True) Begin
        Get ComLastErrorText Of hoRest To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // When successful, the S3 Storage service will respond with a 200 response code,
    // with an XML body.  
    Get ComResponseStatusCode Of hoRest To iTemp1
    If (iTemp1 = 200) Begin
        Showln sResponseStr
        Showln "File uploaded."
    End
    Else Begin
        // Examine the request/response to see what happened.
        Get ComResponseStatusCode Of hoRest To iTemp1
        Showln "response status code = " iTemp1
        Get ComResponseStatusText Of hoRest To sTemp1
        Showln "response status text = " sTemp1
        Get ComResponseHeader Of hoRest To sTemp1
        Showln "response header: " sTemp1
        Showln "response body: " sResponseStr
        Showln "---"
        Get ComLastRequestStartLine Of hoRest To sTemp1
        Showln "LastRequestStartLine: " sTemp1
        Get ComLastRequestHeader Of hoRest To sTemp1
        Showln "LastRequestHeader: " sTemp1
    End



End_Procedure