PowerBuilder

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.

PowerBuilder

integer li_rc
integer li_Success
oleobject loo_Crypt
string ls_FileToUploadPath
string ls_HashStr
oleobject loo_Rest
integer li_BTls
integer li_Port
integer li_BAutoReconnect
oleobject loo_AuthAws
oleobject loo_FileStream
string ls_ResponseStr

li_Success = 0

// 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.
loo_Crypt = create oleobject
li_rc = loo_Crypt.ConnectToNewObject("Chilkat.Crypt2")
if li_rc < 0 then
    destroy loo_Crypt
    MessageBox("Error","Connecting to COM object failed")
    return
end if
loo_Crypt.EncodingMode = "hex"
loo_Crypt.HashAlgorithm = "sha-256"
ls_FileToUploadPath = "qa_data/xml/hamlet.xml"
ls_HashStr = loo_Crypt.HashFileENC(ls_FileToUploadPath)

loo_Rest = create oleobject
li_rc = loo_Rest.ConnectToNewObject("Chilkat.Rest")

// Connect to the Amazon AWS REST server.
li_BTls = 1
li_Port = 443
li_BAutoReconnect = 1
li_Success = loo_Rest.Connect("s3.amazonaws.com",li_Port,li_BTls,li_BAutoReconnect)

// ----------------------------------------------------------------------------
// 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.
loo_AuthAws = create oleobject
li_rc = loo_AuthAws.ConnectToNewObject("Chilkat.AuthAws")

loo_AuthAws.AccessKey = "AWS_ACCESS_KEY"
loo_AuthAws.SecretKey = "AWS_SECRET_KEY"
loo_AuthAws.ServiceName = "s3"
// Provide the pre-computed SHA-256 here:
loo_AuthAws.PrecomputedSha256 = ls_HashStr

li_Success = loo_Rest.SetAuthAws(loo_AuthAws)

// Add an Expect: 100-continue request header
loo_Rest.AddHeader("Expect","100-continue")

// Set the bucket name via the HOST header.
// In this case, the bucket name is "chilkat100".
loo_Rest.Host = "chilkat100.s3.amazonaws.com"

loo_FileStream = create oleobject
li_rc = loo_FileStream.ConnectToNewObject("Chilkat.Stream")

loo_FileStream.SourceFile = ls_FileToUploadPath

// 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.
ls_ResponseStr = loo_Rest.FullRequestStream("PUT","/hamlet.xml",loo_FileStream)
if loo_Rest.LastMethodSuccess <> 1 then
    Write-Debug loo_Rest.LastErrorText
    destroy loo_Crypt
    destroy loo_Rest
    destroy loo_AuthAws
    destroy loo_FileStream
    return
end if

// When successful, the S3 Storage service will respond with a 200 response code,
// with an XML body.  
if loo_Rest.ResponseStatusCode = 200 then
    Write-Debug ls_ResponseStr
    Write-Debug "File uploaded."
else
    // Examine the request/response to see what happened.
    Write-Debug "response status code = " + string(loo_Rest.ResponseStatusCode)
    Write-Debug "response status text = " + loo_Rest.ResponseStatusText
    Write-Debug "response header: " + loo_Rest.ResponseHeader
    Write-Debug "response body: " + ls_ResponseStr
    Write-Debug "---"
    Write-Debug "LastRequestStartLine: " + loo_Rest.LastRequestStartLine
    Write-Debug "LastRequestHeader: " + loo_Rest.LastRequestHeader
end if



destroy loo_Crypt
destroy loo_Rest
destroy loo_AuthAws
destroy loo_FileStream