(SQL Server) S3 Resume Download

Suppose an S3 download of a very large file failed for some reason and you have a partial file on disk. Rather than restart the entire download, you wish to download the remaining portion. This example demonstrates how to finish a previously failed download.

Note: This example requires Chilkat v9.5.0.83 or above.

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

-- Important: See this note about string length limitations for strings returned by sp_OAMethod calls.
--
CREATE PROCEDURE ChilkatSample
AS
BEGIN
    DECLARE @hr int
    DECLARE @iTmp0 int
    -- Important: Do not use nvarchar(max).  See the warning about using nvarchar(max).
    DECLARE @sTmp0 nvarchar(4000)
    -- This example requires the Chilkat API to have been previously unlocked.
    -- See Global Unlock Sample for sample code.

    DECLARE @rest int
    -- Use "Chilkat_9_5_0.Rest" for versions of Chilkat < 10.0.0
    EXEC @hr = sp_OACreate 'Chilkat.Rest', @rest OUT
    IF @hr <> 0
    BEGIN
        PRINT 'Failed to create ActiveX component'
        RETURN
    END

    -- Connect to the Amazon AWS REST server.
    DECLARE @bTls int
    SELECT @bTls = 1
    DECLARE @port int
    SELECT @port = 443
    DECLARE @bAutoReconnect int
    SELECT @bAutoReconnect = 1
    DECLARE @success int
    EXEC sp_OAMethod @rest, 'Connect', @success OUT, 's3.amazonaws.com', @port, @bTls, @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.
    DECLARE @authAws int
    -- Use "Chilkat_9_5_0.AuthAws" for versions of Chilkat < 10.0.0
    EXEC @hr = sp_OACreate 'Chilkat.AuthAws', @authAws OUT

    EXEC sp_OASetProperty @authAws, 'AccessKey', 'AWS_ACCESS_KEY'
    EXEC sp_OASetProperty @authAws, 'SecretKey', 'AWS_SECRET_KEY'
    EXEC sp_OASetProperty @authAws, 'ServiceName', 's3'
    EXEC sp_OAMethod @rest, 'SetAuthAws', @success OUT, @authAws

    -- Set the bucket name via the HOST header.
    -- In this case, the bucket name is "chilkat100".
    EXEC sp_OASetProperty @rest, 'Host', 'chilkat100.s3.amazonaws.com'

    -- We want to continue downloading a file.
    -- The relative local filepath of our previously partially downoaded file is: qa_output/hamlet.xml
    -- Let's find out how many bytes are already downloaded.
    DECLARE @fac int
    -- Use "Chilkat_9_5_0.FileAccess" for versions of Chilkat < 10.0.0
    EXEC @hr = sp_OACreate 'Chilkat.FileAccess', @fac OUT

    DECLARE @localFilepath nvarchar(4000)
    SELECT @localFilepath = 'qa_output/hamlet.xml'
    -- Note: The FileSize method returns a signed 32-bit integer.  If the file is potentially larger than 2GB, call FileSizeStr instead to return
    -- the size of the file as a string, then convert to an integer value.
    DECLARE @sz int
    EXEC sp_OAMethod @fac, 'FileSize', @sz OUT, @localFilepath
    IF @sz > 0
      BEGIN

        PRINT 'sz = ' + @sz

        -- If the sz equals 42375 bytes, then we want to add a Range header that looks like this:
        -- Range: bytes=42375-
        DECLARE @sbRange int
        -- Use "Chilkat_9_5_0.StringBuilder" for versions of Chilkat < 10.0.0
        EXEC @hr = sp_OACreate 'Chilkat.StringBuilder', @sbRange OUT

        EXEC sp_OAMethod @sbRange, 'Append', @success OUT, 'bytes='
        EXEC sp_OAMethod @sbRange, 'AppendInt', @success OUT, @sz
        EXEC sp_OAMethod @sbRange, 'Append', @success OUT, '-'
        EXEC sp_OAMethod @sbRange, 'GetAsString', @sTmp0 OUT
        EXEC sp_OAMethod @rest, 'AddHeader', @success OUT, 'Range', @sTmp0

        EXEC sp_OAMethod @sbRange, 'GetAsString', @sTmp0 OUT
        PRINT 'Added Range: ' + @sTmp0
      END

    -- Send the request to download the remainder of the file.
    EXEC sp_OAMethod @rest, 'SendReqNoBody', @success OUT, 'GET', '/hamlet.xml'
    IF @success <> 1
      BEGIN
        EXEC sp_OAGetProperty @rest, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @rest
        EXEC @hr = sp_OADestroy @authAws
        EXEC @hr = sp_OADestroy @fac
        EXEC @hr = sp_OADestroy @sbRange
        RETURN
      END

    -- Read the response header.
    DECLARE @responseStatusCode int
    EXEC sp_OAMethod @rest, 'ReadResponseHeader', @responseStatusCode OUT
    IF @responseStatusCode < 0
      BEGIN
        EXEC sp_OAGetProperty @rest, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @rest
        EXEC @hr = sp_OADestroy @authAws
        EXEC @hr = sp_OADestroy @fac
        EXEC @hr = sp_OADestroy @sbRange
        RETURN
      END


    PRINT 'Response status code = ' + @responseStatusCode

    -- We expect a 200 or 206 response status if the file data is coming.
    -- Otherwise, we'll get a string response body with an error message(or no response body).
    IF (@responseStatusCode = 200) or (@responseStatusCode = 206)
      BEGIN

        DECLARE @bodyStream int
        -- Use "Chilkat_9_5_0.Stream" for versions of Chilkat < 10.0.0
        EXEC @hr = sp_OACreate 'Chilkat.Stream', @bodyStream OUT

        -- The stream's sink will be a file.
        -- We will append to the file..
        EXEC sp_OASetProperty @bodyStream, 'SinkFile', @localFilepath

        -- Indicate that we wish to append to the output file.
        -- The SinkFileAppend property was added in Chilkat v9.50.83
        EXEC sp_OASetProperty @bodyStream, 'SinkFileAppend', 1

        -- Read the response body to the stream.  Given that we've
        -- set the stream's sink to a file, it will stream directly
        -- to the file.
        EXEC sp_OAMethod @rest, 'ReadRespBodyStream', @success OUT, @bodyStream, 1
        IF @success <> 1
          BEGIN
            EXEC sp_OAGetProperty @rest, 'LastErrorText', @sTmp0 OUT
            PRINT @sTmp0
            EXEC @hr = sp_OADestroy @rest
            EXEC @hr = sp_OADestroy @authAws
            EXEC @hr = sp_OADestroy @fac
            EXEC @hr = sp_OADestroy @sbRange
            EXEC @hr = sp_OADestroy @bodyStream
            RETURN
          END


        PRINT 'Successfully downloaded the file.'

      END
    ELSE
      BEGIN
        DECLARE @errResponse nvarchar(4000)
        EXEC sp_OAMethod @rest, 'ReadRespBodyString', @errResponse OUT
        EXEC sp_OAGetProperty @rest, 'LastMethodSuccess', @iTmp0 OUT
        IF @iTmp0 <> 1
          BEGIN
            EXEC sp_OAGetProperty @rest, 'LastErrorText', @sTmp0 OUT
            PRINT @sTmp0
          END
        ELSE
          BEGIN

            PRINT @errResponse
          END
      END

    EXEC @hr = sp_OADestroy @rest
    EXEC @hr = sp_OADestroy @authAws
    EXEC @hr = sp_OADestroy @fac
    EXEC @hr = sp_OADestroy @sbRange
    EXEC @hr = sp_OADestroy @bodyStream


END
GO