Ruby

S3 Resume Download

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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.

Ruby

require 'chilkat'

success = false

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

rest = Chilkat::CkRest.new()

# Connect to the Amazon AWS REST server.
bTls = true
port = 443
bAutoReconnect = true
success = rest.Connect("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.
authAws = Chilkat::CkAuthAws.new()
authAws.put_AccessKey("AWS_ACCESS_KEY")
authAws.put_SecretKey("AWS_SECRET_KEY")
authAws.put_ServiceName("s3")
success = rest.SetAuthAws(authAws)

# Set the bucket name via the HOST header.
# In this case, the bucket name is "chilkat100".
rest.put_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.
fac = Chilkat::CkFileAccess.new()
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.
sz = fac.FileSize(localFilepath)
if (sz > 0)
    print "sz = " + sz.to_s() + "\n";

    # If the sz equals 42375 bytes, then we want to add a Range header that looks like this:
    # Range: bytes=42375-
    sbRange = Chilkat::CkStringBuilder.new()
    sbRange.Append("bytes=")
    sbRange.AppendInt(sz)
    sbRange.Append("-")
    rest.AddHeader("Range",sbRange.getAsString())
    print "Added Range: " + sbRange.getAsString() + "\n";
end

# Send the request to download the remainder of the file.
success = rest.SendReqNoBody("GET","/hamlet.xml")
if (success != true)
    print rest.lastErrorText() + "\n";
    exit
end

# Read the response header.
responseStatusCode = rest.ReadResponseHeader()
if (responseStatusCode < 0)
    print rest.lastErrorText() + "\n";
    exit
end

print "Response status code = " + responseStatusCode.to_s() + "\n";

# 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))

    bodyStream = Chilkat::CkStream.new()

    # The stream's sink will be a file.
    # We will append to the file..
    bodyStream.put_SinkFile(localFilepath)

    # Indicate that we wish to append to the output file.
    # The SinkFileAppend property was added in Chilkat v9.50.83
    bodyStream.put_SinkFileAppend(true)

    # 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.
    success = rest.ReadRespBodyStream(bodyStream,true)
    if (success != true)
        print rest.lastErrorText() + "\n";
        exit
    end

    print "Successfully downloaded the file." + "\n";

else
    errResponse = rest.readRespBodyString()
    if (rest.get_LastMethodSuccess() != true)
        print rest.lastErrorText() + "\n";
    else
        print errResponse + "\n";
    end

end