CkPython

S3 Resume Download

See more Amazon S3 (new) Examples

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.

CkPython

import sys
import chilkat

success = False

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

rest = chilkat.CkRest()

# 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()
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()
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 = " + str(sz))

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

# Send the request to download the remainder of the file.
success = rest.SendReqNoBody("GET","/hamlet.xml")
if (success != True):
    print(rest.lastErrorText())
    sys.exit()

# Read the response header.
responseStatusCode = rest.ReadResponseHeader()
if (responseStatusCode < 0):
    print(rest.lastErrorText())
    sys.exit()

print("Response status code = " + str(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)):

    bodyStream = chilkat.CkStream()

    # 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())
        sys.exit()

    print("Successfully downloaded the file.")

else:
    errResponse = rest.readRespBodyString()
    if (rest.get_LastMethodSuccess() != True):
        print(rest.lastErrorText())
    else:
        print(errResponse)