Will the response timer on google app engine start upon submitting the web page's form?
If I'm going to upload a file that is greater than 1MB, I could split the files to 1MB to fit in the limitation of the Google App Engine Datastore. Now, my concern is if the client's internet connection is slow, it would eat up the 30 seconds timer right? If this is the case, it is impossible to upload large files with slow connection?
The 30 second response time limit only applies to code execution. So the uploading of the actual file as part of the request body is excluded from that. The timer will only start once the request is fully sent to the server by the client, and your code starts handling the submitted request. Hence it doesn't matter how slow your client's connection is.
As an side note, Instead of splitting your file into multiple parts, try using the blobstore. I am using it for images and it raises the storage limit to 50MB. (Remember to enable billing to get access to the blobstore)