DropBox synchronization technique.

Question

I am currently developing an application using dropbox c# API.

DropBox is able to capture changes on their server and also the changes in their client almost immediately.

What technique they use to synchronize this 2 replicas?

Wish someone can provide me some clue to start with, I try to avoid the timer base synchronization.

Thanks.

Answer 1

For client changes, they might use file system watcher. If there is a change in dropbox folder, they ll trigger the API to update the drop box server.

I am not sure about the server side changes, But there should be some timer mechanism to poll the server to see the changes..

Cheers

Answer 2

I don't know what they use. But you can use filesystemwatcher from c#. That will allow you to catch a file change event. It is not the easiest thing to work with, but simple to use.

To make sure that old revisions of the file to not overwrite the new, I guess they use a revision counter, which is often the case.

To identify if the file is changed from the current stored file, I imagine they may use a number of checks

if (local[file.name].size != server[file.name].size)
{
    file.changed = true;
}
else if (local[file.name].md5 != server[file.name].md5)
{
    file.changed = true;
}
else
{
    file.changed = false;
}