The synchronizer's work is done from the network proxy's main loop.
A minor problem with the old synchronizer was that it considered itself
out of date if the network was out of date. This was too generic: the
network can have pending requests unrelated to the synchronizer. This
resulted in the synchronizer often unnecessarily flipping the wallet
between up-to-date and not-up-to-date, and causing unnecessary calls
to wallet.save_transactions(). This was observable when opening the
network dialog box: frequently just opening it would cause a wallet
status change and transaction flush, simply because the network dialog
sends a get_parameters() request. This rework of the synchronizer does
not have that issue.
This is a layering violation - the SocketPipe doesn't own
the socket and provides no other way to close the socket, leading
to unnecessary complexity like that in interface.py.
I looked at deamon.py and NetworkProxy - the two other users,
and they don't close the sockets explicitly, just let them be
garbage collected.
Set timeout and socket options on all simple sockets. At present
some code paths can miss it, such as when the SSL certificate is
CA-signed.
Add a missing check for failure.
Remove interface communication out of blockchain.py
into network.py. network.py handles protocol requests
for headers and chunks. blockchain.py continues to
handle their analysis and verification.
If an interface provides a header chain that doesn't
connect, it is dismissed, as per a previous TODO comment.
This removes a thread and another source of timeouts.
I see no performance issues with this when truncating the
blockchain.
Rename 'result' to 'header' for clarity.
