Transactions from an invalid block should be put back into the backlog

[r-marques]

When a block is marked invalid the transactions in the block need to be re-assigned and put back into the backlog.

The difficult part is to decide which node should do it. A simple solution would be to have a changefeed listening to updates on the bigchain table (the only updates permitted should be appending new votes) and everytime a new vote comes in we check if a majority decision was reached. If so and if the decision is invalid put the transactions back into the backlog. Since the primary key in the backlog table is the id of the transaction even if several nodes try to do this at the same time there will be no duplicated transactions in the backlog.

[rhsimplex]

Ok, trying to get some understanding here. It seems the functions involved from core.py is write_vote.
write_vote occasionally looks up a block by primary key, and appends a new vote to the votes field at that record.

So the changefeed will look something like

feed = r.table('bigchain').filter(r.row['votes']).changes().run(self.conn)

Which I suppose will go somewhere in processes.py (somewhere in the map_bigchain function)? When a majority invalid vote happens (btw, how does bigchain know what a majority is...from the number of keys?) then all transactions are put back into q_new_transactions or inserted directly? I think inserted directly. The question is where does the function which does that go...in block.py?

Do the votes currently trigger anything at all? It looks like the votes get written but are never used again, correct?

Finally, should an invalidated block be deleted once all of its transactions are liquidated?

[r-marques]

So the changefeed will look something like

feed = r.table('bigchain').filter(r.row['votes']).changes().run(self.conn)

Which I suppose will go somewhere in processes.py (somewhere in the map_bigchain function)?

We can use the already existing changefeed r.table('bigchain').changes().run(b.conn) and just act on updates assuming that the only updates in bigchain table will be new votes.
You can put the new_val in a queue and then create a process that will read from the queue, check if the block was decided invalid and if so write the transactions back to the backlog using write_transactions in every transaction in the block.