1. Save pre-commit state in the beginning of end block.
2. Provide an interface for custom elections to rollback on crash recovery.
3. Simplify pre-commit management.
4. Add crash recovery for updert-validator and chain migration elecitons.
- Do not conclude migration election if there is a migration in progress.
- Rewrite election tests to not use mocks and assert many different things.
- Record concluded elections in the `election` collection.
* Problem: We need a way to synchronize a halt to block production to allow for upgrades across breaking changes.
* Solution: Created `MigrationElection`.
* Problem: Need documentation for `migration` elections.
* Solution: Updated the docs.
* Problem: `MigrationElection` needs 'new' CLI method.
* Solution: Updated the definition of `election` to include the new `migration` type.
* Problem: The way `end_block` checks for concluded elections assumes there is only one type of election (so we can't conclude an `upsert-validator` and a `chain-migration` at the same height).
* Solution: Re-engineered the code in `Elections` to conclude multiple elections in the same block. If more than one election change the validator set, only one of them is applied.
* Problem: Tendermint change to store validator changes at height h+2 will break `Election.get_status`.
* Solution: Reworked `get_validator_change` to look at only the latest block height or less.
* Problem: No good way to check for val set absence.
Solution: Make get_validator_set/get_validators return None/[] when there are no validators yet.
* Problem: Incompatible ABCI chain upgrades.
Solution: Record known chains and sync through InitChain. Triggering the migration and adjusting other ABCI endpoints will follow.
* Problem: `run_upsert_validator_approve` was getting the voting power in a convoluted way
Solution: Changed it to get the voting power from the election outputs
* Problem: `run_upsert_validator_approve` casts votes for *all* voters, not just the user calling the command
Solution: Filter vote txs by the users public key
* Problem: Docs needed a more specific description of how to input the path to the private-key file
Solution: Changed the wording a bit
* Problem: Source files contain no license info
Solution: Add comments with SPDX license info to source files
* Python 3 files don't need # -*- coding: utf-8 -*-
* Problem: RethinkDB, change feed, old mongo, admin interface are not supported any longer.
Solution: Remove unsupported functionality. Bring the MongoDB backend implementation completely to the localmongodb package. Fix the test setup.
* Problem: Nothing depends on multipipes any longer.
Solution: Remove multipipes from setup.py.
* Problem: The how-to-run-tests doc uses --database-backend.
Solution: Do not include the --database-backend option into the documented pytest usage.
* Problem: The backends docs are outdated.
Solution: Document MongoDB as the default and only backend for BigchainDB.
* Problem: The inputs fixtures uses old blocks API.
Solution: Change the inputs fixtures to use the new blocks API.
* Problem: rethinkdb package is not used anymore.
Solution: Remove the rethinkdb dependency from setup.py.
* Problem: The abci-marked tests use outdated Mongo conn.
Solution: Replace MongoDBConnection with LocalMongoDBConnection for them.
