- Prevent zero network ID ([#9763](https://github.com/paritytech/parity-ethereum/pull/9763)) and drop support for Olympic testnet ([#9801](https://github.com/paritytech/parity-ethereum/pull/9801)): The Olympic test net is dead for years and never used a chain ID but network ID zero. Parity Ethereum is now preventing the network ID to be zero, thus Olympic support is dropped. Make sure to chose positive non-zero network IDs in future.
- Multithreaded snapshot creation ([#9239](https://github.com/paritytech/parity-ethereum/pull/9239)): adds a CLI argument `--snapshot-threads` which specifies the number of threads. This helps improving the performance of full nodes that wish to provide warp-snapshots for the network. The gain in performance comes with a slight drawback in increased snapshot size.
- Expose config max-round-blocks-to-import ([#9439](https://github.com/paritytech/parity-ethereum/pull/9439)): Parity Ethereum imports blocks in rounds. If at the end of any round, the queue is not empty, we consider it to be _importing_ and won't notify pubsub. On large re-orgs (10+ blocks), this is possible. The default `max_round_blocks_to_import` is increased to 12 and configurable via the `--max-round-blocks-to-import` CLI flag. With unstable network conditions, it is advised to increase the number. This shouldn't have any noticeable performance impact unless the number is set to really large.
- Increase Gas-floor-target and Gas Cap ([#9564](https://github.com/paritytech/parity-ethereum/pull/9564)): the default values for gas floor target are `8_000_000` and gas cap `10_000_000`, similar to Geth 1.8.15+.
- Produce portable binaries ([#9725](https://github.com/paritytech/parity-ethereum/pull/9725)): we now produce portable binaries, but it may incur some performance degradation. For ultimate performance it's now better to compile Parity Ethereum from source with `PORTABLE=OFF` environment variable.
- RPC: `parity_allTransactionHashes` ([#9745](https://github.com/paritytech/parity-ethereum/pull/9745)): Get all pending transactions from the queue with the high performant `parity_allTransactionHashes` RPC method.
- Support `eth_chainId` RPC method ([#9783](https://github.com/paritytech/parity-ethereum/pull/9783)): implements EIP-695 to get the chainID via RPC.
- AuRa: finalize blocks ([#9692](https://github.com/paritytech/parity-ethereum/pull/9692)): The AuRa engine was updated to emit ancestry actions to finalize blocks. The full client stores block finality in the database, the engine builds finality from an ancestry of `ExtendedHeader`; `is_epoch_end` was updated to take a vec of recently finalized headers; `is_epoch_end_light` was added which maintains the previous interface and is used by the light client since the client itself doesn't track finality.
- Light-fetch: Differentiate between out-of-gas/manual throw and use required gas from response on failure ([#9824](https://github.com/paritytech/parity-ethereum/pull/9824))
- Drops support for olympic testnet, closes [#9800](https://github.com/paritytech/parity-ethereum/issues/9800) ([#9801](https://github.com/paritytech/parity-ethereum/pull/9801))
- Replace `tokio_core` with `tokio` (`ring` -> 0.13) ([#9657](https://github.com/paritytech/parity-ethereum/pull/9657))
- Support eth_chainId RPC method ([#9783](https://github.com/paritytech/parity-ethereum/pull/9783))
- Verify block syncing responses against requests ([#9670](https://github.com/paritytech/parity-ethereum/pull/9670))
- Add a new RPC `parity_submitWorkDetail` similar `eth_submitWork` but return block hash ([#9404](https://github.com/paritytech/parity-ethereum/pull/9404))
- Resumable EVM and heap-allocated callstack ([#9360](https://github.com/paritytech/parity-ethereum/pull/9360))
- Hardfork the testnets ([#9562](https://github.com/paritytech/parity-ethereum/pull/9562))
- Calculate sha3 instead of sha256 for push-release. ([#9673](https://github.com/paritytech/parity-ethereum/pull/9673))
- Ethcore-io retries failed work steal ([#9651](https://github.com/paritytech/parity-ethereum/pull/9651))
- Fix(light_fetch): avoid race with BlockNumber::Latest ([#9665](https://github.com/paritytech/parity-ethereum/pull/9665))
- Test fix for windows cache name... ([#9658](https://github.com/paritytech/parity-ethereum/pull/9658))
- Refactor(fetch) : light use only one `DNS` thread ([#9647](https://github.com/paritytech/parity-ethereum/pull/9647))
- Ethereum libfuzzer integration small change ([#9547](https://github.com/paritytech/parity-ethereum/pull/9547))
- Cli: remove reference to --no-ui in --unlock flag help ([#9616](https://github.com/paritytech/parity-ethereum/pull/9616))
- Remove master from releasable branches ([#9655](https://github.com/paritytech/parity-ethereum/pull/9655))
- Ethcore/VerificationQueue don't spawn up extra `worker-threads` when explictly specified not to ([#9620](https://github.com/paritytech/parity-ethereum/pull/9620))
- New ethabi ([#9511](https://github.com/paritytech/parity-ethereum/pull/9511))
- Remove initial token for WS. ([#9545](https://github.com/paritytech/parity-ethereum/pull/9545))
- Net_version caches network_id to avoid redundant aquire of sync readlock ([#9544](https://github.com/paritytech/parity-ethereum/pull/9544))
- Correct before_script for nightly build versions ([#9543](https://github.com/paritytech/parity-ethereum/pull/9543))
- Deps: bump kvdb-rocksdb to 0.1.4 ([#9539](https://github.com/paritytech/parity-ethereum/pull/9539))
- State: test when contract creation fails, old storage values should re-appear ([#9532](https://github.com/paritytech/parity-ethereum/pull/9532))
- Allow dropping light client RPC query with no results ([#9318](https://github.com/paritytech/parity-ethereum/pull/9318))
- Bump master to 2.2.0 ([#9517](https://github.com/paritytech/parity-ethereum/pull/9517))
- Enable all Constantinople hard fork changes in constantinople_test.json ([#9505](https://github.com/paritytech/parity-ethereum/pull/9505))
- [Light] Validate `account balance` before importing transactions ([#9417](https://github.com/paritytech/parity-ethereum/pull/9417))
- In create memory calculation is the same for create2 because the additional parameter was popped before. ([#9522](https://github.com/paritytech/parity-ethereum/pull/9522))
- Update patricia trie to 0.2.2 ([#9525](https://github.com/paritytech/parity-ethereum/pull/9525))
- Replace hardcoded JSON with serde json! macro ([#9489](https://github.com/paritytech/parity-ethereum/pull/9489))
- Fix typo in version string ([#9516](https://github.com/paritytech/parity-ethereum/pull/9516))
