Add shard_chain.py and collation.py

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Description

A basic architecture of basic sharding with many TODO tags. There are two main files:

1. sharding/shard_chain.py

• The ShardChain inherits from ethereum.pow.chain.Chain, this object maintains main top-level blocks and shard chain currently, perhaps will be separated if we use networkid to connect to different shard chain.
• New fields
  • shardId - the shard ID of the shard
  • parent_blocks[block_hash] - a dictionary of list which key is the hash of collation header and value is a list of block_hash. This object is used to store parent blocks of the specific collation.
  • shard_state_map[(shardId, block_hash)] - a dictionary which key is (shardId, block_hash) and value is the corresponding state root
  • shard_state - the most recent applied shard state
• TODO
  • [ ] Store previous shard states that haven’t included in top-level block temporarily
  • [ ] def get_shard_head_state should find the state of Longest Shard Chain

    2. sharding/collator.py

• A collator may call these functions:
  • create_collation(chain, txqueue=None, prev_state=None, coinbase='\x35' * 20, children_header=[]) - create a new collation
  • verify_collation_header(chain, collation_header, prev_state=None, children_header=[], main_chain_included=False) - verify a collation header
  • verify_collation - verify the execution result of a collation
  • sign_collation_header(chain, collation_header, local_validation_code_addr) - sign a collation with local_validation_code_addr
  • apply_collation(chain, prev_state, collation, block_hash, children_header=[]) - apply a collation to shard chain
• TODO
  • [ ] Call contracts to verify signatures
  • [ ] The algorithm to sign the collation
  • [ ] Apply finalization and incentives
  • [ ] Optimize the times of calling call_sample_function and call_validation_code_addr

Installation

For more details of environment, please refer to pyethereum.

sudo apt-get install libssl-dev build-essential automake pkg-config libtool libffi-dev libgmp-dev

git clone https://github.com/ethereum/sharding/

cd sharding

pip install -r requirements.txt

To install the dependencies necessary for development (testing, ...), run:

pip install -r dev_requirements.txt

Simple Scenario Test

A simple script to describe how would the nodes use this library in sharding/tests/test_depth_one.py. In this test, there are only shard 0 and shard 1.

sharding_config['MAX_SHARD_DEPTH'] = 1
sharding_config['SHARD_CHILD_COUNT'] = 1
sharding_config['SIGNATURE_COUNT'] = 1

Four nodes:

• ms_signer: the signer of shard 0
• ms_collator: the collator of shard 0
• cs_signer: the signer of shard 1
• cs_collator: the collator of shard 1

Scenario

1. cs_collator creates a collation of shard 1
2. cs_signer verifies and signs the collation of shard 1 and broadcasts it
3. ms_collator creates a collation of shard 0, includes the collation of shard 1 as one of its child
4. ms_signer verifies and signs the collation of shard 0 and broadcast it
5. ms_signer mines a block of top-level
6. All of the nodes get the block and apply the collation of shard 0 or shard 1
   • The input prev_state is the state of SERENITY_FORK_BLKNUM
   • chain.shard_state may be updated
   • chain.parent_blocks would be updated
   • chain.shard_state_map would be updated
7. cs_collator creates next collation of shard 1
   • Note that the input prev_state is the result of calling chain.get_prev_state(collation.header.parent_block_hash)
8. cs_signer verifies and signs the new collation of shard 1
   • Note that the input prev_state is the result of calling chain.get_prev_state(collation.header.parent_block_hash)

How to run

pytest sharding/tests/test_depth_one.py -s

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