Block Rotation

Introduction

SKALE Chain Block rotation is set by the rotate_after_block parameter in static_schain_params.json. The current default value is 1,024,000 blocks and is tuned by performance of consensus, skaled, and node storage.

Each SKALE Chain maintains a minimum to maximum number of blocks, currently 4,096,000 to 5,119,999 blocks.

Rotation is performed across 4 databases. Each database contains:

  • blocks

  • transactions and their receipts

  • log blooms

  • "best" (lastBlockHash, best block of the canonical chain)

  • "chainStart" (firstBlockHash, used when full chain isn’t available, for example after snapshot import)

Specification

  • SKALED maintains not an exact amount of blocks set in the config, but at least this amount.

  • Config parameter rotate_after_block sets the number of blocks after which skaled rotates 1 out of 4 databases. As a result, skaled maintains a minimum of rotate_after_block * 4, and a maximum rotate_after_block * 5 – 1 blocks.

  • Database rotation happens just before a new block is inserted.

API Changes

Calls Changes

eth_getBlockByNumber/eth_getBlockByHash

may return null

eth_getBlockTransactionCountByNumber/eth_getBlockTransactionCountByHash

may return null

eth_getUncleCountByBlockNumber/eth_getUncleCountByBlockHash

may return null

eth_getTransactionByBlockHashAndIndex/eth_getTransactionByBlockNumberAndIndex

may return null

eth_getUncleByBlockHashAndIndex/eth_getUncleByBlockNumberAndIndex

may return null

eth_getTransactionByHash

may return null

eth_getTransactionReceipt

may return null

eth_getFilterLogs/eth_getLogs

will treat removed blocks as if they have 0 logs

Mechanisms

Rotation is performed in the following DBs: blocks_and_extras

This database contains:

  • Blocks

  • Transactions and their receipts

  • Log blooms

  • “best” and “chainStart”

See database_layout.rst

Directory with DB contains subdirectories:

  1. 0.db

  2. 1.db

  3. 2.db

  4. 3.db

  5. 4.db

These directories are created automatically.

On rotation, one directory is deleted and re-created. The order of rotation is 0→4→3→2→1→0

The “current” piece for writing is marked with the key:

const std::string current_piece_mark_key =
    "ead48ec575aaa7127384dee432fc1c02d9f6a22950234e5ecf59f35ed9f6e78d"

with an empty value.

On rotation, this key is killed in old current piece and is created in new current piece.

On start, it’s searched in all pieces.

Insert/update operations go to current piece.

Read operations are performed in all pieces from most recent to least recent, until found.

Kill operations are performed in all pieces.

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