Add README.md to domain-executor

Author: liuchengxu

domains/client/domain-executor/README.md

@@ -0,0 +1,21 @@
+# Domain Executor
+
+## Overview
+
+Each executor instance, whether for system domain or core domain, consists of these components:
+
+- `BundleProducer`: Produce a bundle on new slot.
+  - `BundleElectionSolver`: Attempt to solve the bundle election challenge on each each slot in order to be allowed to author a bundle.
+  - `DomainBundleProposer`: Collect the transactions from transaction pool and a range of receipts upon solving the bundle election challenge successfully.
+- `BundleProcessor`: On each imported primary block, the bundle processor extracts the domain-specific bundles from the primary block, compiles the bundles to a list of extrinsics, construct a custom `BlockBuilder` with compiled extrinsics, execute and import the domain block. The receipt of processing the domain block is stored locally and then submitted to the primary chain in some bundle later.
+- domain worker: Run the components `BundleProducer` and `BundleProcessor` on the arrived events(new_slot, import_primary_block).
+- `GossipMessageValidator`: Validate the bundle gossiped from the domain node peers. Currently, this part is inactive and will be re-enabled in the future.
+
+## Modules structure
+
+- `domain_{block_processor,bundle_producer,bundle_proposer,worker}.rs`/`gossip_message_validator`
+  - General executor components, sharing the common logics between system domain and core domain.
+- `system_{block_processor,bundle_producer,bundle_proposer,worker}.rs`/`system_gossip_message_validator`
+  - Executor components specfic to the system domain.
+- `core_{block_processor,bundle_producer,bundle_proposer,worker}.rs`/`core_gossip_message_validator`
+  - Executor components specfic to the core domain.