ev-node-explainer

ev-node Architecture Explainer

ev-node is a sovereign rollup framework that allows building rollups on any Data Availability (DA) layer. It follows a modular architecture where components can be swapped.

Reference files:

• block-architecture.md - Block package deep dive
• da-sequencing.md - DA and sequencing deep dive

Core Principles

1. Zero-dependency core - core/ contains only interfaces, no external deps
2. Modular components - Executor, Sequencer, DA are pluggable
3. Two operating modes - Aggregator (produces blocks) and Sync-only (follows chain)
4. Separation of concerns - Block production, syncing, and DA submission are independent

Package Overview

Package	Responsibility
core/	Interfaces only (Executor, Sequencer)
types/	Data structures (Header, Data, State, SignedHeader)
block/	Block lifecycle management
execution/	Execution layer implementations (EVM, ABCI)
node/	Node initialization and orchestration
pkg/p2p/	libp2p-based networking
pkg/store/	Persistent storage
pkg/da/	DA layer abstraction

Block Package Deep Dive

The block package is the most complex part of ev-node. See block-architecture.md for the complete breakdown.

Component Summary

Components struct:
├── Executor    - Block production (Aggregator only)
├── Reaper      - Transaction scraping (Aggregator only)
├── Syncer      - Block synchronization
├── Submitter   - DA submission and inclusion
└── Cache       - Unified state caching

Entry Points

• NewAggregatorComponents() - Full node that produces and syncs blocks
• NewSyncComponents() - Non-aggregator that only syncs

Key Data Types

Header - Block metadata (height, time, hashes, proposer) Data - Transaction list with metadata SignedHeader - Header with proposer signature State - Chain state (last block, app hash, DA height)

Block Production Flow (Aggregator)

Sequencer.GetNextBatch()
    │
    ▼
Executor.ExecuteTxs()
    │
    ├──► SignedHeader + Data
    │
    ├──► P2P Broadcast
    │
    └──► Submitter Queue
            │
            ▼
        DA Layer

Block Sync Flow (Non-Aggregator)

┌─────────────────────────────────────┐
│           Syncer                     │
├─────────────┬─────────────┬─────────┤
│ DA Worker   │ P2P Worker  │ Forced  │
│             │             │ Incl.   │
└──────┬──────┴──────┬──────┴────┬────┘
       │             │           │
       └─────────────┴───────────┘
                  │
                  ▼
          processHeightEvent()
                  │
                  ▼
          ExecuteTxs → Update State

Data Availability Layer

The DA layer abstracts blob storage. ev-node uses Celestia but the interface is pluggable. See da-sequencing.md for full details.

Namespaces

DA uses 29-byte namespaces (1 byte version + 28 byte ID). Three namespaces are used:

Namespace	Purpose
Header	Block headers
Data	Transaction data (optional, can share with header)
Forced Inclusion	User-submitted txs for censorship resistance

DA Client Interface

type Client interface {
    Submit(ctx, data [][]byte, gasPrice, namespace, options) ResultSubmit
    Retrieve(ctx, height uint64, namespace) ResultRetrieve
    Get(ctx, ids []ID, namespace) ([]Blob, error)
}

Key Files

File	Purpose
pkg/da/types/types.go	Core types (Blob, ID, Commitment)
pkg/da/types/namespace.go	Namespace handling
block/internal/da/client.go	DA client wrapper
block/internal/da/forced_inclusion_retriever.go	Forced tx retrieval

---

Sequencing

Sequencers order transactions for block production. See da-sequencing.md for full details.

Two Modes

Mode	Mempool	Forced Inclusion	Use Case
Single	Yes	Yes	Traditional rollup
Based	No	Only source	High liveness guarantee

Sequencer Interface

type Sequencer interface {
    SubmitBatchTxs(ctx, req) (*SubmitBatchTxsResponse, error)
    GetNextBatch(ctx, req) (*GetNextBatchResponse, error)
    VerifyBatch(ctx, req) (*VerifyBatchResponse, error)
    SetDAHeight(height uint64)
    GetDAHeight() uint64
}

ForceIncludedMask

Batches include a mask distinguishing tx sources:

type Batch struct {
    Transactions      [][]byte
    ForceIncludedMask []bool  // true = from DA (must validate)
}

This allows the execution layer to skip validation for already-validated mempool txs.

Key Files

File	Purpose
core/sequencer/sequencing.go	Core interface
pkg/sequencers/single/sequencer.go	Hybrid sequencer
pkg/sequencers/based/sequencer.go	Pure DA sequencer
pkg/sequencers/common/checkpoint.go	Shared checkpoint logic

---

Forced Inclusion

Forced inclusion prevents sequencer censorship:

1. User submits tx directly to DA layer
2. Syncer detects tx in forced-inclusion namespace
3. Grace period starts (adjusts based on block fullness)
4. If not included by sequencer within grace period → sequencer marked malicious
5. Tx gets included regardless

Key Files

File	Purpose
block/public.go	Exported types and factories
block/components.go	Component creation
block/internal/executing/executor.go	Block production
block/internal/syncing/syncer.go	Sync orchestration
block/internal/submitting/submitter.go	DA submission
block/internal/cache/manager.go	Unified cache

Common Questions

How does block production work?

The Executor runs executionLoop():

1. Wait for block time or new transactions
2. Get batch from sequencer
3. Execute via execution layer
4. Create SignedHeader + Data
5. Broadcast to P2P
6. Queue for DA submission

How does syncing work?

The Syncer coordinates three workers:

• DA Worker - Fetches confirmed blocks from DA
• P2P Worker - Receives gossiped blocks
• Forced Inclusion - Monitors for censored txs

All feed into processHeightEvent() which validates and executes.

What happens if DA submission fails?

Submitter has retry logic with exponential backoff. Status codes:

• TooBig - Splits blob into chunks
• AlreadyInMempool - Skips (duplicate)
• NotIncludedInBlock - Retries with backoff
• ContextCanceled - Request canceled

How is state recovered after crash?

The Replayer syncs execution layer from disk:

1. Load last committed height from store
2. Check execution layer height
3. Replay any missing blocks
4. Ensure consistency before starting

Architecture Diagrams

For detailed component diagrams and state machines, see block-architecture.md.