Polkadot REST API

A REST service for interacting with Polkadot SDK-based blockchain nodes, rewritten from the ground up in Rust.

Public Instances

Parity hosts public instances of the Polkadot REST API for the following chains:

Chain	URL
Polkadot	https://polkadot-relay-rest-api.parity.io/v1
Kusama	https://kusama-relay-rest-api.parity.io/v1
Westend	https://westend-relay-rest-api.parity.io/v1
Polkadot Asset Hub	https://polkadot-hub-rest-api.parity.io/v1
Kusama Asset Hub	https://kusama-hub-rest-api.parity.io/v1
Westend Asset Hub	https://westend-hub-rest-api.parity.io/v1

Interactive API documentation is available at /docs on each instance (e.g., Polkadot Docs).

Usage Limits & Production Warning

These public instances are subject to rate limiting and are not intended for production use. For consistent testing or development, it is highly recommended to implement a retry strategy (e.g., exponential backoff) to handle potential request throttling gracefully.

Implementation Details

Logging

Logging levels supported are trace, debug, info, http, warn, error. http level allows for the emission of http information logging (method, route, elapsed time, success code). However currently tracing does not support http. To mitigate this, http level falls back to debug for successful logs, warn for 4** request logs, and error for 5**

Metrics and Monitoring

The API exposes Prometheus metrics at /metrics. To enable metrics collection, set:

export SAS_METRICS_ENABLED=true

A sample Grafana dashboard is provided in metrics/grafana/provisioning/dashboards/ for visualizing metrics.

docker compose

When running locally with docker compose, the Grafana dashboard is accessible at http://localhost:3000/d/polkadot-rest-api

If needed, the login and password for grafana are set to "admin" and "admin" respectfully.

All container resources are shown despite only the rest-api container being useful. To map the short ids for a container name you can run

docker ps --format '{{.ID}}: {{.Names}}'

Prometheus is accessible at http://localhost:9090/

Loki logs can be viewed in Grafana at Explore > Loki (select Loki as the datasource and query with {service_name="polkadot-rest-api"})

Benchmarks

Benchmark Workflows

The repository includes two main benchmark workflows that run automatically on pushes and pull requests to the main branch:

1. Benchmark workflow

• Builds and starts the server
• Runs performance tests against all configured endpoints
• Measures throughput (requests/second) and latency metrics (P50, P90, P99)
• Publishes results to GitHub Pages for historical tracking

GitHub Pages Dashboard: https://paritytech.github.io/polkadot-rest-api/dev/bench/

2. Benchmark Comparison (vs Sidecar)

• Runs benchmarks against public Sidecar instance
• Calculates performance differences and improvements
• Generates comparison reports with percentage differences
• Publishes comparison metrics to GitHub Pages for trend analysis

GitHub Pages Dashboard: https://paritytech.github.io/polkadot-rest-api/dev/bench/comparison/

Benchmark Metrics

Both workflows track the following metrics:

• Throughput: Requests per second (higher is better)
• Average Latency: Mean response time in milliseconds (lower is better)
• P50 Latency: 50th percentile latency (lower is better)
• P90 Latency: 90th percentile latency (lower is better)
• P99 Latency: 99th percentile latency (lower is better)

Testing

Unit Tests

Unit tests are embedded in the source code and test individual functions and modules.

Run all unit tests:

cargo test --workspace --all-features

Integration Tests

These tests are located in crates/integration_tests/tests/.

Available Integration Test Suites

1. basic.rs - Tests basic API endpoints (health, version)
2. latest.rs - Tests endpoints with the latest blockchain data
3. historical.rs - Tests endpoints with historical blockchain data

Test Configuration

Test definitions are located in crates/integration_tests/tests/config/test_config.json. To add new integration tests, add them to this configuration file.

Running Integration Tests

Step 1: Start the API server in one terminal

For Polkadot:

export SAS_SUBSTRATE_URL=wss://rpc.polkadot.io
cargo run --release --bin polkadot-rest-api

For Kusama:

export SAS_SUBSTRATE_URL=wss://kusama-rpc.polkadot.io
cargo run --release --bin polkadot-rest-api

Step 2: Run tests in another terminal

# Run all integration tests
cargo test --package integration_tests

# Run a specific test suite (recommended - cleaner output)
cargo test --package integration_tests --test historical  # All historical tests
cargo test --package integration_tests --test latest      # All latest tests
cargo test --package integration_tests --test basic       # All basic tests

Running tests for a specific chain:

# Historical tests (use fixtures for regression testing)
cargo test --package integration_tests --test historical test_historical_polkadot
cargo test --package integration_tests --test historical test_historical_kusama
cargo test --package integration_tests --test historical test_historical_asset_hub_polkadot
cargo test --package integration_tests --test historical test_historical_asset_hub_kusama

# Latest tests (test against live blockchain data)
cargo test --package integration_tests --test latest test_latest_polkadot
cargo test --package integration_tests --test latest test_latest_kusama
cargo test --package integration_tests --test latest test_latest_asset_hub_polkadot
cargo test --package integration_tests --test latest test_latest_asset_hub_kusama

Viewing test output:

By default, cargo captures test output. To see the detailed test progress with checkmarks and colored output, add -- --nocapture:

cargo test --package integration_tests --test historical test_historical_polkadot -- --nocapture

Example output:

Running 2 historical test cases for chain: polkadot

✓ /v1/blocks/{blockId} (block 1000000)
✓ /v1/blocks/{blockId} (block 10000000)

════════════════════════════════════════════════════════════
Historical Test Results for polkadot
════════════════════════════════════════════════════════════
  ✓ Passed: 2
  ✗ Failed: 0
════════════════════════════════════════════════════════════

Updating Test Fixtures

To update test fixtures with current blockchain data:

./scripts/update_fixtures.sh

Using .env files

The application supports configuration via .env files (for example, .env or .env.polkadot), allowing you to define all environment variables in one place. A sample configuration is available in .env.sample. To start polkadot-rest-api with a specific .env file, pass the file path as a command-line argument:

cargo run --release --bin polkadot-rest-api -- --env-file .env.polkadot

This command loads the environment variables specified in .env.polkadot file, which should be located in the project's root directory.

Multi-Chain Configuration

For Asset Hub deployments that need relay chain access (e.g., for useRcBlock parameter support or /rc/ related endpoints), configure SAS_SUBSTRATE_MULTI_CHAIN_URL:

# Primary connection: Asset Hub
export SAS_SUBSTRATE_URL=wss://polkadot-asset-hub-rpc.polkadot.io

# Additional chain: Relay chain (enables useRcBlock)
export SAS_SUBSTRATE_MULTI_CHAIN_URL='[{"url":"wss://rpc.polkadot.io","type":"relay"}]'

Supported chain types:

• relay - Relay chain (Polkadot, Kusama, Westend, etc.)
• assethub - Asset Hub parachain
• parachain - Generic parachain