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Lasso is configured via environment variables for runtime settings and YAML files for routing configuration. This page documents all available environment variables.

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Core Configuration

Required and recommended settings for running Lasso.
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SECRET_KEY_BASE
string
required
Phoenix signing and encryption secret. Must be at least 64 bytes. Generate with mix phx.gen.secret.
SECRET_KEY_BASE=$(mix phx.gen.secret)
Required in production. Omit in development (auto-generated).
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PHX_HOST
string
default:"localhost"
Public hostname for URL generation. Set to your domain in production.
PHX_HOST=rpc.example.com
Required in production for correct URL generation in responses and redirects.
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PHX_SERVER
string
default:"false"
Set to true to start the HTTP server. Required for releases and production deployments.
PHX_SERVER=true
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PORT
integer
default:"4000"
HTTP listener port.
PORT=4000
Useful for running multiple instances locally:
PORT=4001 iex -S mix phx.server
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PHX_SCHEME
string
default:"https"
URL scheme for external access. Automatically set to https in production.
PHX_SCHEME=https
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LASSO_NODE_ID
string
required
Unique, stable identifier for this node instance. Used for state partitioning (circuit breakers, metrics) via {provider_id, node_id} keys.
LASSO_NODE_ID=us-east-1
Convention: Use geographic region names when deploying one node per region (e.g., us-east-1, eu-west-1, ap-southeast-1).Required in production. Defaults to "local" in development.

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Clustering

Optional configuration for multi-node clustering.
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CLUSTER_DNS_QUERY
string
DNS name that resolves to all node IPs for automatic cluster discovery.
CLUSTER_DNS_QUERY=lasso.internal
Both CLUSTER_DNS_QUERY and CLUSTER_NODE_BASENAME must be set for clustering to activate.
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CLUSTER_NODE_BASENAME
string
Erlang distribution node basename.
CLUSTER_NODE_BASENAME=lasso
Nodes will be named <basename>@<ip> (e.g., lasso@10.0.1.5).

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Clustering Example

# Node 1 (us-east)
LASSO_NODE_ID=us-east-1
CLUSTER_DNS_QUERY=lasso.internal
CLUSTER_NODE_BASENAME=lasso

# Node 2 (eu-west)
LASSO_NODE_ID=eu-west-1
CLUSTER_DNS_QUERY=lasso.internal
CLUSTER_NODE_BASENAME=lasso
Nodes poll DNS every 5 seconds and automatically join the cluster. See Deployment Guide for details.

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Provider API Keys

API keys for RPC providers. Used in profile YAML via ${VAR_NAME} substitution.
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DRPC_API_KEY
string
dRPC API key. Get yours at https://drpc.org/
DRPC_API_KEY=your_drpc_api_key_here
Use in profile:
url: "https://eth.drpc.org/${DRPC_API_KEY}"
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ALCHEMY_API_KEY
string
Alchemy API key. Get yours at https://dashboard.alchemy.com/
ALCHEMY_API_KEY=your_alchemy_api_key_here
Use in profile:
url: "https://eth-mainnet.g.alchemy.com/v2/${ALCHEMY_API_KEY}"
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LAVA_API_KEY
string
Lava Network API key. Get yours at https://gateway.lavanet.xyz/
LAVA_API_KEY=your_lava_api_key_here
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ONE_RPC_API_KEY
string
1RPC API key. Get yours at https://www.1rpc.io/
ONE_RPC_API_KEY=your_1rpc_api_key_here
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CHAINSTACK_API_KEY
string
Chainstack API key. Get yours at https://console.chainstack.com/
CHAINSTACK_API_KEY=your_chainstack_api_key_here
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NODEREAL_API_KEY
string
NodeReal API key. Get yours at https://nodereal.io/
NODEREAL_API_KEY=your_nodereal_api_key_here

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Custom API Keys

You can use any environment variable in your profile configurations: 
providers:
  - id: "custom_provider"
    url: "https://rpc.example.com/v1/${MY_CUSTOM_API_KEY}"

export MY_CUSTOM_API_KEY=secret-key-here
Important: Unresolved variables crash at startup to prevent silent misconfiguration.

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Optional Settings

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LASSO_VM_METRICS_ENABLED
boolean
default:"true"
Enable VM metrics collection (memory, CPU, process counts).
LASSO_VM_METRICS_ENABLED=false
Set to false in production SaaS environments where VM metrics aren’t relevant.
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DATABASE_URL
string
PostgreSQL connection URL. Only used in cloud/SaaS deployments for persistent storage.
DATABASE_URL=postgresql://user:pass@host:5432/database
Not required for standalone deployments. Lasso uses in-memory ETS tables by default.

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.env File Support

Lasso loads environment variables from a .env file in the project root if present: 
# .env
LASSO_NODE_ID=local-dev
ALCHEMY_API_KEY=your-key-here
DRPC_API_KEY=another-key
Precedence: System environment variables override .env file values.

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Example .env File

# Core configuration
SECRET_KEY_BASE=your-secret-key-base-here
PHX_HOST=localhost
PORT=4000
LASSO_NODE_ID=local-dev

# Provider API keys
ALCHEMY_API_KEY=your_alchemy_api_key_here
DRPC_API_KEY=your_drpc_api_key_here
LAVA_API_KEY=your_lava_api_key_here
ONE_RPC_API_KEY=your_1rpc_api_key_here
CHAINSTACK_API_KEY=your_chainstack_api_key_here
NODEREAL_API_KEY=your_nodereal_api_key_here

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Production Checklist

Before deploying to production:
  • SECRET_KEY_BASE set (64+ bytes)
  • PHX_HOST set to public hostname
  • PHX_SERVER=true set
  • LASSO_NODE_ID set to unique, stable value
  • PORT configured for your infrastructure
  • API keys set for all BYOK providers in profiles
  • Environment variable substitution tested (startup should crash on unresolved vars)
  • Keys stored securely (secrets manager, not version control)
  • CLUSTER_DNS_QUERY set and resolving correctly
  • CLUSTER_NODE_BASENAME set
  • Erlang distribution ports open between nodes (4369 + epmd range)
  • Each node has unique LASSO_NODE_ID
  • Health check monitoring GET /api/health
  • TLS terminated at reverse proxy/load balancer
  • Structured JSON log drain configured
  • Rate limits configured in profile frontmatter

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Development vs Production

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Development

# Minimal development setup
LASSO_NODE_ID=local-dev
PORT=4000

# Optional: Add API keys for BYOK providers
ALCHEMY_API_KEY=your-key-here
Run with: 
mix phx.server

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Production

# Required
SECRET_KEY_BASE=<64+ byte secret>
PHX_HOST=rpc.example.com
PHX_SERVER=true
LASSO_NODE_ID=us-east-1

# Recommended
PORT=4000
PHX_SCHEME=https

# Provider keys (as needed)
ALCHEMY_API_KEY=<key>
DRPC_API_KEY=<key>

# Clustering (optional)
CLUSTER_DNS_QUERY=lasso.internal
CLUSTER_NODE_BASENAME=lasso
Run with: 
MIX_ENV=prod mix release
_build/prod/rel/lasso/bin/lasso start

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Environment Variable Precedence

  1. System environment variables (highest priority)
  2. .env file (loaded at startup)
  3. Application defaults (config/runtime.exs)
Example: 
# .env file
PORT=4000

# System override
PORT=5000 mix phx.server  # Uses 5000, not 4000

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Next Steps

Deployment Guide

Learn how to deploy Lasso in production

Profile Configuration

Configure chains and routing policies