HDF Examples

This page showcases common real-world use cases for HDF and the LUTX toolchain.

1. Nginx Virtual Host Generation

HDF is perfect for managing many similar virtual host configurations.

Data (`vhosts.hdf`)

(vhosts
  (vhost
    (domain "example.com")
    (root "/var/www/example")
    (php true)
  )
  (vhost
    (domain "api.example.com")
    (root "/var/www/api")
    (php true)
  )
)

Template (`nginx.lutx`)

{{ 
  local hosts = hdf_query("vhosts.vhost")
  for _, h in ipairs(hosts) do
    local cfg = string.format([[
server {
    listen 80;
    server_name %s;
    root %s;
    index index.php index.html;
}]], h.domain, h.root)
    
    save("sites-enabled/" .. h.domain .. ".conf", cfg)
  end
}}

2. Docker Compose with Environment Selection

Use HDF to maintain a single source of truth for different environments (Staging vs. Production).

Data (`env.hdf`)

(environments
  (prod
    (image "webapp:v2.5.0")
    (replicas 5)
    (db_host "db.prod.internal")
  )
  (staging
    (image "webapp:latest")
    (replicas 1)
    (db_host "localhost")
  )
)

Command

./bin/lutx --dataset env.hdf --simple-query 'environments.(prod)' docker-compose.tpl

3. Complex Data Exports (CSV Replacement)

Exporting complex state that CSV cannot handle.

(audit_log
  (event
    (timestamp "2026-02-19T10:00:00Z")
    (user "admin")
    (action "login")
    (metadata
      (ip "1.2.3.4")
      (user_agent "Mozilla/5.0...")
    )
  )
)

4. Protobuf Schema Definitions

Define your schemas in HDF and generate .proto files for different services.

(message User
  (field int32 id 1)
  (field string email 2)
  (field bool active 3)
)