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Dubly is configured entirely through environment variables. This allows for easy deployment across different environments and container orchestration platforms.

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Required Variables

These variables must be set for Dubly to start.
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DUBLY_PASSWORD
string
required
API password for authentication. Required for all /api/* endpoints via the X-API-Key header.Security Note: Use a strong, randomly generated password. This is the only authentication mechanism for the admin UI and API.
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DUBLY_DOMAINS
string
required
Comma-separated list of allowed domains for short links.Example: short.io,go.example.com,links.company.comDomain matching is case-insensitive. Only links with these domains can be created or accessed.

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Server Configuration

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DUBLY_PORT
string
default:"8080"
Port number the HTTP server listens on.Example: 3000
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DUBLY_APP_NAME
string
default:"Dubly"
Application name displayed in the admin UI.Example: Company Links

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Database Configuration

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DUBLY_DB_PATH
string
default:"./dubly.db"
Path to the SQLite database file. Will be created automatically if it doesn’t exist.Example: /var/lib/dubly/dubly.dbThe database file should be on a persistent volume in production environments.

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Geolocation

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DUBLY_GEOIP_PATH
string
default:""
Path to the MaxMind GeoLite2-City.mmdb file for IP geolocation lookups.Example: /var/lib/dubly/GeoLite2-City.mmdbWhen not set or empty, geolocation is gracefully disabled. Analytics will still be collected but without geographic data (country, city, region, coordinates will be empty).Download the GeoLite2 database from MaxMind.

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Analytics Configuration

Dubly uses an in-memory buffer for click analytics that periodically flushes to the database. These settings control the buffering behavior.
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DUBLY_FLUSH_INTERVAL
duration
default:"30s"
How often the analytics buffer is flushed to disk.Format: Duration string (e.g., 10s, 1m, 90s)Example: 60s for one minute intervalsShorter intervals mean more frequent writes (higher I/O) but less data loss on crashes. Must be a positive value.
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DUBLY_BUFFER_SIZE
integer
default:"50000"
Maximum number of click events held in memory before flushing.Example: 100000When the buffer is full, new clicks are dropped rather than blocking redirects. Size this based on your expected traffic volume and flush interval. Must be a positive value.

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Cache Configuration

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DUBLY_CACHE_SIZE
integer
default:"10000"
Maximum number of short links cached in memory for fast redirects.Example: 25000The cache uses an LRU (Least Recently Used) eviction policy. Higher values reduce database lookups for popular links but consume more memory. Must be a positive value.Memory estimate: Each cached entry uses approximately 200-300 bytes, so the default 10,000 entries use roughly 2-3 MB of RAM.

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Validation

Dubly validates configuration on startup:
  • DUBLY_PASSWORD and DUBLY_DOMAINS must be non-empty
  • DUBLY_FLUSH_INTERVAL, DUBLY_BUFFER_SIZE, and DUBLY_CACHE_SIZE must be positive values
  • Invalid values for numeric/duration fields fall back to defaults
  • Invalid domain list format will cause startup failure

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Example Configuration

# Required
export DUBLY_PASSWORD="your-secure-random-password"
export DUBLY_DOMAINS="short.io,go.example.com"

# Optional - Server
export DUBLY_PORT="8080"
export DUBLY_APP_NAME="Company Links"

# Optional - Database
export DUBLY_DB_PATH="/var/lib/dubly/dubly.db"

# Optional - Geolocation
export DUBLY_GEOIP_PATH="/var/lib/dubly/GeoLite2-City.mmdb"

# Optional - Analytics
export DUBLY_FLUSH_INTERVAL="30s"
export DUBLY_BUFFER_SIZE="50000"

# Optional - Cache
export DUBLY_CACHE_SIZE="10000"

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