Configuration

The DS server supports layered TOML configuration plus env-var overrides.

Load order (later wins):

built-in defaults
config/default.toml (if present)
config/<profile>.toml (if present; selected with --profile)
config/local.toml (if present; intended for local overrides)
--config <path> override file
environment variables

CLI options:

Flag	Description
`--profile <name>`	Loads `config/<name>.toml`
`--config <path>`	Loads an additional TOML file last

Sample config files in this repo:

config/default.toml (baseline defaults)
config/dev.toml (development overrides)
config/prod.toml (production example)

Example:

cargo run -- --profile dev
cargo run -- --profile prod --config /etc/durable-streams/override.toml

Environment variables use the DS_ prefix with double-underscore section separators (e.g., DS_SERVER__PORT).

Server

Variable	Default	Description
`DS_SERVER__PORT`	`4437`	TCP port to listen on
`DS_HTTP__CORS_ORIGINS`	`*`	Allowed CORS origins. `*` allows all. Multiple origins can be comma-separated (e.g., `https://app.example.com,https://admin.example.com`).
`RUST_LOG`	`info`	Log level filter (tracing format: `debug`, `info`, `warn`, `error`, or per-module like `durable_streams=debug`). Takes precedence over `DS_LOG__RUST_LOG`.
`DS_LOG__RUST_LOG`	`info`	Default log level filter, applied through the TOML config layer. Overridden by `RUST_LOG` when both are set.

Transport (optional direct TLS)

Variable	Default	Description
`DS_TLS__CERT_PATH`	unset	Path to PEM certificate for direct TLS termination. Must be set together with `DS_TLS__KEY_PATH`.
`DS_TLS__KEY_PATH`	unset	Path to PEM/PKCS#8 private key for direct TLS termination. Must be set together with `DS_TLS__CERT_PATH`.

Protocol

Variable	Default	Description
`DS_SERVER__LONG_POLL_TIMEOUT_SECS`	`30`	How long to hold a long-poll request before returning `204 No Content`. Set lower (e.g., `2`) for fast-feedback testing.
`DS_SERVER__SSE_RECONNECT_INTERVAL_SECS`	`60`	SSE reconnect interval in seconds (matches Caddy's `sse_reconnect_interval`). Enables CDN request collapsing. Set to `0` to disable.

Memory limits

Variable	Default	Description
`DS_LIMITS__MAX_MEMORY_BYTES`	`104857600` (100 MB)	Maximum total memory across all streams. Appends exceeding this return `413 Payload Too Large`.
`DS_LIMITS__MAX_STREAM_BYTES`	`10485760` (10 MB)	Maximum bytes per individual stream.

Storage

Variable	Default	Description
`DS_STORAGE__MODE`	`memory`	Storage backend mode: `memory`, `file-fast`, `file-durable`, `acid` (alias: `redb`).
`DS_STORAGE__DATA_DIR`	`./data/streams`	Root directory for persistent backends (`file-*`, `acid`).
`DS_STORAGE__ACID_SHARD_COUNT`	`16`	Number of redb shards when `DS_STORAGE__MODE=acid`; must be power-of-2 in `1..=256` (invalid values return an error).

Sync service (e2e stack)

These variables configure the sync service container, not the DS server itself:

Variable	Default	Description
`ELECTRIC_URL`	`http://electric:3000`	Electric SQL Shape API base URL
`DS_SERVER_URL`	`http://server:4437`	DS server URL (internal Docker network)
`POSTGRES_URL`	`postgresql://postgres:password@postgres:5432/durable_streams`	Postgres connection string

Example

# Development (fast timeouts for testing)
DS_SERVER__LONG_POLL_TIMEOUT_SECS=2 DS_SERVER__SSE_RECONNECT_INTERVAL_SECS=5 cargo run

# Development profile from TOML
cargo run -- --profile dev

# Production (restricted CORS, custom port)
DS_SERVER__PORT=8080 DS_HTTP__CORS_ORIGINS=https://app.example.com cargo run

# Optional direct TLS (proxy->server encryption or direct serving)
DS_TLS__CERT_PATH=/etc/ds/tls/server.crt DS_TLS__KEY_PATH=/etc/ds/tls/server.key cargo run

# Debug logging
RUST_LOG=debug cargo run

Durable Streams Reference