Configuration

tael serve reads its configuration from flags first, then environment variables, then sensible defaults. Most deployments only set a directory or two; everything below is optional.

Addresses & directories

Name
TAEL_OTLP_GRPC_ADDR
Type
default 127.0.0.1:4317
Description
OTLP gRPC ingest address. Flag: --otlp-grpc-addr.
Name
TAEL_REST_API_ADDR
Type
default 127.0.0.1:7701
Description
REST API address. Flag: --rest-api-addr.
Name
TAEL_DATA_DIR
Type
default ~/.tael/data
Description
Where hot-tier and cold-tier data live. Flag: --data-dir.
Name
TAEL_WAL_DIR
Type
default ~/.tael/wal_files
Description
Write-ahead log directory. Flag: --wal-dir. (Also honors WALRUS_DATA_DIR.)

Storage backend

Name
TAEL_STORAGE
Type
tael-backend (default) | duckdb
Description
Selects the storage engine. Flag: --storage. See Storage & Blobs.

Tiering & retention

These tune the tael-backend engine's hot→cold rolloff and retention.

Name
TAEL_HOT_TIER_HOURS
Type
default 24
Description
How many hours of data the hot LSM tier holds before rolling off to the Parquet cold tier.
Name
TAEL_COMPACT_INTERVAL_SECS
Type
default 3600
Description
Interval for compaction, retention enforcement, and blob garbage collection.
Name
TAEL_TRACE_RETENTION_DAYS
Type
default 365
Description
How long span metadata is kept in the cold tier.

Payloads (prompts, completions, large log bodies) are stored as content-addressed blobs on an independent retention clock, so you can keep a year of span metadata while expiring heavy payloads much sooner.

Other

Name
RUST_LOG
Type
default info
Description
Server log level (error, warn, info, debug, trace).

Cluster coordination (advanced)

Single-node is the default. Setting TAEL_CLUSTER_LISTEN turns on gossip-based coordination and WAL replication for high-availability deployments.

Name
TAEL_CLUSTER_LISTEN
Type
addr
Description
UDP gossip listen address. Coordination is off unless this is set.
Name
TAEL_CLUSTER_ADVERTISE
Type
addr
Description
Address peers reach this node on. Defaults to the listen address.
Name
TAEL_CLUSTER_SEEDS
Type
csv
Description
Seed peers' gossip addresses.
Name
TAEL_CLUSTER_ID
Type
default tael
Description
Replication-group id that peers must share.
Name
TAEL_NODE_ID
Type
string
Description
This node's id (defaults to the advertise address).
Name
TAEL_WAL_STANDBYS
Type
csv
Description
Standby REST endpoints to replicate the WAL to (e.g. http://standby-1:7701,...).
Name
TAEL_WAL_REQUIRED_ACKS
Type
int
Description
Number of standby acks required before a write is considered durable.
Name
TAEL_QUERY_SHARDS
Type
csv
Description
Query-tier shard endpoints to fan out reads across.

Cluster setup, WAL replication, and query-tier fan-out are documented in depth in the project's docs/tael-server-scaling-ha.md.