---

title: 'Runtime' sidebar_label: 'Runtime' description: 'Runtime YAML reference'

The runtime section specifies configuration settings for the Spice runtime.

runtime.auth

runtime.auth.api-key

Spice supports adding optional authentication to its API endpoints via configurable API keys. Learn more.

API key authentication supports the following configuration parameters:

Parameter name	Optional	Default	Description
enabled	Yes	true	Defaults to true. Whether API key authentication is enabled
keys	Yes	[]	A list of API keys used to authenticate requests.

runtime.dataset_load_parallelism

This setting specifies the maximum number of datasets that can be loaded in parallel during startup. By default, the number of parallel datasets is unlimited.

runtime.caching

This setting specifies cache settings for supported Runtime components:

• sql_results: Specifies cache settings for results from SQL queries.
• search_results: Specifies cache settings for results from searches.
• embeddings: Specifies cache settings for embeddings requests.

Runtime caches support common configuration parameters:

Parameter name	Optional	Default	Description
enabled	Yes	true	Defaults to true.
max_size	Yes	128MiB	Maximum cache size. Defaults to 128MiB.
eviction_policy	Yes	lru	Cache replacement policy when the cache reaches max_size. Defaults to lru. Supports lru (Least Recently Used) and tiny_lfu (Tiny Least Frequently Used, higher hit rate for skewed access patterns).
item_ttl	Yes	1s	Cache entry expiration duration (Time to Live). Defaults to 1 second.
hashing_algorithm

runtime.caching.search_results

The search results cache section specifies runtime search cache configuration. Learn more.

The search results cache supports the common cache configuration parameters.

runtime.caching.embeddings

The embeddings cache section specifies runtime embeddings requests cache configuration. Learn more.

The embeddings cache supports the common cache configuration parameters.

runtime.caching.sql_results

The SQL results cache section specifies runtime SQL query cache configuration. Learn more.

In addition to the common cache configuration parameters, sql_results also supports the following parameters:

Parameter name	Optional	Default	Description
cache_key_type	Yes	plan	Determines how cache keys are generated. Defaults to plan. plan uses the query's logical plan, while sql uses the raw SQL query string.
encoding	Yes	none	Compression algorithm for cached results. Defaults to none. Supports none or zstd.
stale_while_revalidate_ttl	Yes	0s	Duration to serve stale cache entries while revalidating in the background. When set to a non-zero value, expired cache entries continue to be served while a background refresh occurs. Defaults to 0s (disabled).

:::info

runtime.results_cache has been deprecated and will be removed in a future release. If runtime.results_cache is specifed in the spicepod it will override the runtime.caching.sql_results settings if it is not defined.

:::

Choosing a cache_key_type

• plan (Default): Uses the query's logical plan as the cache key. Matches semantically equivalent queries but requires query parsing.
• sql: Uses the raw SQL string as the cache key. Provides faster lookups but requires exact string matches. Queries with dynamic functions, such as NOW(), may produce unexpected results. Use sql only when results are predictable.

Use sql for the lowest latency with identical queries that do not include dynamic functions. Use plan for greater flexibility.

Choosing a hashing_algorithm

• xxh3 (Default): Uses the XXH3 algorithm for hashing the cache keys. XXH3 is a fast, non-cryptographic hash algorithm that provides high performance and good distribution. It is suitable for scenarios where speed is critical and cryptographic security is not required.
• siphash: Uses the SipHash1-3 algorithm for hashing the cache keys, the default hashing algorithm of Rust. This hashing algorithm is a secure algorithm that implements verified protections against "hash flooding" denial of service (DoS) attacks. Reasonably performant, and provides a high level of security.
• ahash: Uses the AHash algorithm for hashing the cache keys. The AHash algorithm is a high quality hashing algorithm, and has claimed resistance against hashing DoS attacks. AHash has higher performance than SipHash1-3, especially when used with cache_key_type: plan.
• blake3: Uses the BLAKE3 cryptographic hash function. BLAKE3 is a fast, parallelizable hash function that provides cryptographic security while maintaining high performance. It is suitable for scenarios requiring both speed and cryptographic guarantees.
• xxh32, xxh64, : Variants of the XXH hashing algorithm with different output sizes. These algorithms offer a balance between speed and collision resistance, with larger hash sizes providing better collision resistance at the cost of performance.

Use xxh3 (the default) for its superior speed in most scenarios. Use ahash, xxh64 or xxh128 for reduced collision probability when caching a large number of queries. Use blake3 when cryptographic security is required. Use siphash when protection against hash flooding attacks is a priority.

runtime.params

Optional. Global key-value parameters for the runtime.

HTTP Rate Control

HTTP-based connectors (HTTP/HTTPS, GraphQL, GitHub) support the following rate control defaults:

Parameter Name	Description
http_max_concurrent_requests	Default maximum concurrent HTTP requests per upstream origin. Can be overridden per-dataset with max_concurrent_requests.
http_requests_per_second_limit	Default maximum HTTP requests per second per upstream origin. Can be overridden per-dataset with requests_per_second_limit.
http_requests_per_minute_limit	Default maximum HTTP requests per minute per upstream origin. Can be overridden per-dataset with requests_per_minute_limit.
http_rate_control_jitter_min	Default minimum random delay before HTTP requests when rate control is active. Defaults to 5ms when a rate limit is configured. Can be overridden per-dataset.
http_rate_control_jitter_max	Default maximum random delay before HTTP requests when rate control is active. Defaults to 10ms when a rate limit is configured. Can be overridden per-dataset.

Spatial SQL Functions (opt-in)

PostGIS-style spatial ST_* SQL functions (via geodatafusion) can be optionally registered with the SQL engine.

Parameter Name	Description
geo	Set to enabled to register ST_* spatial functions. Requires a spiced binary built with the geo Cargo feature (cargo build -p spiced --features geo). Unset by default.

Both gates must be satisfied: the binary must be built with --features geo and runtime.params.geo: enabled must be set in the Spicepod. Standard distributions of spiced do not include the geo feature, so spatial functions remain unregistered unless you produce a custom build.

Spice Cayenne (engine-global)

Engine-global tuning for the Spice Cayenne data accelerator. These apply to every Cayenne-accelerated dataset in the instance and are not valid under a dataset's acceleration.params (per-dataset Cayenne parameters are documented on the Cayenne accelerator page).

Parameter Name	Description
cayenne_footer_cache_mb	Size of the engine-wide in-memory Vortex footer cache in megabytes, shared across all Cayenne datasets. Defaults to 128.
cayenne_filter_propagation	Enables Cayenne's filter-propagation optimizer rules. Accepts enabled or disabled; defaults to disabled.
cayenne_optimizer_rules	Selects which Cayenne optimizer rules run. Accepts auto (default), all, none / disabled, or a comma-separated list of rule names.
cayenne_compaction_memory_fraction	Fraction of the query memory pool reserved for the dedicated Cayenne compaction pool. Defaults to 0.2 (clamped to a supported range). Applied only when a Cayenne dataset is enabled and dedicated thread pools are not disabled.
cayenne_sort_merge_min_rows	Advanced anti-join tuning: row-count threshold above which filter propagation switches to a sort-merge strategy. Internally tuned default.

runtime.source_rate_control

Optional. Configures how Spice limits outbound requests to upstream data sources, and optionally enables cluster-wide coordination through persisted state in object storage.

Without state_location, rate limits are local to each Spice instance. When state_location is set, Spice instances coordinate through object storage so that a configured limit is shared across the cluster. For example, requests_per_second_limit: 20 means approximately 20 RPS total across all replicas, not 20 RPS per replica.

Parameter Name	Optional	Default	Description
state_location	Yes	-	Root URI for globally persisted rate-control state (e.g. s3://bucket/path/). Enables cluster-wide rate control when set. Without this, limits are local to each Spice instance.
params	Yes	-	Object-store authentication parameters for state_location. Supports the same keys as other object-store configurations (e.g. s3_region, s3_key, s3_secret for S3; account, access_key for Azure). Supports ${ secrets:NAME } references.
refresh_interval	Yes	30s	How often each instance refreshes and persists per-source rate-control state. Longer intervals reduce object-store writes but adapt more slowly to demand changes.
github_concurrent_connections_limit	Yes	10

HTTP/API rate limits are configured through runtime.params (cluster defaults) and per-dataset overrides. Precedence is:

When state_location is set, the configured RPS/RPM quota is converted into a token budget per lease window and distributed across replicas using a demand-weighted leased token-bucket model.

runtime.functions

Controls whether functions declared in the top-level functions: section (and tools: entries with as_sql: true) are registered with the SQL engine. Defaults to disabled.

Parameter	Optional	Default	Description
enabled	Yes	false	When true, the runtime registers functions: entries and exposes them via SQL and /v1/functions.

When disabled, the functions: block is parsed but not registered, list_udfs() returns no user-source rows, and GET /v1/functions returns an empty array.

See the Functions Spicepod reference for the function declaration schema.

runtime.shutdown_timeout

Controls how long Spice waits for connections to be gracefully drained and for components to shut down cleanly during runtime termination. Defaults to 30 seconds.

runtime.tls

The TLS section specifies the configuration for enabling Transport Layer Security (TLS) for all endpoints exposed by the runtime. Learn more about enabling TLS.

In addition to configuring TLS via the manifest, TLS can also be configured via spiced command line arguments using the --tls-enabled true flag along with --tls-certificate/--tls-certificate-file and --tls-key/--tls-key-file.

Certificate Hot-Reload

Spice can hot-reload TLS certificates and client CA files for runtime endpoints. Update the certificate, key, or CA file on disk, then send SIGHUP to the Spice process to reload without restart. Only file-based certificates/keys/CA are hot-reloaded (not inline PEM). Existing connections are not interrupted; only new connections use the updated files. If reload fails, the previous certificate remains active and a warning is logged.

Steps:

1. Replace the certificate/key/CA file on disk.
2. Send SIGHUP to the Spice process (e.g., kill -SIGHUP <pid>).
3. Check logs for reload confirmation or errors.

runtime.tls.enabled

Enables or disables TLS for the runtime endpoints.

runtime.tls.certificate

The TLS certificate to use for securing the runtime endpoints. The certificate can also come from secrets.

runtime.tls.certificate_file

The path to the TLS PEM-encoded certificate file. Only one of certificate or certificate_file must be used.

runtime.tls.key

The TLS key to use for securing the runtime endpoints. The key can also come from secrets.

runtime.tls.key_file

The path to the TLS PEM-encoded key file. Only one of key or key_file must be used.

runtime.tls.client_auth_mode

:::info Enterprise Feature mTLS (client certificate authentication) is included in the Enterprise distribution of Spice.ai. Learn more. :::

Controls whether the runtime requires, requests, or ignores client certificates on its public endpoints (HTTP, Flight, Metrics). Defaults to none.

Mode	Behavior
none (default)	Standard one-way TLS. No client certificate is requested.
request	The server sends a CertificateRequest but accepts connections without a certificate. Presented certificates are verified against the configured CA. Useful for migration or audit-only deployments.
required	A valid client certificate is required. The Flight (gRPC) listener rejects connections without a certificate at the TLS handshake. The HTTP listener admits no-cert connections so /health and /v1/ready remain accessible for Kubernetes probes, but all other HTTP endpoints return 401 without a verified client certificate. The metrics listener has no client-auth gate.

Requires client_auth_ca_file or client_auth_ca to be set when mode is request or required.

runtime.tls.client_auth_ca_file

Path to a PEM-encoded CA bundle used to verify client certificates. The file is watched for changes and reloaded atomically alongside the server certificate and key.

runtime.tls.client_auth_ca

Inline PEM (or ${ secrets:... }) form of the client CA bundle. Mutually exclusive with client_auth_ca_file. Inline material is loaded once at startup and is not hot-reloaded.

runtime.task_history

The task history section specifies runtime task history configuration. For more details, see the Task History documentation.

Parameter name	Optional	Description
enabled	Yes	Defaults to true.
captured_output	Yes	Specifies the level of output captured by the task history table. Defaults to none.
captured_plan	Yes	Controls SQL query plan capture. Options: none (default), explain, or explain analyze. Query plans are captured asynchronously after query completion.
min_sql_duration	Yes	Minimum query execution duration before a plan is captured. Only queries exceeding this threshold are captured. Example: 5s.
min_plan_duration	Yes	Minimum plan execution duration before a plan is captured. This threshold applies to the execution time of the EXPLAIN operation itself. Example: 10s.
retention_period

runtime.cors

The CORS section specifies the configuration for enabling Cross-Origin Resource Sharing (CORS) for the HTTP endpoint. By default, CORS is disabled.

Default configuration:

runtime.cors.enabled

Enables or disables CORS for the HTTP endpoint. Defaults to false.

runtime.cors.allowed_origins

A list of allowed origins for CORS requests. Defaults to ["*"], which permits all origins.

Example:

This configuration permits requests only from the https://example.com origin.

runtime.query.memory_limit

The memory_limit parameter sets a memory usage cap for the Spice runtime query engine. This limit applies only to the query engine and should be used in addition to other memory configuration options, such as duckdb_memory_limit. When the limit is reached, DataFusion spills intermediate data to disk using the directory configured in runtime.query.temp_directory.

If not specified, defaults to 90% of total system memory (container-aware).

Specify the value as a size, for example 4GiB or 1024MiB.

For detailed memory information, see Memory.

runtime.query.spill_compression

The spill_compression parameter configures compression for spill files generated during large query execution in the Spice runtime.

Supported values:

• zstd (default): Enables high compression ratios for spill files, reducing disk usage but with moderate (de)compression speed.
• lz4_frame: Provides faster (de)compression, resulting in larger spill files and potentially higher disk usage.
• uncompressed: Disables compression. Spill files will be the largest, but with no (de)compression overhead.

This setting controls the trade-off between disk space usage and query performance for large-scale analytics workloads.

runtime.query.temp_directory

The path to a temporary directory that Spice uses for query and acceleration operations that spill to disk. For more details, see the Managing Memory Usage documentation and the DuckDB Data Accelerator documentation.

runtime.output_level

Controls verbosity in addition to the existing CLI and environment variable support.. Supported values are info, verbose, and very_verbose. The value is applied in the following priority: CLI, environment variables, then YAML configuration.

runtime.telemetry

The telemetry section configures runtime telemetry collection and export. Learn more.

runtime.telemetry.enabled

Enables or disables runtime telemetry collection. Defaults to true.

runtime.telemetry.metric_prefix {#runtimetelemetrymetric_prefix}

Optional string prepended to every exported metric name. Useful for namespacing Spice metrics in shared backends (e.g. Datadog, Grafana Cloud, New Relic) so they do not collide with metrics from other services. Defaults to no prefix.

The prefix applies to all metric readers — the Prometheus scrape endpoint (--metrics), the cluster on-demand OTLP reader, and the otel_exporter push exporter — because OpenTelemetry views are configured at the meter-provider level rather than per reader.

With this configuration, the runtime metric query_duration_ms is exported as spiceai.query_duration_ms.

runtime.telemetry.properties {#runtimetelemetryproperties}

Map of custom key/value attributes attached to telemetry metrics emitted by spiced. Applied as OpenTelemetry resource attributes on the runtime's MeterProvider, so they appear as dimensions/tags on every metric exported via the Prometheus scrape endpoint, the cluster on-demand OTLP reader, and the otel_exporter push exporter. Defaults to empty.

The standard OpenTelemetry environment variables (OTEL_SERVICE_NAME, OTEL_RESOURCE_ATTRIBUTES) are still honored and act as defaults; explicit properties entries take precedence on key conflicts.

For backends that map OTLP resource attributes to tags through additional configuration (e.g. Datadog), see the Datadog OTLP guide.

runtime.telemetry.otel_exporter

Configures an OpenTelemetry metrics exporter to push metrics to an OpenTelemetry collector. The exporter automatically infers the protocol (gRPC or HTTP) based on the endpoint configuration.

Parameter name	Optional	Default	Description
enabled	Yes	true	Whether the OpenTelemetry exporter is enabled.
endpoint	No	-	The OpenTelemetry collector endpoint. Protocol is inferred from the format (see examples below).
push_interval	Yes	60s	How frequently metrics are pushed to the collector. Specify as a duration.
metrics	Yes	[]	List of metric names to export. When empty (default), all metrics are exported.
headers	Yes	{}	Map of headers to send with each export request. For HTTP these are sent as HTTP headers; for gRPC they are sent as metadata entries (keys must be lowercase ASCII). Values support the ${secrets:...} replacement syntax for loading credentials from a secret store.

Protocol inference:

• gRPC (default): Use a bare host:port endpoint without a scheme (e.g., localhost:4317). gRPC uses port 4317 by default.
• HTTP: Include the http:// or https:// scheme and the /v1/metrics path (e.g., http://localhost:4318/v1/metrics). HTTP uses port 4318 by default.

Examples:

gRPC configuration:

HTTP configuration:

With metric filtering (export only specific metrics):

:::caution Filtering happens after metric_prefix is applied The whitelist is matched against the final metric name, after runtime.telemetry.metric_prefix has been prepended. If you set metric_prefix: 'spiceai.', the entries under metrics: must include the prefix (e.g. spiceai.query_duration_ms), otherwise nothing will match and no metrics will be exported. :::

Authenticated exporters:

For collectors that require authentication, set the headers map. Load credentials from a secret store via ${secrets:...} rather than committing them to source.

Datadog (OTLP/HTTP) — replace us3 with your Datadog site:

Grafana Cloud (OTLP/HTTP) — use the base64 instanceID:accessPolicyToken from the Grafana Cloud OpenTelemetry connection page:

gRPC collector with auth metadata (keys must be lowercase ASCII):

runtime.metrics

Specifies metrics that are disabled by default.

Following metrics are disabled by default:

• dataset_acceleration_max_timestamp_before_refresh_ms
• dataset_acceleration_max_timestamp_after_refresh_ms
• dataset_acceleration_refresh_lag_ms
• dataset_acceleration_ingestion_lag_ms

For details about these metrics, see Observability.

runtime.flight

Configures Arrow Flight protocol settings for the runtime.

Parameter name	Optional	Default	Description
max_message_size	Yes	-	Maximum size of a single Arrow Flight message.
do_put_rate_limit_enabled	Yes	true	Whether rate limiting is applied to DoPut Arrow Flight operations.

runtime.mcp

Configures settings for the Spice MCP server endpoint (/v1/mcp).

runtime.mcp.allowed_hosts

Controls which Host header values are accepted on the /v1/mcp endpoint. This prevents DNS rebinding attacks against the MCP server.

Behavior	Configuration
Default (not set)	Only localhost, 127.0.0.1, and ::1 are permitted. Requests with any other Host value receive 403 Forbidden.
Explicit list	Replaces the defaults entirely. Only the listed hosts are accepted.
Wildcard (["*"])	Disables host checking — all Host header values are accepted.

To disable host checking entirely:

Each entry can be a bare hostname (example.com), a host-port pair (example.com:8090), or a full origin URL (https://example.com).

runtime.ready_state

Controls when the runtime readiness probe (/v1/ready) reports the runtime as ready. This is particularly useful for Kubernetes readiness probes.

Value	Description
on_load (default)	The runtime reports ready after all components (datasets, models, etc.) have loaded successfully.
on_registration	The runtime reports ready as soon as all components have been registered, before they finish loading.

runtime.scheduler

Configures the cluster scheduler when running Spice in cluster mode. This section is relevant only when using --role scheduler.

Parameter name	Optional	Default	Description
state_location	No	-	Root URI for shared cluster state storage (e.g. s3://bucket/path/).
params	Yes	-	Object store parameters (e.g. aws_region).
partition_assignment_interval	Yes	30s	How often the scheduler runs partition assignment cycles.
max_partition_assignments_per_interval	Yes	100	Maximum number of partition assignments per interval.
max_partitions_per_executor	Yes	1000	Maximum number of partitions assigned to a single executor.
partition_discovery_timeout	Yes	60s	How long the scheduler waits for executor discovery before timing out.