Configuration Guide

Custos server can be configured using a YAML configuration file instead of environment variables. This guide explains how to set up and use the configuration system.

Quick Start

1. Place your configuration file at config/custos.yaml
2. Start the server:

   ./custos
   

The server will automatically load the configuration file. If the config file is not found at the resolved path, the server exits with an error — make sure config/custos.yaml exists (or override CONFIG_PATH).

Configuration File Location

By default, the server looks for the configuration file at config/custos.yaml. You can customize this location using the CONFIG_PATH environment variable:

CONFIG_PATH=/etc/custos/config.yaml ./custos

Configuration Structure

Core Configuration

The core section contains essential server settings:

core:
  database:
    url: "admin:admin@tcp(localhost:3306)/custos?parseTime=true&charset=utf8mb4"
  api:
    port: 8080
  log_level: "info"

• database.url: MariaDB / MySQL DSN (the server uses the go-sql-driver/mysql driver). Required.
• api.port: HTTP API port (default: 8080)
• log_level: Logging level (info, debug, warn, error)

Auth Configuration

The verifier and caller resolver read this block. The loader refuses to boot when either OIDC field is empty; the cache TTL is capped at 60s.

core:
  auth:
    oidc:
      issuer:   "${OIDC_ISSUER_URL}"
      audience: "${OIDC_AUDIENCE}"
    cache_ttl: "30s"

Key	Default	Notes
core.auth.oidc.issuer	(required)	OIDC issuer URL. The verifier discovers JWKS from <issuer>/.well-known/openid-configuration. Empty → boot fails with core.auth.oidc.issuer is required.
core.auth.oidc.audience	(required)	Expected aud claim. Usually the client_id registered with the IdP. Empty → boot fails with core.auth.oidc.audience is required.
core.auth.cache_ttl	30s	TTL of the in-process caller + privilege cache, keyed by OIDC sub. Any time.Duration string (s, m). Zero or negative → 30s. Values above 60s are capped at 60s at boot and a WARN is logged.

Public routes (those that bypass JWT verification) are declared in code via router.Public(...). There is no YAML allowlist.

Connector Configuration

The connectors section defines which connectors are enabled and their settings.

SLURM Association Mapper

connectors:
  slurm-mapper:
    type: "slurm-association-mapper"
    enabled: true
    slurm_api:
      url: "https://slurm-api.example.com"
      version: "0.0.38"
      username: "slurm_admin"
      token: "${SLURM_TOKEN}"

SLURM Usage Monitor

  slurm-usage-monitor:
    type: "slurm-usage-monitor"
    enabled: true
    slurm_api:
      url: "https://slurm-api.example.com"
      version: "0.0.38"
      username: "slurm_admin"
      token: "${SLURM_TOKEN}"
    cluster_id: "slurm-cluster"

COmanage Identity Provisioner

  comanage-provisioner:
    type: "comanage-identity-provisioner"
    enabled: true
    registry:
      url: "https://comanage.example.org"
      co_id: 1
      api_user: "comanage_api_user"
      api_key: "${COMANAGE_API_KEY}"
    unix_cluster:
      id: 10
      person_id_type: "eppn"
    provisioning:
      custos_cluster_id: "cluster-001"
      default_shell: "/bin/bash"
      homedir_prefix: "/home/"
      http_timeout: "30s"

AMIE Processor

  amie-processor:
    type: "amie-processor"
    enabled: true
    credentials:
      base_url: "https://amie.xsede.org"
      site_code: "XSEDE"
      api_key: "${AMIE_API_KEY}"
    cluster:
      id: "cluster-001"
    polling:
      poll_interval: "30s"
      worker_interval: "5s"
      poller_enabled: true
    timeouts:
      connect_timeout: "5s"
      read_timeout: "20s"

Environment Variable Substitution

The configuration parser supports environment variable substitution using the ${VAR_NAME} syntax. This allows you to:

1. Keep sensitive values (API keys, passwords) out of version control
2. Use different values for different deployment environments
3. Reference environment variables directly in the config file

Example

core:
  database:
    url: "${DATABASE_URL}"

In your shell:

export DATABASE_URL="admin:admin@tcp(localhost:3306)/custos?parseTime=true&charset=utf8mb4"
./custos

If an environment variable referenced in the config file is not set, it will remain unexpanded:

token: "${MISSING_TOKEN}"  # Will not be replaced if MISSING_TOKEN is not set

Environment Overrides

A small set of process-level knobs aren't in the YAML — they're read directly from the environment at boot.

Variable	Default	Purpose
CONFIG_PATH	config/custos.yaml	Override the config file location.
DB_MAX_OPEN_CONNS	25	Maximum open database connections.
DB_MAX_IDLE_CONNS	5	Maximum idle database connections.

Enabling/Disabling Connectors

The configuration supports any number of connectors with any names. Each connector is identified by its type field which determines which loader is used:

connectors:
  connector-name:  # Can be any identifier
    type: "slurm-association-mapper"  # Determines which loader to use
    enabled: true
    # Connector-specific configuration

To disable a connector, set enabled: false:

connectors:
  slurm-mapper:
    type: "slurm-association-mapper"
    enabled: false
    # Rest of configuration is still required but will be ignored

When a connector is disabled:

• It will not be loaded on server startup
• An info log message will indicate it's disabled
• The server will continue to function normally

Supported Connector Types

• slurm-association-mapper - SLURM Association Mapper
• slurm-usage-monitor - SLURM Usage Monitor
• comanage-identity-provisioner - COmanage Identity Provisioner
• amie-processor - AMIE Processor

New connector types can be added by:

1. Implementing the connector package
2. Adding the loader function to internal/connectors/loader.go
3. Mapping the type to the loader in connectorLoaders map

Configuration Validation

The configuration is validated during parsing. Common issues:

1. Missing required fields: If core.database.url is missing, the server will fail to start
2. Invalid YAML syntax: Check your YAML indentation and structure
3. Undefined environment variables: Variables referenced with ${VAR} will be left as-is if not set

Logging

Configuration loading is logged at the INFO level:

{
  "time": "2026-06-12T10:30:45Z",
  "level": "INFO",
  "msg": "loaded config",
  "path": "config/custos.yaml"
}

Connector loading logs indicate which connectors are enabled or disabled:

{
  "time": "2026-06-12T10:30:46Z",
  "level": "INFO",
  "msg": "loading SLURM Association Mapper connector"
}

Adding New Connectors

To add a new connector type:

1. Implement the connector package with a LoadConnector function
2. Update internal/connectors/loader.go to import the new connector
3. Add the type-to-loader mapping in the connectorLoaders map:

connectorLoaders := map[string]func(context.Context, *sqlx.DB, *events.Bus, *service.Service, *sync.WaitGroup, *http.ServeMux, *config.ConnectorConfig) error{
    "my-new-connector": mynewconnector.LoadConnector,
    // ... existing connectors
}

4. Add the connector to your config file with the corresponding type

No code changes are required elsewhere — the configuration system is fully extensible.

Example Complete Configuration

See config/custos.yaml for a complete example configuration with all connectors.