Configuration

Watt is configured with a configuration file. It supports the use of environment variables as setting values with environment variable placeholders.

Configuration Files

Watt automatically detects and loads configuration files found in the current working directory with the file names listed here.

Alternatively, you can use the --config option to specify a configuration file path for most wattpm CLI commands. The configuration examples in this reference use the JSON format.

Supported File Formats

For detailed information on supported file formats and extensions, please visit our Supported File Formats and Extensions page.

Settings

Configuration settings containing sensitive data should be set using environment variable placeholders.

info

The autoload and applications settings can be used together, but at least one of them must be provided. When the configuration file is parsed, autoload configuration is translated into applications configuration.

autoload

The autoload configuration is intended to be used with monorepo applications. autoload is an object with the following settings:

• path (required, string) - The path to a directory containing the microservices to load. In a traditional monorepo application, this directory is typically named packages.
• exclude (array of strings) - Child directories inside path that should not be processed.
• mappings (object) - Each microservice is given an ID and is expected to have a Platformatic configuration file. By default, the ID is the microservice's directory name, and the configuration file is expected to be a well-known Platformatic configuration file. mappings can be used to override these default values. Supported properties are the same of entries in application, except path, url, and gitBranch.

preload

The preload configuration is intended to be used to register Application Performance Monitoring (APM) agents. preload should contain a path or a list of paths pointing to a CommonJS or ES module that is loaded at the start of the app worker thread.

applications

applications is an array of objects that defines the microservices managed by the runtime. Each application object supports the following settings:

• id (required, string) - A unique identifier for the microservice. When working with the Platformatic Gateway, this value corresponds to the id property of each object in the applications section of the config file. When working with client objects, this corresponds to the optional applicationId property or the name field in the client's package.json file if a applicationId is not explicitly provided.

• path (required, string) - The path to the directory containing the microservice. It can be omitted if url is provided.

• url (required, string) - The URL of the application remote GIT repository, if it is a remote application. It can be omitted if path is provided.

• gitBranch (string) - The branch of the application to resolve.

• config (string) - The configuration file used to start the microservice.

• useHttp (boolean) - The application will be started on a random HTTP port on 127.0.0.1, and exposed to the other applications via that port, on default it is set to false. Set it to true if you are using @fastify/express.

• workers - The number of workers to start for this application. If the application is the entrypoint or if the runtime is running in development mode this value is ignored and hardcoded to 1. This can be specified as:

  • number - A fixed number of workers
  • object - Advanced worker configuration with the following properties:
    • static (number) - A fixed number of workers
    • dynamic (boolean) - Enable dynamic worker scaling. This is only meaningful when set to false to disable dynamic scaling for this application.
    • minimum (number) - Minimum number of workers when using dynamic scaling
    • maximum (number) - Maximum number of workers when using dynamic scaling

• health (object): Configures the health check for each worker of the application. It supports all the properties also supported in the runtime health property. The values specified here overrides the values specified in the runtime.

• arguments (array of strings) - The arguments to pass to the application. They will be available in process.argv.

• envfile (string) - The path to an .env file to load for the application. By default, the .env file is loaded from the application directory.

• env (object) - An object containing environment variables to set for the application. Values set here takes precedence over values set in the envfile.

• sourceMaps (boolean) - If true, source maps are enabled for the application. Default: false.

• packageManager (string) - The package manager to use when using the install-dependencies or the resolve commands of wattpm-utils. Default is to autodetect it, unless it is specified via command line.

• preload (string or array of strings): A file or a list of files to load before the application code.

• nodeOptions (string): The NODE_OPTIONS to apply to the application. These options are appended to any existing option.

• permissions (object): Configure application-level security permissions to restrict file system access. Supported properties are:

  • fs:
    • read (array of strings): Array of file system paths the application is permitted to read from. Uses the same syntax as Node.js --allow-fs-read.
    • write (array of strings): Array of file system paths the application is permitted to write to. Uses the same syntax as Node.js --allow-fs-write.

  When filesystem permissions are enabled, certain paths are automatically added to maintain application functionality:

  • The current Watt project's node_modules directory
  • The application's own node_modules directory
  • Any node_modules directories found in parent directories of the runtime path

  The security permissions are based on Node.js permission model and therefore the application will have restricted access to native modules, child processes, worker threads, the inspector protocol, and WASI. See the Node.js Permission Model Constraints for complete details.

• dependencies (array of strings): A list of applications that must be started before attempting to start the current application. Note that the runtime will not perform any attempt to detect or solve dependencies cycles.

• telemetry (object): containing an instrumentations array to optionally configure additional open telemetry intrumentations per application, e.g.:

"applications": [
    {
      "id": "api",
      "path": "./services/api",
      "telemetry": {
        "instrumentations": ["@opentelemetry/instrumentation-express"]
      }
    }
  ]

It's possible to specify the name of the export of the instrumentation and/or the options:

"applications": [
    {
      "id": "api",
      "path": "./services/api",
      "telemetry": {
        "instrumentations": [{
          "package": "@opentelemetry/instrumentation-express",
          "exportName": "ExpressInstrumentation",
          "options": {}
        }]
      }
    }
  ]

An alias for applications. If both are present, their content will be merged.

It's also possible to disable the instrumentation by setting the enabled value property to false (env variables are also supported):

"applications": [
    {
      "id": "api",
      "path": "./services/api",
      "telemetry": {
        "enabled": "false",
        "instrumentations": [{
          "package": "@opentelemetry/instrumentation-express",
        }]
      }
    }
  ]

env

An object containing environment variables to set for all applications in the runtime. Any environment variables set in the env object will be merged with the environment variables set in the envfile and env properties of each application, with application-level environment variables taking precedence.

sourceMaps

If true, source maps are enabled for all applications. Default: false. This setting can be overridden at the application level.

resolvedServicesBasePath

The base path, relative to the configuration file to store resolved applications. Each application will be saved in {resolvedServicesBasePath}/{id}. Default: external.

entrypoint

The Platformatic Runtime's entrypoint is a microservice that is exposed publicly. This value must be the ID of an application defined via the autoload or applications configuration.

workers

Configures the default number of workers to start per each application. Some values can be overridden at the application level.

This can be specified as:

• number - A fixed number of workers (minimum 1)
• object - Advanced worker configuration with the following properties:
  • static (number) - A fixed number of workers
  • dynamic (boolean) - Enable dynamic worker scaling (default: false). The dynamic worker scaler automatically adjusts the number of workers for each application based on Event Loop Utilization (ELU) and available system memory. It can be overridden at the application level.
  • minimum (number) - The minimum number of workers that can be used for each application. Default: 1.
  • maximum (number) - The maximum number of workers that can be used for each application. Default: global total value.
  • total (number) - The maximum number of workers that can be used for all applications. Default: os.availableParallelism() (typically the number of CPU cores).
  • maxMemory (number) - The maximum total memory in bytes that can be used by all workers. Default: 90% of the system's total memory.
  • cooldown (number) - The amount of milliseconds the scaling algorithm will wait after making a change before scaling up or down again. This prevents rapid oscillations. Default: 60000.
  • gracePeriod (number) - The amount of milliseconds after a worker is started before the scaling algorithm will start collecting metrics for it. This allows workers to stabilize after startup. Default: 30000.

This value is hardcoded to 1 if the runtime is running in development mode or when applying it to the entrypoint.

workersRestartDelay

Configures the amount of milliseconds to wait before replacing another worker of an application during a restart.

gracefulShutdown

Configures the amount of milliseconds to wait before forcefully killing an application or the runtime.

The object supports the following settings:

• application (number) - The graceful shutdown timeout for an application.
• runtime (number) - The graceful shutdown timeout for the entire runtime.

For both the settings the default is 10000 (ten seconds).

watch

An optional boolean, set to default false, indicating if hot reloading should be enabled for the runtime. If this value is set to false, it will disable hot reloading for any microservices managed by the runtime. If this value is true, then hot reloading for individual microservices is managed by the configuration of that microservice.

Note that watch should be enabled for each individual application in the runtime.

warning

While hot reloading is useful for development, it is not recommended for use in production.

startTimeout

The number of milliseconds to wait before considering an application as failed to start. Default: 30000.

restartOnError

The number of milliseconds to wait before attempting to restart an application that unexpectedly exit.

If not specified or set to true, the default value is 5000, set to 0 or false to disable.

Any value smaller than 10 will cause immediate restart of the application.

This setting is ignored in production, where applications are always restarted immediately.

exitOnUnhandledErrors

When enabled (default), Platformatic automatically installs error handlers for uncaughtException and unhandledRejection events on each worker process. These handlers will automatically restart the affected worker when such errors occur.

Setting this to false disables the automatic error handling, making you responsible for implementing proper error handling in your application code.

health

Configures the health check for each worker. This is enabled only if restartOnError is greater than zero.

The object supports the following settings:

• enabled (boolean): If to enable the health check. Default: true.
• interval (number): The interval between checks in milliseconds. Default: 30000.
• gracePeriod (number): How long after the application started before starting to perform health checks. Default: 30000.
• maxUnhealthyChecks (number): The number of consecutive failed checks before killing the worker. Default: 10.
• maxELU (number): The maximum allowed Event Loop Utilization. The value must be a percentage between 0 and 1. Default: 0.99.
• maxHeapUsed (number): The maximum allowed memory utilization. The value must be a percentage between 0 and 1. Default: 0.99.
• maxHeapTotal (number or string): The maximum allowed memory allocatable by the process. The value must be an amount in bytes, in bytes or in memory units. Default: 4G.
• maxYoungGeneration(number or string): The maximum amount of memory that can be used by the young generation. The value must be an amount in bytes, in bytes or in memory units. The default is calculated from the maxHeapTotal.

telemetry

Open Telemetry is optionally supported with these settings:

• applicationName (required, string) — Name of the application as will be reported in open telemetry. In the runtime case, the name of the applications as reported in traces is ${applicationName}-${applicationId}, where applicationId is the id of the application in the runtime.
• version (string) — Optional version (free form)
• skip (array). Optional list of operations to skip when exporting telemetry defined object with properties:
  • method: GET, POST, PUT, DELETE, PATCH, HEAD, OPTIONS, TRACE
  • path. e.g.: /documentation/json
• exporter (object or array) — Exporter configuration. If not defined, the exporter defaults to console. If an array of objects is configured, every object must be a valid exporter object. The exporter object has the following properties:
  • type (string) — Exporter type. Supported values are console, otlp, zipkin and memory (default: console). memory is only supported for testing purposes.
  • options (object) — These options are supported:
    • url (string) — The URL to send the telemetry to. Required for otlp exporter. This has no effect on console and memory exporters.
    • headers (object) — Optional headers to send with the telemetry. This has no effect on console and memory exporters.

basePath

The base path for the Platformatic Runtime. Set it when your application is deployed under a subpath, for example, /api. The runtime will automatically strip the base path from the incoming requests.

important

OTLP traces can be consumed by different solutions, like Jaeger. See the full list here.

Example JSON object

{
  "telemetry": {
    "applicationName": "test-application",
    "exporter": {
      "type": "otlp",
      "options": {
        "url": "http://localhost:4318/v1/traces"
      }
    }
  }
}

httpCache

The httpCache configuration is used to enable the HTTP cache for the Platformatic Runtime. It can be a boolean or an object with the following settings:

• store (string) - The store to use for the cache. Set an npm package name to use a custom store or path to a file to use a custom store from a file. By default, the memory store is used.
• methods (array) - The HTTP methods to cache. By default, GET and HEAD methods are cached.
• cacheTagsHeader (string) - The header to use for cache tags.
• maxCount (integer) - The maximum number of entries in the cache.
• maxSize (integer) - The maximum size of the cache in bytes.
• maxEntrySize (integer) - The maximum size of a single entry in the cache in bytes.

server

This configures the Platformatic Runtime entrypoint server.

If the entrypoint has also a server configured, then the runtime settings override the application settings.

An object with the following settings:

• hostname — Hostname where Platformatic Service server will listen for connections.
• port — Port where Platformatic Service server will listen for connections.
• http2 (boolean) — Enables HTTP/2 support. Default: false.
• https (object) - Configuration for HTTPS supporting the following options. Requires https.
  • allowHTTP1 (boolean) - If true, the server will also accept HTTP/1.1 connections when http2 is enabled. Default: false.
  • key (required, string, object, or array) - If key is a string, it specifies the private key to be used. If key is an object, it must have a path property specifying the private key file. Multiple keys are supported by passing an array of keys.
  • cert (required, string, object, or array) - If cert is a string, it specifies the certificate to be used. If cert is an object, it must have a path property specifying the certificate file. Multiple certificates are supported by passing an array of keys.

logger

This configures the Platformatic Runtime logger, based on pino.

An object with the following settings:

• level — The log level. Default: info. Valid values are: fatal, error, warn, info, debug, trace, silent.
• transport — Configuration for logging transport, see pino.transport for more information. Can be configured in two ways:
  • As a single transport: An object with properties:
    • target — A string specifying the transport module.
    • options — An object containing options for the transport.
  • As multiple targets: An object with properties:
    • targets — An array of objects, each with:
      • target — A string specifying the transport module.
      • options — An object containing options for the transport.
      • level — The log level for this specific transport.
    • options — An object containing shared options for all targets.
• formatters — Configuration for logging formatters. An object with properties:
  • path (required) — A string specifying the path to the formatters; the file exports a function for bindings and level, see pino.formatters for more information.
• timestamp — The timestamp format to use in logs. Valid values are: epochTime, unixTime, nullTime, isoTime, see pino.timestamp for more information.
• redact — Configuration for redacting sensitive information, see [pino.redact]https://getpino.io/#/docs/redaction) for more information. An object with properties:
  • paths (required) — An array of strings specifying paths to redact.
  • censor — A string to replace redacted values with. Default: [redacted].
• captureStdio — If true, the logger will capture the stdout and stderr streams of the main application. Default: false.
• base — The base logger configuration; setting to null will remove pid and hostname from the logs, otherwise it can be an object to add custom properties to the logs.
• messageKey — The key to use for the log message. Default: msg.
• customLevels — Configuration for custom levels, see pino.customLevels for more information.

undici

This configures the undici global Dispatcher. Allowing to configure the options in the agent as well as interceptors.

Example JSON object

{
  "undici": {
    "keepAliveTimeout": 1000,
    "keepAliveMaxTimeout": 1000,
    "interceptors": [
      {
        "module": "undici-oidc-interceptor",
        "options": {
          "clientId": "{PLT_CLIENT_ID}",
          "clientSecret": "{PLT_CLIENT_SECRET}",
          "idpTokenUrl": "{PLT_IDP_TOKEN_URL}",
          "origins": ["{PLT_EXTERNAL_SERVICE}"]
        }
      }
    ]
  }
}

It's important to note that IDP stands for Identity Provider, and its token url is the URL that will be called to generate a new token.

applicationTimeout

The number of milliseconds to wait when invoking another application using the its plt.local before considering the request timed out. Default: 300000 (5 minutes).

messagingTimeout

The number of milliseconds to wait when invoking another application using the its globalThis.platformatic.messaging.send before considering the request timed out. Default: 300000 (5 minutes).

metrics

This configures the Platformatic Runtime Prometheus server. The Prometheus server exposes aggregated metrics from the Platformatic Runtime applications.

• enabled (boolean or string). If true, the Prometheus server will be started. Default: true.
• hostname (string). The hostname where the Prometheus server will be listening. Default: 0.0.0.0.
• port (number). The port where the Prometheus server will be listening. Default: 9090.
• endpoint (string). The endpoint where the Prometheus server will be listening. Default: /metrics.
• auth (object). Optional configuration for the Prometheus server authentication.
  • username (string). The username for the Prometheus server authentication.
  • password (string). The password for the Prometheus server authentication.
• readiness (object or boolean, default: true). Optional configuration for the Prometheus server readiness checks. If set to true, default readiness checks are enabled. If an object is provided, it can include:
  • endpoint (string). The endpoint for the Prometheus server readiness checks. Default: /ready.
  • success (object). The success criteria for the Prometheus server readiness checks.
    • statusCode (number). The HTTP status code indicating success. Default: 200.
    • body (string). The response body indicating success. Default: OK.
  • fail (object). The failure criteria for the Prometheus server readiness checks.
    • statusCode (number). The HTTP status code indicating failure. Default: 500.
    • body (string). The response body indicating failure. Default: ERR.
• liveness (object or boolean, default: true). Optional configuration for the Prometheus server liveness checks. If set to true, default liveness checks are enabled. If an object is provided, it can include:
  • endpoint (string). The endpoint for the Prometheus server liveness checks. Default: /status.
  • success (object). The success criteria for the Prometheus server liveness checks.
    • statusCode (number). The HTTP status code indicating success. Default: 200.
    • body (string). The response body indicating success. Default: OK.
  • fail (object). The failure criteria for the Prometheus server liveness checks.
    • statusCode (number). The HTTP status code indicating failure. Default: 500.
    • body (string). The response body indicating failure. Default: ERR.
• plugins (array of string): A list of Fastify plugin to add to the Prometheus server.
• applicationLabel (string, default: 'applicationId'): The label name to use for the application identifier in metrics (e.g., 'applicationId', 'serviceId', or any custom label name).
• timeout (number, default: 10000): The timeout to wait for each worker metrics before skipping it.
• otlpExporter (object): Optional configuration for exporting Prometheus metrics to an OpenTelemetry Protocol (OTLP) endpoint. This enables pushing metrics to OTLP-compatible collectors like OpenTelemetry Collector, Grafana Cloud, or other observability platforms. The object supports the following settings:
  • enabled (boolean or string): Enable or disable OTLP metrics export. Default: true if endpoint is configured.
  • endpoint (required, string): OTLP endpoint URL for metrics (e.g., http://localhost:4318/v1/metrics).
  • interval (number or string): Interval in milliseconds between metric pushes. Default: 60000 (60 seconds).
  • headers (object): Additional HTTP headers for authentication or custom metadata. Common use cases include API keys or authentication tokens.
  • serviceName (string): Service name for OTLP resource attributes. Defaults to the application ID.
  • serviceVersion (string): Service version for OTLP resource attributes. Optional.

Example OTLP Metrics Configuration

{
  "metrics": {
    "enabled": true,
    "port": 9090,
    "otlpExporter": {
      "endpoint": "http://otel-collector:4318/v1/metrics",
      "interval": 30000,
      "headers": {
        "x-api-key": "{OTLP_API_KEY}"
      },
      "serviceName": "my-platformatic-app",
      "serviceVersion": "1.0.0"
    }
  }
}

If the metrics object is not provided, the Prometheus server will not be started.

managementApi

Warning: Experimental. The feature is not subject to semantic versioning rules. Non-backward compatible changes or removal may occur in any future release. Use of the feature is not recommended in production environments.

An optional object that configures the Platformatic Management Api. If this object is not provided, the Platformatic Management Api will be started by default. If enabled, it will listen to UNIX Socket/Windows named pipe located at platformatic/pids/<PID> inside the OS temporary folder.

• logs (object). Optional configuration for the runtime logs.
  • maxSize (number). Maximum size of the logs that will be stored in the file system in MB. Default: 200. Minimum: 5.

scheduler

An optional array of objects to configure HTTP call triggered by cron jobs. Every object has:

• enabled (boolean or string). Optional. If false the scheduler is disabled. Default: true.
• name (string): The job name
• cron (string): the crontab schedule expession. See https://crontab.guru/examples.html for some examples.
• callbackUrl (string): the HTTP URL to be called
• method (string): Optional, can be GET, POST, PUT, PATCH, DELETE. Default: GET.
• body (string or object). Optional.
• headers (object). Optional. Headers added to the HTTP call.
• maxRetry (number). Number of attempts for the HTTP call. Default: 3

Example Scheduler

{
  "scheduler": [
    {
      "name": "test",
      "callbackUrl": "http://mytarget",
      "cron": "0 * * * *",
      "mehod": "GET"
    }
  ]
}

verticalScaler

warning

The verticalScaler configuration is deprecated and will be removed in a future version. These options are now mapped to the equivalent properties in the workers configuration. Please use the workers configuration instead.

The verticalScaler configuration is used to enable the vertical scaling for the Platformatic Runtime. The vertical scaler automatically adjusts the number of workers for each application based on Event Loop Utilization (ELU) and available system memory.

The scaler operates in two modes:

• Reactive Mode: Triggers scaling checks immediately when any worker's ELU exceeds the scaleUpELU threshold
• Periodic Mode: Runs scaling checks at regular intervals defined by scaleIntervalSec

When scaling up, the algorithm ensures there is sufficient available memory to accommodate new workers based on the application's average heap usage. Available memory is calculated as maxTotalMemory - currently used memory, where used memory is obtained from cgroup files in containerized environments or from the operating system otherwise.

Configuration options:

• enabled (boolean or string). If false the vertical scaling is disabled. Default: true.
• maxTotalWorkers (number). The maximum number of workers that can be used for all applications. Default: os.availableParallelism() (typically the number of CPU cores).
• maxTotalMemory (number). The maximum total memory in bytes that can be used by all workers. Default: 90% of the system's total memory.
• minWorkers (number). The minimum number of workers that can be used for each application. It can be overridden at application level. Default: 1.
• maxWorkers (number). The maximum number of workers that can be used for each application. It can be overridden at application level. Default: global maxTotalWorkers value.
• cooldownSec (number). The amount of seconds the scaling algorithm will wait after making a change before scaling up or down again. This prevents rapid oscillations. Default: 60.
• scaleUpELU (deprecated, number). This property is deprecated and currently unused. The ELU threshold for scaling up is hardcoded to 0.8.
• scaleDownELU (deprecated, number). This property is deprecated and currently unused. The ELU threshold for scaling down is hardcoded to 0.2.
• timeWindowSec (deprecated, number). This property is deprecated and currently unused. The time window for scale-up decisions is hardcoded to 10 seconds.
• scaleDownTimeWindowSec (deprecated, number). This property is deprecated and currently unused. The time window for scale-down decisions is hardcoded to 60 seconds.
• gracePeriod (number). The amount of milliseconds after a worker is started before the scaling algorithm will start collecting metrics for it. This allows workers to stabilize after startup. Default: 30000.
• scaleIntervalSec (deprecated, number). This property is deprecated and currently unused. The interval for periodic scaling checks is hardcoded to 60 seconds.
• applications (object). An object with application-specific scaling configuration. Each key is an application ID, with an object value containing:
  • minWorkers (number). The minimum number of workers that can be used for this application. Default: 1.
  • maxWorkers (number). The maximum number of workers that can be used for this application. Default: global maxWorkers value.

Notes:

• Applications with a fixed workers configuration or entrypoint applications on systems without reusePort support will have their min/max workers automatically set to their current value to prevent scaling.
• The scaler tracks heap memory usage and will not scale up if there is insufficient available memory, even if ELU thresholds are met.
• By default, the scaler uses 90% of total system memory as the memory limit to provide a safety buffer and prevent out-of-memory situations.

policies

The policies configuration is used to define security policies that control communication between applications in the runtime. The security model follows an "allow by default" approach, meaning all inter-application communication is permitted unless explicitly restricted.

Configuration options:

• deny (object). An object that defines communication restrictions between applications. The key is the source application ID, and the value is the target application ID that should be blocked (the value can also be an array of IDs). The blocking is bidirectional. For example, denying communication from application-1 to application-2 will also automatically block communication from application-2 to application-1.

When policies are configured, fetch requests or messaging API calls between blocked application will throw an exception.

Setting and Using ENV placeholders

The value for any configuration setting can be replaced with an environment variable by adding a placeholder in the configuration file, for example {PLT_ENTRYPOINT}.

If an .env file exists it will automatically be loaded by Platformatic using dotenv. For example:

.env

PLT_ENTRYPOINT=application

The .env file must be located in the same folder as the Platformatic configuration file or in the current working directory. Each application would also see their respective .env file loaded if they are located in a subdirectory. This can be configured by the envfile property in the application configuration.

Environment variables can also be set directly on the command line, for example:

PLT_ENTRYPOINT=application npx wattpm start

note

Learn how to set and use environment variable placeholders documentation.

PLT_ROOT

The {PLT_ROOT} placeholder is automatically set to the directory containing the configuration file, so it can be used to configure relative paths. See our documentation to learn more on PLT_ROOT placeholders.

Issues

If you run into a bug or have a suggestion for improvement, please raise an issue on GitHub or join our Discord feedback channel.