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Trial Parameters

The trial parameters are a set of parameters that define the details of a trial. They may be generated from the default parameters provided to the Orchestrator (see Parameter File), and updated by the pre-trial hooks (see TrialParameters and register_pre_trial_hook). Or they can be provided whole to the trial start call (see start_trial).

In the parameters, are optional config messages for the trial, environment and actors. The trial config is only used by the pre-trial hooks, whereas the other configs are sent to their respective destination at the start of the trial. The config protobuf messages are defined in the spec file.

The pre-trial hooks exist to allow dynamic parameter setting at the start of a trial, with the use of the trial config. Another way to set the parameters dynamically is by providing them to the start trial call. The parameters of the trial start call take priority over all others, and thus when provided, the default parameters will be ignored and the pre-trial hooks will not be called.

Parameters reference

  • config: User defined configuration sent to the first trial pre-hook before the start of the trial. The type is defined in the spec file under section trial:config_type. DEFAULT: not set.
  • max_steps: The maximum number of time steps (ticks) that the trial will run before requesting a soft termination at the next step. DEFAULT: 0 (infinite nb steps).
  • max_inactivity: The number of seconds of inactivity after which a trial will be hard terminated. "Activity" is defined as a message received by the Orchestrator from a user component. If 0, the trial will not be terminated because of inactivity. DEFAULT: 30 seconds.
  • nb_buffered_ticks: The number of ticks (steps) to buffer in the Orchestrator before sending the data to the datalog. In effect, this is the delay available for past data (e.g. rewards) to still make it in the correct normal sample of the datalog (as opposed to be sent to the datalog as an out-of-sync sample). This must be larger than 1. DEFAULT: 2.
  • datalog_endpoint: Endpoint of the datalog service. DEFAULT: not set (data logging is disabled).
  • datalog_exclude_fields: List of fields to exclude from the data samples sent to the datalog service.
  • environment_config: User defined configuration sent to the environment at the start of the trial. The type is defined in spec file under section environment:config_type. DEFAULT: not set.
  • environment_name: The name of the environment. DEFAULT: "env".
  • environment_endpoint: Endpoint of the environment service. DEFAULT: context discovery endpoint (the Directory will be inquired).
  • environment_implementation: The name of the implementation to run the environment. This must match an implementation that is defined at the endpoint. DEFAULT: not set (an arbitrary implementation will be chosen at runtime).
  • Actors
    • config: User defined configuration sent to the actor at the start of the trial. The type is defined in the spec file under section actor_classes:config_type for the appropriate actor class. DEFAULT: not set.
    • name: The name of the actor (must be unique in the trial). DEFAULT: none (required parameter).
    • class_name: The name of the actor class. This must match a value in the spec file under section actor_classes:name. DEFAULT: none (required parameter).
    • endpoint: Endpoint of the actor. This can be "cogment://client", which indicates a client actor. DEFAULT: context discovery endpoint (the Directory will be inquired).
    • implementation: The name of the implementation to run this actor. This must match an implementation that is defined at the endpoint. DEFAULT: not set (an arbitrary implementation will be chosen at runtime).
    • initial_connection_timeout: Maximum amount of time (in seconds) to wait for an actor to connect to a new trial, after which it is considered unavailable for the trial duration. If the wait is too long (see max_inactivity), the trial may be terminated. The trial may wait longer than the requested timeout. DEFAULT: 0.0 (no timeout; indefinite wait).
    • response_timeout: Maximum amount of time (in seconds) to wait for an actor to respond with an action after an observation is sent, after which it is considered unavailable. If the wait is too long, the trial may be terminated (see max_inactivity). The trial may wait longer than the requested timeout. DEFAULT: 0.0 (no timeout; indefinite wait).
    • optional: If set (true), the actor is optional. An optional actor is not necessary for a trial to continue. If an actor is required (i.e not optional), the trial will be terminated if the actor is not available. DEFAULT: false.
    • default_action: This is only relevant for optional actors (see optional). If set, and the actor is not available, the environment will receive this action (the environment will not be informed that the actor is unavailable). If not set, the environment will be informed that the actor is unavailable (the environment will not receive an action). The type is defined in the spec file under section actor_classes:action:space for the appropriate actor class. DEFAULT: not set.

Parameter file

The parameter file serves to initialize the Orchestrator default parameters. It is able to set all parameters except for the configs and actor default actions.

The file uses the YAML configuration language. It consists of one top level YAML section called trial_params. Any other top level section will be ignored.

The layout is hierarchical, so the name of the parameters may be different than the parameter description above:

  • max_steps
  • max_inactivity
  • nb_buffered_ticks
  • datalog: List of parameters related to the data logger. If this section is not present, data logging is disabled.
    • endpoint
    • exclude_fields
  • environment: List of parameters for the environment
    • name
    • endpoint
    • implementation
  • actors: List of actor parameter sets. Note that as defaults, the number of actors may not be suited for all trials.
    • name
    • actor_class
    • endpoint
    • implementation
    • initial_connection_timeout
    • response_timeout
    • optional

E.g.:

trial_params:
max_steps: 1000
max_inactivity: 30
nb_buffered_ticks: 5

datalog:
endpoint: grpc://logserver:9000
exclude_fields: [messages, actions]

environment:
name: Arena
endpoint: grpc://env:9000
implementation: simple

actors:
- name: Alice
actor_class: BigPlayer
endpoint: cogment://discover
implementation:
- name: Bob
actor_class: BigPlayer
endpoint: grpc://bp2:9000
implementation: Test
initial_connection_timeout: 10.0
- name: Carol
actor_class: SmallPlayer
endpoint: grpc://sp:9000
implementation: DQN_Hotel3
initial_connection_timeout: 5.0
optional: True
- name: Dave
actor_class: SmallPlayer
endpoint: cogment://discover/service?id=8390256
implementation: DNN_Karma3.1.17
initial_connection_timeout: 3.0
optional: True
- name: Olivia
actor_class: Referee
endpoint: cogment://client
implementation: Standard
response_timeout: 20.0

Parameters and pre-trial hooks

If no parameters were given to the trial start call, the default parameters and pre-trial hooks are used. And if no pre-trial hooks are defined, the default parameters will be used directly to start the trial.

Pre-trial hooks are gRPC services that may be called to set up the parameters for a new trial. Multiple hooks can be defined and they will all be called in order, in a pipeline fashion (i.e. the output of one becomes the input of the next). The first hook service to be called will receive the default parameters (augmented by the trial config that may be given to the trial start call). The output of the last hook is used as final parameters to start the new trial. The response of the last hook will be waited on before the trial starts.

The hooks will be called to update or generate all the parameter data (presented here) in addition to the configurations for the environment and the actors (if needed).

Pre-trial hooks are defined on the command line (or an environment variable) when starting the Orchestrator.

Cogment endpoints

Cogment endpoints are basic URLs (scheme://host/path?query) that can have one of two schemes: grpc or cogment. The path and query are optional, but a valid endpoint must have a scheme and a host.

The context is used to determine what API service will be used to connect to the endpoint; e.g. if this is the endpoint for an environment, then the EnvironmentSP gRPC API will be used.

grpc scheme

The grpc scheme is used to access a network resource using one of the Cogment gRPC API directly, without the need of a Directory. An endpoint with this scheme is also called a grpc endpoint. The rest of the URL is a standard HTTP address (with port) and points to the gRPC server waiting for connection. E.g.:

grpc://10.0.123.5:9000
grpc://SomeServer:9011
grpc://second.actors.base.com:9050

cogment scheme

The cogment scheme is specific to Cogment and has two possible hosts: client or discover.

client host

The client host is used in the very specific case of an actor being a "client actor". This endpoint (i.e. exactly "cogment://client") is a special endpoint. Only actors can use this endpoint. In this case, the actor with such an endpoint will connect as a client, the Orchestrator being the server. The client will connect to the actor port of the [Orchestrator][../reference/cli/orchestrator.md].

discover host

The discover host is to indicate that a directory needs to be inquired. An endpoint with this host (i.e. starting with "cogment://discover") is also called a discovery endpoint.

The directory returns an actual endpoint where to reach the service; either a grpc endpoint (e.g. grpc://10.5.134.2:9000), or for an actor, it can also be a special endpoint (e.g. cogment://client). The result should be another discovery endpoint.

The endpoint for the directory must be a grpc endpoint and is provided beforehand (e.g. for the [Orchestrator][../reference/cli/orchestrator.md], it is an option on start).

With a context discovery endpoint there is no path in the URL, and some of the details of the service will be obtained from the context of the endpoint (i.e. where the endpoint was provided and for what). This type of endpoint is the simplest form of discovery endpoint and is the default when no endpoint is provided (where discovery endpoints are valid).

E.g.:

cogment://discover
cogment://discover?tag=blue
cogment://discover?tag=red&zone=1

If these endpoints were provided for actors, they would be equivalent these explicit discovery endpoints:

cogment://discover/actor?__actor_class=xxx&__implementation=yyy
cogment://discover/actor?__actor_class=xxx&__implementation=yyy&?tag=blue
cogment://discover/actor?__actor_class=xxx&__implementation=yyy&?tag=red&zone=1

Where "xxx" and "yyy" are values taken from the context. For each type of endpoint, the context provides the path and these properties (if available):

  • For actors: path is actor, properties are __actor_class and __implementation
  • For environment: path is environment and property is __implementation
  • For all other types, no properties are provided and the path is as described below

An explicit discovery endpoint is a discovery endpoint with a path, and needs to explicitly provide all the necessary information in the URL to the directory (the context of the endpoint will be ignored). In other words, no context property will be implicitly added to the query sent to the directory, the user is fully responsible to match the URL (and query) to the need.

Discovery path

There are two categories of path for discovery endpoints, one for generic service types and the other for specific service types.

The generic path service is used to find services of any type. In this case, the query is __id=XXX where XXX is a 64 bit unsigned integer representing the ID of a service registered in the directory, e.g.:

cogment://discover/service?__id=67834892
cogment://discover/service?__id=42

The specific paths are used to find a specific type of service:

  • actor: To find an actor service
  • environment: To find an environment service
  • datalog: To find a data logger service
  • prehook: To find a pre-trial hook service
  • lifecycle: To find a service offering trial life scycle management
  • actservice: To find a service offering client actor connection
  • datastore: To find a data store service
  • modelregistry: To find a model registry service

The prehook, lifecycle, actservice, datastore and modelregistry paths are not for use in the trial parameters. The prehook path is for use on the command line of the Orchestrator. The others are for use by services themselves, e.g. to find an Orchestrator to connect to.

Discovery query

Following the path in the discovery endpoint, is the optional query; properties to find a suitable service. All the properties provided in the query must match properties registered in the directory (with some exceptions, see below). Which properties are acceptable depends on the directory (and how the services are registered in the directory).

The query in the discovery endpoint must follow these guidelines:

  • Entries are separated by the ampersand (&)
  • Property name and associated value are separated by an equal sign (=)
  • Property names and values must be composed of only these characters: A-Z, a-z, 0-9, underscore (_), dash (-)
  • Property values are optional
  • Property names starting with a double underscore (__) are reserved. E.g __authentication-token

E.g.:

cogment://discover/actor?__implementation=d3qn
cogment://discover/environment?__implementation=fqdn3&type=fast-2x&ping=low
cogment://discover/datalog?name=high&open&color=green_blue
Reserved query properties

Some endpoint query properties are reserved for Cogment use. They may be interpreted by other services than the directory, and thus may not correspond to directory properties that participate in service discovery. Some of these names may not be used as properties to inquire from (or register in) the directory. They may be used for special purposes that differ for each name.

  • __actor_class: This is a property name implicitly used by Cogment. It is registered in the Directory for services that were implicitly registered by Cogment or a Cogment SDK. It is also used by Cogment to inquire for context discovery endpoints.
  • __authentication-token: This query property is not a directory property. It is used to provide authentication to the directory. The value (and need) depends on the directory implementation and/or how the registration of the service is made in the directory. This is not registered as a property in the Directory.
  • __id: This query property is not a directory property. It is used to provide a service ID for inquiry to the directory for a specific service. This is not registered as a property in the Directory.
  • __implementation: This is a property name implicitly used by Cogment. It is registered in the Directory for services that were implicitly registered by Cogment or a Cogment SDK. It is also used by Cogment to inquire for context discovery endpoints.