.. _namespaces-guide:

Using Namespaces
================

A namespace is a logical grouping of jobs and named actors. When an actor is
named, its name must be unique within the namespace.

In order to set your applications namespace, it should be specified when you
first connect to the cluster.

.. tab-set::

    .. tab-item:: Python

        .. literalinclude:: ./doc_code/namespaces.py
          :language: python
          :start-after: __init_namespace_start__
          :end-before: __init_namespace_end__

    .. tab-item:: Java

        .. code-block:: java

          System.setProperty("ray.job.namespace", "hello"); // set it before Ray.init()
          Ray.init();

    .. tab-item:: C++

        .. code-block:: c++

          ray::RayConfig config;
          config.ray_namespace = "hello";
          ray::Init(config);

Please refer to `Driver Options <configure.html#driver-options>`__ for ways of configuring a Java application.

Named actors are only accessible within their namespaces.

.. tab-set::

    .. tab-item:: Python

        .. literalinclude:: ./doc_code/namespaces.py
          :language: python
          :start-after: __actor_namespace_start__
          :end-before: __actor_namespace_end__

    .. tab-item:: Java

        .. code-block:: java

            // `ray start --head` has been run to launch a local cluster.

            // Job 1 creates two actors, "orange" and "purple" in the "colors" namespace.
            System.setProperty("ray.address", "localhost:10001");
            System.setProperty("ray.job.namespace", "colors");
            try {
                Ray.init();
                Ray.actor(Actor::new).setName("orange").remote();
                Ray.actor(Actor::new).setName("purple").remote();
            } finally {
                Ray.shutdown();
            }

            // Job 2 is now connecting to a different namespace.
            System.setProperty("ray.address", "localhost:10001");
            System.setProperty("ray.job.namespace", "fruits");
            try {
                Ray.init();
                // This fails because "orange" was defined in the "colors" namespace.
                Ray.getActor("orange").isPresent(); // return false
                // This succeeds because the name "orange" is unused in this namespace.
                Ray.actor(Actor::new).setName("orange").remote();
                Ray.actor(Actor::new).setName("watermelon").remote();
            } finally {
                Ray.shutdown();
            }

            // Job 3 connects to the original "colors" namespace.
            System.setProperty("ray.address", "localhost:10001");
            System.setProperty("ray.job.namespace", "colors");
            try {
                Ray.init();
                // This fails because "watermelon" was in the fruits namespace.
                Ray.getActor("watermelon").isPresent(); // return false
                // This returns the "orange" actor we created in the first job, not the second.
                Ray.getActor("orange").isPresent(); // return true
            } finally {
                Ray.shutdown();
            }

    .. tab-item:: C++

        .. code-block:: c++

            // `ray start --head` has been run to launch a local cluster.

            // Job 1 creates two actors, "orange" and "purple" in the "colors" namespace.
            ray::RayConfig config;
            config.ray_namespace = "colors";
            ray::Init(config);
            ray::Actor(RAY_FUNC(Counter::FactoryCreate)).SetName("orange").Remote();
            ray::Actor(RAY_FUNC(Counter::FactoryCreate)).SetName("purple").Remote();
            ray::Shutdown();

            // Job 2 is now connecting to a different namespace.
            ray::RayConfig config;
            config.ray_namespace = "fruits";
            ray::Init(config);
            // This fails because "orange" was defined in the "colors" namespace.
            ray::GetActor<Counter>("orange"); // return nullptr;
            // This succeeds because the name "orange" is unused in this namespace.
            ray::Actor(RAY_FUNC(Counter::FactoryCreate)).SetName("orange").Remote();
            ray::Actor(RAY_FUNC(Counter::FactoryCreate)).SetName("watermelon").Remote();
            ray::Shutdown();

            // Job 3 connects to the original "colors" namespace.
            ray::RayConfig config;
            config.ray_namespace = "colors";
            ray::Init(config);
            // This fails because "watermelon" was in the fruits namespace.
            ray::GetActor<Counter>("watermelon"); // return nullptr;
            // This returns the "orange" actor we created in the first job, not the second.
            ray::GetActor<Counter>("orange");
            ray::Shutdown();

Specifying namespace for named actors
-------------------------------------

You can specify a namespace for a named actor while creating it. The created actor belongs to
the specified namespace, no matter what namespace of the current job is.

.. tab-set::

    .. tab-item:: Python

        .. literalinclude:: ./doc_code/namespaces.py
          :language: python
          :start-after: __specify_actor_namespace_start__
          :end-before: __specify_actor_namespace_end__


    .. tab-item:: Java

        .. code-block:: java

            // `ray start --head` has been run to launch a local cluster.

            System.setProperty("ray.address", "localhost:10001");
            try {
                Ray.init();
                // Create an actor with specified namespace.
                Ray.actor(Actor::new).setName("my_actor", "actor_namespace").remote();
                // It is accessible in its namespace.
                Ray.getActor("my_actor", "actor_namespace").isPresent(); // return true

            } finally {
                Ray.shutdown();
            }

    .. tab-item:: C++

        .. code-block:: c++

            // `ray start --head` has been run to launch a local cluster.
            ray::RayConfig config;
            ray::Init(config);
            // Create an actor with specified namespace.
            ray::Actor(RAY_FUNC(Counter::FactoryCreate)).SetName("my_actor", "actor_namespace").Remote();
            // It is accessible in its namespace.
            ray::GetActor<Counter>("my_actor", "actor_namespace");
            ray::Shutdown();


Anonymous namespaces
--------------------

When a namespace is not specified, Ray will place your job in an anonymous
namespace. In an anonymous namespace, your job will have its own namespace and
will not have access to actors in other namespaces.

.. tab-set::

    .. tab-item:: Python

        .. literalinclude:: ./doc_code/namespaces.py
          :language: python
          :start-after: __anonymous_namespace_start__
          :end-before: __anonymous_namespace_end__

    .. tab-item:: Java

        .. code-block:: java

            // `ray start --head` has been run to launch a local cluster.

            // Job 1 connects to an anonymous namespace by default.
            System.setProperty("ray.address", "localhost:10001");
            try {
                Ray.init();
                Ray.actor(Actor::new).setName("my_actor").remote();
            } finally {
                Ray.shutdown();
            }

            // Job 2 connects to a _different_ anonymous namespace by default
            System.setProperty("ray.address", "localhost:10001");
            try {
                Ray.init();
                // This succeeds because the second job is in its own namespace.
                Ray.actor(Actor::new).setName("my_actor").remote();
            } finally {
                Ray.shutdown();
            }

    .. tab-item:: C++

        .. code-block:: c++

            // `ray start --head` has been run to launch a local cluster.

            // Job 1 connects to an anonymous namespace by default.
            ray::RayConfig config;
            ray::Init(config);
            ray::Actor(RAY_FUNC(Counter::FactoryCreate)).SetName("my_actor").Remote();
            ray::Shutdown();

            // Job 2 connects to a _different_ anonymous namespace by default
            ray::RayConfig config;
            ray::Init(config);
            // This succeeds because the second job is in its own namespace.
            ray::Actor(RAY_FUNC(Counter::FactoryCreate)).SetName("my_actor").Remote();
            ray::Shutdown();

.. note::

     Anonymous namespaces are implemented as UUID's. This makes it possible for
     a future job to manually connect to an existing anonymous namespace, but
     it is not recommended.


Getting the current namespace
-----------------------------
You can access to the current namespace using :ref:`runtime_context APIs <runtime-context-apis>`.

.. tab-set::

    .. tab-item:: Python

        .. literalinclude:: ./doc_code/namespaces.py
          :language: python
          :start-after: __get_namespace_start__
          :end-before: __get_namespace_end__


    .. tab-item:: Java

        .. code-block:: java

            System.setProperty("ray.job.namespace", "colors");
            try {
                Ray.init();
                // Will print namespace name "colors".
                System.out.println(Ray.getRuntimeContext().getNamespace());
            } finally {
                Ray.shutdown();
            }

    .. tab-item:: C++

        .. code-block:: c++

            ray::RayConfig config;
            config.ray_namespace = "colors";
            ray::Init(config);
            // Will print namespace name "colors".
            std::cout << ray::GetNamespace() << std::endl;
            ray::Shutdown();