Elements

Reviewed on: 2020-02-04

This directory contains an example implementation of a session that instantiates a single element proposer.

The element proposer connects to the ElementManager service offered by the session, and uses that service to add a simple_element to the session.

The simple_element then connects to the ElementPing service exposed to it by the session notifies the session that it has been successfully instantiated.

Element Session

The element session is configured to:

1. Declare a static child: the element_proposer.
2. Declare a child collection with a name which matches the one passed to the ElementManagement library.
3. Expose the ElementManager service.
4. Expose the ElementPing service.
5. Offer the ElementManager service to the element_proposer child.
6. Offer the ElementPing service to the child collection mentioned above.

Details of how this is done can be found in the element_session.cml file.

Once the session is launched, it exposes the aforementioned services and starts handling requests.

Element Proposer

The element proposer is configured to use the ElementManager service. Details of how this is done can be found in the element_proposer.cml file.

Once the element proposer is started it connects to the ElementManager service and attempts to add an element (simple_element) to the session.

Simple Element

The simple element is configured to use the ElementPing service. Details of how this is done can be found in the simple_element.cml file.

Once the simple element is started, it will call ElementPing::Ping(). The session receives the ping and log a confirmation.

Building element_session

The example sessions are included in the build when you include //src/session with your fx set:

fx set <PRODUCT>.<BOARD> --with-base=//src/session,//src/session/bin/session_manager:session_manager.config

To see a list of possible products, run: fx list-products.

To see a list of possible boards, run: fx list-boards.

Running element_session

Boot into element_session

To boot into element_session, edit the session manager cml file to set the element session's component url as the argument:

"args": [ "-s", "fuchsia-pkg://fuchsia.com/element_session#meta/element_session.cm" ],

and run

fx update

To build the relevant components and boot into the session, follow the instructions in //src/session/README.md.

Launch element_session from Command Line

To instruct a running session_manager to launch the session, run:

fx shell session_control launch fuchsia-pkg://fuchsia.com/element_session#meta/element_session.cm

The last command should output a message stating that the session was launched. fx log should show a message saying element's ping has been received:

[00016.031278][25622][25624][element_session] INFO: Element did ping session.

Testing

Add --with //src/session:tests to your existing fx set command will include the element_session unit tests in the build. The resulting fx set looks like:

fx set <PRODUCT>.<BOARD> --with-base=//src/session,//src/session/bin/session_manager:session_manager.config --with //src/session:tests

To see a list of possible products, run: fx list-products.

To see a list of possible boards, run: fx list-boards.

The tests are available in the element_session_tests, element_proposer_tests, and simple_element_tests packages.

$ fx test element_session_tests
$ fx test element_proposer_tests
$ fx test simple_element_tests

Source Layout

The entry point and session units tests are located in src/main.rs.