@google-labs/breadboard-web v1.8.1

Breadboard Web Runtime

This is the package that contains all necessary infrastructure to run a Breadboard application in a web browser.

The Worker Communication Protocol

The worker communicates with its host using a simple message protocol. The protocol is defined in protocol.ts and documented in the API documentation.

The general message format used to communicate with the worker consists of three parts:

• The id of the message (optional)
• The type of the message
• The data payload of the message

The payload will vary depending on the type of the message.

Some messages are "one-way" messages and some are "round-trip" messages. The difference is that the sender of a "round-trip" message expects a response from the receiver.

The presence of the id field indicates that this is a "round-trip" message. The receiver of this message must respond with a message of the same type and the same id.

The protocol allows the following types of messages:

• load -- sent by the host to load the board
• start -- sent by the host to load the board and to start running it
• input -- sent by the worker when the board is requesting input (a round-trip message)
• output -- sent by the worker when the board is producing output
• beforehandler -- sent by the worker when the board is about to run a handler for a node. These messages are useful for indicating the progress of the board's run.
• proxy -- sent by the worker when the board is requesting a proxy object (a round-trip message)
• end -- sent by the worker when the board is done running
• error -- sent by the worker when an error occurs

Any other types of messages cause an error to be thrown by the worker and abort running of the board.

Typical Lifecycle

The typical worker lifecycle is as follows:

1. The host sends a load message to the worker, supplying the board to load.
2. The worker loads the board and sends a load message with the information about the board back to the host.
3. The host sends a start message to the worker.
4. The worker loads the board and sends a beforehandler message to the host for each node that is about to be run.
5. The worker sends an input message to the host for each node that requires input.
6. The host responds to each input message with an input message containing the input values for the node.
7. The worker sends an output message to the host for each node that is producing output.
8. The worker sends a proxy message to the host for each node that is requesting a proxy object.
9. The host responds to each proxy message with a proxy message containing the proxy object for the node.
10. The worker sends an end message to the host when the board is done running.
11. If an error occurs, the worker sends an error message to the host.

Firebase bits

Must have firebase CLI installed:

npm install -g firebase-tools

Set project (PROJECT_ID is the ID of the project in the Firebase console):

firebase use --add ${PROJECT_ID}