bokeh.client.session

Provide a session object to service Bokeh documents in external Python clients to a Bokeh server.

Use-Cases

A client session has two primary uses:

• Implementing automated testing infrastructure around Bokeh server applications.

• Creating and customizing specific sessions of a Bokeh server application (running in the Bokeh server) before passing them on to a specific viewer.

class ClientSession(session_id: ID | None = None, websocket_url: str = 'ws://localhost:5006/ws', io_loop: IOLoop | None = None, arguments: Dict[str, str] | None = None, max_message_size: int = 20971520)

Represents a websocket connection to a server-side session.

Each server session stores a Document, which is kept in sync with the corresponding Document for this ClientSession instance. Updates on either side of the connection will automatically propagate to the other side, as long as the connection is open.

ClientSession objects can (and usually should) be used as a context manager so that the session is properly closed:

with pull_session(url=app_url) as mysession:
    # customize session here
    script = server_session(session_id=mysession.id, url=app_url)
    return render_template("embed.html", script=script, template="Flask")

If you do not use ClientSession in this way, it is up to you to ensure that mysession.close() is called.

Public Data Attributes:

connected	Whether this session is currently connected.
error_reason
error_code
error_detail
url
document	A Document that will be kept in sync with the corresponding Document on the server.
id	A unique ID for this session.
token	A JWT token to authenticate the session.

Public Methods:

__init__([session_id, websocket_url, ...])	A connection which attaches to a particular named session on the server.
__enter__()
__exit__(exc_type, exc_value, exc_traceback)
connect()	Connect to a Bokeh server at the configured URL.
close([why])	Close the connection to the server.
force_roundtrip()	Force a round-trip request/reply to the server, sometimes needed to avoid race conditions.
check_connection_errors()	Raises an error, when the connection could not have been established.
pull()	Pull the server's state and set it as session.document.
push([document])	Push the given document to the server and record it as session.document.
request_server_info()	Ask for information about the server.
show([obj, browser, new])	Open a browser displaying this session.

---

__init__(session_id: ID | None = None, websocket_url: str = 'ws://localhost:5006/ws', io_loop: IOLoop | None = None, arguments: Dict[str, str] | None = None, max_message_size: int = 20971520)

A connection which attaches to a particular named session on the server.

Always call either pull() or push() immediately after creating the session (until these are called session.document will be None).

The push_session() and pull_session() functions will construct a ClientSession and push or pull in one step, so they are a good way to obtain a ClientSession.

Parameters

• session_id (str) – The name of the session or None to generate one

• websocket_url (str) – Websocket URL to connect to

• io_loop (IOLoop, optional) – The IOLoop to use for the websocket

• arguments (dict[str, str], optional) –

  A dictionary of key/values to be passed as HTTP request arguments to Bokeh application code (default: None)

  Note that should only be provided when pulling new sessions. If session_id is not None, or a session with session_id already exists, these arguments will have no effect.

• max_message_size (int, optional) – Configure the Tornado max websocket message size. (default: 20 MB)

check_connection_errors() → None

Raises an error, when the connection could not have been established.

Should be used, after a call to connect.

Returns

None

close(why: str = 'closed') → None

Close the connection to the server.

connect() → None

Connect to a Bokeh server at the configured URL.

force_roundtrip() → None

Force a round-trip request/reply to the server, sometimes needed to avoid race conditions. Mostly useful for testing.

Outside of test suites, this method hurts performance and should not be needed.

Returns

None

pull() → None

Pull the server’s state and set it as session.document.

If this is called more than once, session.document will be the same object instance but its contents will be overwritten.

Automatically calls connect() before pulling.

push(document: Document | None = None) → None

Push the given document to the server and record it as session.document.

If this is called more than once, the Document has to be the same (or None to mean session.document).

Note

Automatically calls connect() before pushing.

Parameters

document (Document, optional) – The document that will be kept in sync with the server document. None to use session.document or create a new document.

request_server_info() → ServerInfo

Ask for information about the server.

Returns

A dictionary of server attributes.

show(obj: LayoutDOM | None = None, browser: str | None = None, new: Literal['tab', 'window'] = 'tab') → None

Open a browser displaying this session.

Parameters

• obj (LayoutDOM object, optional) – a Layout (Row/Column), Plot or Widget object to display. The object will be added to the session’s document.

• browser (str, optional) – browser to show with (default: None) For systems that support it, the browser argument allows specifying which browser to display in, e.g. “safari”, “firefox”, “opera”, “windows-default” (see the webbrowser module documentation in the standard lib for more details).

• new (str, optional) – new file output mode (default: “tab”) For file-based output, opens or raises the browser window showing the current output file. If new is ‘tab’, then opens a new tab. If new is ‘window’, then opens a new window.

property connected: bool

Whether this session is currently connected.

property document: bokeh.document.document.Document

A Document that will be kept in sync with the corresponding Document on the server.

This value is initialized when pull() or push() succeeds. It will be None until then.

property id: ID

A unique ID for this session.

property token: str

A JWT token to authenticate the session.

pull_session(session_id: ID | None = None, url: str = 'default', io_loop: IOLoop | None = None, arguments: Dict[str, str] | None = None, max_message_size: int = 20971520) → ClientSession

Create a session by loading the current server-side document.

session.document will be a fresh document loaded from the server. While the connection to the server is open, changes made on the server side will be applied to this document, and changes made on the client side will be synced to the server.

If you don’t plan to modify session.document you probably don’t need to use this function; instead you can directly show_session() or server_session() without downloading the session’s document into your process first. It’s much more efficient to avoid downloading the session if you don’t need to.

In a production scenario, the session_id should be unique for each browser tab, which keeps users from stomping on each other. It’s neither scalable nor secure to use predictable session IDs or to share session IDs across users.

For a notebook running on a single machine, session_id could be something human-readable such as "default" for convenience.

If you allow pull_session() to generate a unique session_id, you can obtain the generated ID with the id property on the returned ClientSession.

Parameters

• session_id (string, optional) – The name of the session, None to autogenerate a random one (default: None)

• url – (str, optional): The URL to a Bokeh application on a Bokeh server can also be “default” which will connect to the default app URL

• io_loop (tornado.ioloop.IOLoop, optional) – The IOLoop to use for the websocket

• arguments (dict[str, str], optional) –

  A dictionary of key/values to be passed as HTTP request arguments to Bokeh application code (default: None)

  Note that should only be provided when pulling new sessions. If session_id is not None, or a session with session_id already exists, these arguments will have no effect.

• max_message_size (int, optional) – Configure the Tornado max websocket message size. (default: 20 MB)

Returns

A new ClientSession connected to the server

Return type

ClientSession

push_session(document: Document, session_id: ID | None = None, url: str = 'default', io_loop: IOLoop | None = None, max_message_size: int = 20971520) → ClientSession

Create a session by pushing the given document to the server, overwriting any existing server-side document.

session.document in the returned session will be your supplied document. While the connection to the server is open, changes made on the server side will be applied to this document, and changes made on the client side will be synced to the server.

In a production scenario, the session_id should be unique for each browser tab, which keeps users from stomping on each other. It’s neither scalable nor secure to use predictable session IDs or to share session IDs across users.

For a notebook running on a single machine, session_id could be something human-readable such as "default" for convenience.

If you allow push_session() to generate a unique session_id, you can obtain the generated ID with the id property on the returned ClientSession.

Parameters

• document – (bokeh.document.Document) The document to be pushed and set as session.document

• session_id – (string, optional) The name of the session, None to autogenerate a random one (default: None)

• url – (str, optional): The URL to a Bokeh application on a Bokeh server can also be “default” which will connect to the default app URL

• io_loop – (tornado.ioloop.IOLoop, optional) The IOLoop to use for the websocket

• max_message_size (int, optional) – Configure the Tornado max websocket message size. (default: 20 MB)

Returns

ClientSession

A new ClientSession connected to the server

show_session(session_id: ID | None = None, url: str = 'default', session: ClientSession | None = None, browser: str | None = None, new: BrowserTarget = 'tab', controller: BrowserLike | None = None) → None

Open a browser displaying a session document.

If you have a session from pull_session() or push_session you can show_session(session=mysession). If you don’t need to open a connection to the server yourself, you can show a new session in a browser by providing just the url.

Parameters

• session_id (string, optional) – The name of the session, None to autogenerate a random one (default: None)

• url – (str, optional): The URL to a Bokeh application on a Bokeh server can also be “default” which will connect to the default app URL

• session (ClientSession, optional) – session to get session ID and server URL from If you specify this, you don’t need to specify session_id and url

• browser (str, optional) – browser to show with (default: None) For systems that support it, the browser argument allows specifying which browser to display in, e.g. “safari”, “firefox”, “opera”, “windows-default” (see the webbrowser module documentation in the standard lib for more details).

• new (str, optional) – new file output mode (default: “tab”) For file-based output, opens or raises the browser window showing the current output file. If new is ‘tab’, then opens a new tab. If new is ‘window’, then opens a new window.

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