Livebook Smart Cells

ExeQute ships four Livebook smart cells that appear in the +Smart dropdown once the package is loaded in a notebook. They require kino, vega_lite, and kino_vega_lite to be available.

Mix.install([
  {:exe_qute, "~> 0.1"},
  {:kino, "~> 0.14"},
  {:vega_lite, "~> 0.1"},
  {:kino_vega_lite, "~> 0.1"}
])

KDB+ Connection

Creates a persistent connection to a KDB+ instance and binds it to a Livebook variable.

Fields

Generated code

{:ok, conn} = ExeQute.connect(host: "localhost", port: 5001)

With credentials:

{:ok, conn} = ExeQute.connect(
  host: "tp-host",
  port: 9600,
  username: "trader",
  password: System.fetch_env!("LB_KDB_PASS")
)

The password is never stored in the notebook — it is read from the Livebook secrets store at evaluation time.

KDB+ Query

Runs a q expression against a connection and displays the result as a tabbed widget with Table, Tree, and Raw views.

Fields

Sidebar browser

The left sidebar lists all tables and functions in the selected namespace. Clicking a table populates the query area with select[N] from tablename. Clicking a function populates it with funcname[].

Generated code

{:ok, result} = ExeQute.query(conn, "select from trade")
ExeQute.display(result, "select from trade")

ExeQute.display/2 renders a Kino.Layout.tabs widget. The Table tab uses Kino.DataTable and is shown when the result is a list of maps. The Tree tab uses Kino.Tree. Raw always shows the inspected value.

KDB+ Subscribe

Opens a long-lived tickerplant subscriber connection and binds it to a variable. The subscriber is started via ExeQute.Subscriber.start_or_find/1, which means re-evaluating the cell reuses the existing TCP connection rather than opening a new one.

Fields

Generated code

{:ok, tp} = ExeQute.Subscriber.start_or_find(host: "tp-host", port: 9600)

Pass the variable to a KDB+ Chart cell or use it directly with ExeQute.subscribe/3:

{:ok, ref} = ExeQute.subscribe(tp, "trade", fn {_table, raw} ->
  rows = ExeQute.to_rows(raw)
  IO.inspect(rows)
end)

KDB+ Chart

Subscribes to a tickerplant table and renders a live-updating Kino.VegaLite chart alongside a Kino.DataTable. Both update on every push from the tickerplant.

Fields

Tabs

• Chart — live Kino.VegaLite updating on every tickerplant message
• Data — Kino.DataTable showing the most recent rows; useful for confirming data is arriving before the chart axes are tuned

Changing parameters without re-evaluating

All visual parameters (x/y field, type, chart type, color field, window) can be changed directly in the smart cell UI after the cell has been evaluated. The change takes effect on the next data tick — the subscription is not interrupted. Re-evaluation is only required when the subscriber, table, or symbol filter changes.

X type behaviour

Generated code

{:ok, chart} =
  ExeQute.subscribe(tp, "trade", ["AAPL", "MSFT"], fn {_table, raw} ->
    rows = ExeQute.to_rows(raw)
    ...
  end)

The full generated code is more involved; it sets up the VegaLite spec, a Kino.Frame for live re-rendering, an Agent buffer, and an ETS config table that the smart cell server writes to when you change UI fields.

Typical notebook layout

A minimal Livebook notebook for live KDB+ monitoring looks like this:

[KDB+ Connection]   → binds `conn`
[KDB+ Subscribe]    → binds `tp`
[KDB+ Query]        → ad-hoc exploration using `conn`
[KDB+ Chart]        → live chart from `tp`, table "trade", x: time, y: price
[KDB+ Chart]        → live chart from `tp`, table "bbo",   x: sym,  y: bid

The connection and subscriber cells only need to be evaluated once per session. Chart cells can be re-evaluated to change the subscription target; visual parameters can be adjusted in the cell UI at any time without interrupting the data feed.