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Introduction

This application is a real-time simulation of a stock ticker. It displays a real-time table of a simulated collection of stocks that one might find listed on an exchange. Their key properties such as current price and daily movement are simulated in the Java Swim application located in the /server directory of this repository. A single MapDownlink is opened by the UI to the stocks lane of the backend application's SymbolsAgent. This downlink syncs with the lane's state containing pricing for all entries and then receives follow-on price updates until the downlink is closed. With each update received, UI local state and table content is updated.

See a hosted version of this app running at https://stocks-simulated.nstream-demo.io.

Running the example

This default implementation simulates 20K stocks by default.

cd server
mvn clean compile exec:java

You may change the number of stocks by setting the NUM_STOCKS environment variable. To run the application with 50K simulated stocks, use the following commands.

cd server
NUM_STOCKS=50000
mvn clean compile exec:java

Viewing the UI

The UI is built using React bootstrapped with Vite and AG Grid for the table component.

cd ui
npm install
npm run dev

Then head to localhost:5173 to see it in action.

Streaming APIs

The swim-cli is the simplest way to fetch or stream data from the web agents in this application

"swim-cli" installation

swim-cli installation details available here: https://www.swimos.org/backend/cli/

Application APIs

Note:

  • Below swim-cli commands for introspection are for streaming locally running application.
  • There is a hosted version of this application running here: https://stocks-simulated.nstream-demo.io/
  • To stream APIs for the hosted version, replace warp://localhost:9001 in below commands with warps://stocks-simulated.nstream-demo.io

(Below, Stock ticker symbol "AAAA" is used as an example)

  1. SYMBOLS:
  • List of various stocks' current price, trading volume, bid/ask if any, and the price movement in the stock price.
swim-cli sync -h warp://localhost:9001 -n /symbols -l stocks
  1. STOCK:
  • A particular stock's current status details (current price, trading volume, bid/ask if any, and the price movement in the stock price)
swim-cli sync -h warp://localhost:9001 -n /stock/AAAA -l status
  • A particular stock's previous close price details
swim-cli sync -h warp://localhost:9001 -n /stock/AAAA -l previousClose

Introspection APIs

The Swim runtime exposes its internal subsystems as a set of meta web agents.

Use the swim:meta:host agent to introspect a running host. Use the pulse lane to stream high level stats:

swim-cli sync -h warp://localhost:9001 -n swim:meta:host -l pulse

The nodes lane enumerates all agents running on a host:

swim-cli sync -h warp://localhost:9001 -n swim:meta:host -l nodes

The fragment part of the nodes lane URI can contain a URI subpath filter:

swim-cli sync -h warp://localhost:9001 -n swim:meta:host -l nodes#/

Node Introspection

You can stream the utilization of an individual web agent:

swim-cli sync -h warp://localhost:9001 -n swim:meta:node/%2fsymbols -l pulse

swim-cli sync -h warp://localhost:9001 -n swim:meta:node/%2fstock%2fAAAA -l pulse

And discover its lanes:

swim-cli sync -h warp://localhost:9001 -n swim:meta:node/%2fsymbols -l lanes

swim-cli sync -h warp://localhost:9001 -n swim:meta:node/%2fstock%2fAAAA -l lanes

Mesh introspectiong

swim-cli sync -h warp://localhost:9001 -n swim:meta:edge -l meshes