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Test a WebSocket service

-protocol websocket takes ws:// and wss:// targets. In protocol-direct mode, each iteration connects, sends the -body message, waits for one reply, and closes.

The examples run against the sample app. Start it in its own terminal:

cd examples/sample-app
go run .

It echoes every message at ws://127.0.0.1:8080/ws/echo, with 5 to 15 ms of delay. Localhost is always allowed. For any other host, see Safety.

One command, no file​

vegaload run -target ws://127.0.0.1:8080/ws/echo -protocol websocket \
  -body hello -vus 5 -duration 3s

Each iteration opens a connection, sends hello, waits for the echo, and closes. On a laptop this makes about 1,400 iterations in 3 seconds, with p50 near 10 ms. The report has a Protocols section for the WebSocket calls.

Leave out -body to measure only the handshake: connect and close, with no message. That runs much faster, because the echo delay applies to messages only. It can make tens of thousands of connections in a few seconds.

caution

A handshake-only run opens a new TCP connection each time. The operating system keeps each closed connection's local port reserved for a while (TIME_WAIT). A fast run can use up most of the available local ports. The next run that opens new connections then fails many iterations at once, with near-zero latency. If you see that, wait a minute and run again. It is a limit of the machine running VegaLoad, not of the server.

TLS​

For wss:// targets, VegaLoad checks the certificate. To trust your own CA, pass ca_file with -opt. See TLS with your own CA.

Pass or fail limits​

A threshold can target the protocol:

vegaload run -target ws://127.0.0.1:8080/ws/echo -protocol websocket -body hello \
  -vus 5 -duration 3s -threshold 'p95{protocol="websocket"} < 100ms'

See Thresholds.

A connection with many messages​

A scenario can hold a connection open and send many messages. The script has ws.connect, ws.send, ws.receive and ws.close. It can also carry a value from an HTTP call into a WebSocket call.

http-ws-chain.vl.js (Python: http_ws_chain.py) creates a widget over HTTP, opens the WebSocket, sends a message with the new id, and checks that the echo matches:

vegaload run -vus 5 -duration 10s http-ws-chain.vl.js

The report shows the HTTP and WebSocket calls as two protocols, and each call (connect, send, receive) on its own. The host allow-list is checked for every call, not only the first. See Scenarios.

Options​

vegaload protocols websocket lists the options and the scenario calls. WebSocket takes ca_file, cert_file, key_file and tls_server_name. Connections from a browser page on another origin are refused by the sample app. VegaLoad is not a browser, so this does not affect it.