Operating Modes

There are many different ways of sending data to the Rerun Viewer depending on what you're trying to achieve and whether the Viewer is running in the same process as your code, in another process, or even as a separate web application.

In the official examples, these different modes of operation are exposed via a standardized set of flags that we'll cover below. We will also demonstrate how you can achieve the same behavior in your own code.

Before reading this document, you might want to familiarize yourself with the Rerun application model.

Operating modes operating-modes

The Rerun SDK provides 4 modes of operation: spawn, connect, serve, and save.

All four of them are optional: when none of these modes are active, the client will simply buffer the logged data in memory, waiting for one of these modes to be enabled so that it can flush it.

Spawn spawn

This is the default behavior you get when running all of our C++/Python/Rust examples, and is generally the most convenient when you're experimenting.

C++

RecordingStream::spawn spawns a new Rerun Viewer process using an executable available in your PATH, then streams all the data to it via gRPC. If an external Viewer was already running, spawn will connect to that one instead of spawning a new one.

Python

Call rr.spawn once at the start of your program to start a Rerun Viewer in an external process and stream all the data to it via gRPC. If an external Viewer was already running, spawn will connect to that one instead of spawning a new one.

Rust

RecordingStream::spawn spawns a new Rerun Viewer process using an executable available in your PATH, then streams all the data to it via gRPC. If an external Viewer was already running, spawn will connect to that one instead of spawning a new one.

Connect connect

Connects to a remote Rerun Viewer and streams all the data via gRPC.

You will need to start a stand-alone Viewer first by typing rerun in your terminal.

C++

RecordingStream::connect

Python

rr.connect

Rust

RecordingStream::connect

Serve serve

There are two kinds of serve calls:

• serve_web
• serve_grpc

Both will start a Rerun gRPC server in your process, and stream logged data to it.

The serve_web call starts an additional server which hosts the assets required to run the Rerun Viewer in your browser.

C++

• RecordingStream::serve_grpc.
• serve_web is not available.

Python

• rr.serve_grpc
• rr.serve_web

Rust

• RecordingStream::serve_grpc
• RecordingStream::serve_web

Save save

Streams all logging data into an .rrd file on disk, which can then be loaded into a stand-alone viewer.

To view the saved file, use rerun path/to/file.rrd.

⚠️ RRD files are not yet stable across different versions! ⚠️

C++

Use RecordingStream::save.

Python

Use rr.save.

Rust

Use RecordingStream::save.

Standard Input/Output standard-inputoutput

Streams all logging data to standard output, which can then be loaded by the Rerun Viewer by streaming it from standard input.

C++

Use RecordingStream::stdout.

Check out our dedicated example.

Python

Use rr.stdout.

Check out our dedicated example.

Rust

Use RecordingStream::stdout.

Check out our dedicated example.

Adding the standard flags to your programs adding-the-standard-flags-to-your-programs

We provide helpers for both Python & Rust to effortlessly add and properly handle all of these flags in your programs.

• For Python, checkout the script_helpers module.
• For Rust, checkout our clap integration.

Have a look at the official examples to see these helpers in action.