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Running Rust programs as WebAssembly (WASM)

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Bacalhau supports running jobs as a WebAssembly (WASM) program rather than using a Docker container. This examples demonstrates how to compile a Rust project into WebAssembly and run the program on Bacalhau.


  • You'll need the latest bacalhau client installed by following the getting started instructions.
  • A working Rust installation with the wasm32-wasi target. For example, you can use rustup to install Rust and configure it to build WASM targets.

For those using the notebook, these are installed in hidden cells below.

1. Develop a Rust Program Locally

We can use cargo (which will have been installed by rustup) to start a new project and compile it.

cargo init my-program
     Created binary (application) package

We can then write a Rust program. Rust programs that run on Bacalhau can read and write files, access a simple clock and make use of psudeo-random numbers. They cannot memory-map files or run code on multiple threads.

The below program will make use of the Rust imageproc crate to resize an image through seam carving, based on an example from their repository.

%%writefile ./my-program/src/ 
use image::{open, GrayImage, Luma, Pixel};
use imageproc::definitions::Clamp;
use imageproc::gradients::sobel_gradient_map;
use imageproc::map::map_colors;
use imageproc::seam_carving::*;
use std::path::Path;

fn main() {
let input_path = "inputs/image0.JPG";
let output_dir = "outputs/";

let input_path = Path::new(&input_path);
let output_dir = Path::new(&output_dir);

// Load image and convert to grayscale
let input_image = open(input_path)
.expect(&format!("Could not load image at {:?}", input_path))

// Save original image in output directory
let original_path = output_dir.join("original.png");;

// We will reduce the image width by this amount, removing one seam at a time.
let seams_to_remove: u32 = input_image.width() / 6;

let mut shrunk = input_image.clone();
let mut seams = Vec::new();

// Record each removed seam so that we can draw them on the original image later.
for i in 0..seams_to_remove {
if i % 100 == 0 {
println!("Removing seam {}", i);
let vertical_seam = find_vertical_seam(&shrunk);
shrunk = remove_vertical_seam(&mut shrunk, &vertical_seam);

// Draw the seams on the original image.
let gray_image = map_colors(&input_image, |p| p.to_luma());
let annotated = draw_vertical_seams(&gray_image, &seams);
let annotated_path = output_dir.join("annotated.png");;

// Draw the seams on the gradient magnitude image.
let gradients = sobel_gradient_map(&input_image, |p| {
let mean = (p[0] + p[1] + p[2]) / 3;
Luma([mean as u32])
let clamped_gradients: GrayImage = map_colors(&gradients, |p| Luma([Clamp::clamp(p[0])]));
let annotated_gradients = draw_vertical_seams(&clamped_gradients, &seams);
let gradients_path = output_dir.join("gradients.png");;
let annotated_gradients_path = output_dir.join("annotated_gradients.png");;

// Save the shrunk image.
let shrunk_path = output_dir.join("shrunk.png");;
Overwriting ./my-program/src/

We also need to install the imageproc and image libraries and switch off the default features to make sure that multi-threading is disabled.

%%writefile ./my-program/Cargo.toml
name = "my-program"
version = "0.1.0"
edition = "2021"

version = "0.24.4"
default-features = false
features = ["png", "jpeg", "bmp"]

version = "0.23.0"
default-features = false
Overwriting ./my-program/Cargo.toml

We can now build the Rust program into a WASM blob using cargo.

cd my-program && cargo build --target wasm32-wasi --release
    Updating index
Compiling autocfg v1.1.0
Compiling cfg-if v1.0.0
Compiling getrandom v0.1.16
Compiling bytemuck v1.12.3
Compiling wasi v0.9.0+wasi-snapshot-preview1
Compiling adler v1.0.2
Compiling crc32fast v1.3.2
Compiling typenum v1.15.0
Compiling ppv-lite86 v0.2.17
Compiling miniz_oxide v0.5.4
Compiling safe_arch v0.6.0
Compiling miniz_oxide v0.6.2
Compiling wide v0.7.5
Compiling num-traits v0.2.15
Compiling num-integer v0.1.45
Compiling num-bigint v0.4.3
Compiling num-rational v0.4.1
Compiling rand_core v0.5.1
Compiling num-iter v0.1.43
Compiling flate2 v1.0.24
Compiling rand_chacha v0.2.2
Compiling bitflags v1.3.2
Compiling ttf-parser v0.15.2
Compiling paste v1.0.9
Compiling rawpointer v0.2.1
Compiling matrixmultiply v0.3.2
Compiling png v0.17.7
Compiling num-complex v0.4.2
Compiling approx v0.5.1
Compiling simba v0.7.3
Compiling rand v0.7.3
Compiling color_quant v1.1.0
Compiling either v1.8.0
Compiling byteorder v1.4.3
Compiling ab_glyph_rasterizer v0.1.7
Compiling jpeg-decoder v0.3.0
Compiling custom_derive v0.1.7
Compiling owned_ttf_parser v0.15.2
Compiling conv v0.3.3
Compiling rusttype v0.9.3
Compiling image v0.24.5
Compiling num v0.4.0
Compiling rand_distr v0.2.2
Compiling itertools v0.10.5
Compiling nalgebra v0.30.1
Compiling imageproc v0.23.0
Compiling my-program v0.1.0 (/Users/phil/source/bacalhau-project/examples/workload-onboarding/rust-wasm/my-program)
Finished release [optimized] target(s) in 17.81s

This will generate a WASM file at ./my-program/target/wasm32-wasi/my-program.wasm which can now be run on Bacalhau.

2. Running WASM on Bacalhau

Now that we have a WASM binary, we can upload it to IPFS and use it as input to a Bacalhau job.

The -v switch allows specifying an IPFS CID to mount as a named volume in the job. There is also a -u switch which can download inputs via HTTP.

For this example, we are using an image of the Statue of Liberty that has been pinned to a storage facility.

bacalhau wasm run ./my-program/target/wasm32-wasi/release/my-program.wasm _start \
-v bafybeifdpl6dw7atz6uealwjdklolvxrocavceorhb3eoq6y53cbtitbeu:inputs | tee job.txt
Uploading "./my-program/target/wasm32-wasi/release/my-program.wasm" to server to execute command in context, press Ctrl+C to cancel
Job successfully submitted. Job ID: 702cb81f-cf50-4d4f-b60d-b06e62f36de3
Checking job status... (Enter Ctrl+C to exit at any time, your job will continue running):

Creating job for submission ... done ✅
Finding node(s) for the job ... done ✅
Node accepted the job ... done ✅
Job finished, verifying results ... done ✅
Results accepted, publishing ... Job Results By Node:

To download the results, execute:
bacalhau get 702cb81f-cf50-4d4f-b60d-b06e62f36de3

To get more details about the run, execute:
bacalhau describe 702cb81f-cf50-4d4f-b60d-b06e62f36de3

We can now get the results. When we view the files, we can see the original image, the resulting shrunk image, and the seams that were removed.

rm -rf wasm_results && mkdir -p wasm_results
bacalhau get $(grep "Job ID:" job.txt | cut -f2 -d:) --output-dir wasm_results
Fetching results of job '702cb81f-cf50-4d4f-b60d-b06e62f36de3'...
Results for job '702cb81f-cf50-4d4f-b60d-b06e62f36de3' have been written to...

11:05:14.218 | ??? providerquerymanager/providerquerymanager.go:344 > ERROR bitswap Received provider (12D3KooWGE4R98vokeLsRVdTv8D6jhMnifo81mm7NMRV8WJPNVHb) for cid (QmaxyTrc3zSb6ggUVYgXb9yxVJZ9cXv6Y6u55Czm2eqaWD) not requested
import IPython.display as display