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Production-Ready Text Embeddings with WebAssembly: WasmEdge + GGML

· 17 min read
fr4nk
Software Engineer
Hugging Face

Building production ML inference services that run anywhere—from Raspberry Pi to cloud edge—requires a different approach. This article walks through a complete implementation of a text embedding API using WasmEdge, GGML, and Rust, delivering a 136KB WASM module paired with a 1.8MB async HTTP server that processes embeddings in ~100-200ms per request.

Full implementation: github.com/porameht/wasmedge-ggml-llama-embedding

What We're Building

A production-ready embedding API that transforms text into 384-dimensional vectors using:

  • WebAssembly runtime - Cross-platform portability (ARM, x86, RISC-V)
  • GGML quantization - Efficient model inference (44MB model)
  • Async HTTP server - High-throughput request handling with Tokio
  • Dual-binary architecture - Flexible deployment (WASM-only or full server)
  • Zero-config deployment - Environment variable configuration

Use cases:

  • Semantic search - Index and query millions of documents by meaning
  • RAG pipelines - Retrieval-augmented generation for LLMs
  • Recommendation engines - Find similar products, content, or users
  • Duplicate detection - Identify semantically similar items
  • Edge computing - Run inference locally on IoT devices

The Challenge: Traditional ML Deployment

Traditional ML deployment approaches come with significant overhead:

ApproachBinary SizeDependenciesPortability
Python + PyTorchN/APython runtime + packagesPlatform-dependent
ONNX Runtime~20MBPlatform-specific buildsGood
TensorFlow Serving~500MBHeavy dependenciesPlatform-dependent
WasmEdge + GGML136KBWasmEdge onlyTrue cross-platform

Why WebAssembly for edge computing:

  • Truly cross-platform - Same binary runs on ARM, x86, RISC-V
  • Minimal footprint - 136KB WASM module + 1.8MB server
  • Sandboxed execution - Built-in isolation for multi-tenant environments
  • No runtime dependencies - Just WasmEdge, no Python/Node.js required

System Architecture:

Why WebAssembly for Edge ML?

WebAssembly (Wasm) is the perfect match for edge computing ML inference:

1. True Cross-Platform Deployment

Deploy the same binary to any edge device:

# Build once for WebAssembly
cargo build --target wasm32-wasip1 --release

# Run on ANY edge device - no recompilation needed
# Raspberry Pi (ARM)
wasmedge model.wasm

# Edge server (x86)
wasmedge model.wasm

# IoT gateway (RISC-V)
wasmedge model.wasm

2. Edge-First Security

Critical for multi-tenant edge environments:

# Sandboxed execution - perfect for edge multi-tenancy
wasmedge --dir .:. model.wasm

# Explicit resource control
wasmedge --nn-preload default:GGML:AUTO:model.gguf model.wasm

3. Production Performance Metrics

Verified specifications from the implementation:

MetricValueNotes
WASM Binary136KBPortable inference module
Server Binary1.8MBAsync HTTP API wrapper
Model Size44MBQuantized GGUF format
Cold Start2-3 secondsModel load + initialization
Inference Latency100-200msPer embedding request

The Implementation

Dual-Binary Architecture - Two specialized components working together:

Component 1: WASM Embedding Module (136KB)

src/wasm.rs - The core inference engine

Responsibilities:

  • Load GGUF models via WASI-NN
  • Process text through GGML backend
  • Output pure JSON embeddings
  • Handle context management
  • CLI interface for direct usage

Build command:

cargo build --bin wasm-embedding --target wasm32-wasip1 --release \
--features wasm --no-default-features

Component 2: HTTP Server (1.8MB)

src/server.rs - Production API wrapper

Responsibilities:

  • Async HTTP handling (Warp + Tokio)
  • Process management (spawn WasmEdge)
  • CORS support for web integration
  • Health monitoring
  • Error handling and logging

Build command:

cargo build --bin embedding-api-server --release

Why this architecture?

  • Flexibility - Use WASM alone or full server
  • Performance - Async server handles concurrency
  • Portability - WASM runs anywhere
  • Maintainability - Clear separation of concerns

Let's dive into the implementation details.

1. Environment Configuration

Load runtime settings from environment variables for zero-recompilation deployment:

fn get_options_from_env() -> Value {
let mut options = json!({});
if let Ok(val) = env::var("enable_log") {
options["enable-log"] = serde_json::from_str(val.as_str()).unwrap()
}
if let Ok(val) = env::var("ctx_size") {
options["ctx-size"] = serde_json::from_str(val.as_str()).unwrap()
}
if let Ok(val) = env::var("batch_size") {
options["batch-size"] = serde_json::from_str(val.as_str()).unwrap()
}
if let Ok(val) = env::var("threads") {
options["threads"] = serde_json::from_str(val.as_str()).unwrap()
}
options
}

View configuration code

Available options:

  • enable_log - Detailed logging (token counts, versions)
  • ctx_size - Context window size (default: 512)
  • batch_size - Batch processing size (default: 512)
  • threads - CPU threads for inference (default: 4)

2. WASI-NN Graph Initialization

The core of WASI-NN integration - loading the GGML model:

let graph = GraphBuilder::new(GraphEncoding::Ggml, ExecutionTarget::AUTO)
.config(options.to_string())
.build_from_cache(model_name)
.expect("Create GraphBuilder Failed");

let mut context = graph
.init_execution_context()
.expect("Init Context Failed");

View graph initialization

The WASI-NN Flow:

3. HTTP Server Implementation

The production API wraps the WASM module with an async HTTP server:

async fn generate_embedding(&self, text: &str) -> Result<EmbedResponse> {
let mut child = Command::new("wasmedge")
.arg("--dir").arg(".:.")
.arg("--nn-preload").arg(&format!("default:GGML:AUTO:{}", self.model_path.display()))
.arg(&self.wasm_path)
.arg("default")
.arg(text)
.stdout(Stdio::piped())
.spawn()?;

let mut stdout = Vec::new();
if let Some(mut out) = child.stdout.take() {
out.read_to_end(&mut stdout).await?;
}

let output = String::from_utf8_lossy(&stdout);
let parsed: serde_json::Value = serde_json::from_str(output.trim())?;

Ok(EmbedResponse {
n_embedding: parsed["n_embedding"].as_u64().unwrap() as usize,
embedding: parsed["embedding"].as_array().unwrap()
.iter().filter_map(|v| v.as_f64()).collect()
})
}

View server implementation

API Endpoints:

# Generate embedding
curl -X POST http://localhost:3000/embed \
-H "Content-Type: application/json" \
-d '{"text":"What is the capital of France?"}'

# Health check
curl http://localhost:3000/health

# API info
curl http://localhost:3000/

4. Tensor Processing

Proper tensor dimension handling for embeddings:

fn set_data_to_context(context: &mut GraphExecutionContext, data: Vec<u8>) -> Result<(), Error> {
context.set_input(0, TensorType::U8, &[data.len()], &data)
}

fn get_data_from_context(context: &GraphExecutionContext, index: usize) -> String {
const MAX_OUTPUT_BUFFER_SIZE: usize = 4096 * 20 + 128;
let mut output_buffer = vec![0u8; MAX_OUTPUT_BUFFER_SIZE];
let mut output_size = context.get_output(index, &mut output_buffer).unwrap();
output_size = std::cmp::min(MAX_OUTPUT_BUFFER_SIZE, output_size);
String::from_utf8_lossy(&output_buffer[..output_size]).to_string()
}

View tensor processing

Why 4096 * 20 + 128?

  • Most embedding models output ≤ 4096 dimensions
  • Each float printed as string: ~20 bytes
  • 128 bytes for JSON structure ({"n_embedding":...})

5. Output Format

HTTP Response:

{
"n_embedding": 384,
"embedding": [0.5426, -0.0384, -0.0364, ..., 0.1234]
}

WASM CLI Output:

$ wasmedge --dir .:. --nn-preload default:GGML:AUTO:model.gguf \
wasmedge-ggml-llama-embedding.wasm default "Hello world"

{"n_embedding":384,"embedding":[0.5426,-0.0384,-0.0364,...]}

The WASM module outputs pure JSON (no extra text), making it easy to parse in any language or integrate with shell pipelines.

The Model: All-MiniLM-L6-v2

We use the all-MiniLM-L6-v2 model in GGUF format:

SpecificationValue
Output Dimensions384
Model Size44MB (f16 quantized)
Max Sequence Length256 tokens
Performance~10ms per inference
Use CaseGeneral-purpose embeddings

Download from HuggingFace:

curl -LO https://huggingface.co/second-state/All-MiniLM-L6-v2-Embedding-GGUF/resolve/main/all-MiniLM-L6-v2-ggml-model-f16.gguf

Model comparison:

ModelDimensionsSizeInferenceQuality
MiniLM-L638444MB~10msGood
BERT-Base768440MB~30msBetter
MPNet768440MB~35msBetter
E5-Large10241.3GB~100msBest

Building and Running

Quick Start

# 1. Install WasmEdge with WASI-NN plugin
curl -sSf https://raw.githubusercontent.com/WasmEdge/WasmEdge/master/utils/install.sh | bash -s -- --plugins wasi_nn-ggml
source $HOME/.wasmedge/env

# 2. Install Rust target
rustup target add wasm32-wasip1

# 3. Download model
curl -LO https://huggingface.co/second-state/All-MiniLM-L6-v2-Embedding-GGUF/resolve/main/all-MiniLM-L6-v2-ggml-model-f16.gguf

# 4. Build both binaries
./build-wasm.sh # Builds WASM module (136KB)
cargo build --bin embedding-api-server --release # Builds HTTP server (1.8MB)

# 5. Run the server
./target/release/embedding-api-server

Build time: ~10 seconds (both binaries) Output sizes: 136KB (WASM) + 1.8MB (server)

Build Configuration

The Cargo.toml uses feature flags for optimal binary sizes:

[features]
default = ["server"]
wasm = ["wasmedge-wasi-nn"]
server = ["warp", "tokio", "serde", "anyhow"]

[profile.release]
opt-level = 3 # Maximum optimization
lto = true # Link-time optimization
strip = true # Strip debug symbols

Build targets:

# WASM module only (edge devices)
cargo build --bin wasm-embedding --target wasm32-wasip1 --release \
--features wasm --no-default-features

# HTTP server only (cloud/production)
cargo build --bin embedding-api-server --release

Size comparison:

WASM debug:      450KB
WASM release: 136KB (70% reduction)
Server release: 1.8MB

Edge Computing Use Cases

Run semantic search on IoT devices without cloud dependency:

Option A: HTTP API (Recommended)

import requests
import numpy as np

# Run API server on Raspberry Pi / edge gateway
def get_embedding(text):
response = requests.post('http://localhost:3000/embed',
json={'text': text})
return response.json()['embedding']

# Index sensor documentation locally
docs = [
"Temperature sensor calibration procedure",
"Pressure sensor fault codes",
"Humidity sensor maintenance"
]
doc_embeddings = [get_embedding(doc) for doc in docs]

# Search locally - no internet required
query = "How to fix pressure errors?"
query_emb = get_embedding(query)

# Compute similarity on-device
similarities = [
np.dot(query_emb, doc_emb) / (np.linalg.norm(query_emb) * np.linalg.norm(doc_emb))
for doc_emb in doc_embeddings
]

print(docs[np.argmax(similarities)]) # "Pressure sensor fault codes"

2. Privacy-First Edge RAG

Process sensitive data locally - never send to cloud:

// Healthcare edge device - HIPAA compliant local processing
import { QdrantClient } from '@qdrant/js-client-rest';

async function getEmbedding(text) {
// HTTP API runs LOCALLY on edge device
const response = await fetch('http://localhost:3000/embed', {
method: 'POST',
headers: { 'Content-Type': 'application/json' },
body: JSON.stringify({ text })
});
return (await response.json()).embedding;
}

// Local vector database on edge device
const client = new QdrantClient({ url: 'http://localhost:6333' });

// Index patient data LOCALLY - never leaves device
async function indexPatientRecord(id, record) {
const embedding = await getEmbedding(record);
await client.upsert('patient_records', {
points: [{ id, vector: embedding, payload: { text: record } }]
});
}

// Search patient records LOCALLY - HIPAA compliant
async function searchRecords(query, limit = 5) {
const embedding = await getEmbedding(query);
return await client.search('patient_records', {
vector: embedding,
limit
});
}

3. Offline Edge Gateway Processing

Process data streams on edge gateway with no cloud connectivity:

#!/bin/bash
# Factory floor edge gateway - process sensor logs locally

# Process production line data offline
cat sensor_logs.txt | while read line; do
echo "$line" | wasmedge --dir .:. \
--nn-preload default:GGML:AUTO:model.gguf \
embedding.wasm default "$line" >> production_embeddings.jsonl
done

# Data stays on factory network - never goes to internet
# Perfect for manufacturing, oil & gas, remote locations

Performance Characteristics

Expected Latency

Based on the architecture, each embedding request involves:

# Test direct WASM inference
time wasmedge --dir .:. \
--nn-preload default:GGML:AUTO:model.gguf \
embedding.wasm default "What is the capital of France?"

Typical request timeline:

  • Cold start: 2-3 seconds (initial model load)
  • Inference: 100-200ms per request
  • Model size: 44MB in memory
  • Output: 384-dimensional vector

Performance Considerations

WebAssembly overhead: The WASM sandbox adds safety at a small performance cost:

  • Boundary crossing between WASM and native code
  • Memory isolation for security
  • Portable binary format trade-offs

Trade-off: Prioritizing portability, security, and minimal dependencies over raw speed. Suitable for edge computing where these factors matter more than peak throughput.

Edge Deployment Strategies

1. Edge Serverless (CDN Edge)

Deploy to Cloudflare Workers or Fastly Compute@Edge:

// Run ML inference at CDN edge - closest to users
export default {
async fetch(request) {
const { text } = await request.json();
const wasm = await WebAssembly.instantiateStreaming(
fetch('/embedding.wasm')
);
// ML inference at edge location (not central cloud)
const embedding = wasm.instance.exports.get_embedding(text);
return new Response(JSON.stringify({ embedding }));
}
}

Edge benefits:

  • Sub-50ms latency worldwide
  • No cold start (always warm at edge)
  • Reduced egress costs

2. IoT Edge Gateway

Deploy the HTTP server on Raspberry Pi or industrial edge hardware:

# On Raspberry Pi / edge gateway
export WASM_PATH="./wasmedge-ggml-llama-embedding.wasm"
export MODEL_PATH="./all-MiniLM-L6-v2-ggml-model-f16.gguf"
export PORT=3000

./target/release/embedding-api-server

Server features:

  • CORS enabled - Browser integration ready
  • Async Rust - Handles concurrent requests efficiently
  • Health checks - Monitor edge device status
  • JSON-only API - Easy integration with any language

Perfect for:

  • Smart buildings - Local occupancy analytics
  • Industrial IoT - Real-time equipment monitoring
  • Retail edge - In-store customer insights
  • Vehicle computing - Offline navigation assistance

3. Edge Container Deployment

Production-ready container for edge devices:

FROM rust:1.75 AS builder

WORKDIR /build
COPY Cargo.toml Cargo.lock ./
COPY src ./src

# Build both binaries
RUN rustup target add wasm32-wasip1 && \
cargo build --bin wasm-embedding --target wasm32-wasip1 --release \
--features wasm --no-default-features && \
cargo build --bin embedding-api-server --release

FROM wasmedge/slim:latest

WORKDIR /app
COPY --from=builder /build/target/wasm32-wasip1/release/wasm-embedding.wasm ./wasmedge-ggml-llama-embedding.wasm
COPY --from=builder /build/target/release/embedding-api-server .
COPY all-MiniLM-L6-v2-ggml-model-f16.gguf .

ENV WASM_PATH=/app/wasmedge-ggml-llama-embedding.wasm
ENV MODEL_PATH=/app/all-MiniLM-L6-v2-ggml-model-f16.gguf

EXPOSE 3000
CMD ["./embedding-api-server"]

Edge container footprint:

WasmEdge runtime:    ~50MB
WASM module: 136KB
Server binary: 1.8MB
Model file: 44MB
Total: ~96MB (Edge-optimized)

Compare to typical Python ML deployments requiring 2-3GB+ for runtime, dependencies, and models.

Advanced Features

1. Error Handling

The implementation includes robust error detection:

match context.compute() {
Ok(_) => (),
Err(Error::BackendError(BackendError::ContextFull)) => {
println!("\n[INFO] Context full");
// Could implement context rotation here
}
Err(Error::BackendError(BackendError::PromptTooLong)) => {
println!("\n[INFO] Prompt too long");
// Could implement chunking here
}
Err(err) => {
println!("\n[ERROR] {}", err);
}
}

View error handling code

2. Metadata Extraction

Extract model information and token counts:

let metadata = get_metadata_from_context(&context);
println!("[INFO] llama_commit: {}", metadata["llama_commit"]);
println!("[INFO] llama_build_number: {}", metadata["llama_build_number"]);
println!("[INFO] Number of input tokens: {}", metadata["input_tokens"]);
println!("[INFO] Number of output tokens: {}", metadata["output_tokens"]);

View metadata extraction

3. Performance Tuning

Adjust runtime parameters for your workload:

# High throughput (batch processing)
export ctx_size=2048
export batch_size=512
export threads=8

# Low latency (real-time)
export ctx_size=512
export batch_size=128
export threads=2

# Debug mode
export enable_log=true

Troubleshooting

Issue 1: "unknown option: nn-preload"

Symptom: WasmEdge doesn't recognize --nn-preload

Solution:

# Reinstall with WASI-NN plugin
curl -sSf https://raw.githubusercontent.com/WasmEdge/WasmEdge/master/utils/install.sh | bash -s -- --plugins wasi_nn-ggml
source $HOME/.wasmedge/env

# Verify plugin is installed
wasmedge --version
# Should show: (plugin "wasi_nn") version X.X.X

Issue 2: "Context full" errors

Symptom: Frequent "Context full" errors

Solution:

# Increase context size
export ctx_size=4096

# Or implement context rotation
# (truncate old tokens when context fills)

Issue 3: Slow inference

Symptom: Inference takes >100ms

Check:

# Increase thread count
export threads=8

# Verify CPU isn't throttled
cat /proc/cpuinfo | grep MHz

# Check for memory swapping
free -h

Future Enhancements

1. Batch Processing API

// Process multiple texts in one inference call
fn batch_embed(texts: Vec<String>) -> Vec<Vec<f32>> {
texts.iter().map(|text| {
// Process in parallel
get_embedding(text)
}).collect()
}

2. Model Caching

// Cache loaded models for reuse
lazy_static! {
static ref MODEL_CACHE: Mutex<HashMap<String, Graph>> =
Mutex::new(HashMap::new());
}

3. Streaming Output

// Stream embeddings as they're computed
async fn stream_embedding(text: &str) -> impl Stream<Item = f32> {
// Yield each dimension as computed
}

Comparison with Alternatives

WasmEdge vs Python

Python approach:

from sentence_transformers import SentenceTransformer
model = SentenceTransformer('all-MiniLM-L6-v2')
embedding = model.encode("Hello world")

WasmEdge approach:

wasmedge --dir .:. --nn-preload default:GGML:AUTO:model.gguf \
embedding.wasm default "Hello world"
AspectWasmEdgePython
Startup10ms2-3 seconds
Memory100MB2-3GB
Binary148KBN/A (interpreted)
PortabilityOne binaryPython + deps
SandboxingNativeNone

WasmEdge vs ONNX Runtime

FeatureWasmEdgeONNX
SetupOne commandMulti-step
Model formatGGUFONNX
PerformanceGoodBetter
PortabilityExcellentGood
SandboxingYesNo

Real-World Production Insights

After building this production embedding API, here are the key learnings:

What Works Exceptionally Well

1. Dual-Binary Architecture

  • WASM module: Perfect for batch processing and edge devices
  • HTTP server: Ideal for cloud deployments and microservices
  • Flexibility to choose deployment strategy per environment

2. GGML Quantization

  • 44MB model vs. 440MB unquantized
  • Minimal accuracy loss for embeddings
  • Fast inference without GPU requirements

3. Async Rust Server

  • Tokio handles concurrent requests efficiently
  • Scales with available CPU cores
  • Low memory overhead compared to Python frameworks

Production Deployment Strategies

Strategy 1: Kubernetes Microservice

apiVersion: apps/v1
kind: Deployment
metadata:
name: embedding-api
spec:
replicas: 3
template:
spec:
containers:
- name: embeddings
image: wasmedge-embedding:latest
env:
- name: WASM_PATH
value: "/app/wasmedge-ggml-llama-embedding.wasm"
- name: MODEL_PATH
value: "/app/all-MiniLM-L6-v2-ggml-model-f16.gguf"
resources:
requests:
memory: "256Mi"
cpu: "500m"
limits:
memory: "512Mi"
cpu: "1000m"

Strategy 2: Serverless (AWS Lambda / Cloud Run)

  • Cold start: 2-3 seconds (acceptable for many use cases)
  • Memory: 512MB allocation recommended
  • Timeout: Set to 30 seconds for safety
  • Cost-effective compared to GPU-based alternatives

Strategy 3: Edge Devices (Raspberry Pi / IoT Gateways)

  • Runs on devices with 512MB+ RAM
  • Inference latency: 100-200ms
  • Perfect for local semantic search
  • Zero cloud egress costs

Performance Optimization Tips

1. Model Caching

# Pre-load model to reduce cold starts
export WASMEDGE_PLUGIN_PATH=/usr/local/lib/wasmedge
wasmedge --nn-preload default:GGML:AUTO:model.gguf

2. Concurrent Processing

  • Use tokio::spawn for parallel requests
  • Configure thread pool based on available resources
  • Each request spawns independent WasmEdge process

3. Connection Optimization

  • Reuse HTTP connections
  • Enable keep-alive for repeated requests
  • Consider batching embeddings for bulk operations

When to Use This vs. Alternatives

Use WasmEdge + GGML when:

  • Cross-platform deployment required
  • Resource constraints (memory, disk)
  • No GPU available
  • Edge/IoT deployment
  • Privacy-first requirements (local processing)
  • Serverless/cold start optimization needed

Use alternatives when:

  • GPU acceleration available and ultra-low latency required
  • Training required (not just inference)
  • Very high throughput batch processing needed
  • Working with very large unquantized models

The Future: Where This Technology Shines

Immediate Applications:

  1. Semantic Search as a Service - Index millions of documents affordably
  2. Edge RAG Systems - Run retrieval locally, LLM in cloud
  3. Privacy-Compliant ML - Process medical/financial data on-premise
  4. IoT Intelligence - Smart devices with local understanding
  5. Cost Optimization - Replace expensive GPU APIs

Emerging Opportunities:

  • WebAssembly Component Model for language interop
  • WASI-NN GPU support for hybrid acceleration
  • Larger models (1B+ params) with better quantization
  • Multi-modal embeddings (text + image)
  • Fine-tuning at the edge

The lightweight binary advantage: This project demonstrates that production ML doesn't require massive infrastructure. WebAssembly + GGML makes AI inference accessible with minimal dependencies and true cross-platform portability.

As WASI-NN matures and more models get quantized to GGUF, WebAssembly is becoming increasingly viable for edge ML deployments where portability, security, and minimal footprint are priorities.


Try It Yourself

Get started in 5 minutes:

# 1. Install WasmEdge
curl -sSf https://raw.githubusercontent.com/WasmEdge/WasmEdge/master/utils/install.sh | bash -s -- --plugins wasi_nn-ggml
source $HOME/.wasmedge/env

# 2. Clone and setup
git clone https://github.com/porameht/wasmedge-ggml-llama-embedding
cd wasmedge-ggml-llama-embedding
rustup target add wasm32-wasip1

# 3. Download model
curl -LO https://huggingface.co/second-state/All-MiniLM-L6-v2-Embedding-GGUF/resolve/main/all-MiniLM-L6-v2-ggml-model-f16.gguf

# 4. Build
./build-wasm.sh
cargo build --bin embedding-api-server --release

# 5. Run HTTP server
./target/release/embedding-api-server

Test the API:

# Generate embedding
curl -X POST http://localhost:3000/embed \
-H "Content-Type: application/json" \
-d '{"text":"What is the capital of France?"}'

# Health check
curl http://localhost:3000/health

Resources:

What will you build with portable ML?