mikcar

Sidecar infrastructure services for mik.

Overview

mikcar provides HTTP-based infrastructure services for WASM handlers running in mik:

• Storage - Object storage (S3, GCS, MinIO, local filesystem)
• KV - Embedded key-value store (redb - pure Rust, no external dependencies)
• SQL - Database proxy (Postgres, SQLite)
• Queue - Message queues (Redis Streams, RabbitMQ)
• Secrets - Secret managers (Vault, AWS Secrets Manager, GCP Secret Manager)
• Email - SMTP email (works with any provider)

Same API works locally and in production. Your WASM handlers don't know or care if they're talking to MinIO or AWS S3.

Docker

Two optimized images available:

Image	Size	Queue Support	Base
mikcar	~21MB	No	scratch (musl static)
mikcar-all	~65MB	Redis, RabbitMQ	distroless

Pull from GitHub Container Registry

# Minimal image (no queue) - recommended for most use cases
docker pull ghcr.io/dufeut/mikcar:latest

# Full image with queue support
docker pull ghcr.io/dufeut/mikcar-all:latest

# Pull specific version
docker pull ghcr.io/dufeut/mikcar:0.1.0

Run

docker run -p 3001:3001 \
  -e SIDECAR_TOKEN=secret \
  -e KV_URL=memory:// \
  -e STORAGE_URL=memory:// \
  ghcr.io/dufeut/mikcar:latest --kv --storage

Build locally

# Minimal image (no queue)
docker build -t mikcar .

# Full image with queue support
docker build -f Dockerfile.all -t mikcar:all .

Installation

# Install with default services (storage, kv, sql, secrets, email)
cargo install mikcar

# Install with queue support
cargo install mikcar --features all

# Install specific services only
cargo install mikcar --features storage,kv

Usage

# Run storage service
STORAGE_URL=file:///data mikcar --storage --port 3001

# Run KV service (embedded redb, no external dependencies)
KV_URL=file:///data/kv.redb mikcar --kv --port 3002

# Run SQL service
DATABASE_URL=postgres://user:pass@localhost/db mikcar --sql --port 3003

# Run secrets service
SECRETS_URL=vault://localhost:8200 mikcar --secrets --port 3004

# Run email service
EMAIL_URL=smtp://localhost:1025 mikcar --email --port 3005

# Supercar mode (multiple services on one port)
mikcar --kv --storage --sql --email --port 3001

API

Storage (/storage/*)

GET    /object/{path}    Get object
PUT    /object/{path}    Put object (body = content)
DELETE /object/{path}    Delete object
HEAD   /object/{path}    Check exists + metadata
GET    /list/{prefix}    List objects

Key-Value (/kv/*)

GET    /get/{key}        Get value
POST   /get/batch        Get multiple (body = {keys: [...]})
POST   /set/{key}?ttl=   Set value (body = value)
POST   /set/batch        Set multiple (body = {key: value, ...})
DELETE /del/{key}        Delete key
GET    /keys/{pattern}   List keys matching pattern
POST   /increment/{key}  Increment (atomic)
GET    /exists/{key}     Check if key exists
GET    /ttl/{key}        Get TTL (-1 = no TTL, -2 = not found)
POST   /expire/{key}     Set expiration (body = {seconds: N})

SQL (/sql/*)

POST   /query            Execute SELECT (body = {sql, params})
POST   /execute          Execute INSERT/UPDATE/DELETE
POST   /batch            Execute multiple statements in transaction
POST   /script           Execute JavaScript with SQL in transaction

SQL Script Endpoint

The /sql/script endpoint executes JavaScript code with SQL operations within a single database transaction. This enables complex conditional logic, validation, and multi-step operations with automatic rollback on failure.

Request:

{
  "script": "var user = sql.query('SELECT * FROM users WHERE id = $1', [input.userId]); if (!user.length) throw new Error('User not found'); return { user: user[0] };",
  "input": { "userId": 42 }
}

Response:

{
  "result": { "user": { "id": 42, "name": "Alice" } },
  "queries_executed": 1
}

Script API:

• sql.query(sql, params) - Execute SELECT, returns array of row objects
• sql.execute(sql, params) - Execute INSERT/UPDATE/DELETE, returns rows affected
• input - The input object from the request
• return - Specify the response value

Supported script formats:

// 1. Export default function (recommended)
export default function(input) {
  var users = sql.query("SELECT * FROM users WHERE org = $1", [input.org]);
  return { count: users.length };
}

// 2. Raw code with return (simple scripts)
var users = sql.query("SELECT * FROM users");
return { count: users.length };

// 3. Raw expression (simplest)
sql.query("SELECT COUNT(*) FROM users")

Transaction semantics:

• All SQL operations run in a single transaction
• If the script throws an error, the transaction is rolled back
• If any SQL operation fails, the transaction is rolled back
• Only on successful completion is the transaction committed

Example: Fund transfer with balance check

export default function(input) {
  // Check source account
  var from = sql.query("SELECT id, balance FROM accounts WHERE id = $1", [input.from]);
  if (!from.length) throw new Error("Source account not found");
  if (parseFloat(from[0].balance) < input.amount) throw new Error("Insufficient funds");

  // Check destination account
  var to = sql.query("SELECT id FROM accounts WHERE id = $1", [input.to]);
  if (!to.length) throw new Error("Destination account not found");

  // Perform transfer (atomic - both succeed or both fail)
  sql.execute("UPDATE accounts SET balance = balance - $1 WHERE id = $2", [input.amount, input.from]);
  sql.execute("UPDATE accounts SET balance = balance + $1 WHERE id = $2", [input.amount, input.to]);

  return { success: true, transferred: input.amount };
}

Queue (/queue/*)

POST   /publish/{topic}  Publish message
GET    /subscribe/{topic} Long-poll for messages
POST   /ack/{topic}/{id} Acknowledge message
POST   /push/{queue}     Push to work queue
GET    /pop/{queue}      Pop from work queue

Email (/email/*)

POST   /send             Send single email
POST   /send/batch       Send multiple emails

Request body (POST /send):

{
  "from": "sender@example.com",
  "to": ["recipient@example.com"],
  "cc": ["cc@example.com"],
  "bcc": ["bcc@example.com"],
  "subject": "Hello",
  "text": "Plain text body",
  "html": "<p>HTML body</p>",
  "reply_to": "reply@example.com"
}

Response:

{"id": "message-id", "success": true}

Batch request (POST /send/batch):

{
  "emails": [
    {"from": "...", "to": ["..."], "subject": "...", "text": "..."},
    {"from": "...", "to": ["..."], "subject": "...", "text": "..."}
  ]
}

Authentication

Set SIDECAR_TOKEN or AUTH_TOKEN environment variable. Requests must include:

Authorization: Bearer <token>

The /health endpoint is always accessible without authentication.

Configuration

Variable	Service	Example
STORAGE_URL	storage	file:///data, s3://bucket, memory://
KV_URL	kv	file:///data/kv.redb, memory://
DATABASE_URL	sql	postgres://user:pass@host/db
QUEUE_URL	queue	redis://host:port, amqp://user:pass@host:port
SECRETS_URL	secrets	vault://host:port, awssm://region, gcpsm://project
EMAIL_URL	email	smtp://host:port, smtps://user:pass@host:465
SIDECAR_TOKEN	auth	Bearer token for API authentication

Queue Backends

mikcar acts as an HTTP proxy to queue infrastructure. Supported backends:

Backend	URL Format	Platform
In-memory	memory://	All
Redis Streams	redis://host:port	Linux/macOS
RabbitMQ	amqp://user:pass@host:port	Linux/macOS

Auto-creation: Queues are automatically created on first push:

• Redis: Creates stream + consumer group (XGROUP CREATE ... MKSTREAM)
• RabbitMQ: Declares durable queue

No manual setup required - just push and pop.

Note: Queue requires the all feature or Dockerfile.all. Windows builds only support memory://.

# Redis
QUEUE_URL=redis://localhost:6379 mikcar --queue

# RabbitMQ
QUEUE_URL=amqp://guest:guest@localhost:5672 mikcar --queue

# In-memory (dev only)
QUEUE_URL=memory:// mikcar --queue

Email Backends

SMTP is the universal email protocol - works with any provider.

Provider	URL Format
Local dev (Mailpit)	smtp://localhost:1025
Gmail	smtps://user:app-password@smtp.gmail.com:465
SendGrid	smtps://apikey:SG.xxx@smtp.sendgrid.net:465
AWS SES	smtps://AKIA...:secret@email-smtp.us-east-1.amazonaws.com:465
Resend	smtps://resend:re_xxx@smtp.resend.com:465

Port behavior:

• Ports 25, 1025, 2525: Plain SMTP (no TLS) - for local testing
• Port 465: Implicit TLS (smtps://)
• Port 587: STARTTLS (smtp://)

# Local development with Mailpit
EMAIL_URL=smtp://localhost:1025 mikcar --email

# Production with SendGrid
EMAIL_URL=smtps://apikey:SG.xxx@smtp.sendgrid.net:465 mikcar --email

Library Usage

mikcar can be used as a Rust library to embed sidecars in your own applications (e.g., Tauri, Axum, or custom servers).

Add Dependencies

[dependencies]
mikcar = { git = "https://github.com/dufeut/mikcar", features = ["all"] }
tokio = { version = "1", features = ["full"] }

Example: Single Service

use mikcar::{SidecarBuilder, StorageService};

#[tokio::main]
async fn main() -> anyhow::Result<()> {
    let storage = StorageService::from_url("memory://")?;

    SidecarBuilder::new()
        .port(3001)
        .auth_token("secret")
        .serve(storage)
        .await
}

Example: Multiple Services

use mikcar::{SidecarBuilder, KvService, StorageService, SqlService};

#[tokio::main]
async fn main() -> anyhow::Result<()> {
    let kv = KvService::from_url("memory://")?;
    let storage = StorageService::from_url("memory://")?;
    let sql = SqlService::from_url("postgres://user:pass@localhost/db").await?;

    SidecarBuilder::new()
        .port(3001)
        .auth_token("secret")
        .add(kv)
        .add(storage)
        .add(sql)
        .serve_many()
        .await
}

Example: Tauri Integration

use mikcar::{SidecarBuilder, KvService, StorageService};
use std::sync::Arc;
use tokio::sync::Mutex;

struct AppState {
    sidecars: Arc<Mutex<Option<tokio::task::JoinHandle<()>>>>,
}

#[tauri::command]
async fn start_sidecars(state: tauri::State<'_, AppState>) -> Result<(), String> {
    let kv = KvService::from_url("memory://").map_err(|e| e.to_string())?;
    let storage = StorageService::from_url("memory://").map_err(|e| e.to_string())?;

    let handle = tokio::spawn(async move {
        let _ = SidecarBuilder::new()
            .port(3001)
            .add(kv)
            .add(storage)
            .serve_many()
            .await;
    });

    *state.sidecars.lock().await = Some(handle);
    Ok(())
}

Example: Combined with mik Runtime

use mik::runtime::HostBuilder;
use mikcar::{SidecarBuilder, KvService, StorageService};

#[tokio::main]
async fn main() -> anyhow::Result<()> {
    // Start sidecars on port 3001
    let kv = KvService::from_url("memory://")?;
    let storage = StorageService::from_url("memory://")?;

    tokio::spawn(async move {
        SidecarBuilder::new()
            .port(3001)
            .add(kv)
            .add(storage)
            .serve_many()
            .await
            .unwrap();
    });

    // Start WASM runtime on port 3000
    let host = HostBuilder::new()
        .port(3000)
        .modules_dir("./modules".into())
        .build()
        .await?;

    host.serve().await?;
    Ok(())
}

Exported Types

Type	Description
SidecarBuilder	Builder for configuring and starting sidecars
StorageService	S3/GCS/Azure/local filesystem storage
KvService	Embedded key-value store (redb)
SqlService	PostgreSQL/SQLite proxy
QueueService	Redis Streams/RabbitMQ queues
SecretsService	Vault/AWS/GCP secret managers
EmailService	SMTP email sending
Sidecar trait	Implement custom sidecars

Re-exported Crates

mikcar re-exports commonly used crates for convenience:

use mikcar::axum;        // Web framework
use mikcar::tower;       // Service abstractions
use mikcar::tower_http;  // HTTP middleware

License

MIT