Advanced Topics¶

Rolling updates, multi-arch, init systems, build from source.

Rolling Updates¶

SwarmCracker supports zero-downtime rolling updates via SwarmKit orchestration.

How It Works¶

Manager creates new task with updated spec
SwarmCracker starts new Firecracker VM
VM reports RUNNING status
Manager waits for Monitor period (default: 5s)
Manager stops old task
Executor removes old VM

Update a Service¶

# Update image (triggers rolling update)
swarmctl update svc-nginx --image nginx:1.25

# Update with environment
swarmctl update svc-app --env LOG_LEVEL=debug

Configuration¶

SwarmKit controls update behavior (not SwarmCracker):

Parameter	Default	Description
Parallelism	1	Tasks updated simultaneously
Delay	0s	Wait between batches
Monitor	5s	Verify task stability
Failure Action	pause	On failure: pause/continue/rollback

Multi-Architecture Support¶

SwarmCracker supports multiple CPU architectures via placement constraints.

Supported Architectures¶

Arch	Firecracker Support	Notes
x86_64	✅ Full support	Primary target
arm64	✅ Experimental	AWS Graviton, Ampere

Architecture Constraints¶

# Create service constrained to x86_64 nodes
swarmctl create-service nginx:latest --constraint arch==x86_64

# Create service constrained to arm64 nodes
swarmctl create-service arm-app:latest --constraint arch==arm64

Multi-Arch Images¶

Use OCI image indexes for cross-arch compatibility:

# Build multi-arch image
docker buildx build --platform linux/amd64,linux/arm64 -t myapp:latest .

# SwarmCracker pulls correct variant based on node arch

Init Systems¶

MicroVMs need an init system for proper process management.

Why Init Matters¶

Zombie reaping — Orphan processes must be reaped
Signal handling — Forward SIGTERM to children
Process supervision — Restart failed processes

Supported Init Systems¶

Init	Size	Features
tini	~20KB	Minimal, Docker default
dumb-init	~30KB	Signal proxy, lightweight
s6	~100KB	Process supervision
systemd	Large	Full service management

Configure Init¶

executor:
  init_process: "/sbin/tini"
  init_process_args: ["--", "/bin/sh"]

Rootfs with Init¶

# Install tini in rootfs
curl -fsSL https://github.com/krallin/tini/releases/download/v0.19.0/tini-static -o rootfs/sbin/tini
chmod +x rootfs/sbin/tini

Build from Source¶

Prerequisites¶

Go 1.21+
Git
Make

Clone and Build¶

# Clone repository
git clone https://github.com/restuhaqza/SwarmCracker
cd SwarmCracker

# Build binaries
make build

# Output:
# bin/swarmcracker
# bin/swarmctl

# Install
sudo make install

Build Targets¶

make build         # Build all binaries
make test          # Run tests
make lint          # Run linter
make clean         # Clean build artifacts
make install       # Install to /usr/local/bin
make uninstall     # Remove binaries

Development Build¶

# Build with debug symbols
make build-debug

# Run locally
./bin/swarmcracker run --config config.yaml

systemd Service¶

Run SwarmCracker as a systemd service.

Service File¶

sudo tee /etc/systemd/system/swarmcracker.service <<EOF
[Unit]
Description=SwarmCracker Firecracker Executor
After=network.target

[Service]
Type=simple
User=root
ExecStart=/usr/local/bin/swarmcracker run --config /etc/swarmcracker/config.yaml
Restart=always
RestartSec=5
TimeoutStartSec=180

[Install]
WantedBy=multi-user.target
EOF

Enable Service¶

sudo systemctl daemon-reload
sudo systemctl enable swarmcracker
sudo systemctl start swarmcracker

# Check status
sudo systemctl status swarmcracker

Logs¶

journalctl -u swarmcracker -f

File Management¶

Manage rootfs and kernel images.

Rootfs Directory¶

executor:
  rootfs_dir: "/var/lib/swarmcracker/rootfs"

Kernel Management¶

executor:
  kernel_path: "/usr/share/firecracker/vmlinux"

Image Storage¶

/var/lib/swarmcracker/
├── rootfs/
│   ├── nginx-rootfs.ext4
│   ├── redis-rootfs.ext4
├── kernels/
│   ├── vmlinux-6.1.155
│   ├── vmlinux-5.10
├── config.yaml

Troubleshooting¶

Rolling Update Stuck¶

# Check task status
swarmctl ls-tasks

# Check node availability
swarmctl ls-nodes

# Force rollback if needed
swarmctl update svc-nginx --rollback

Init Process Missing¶

# Check init in rootfs
ls rootfs/sbin/tini

# Verify init binary
file rootfs/sbin/tini

Build Fails¶

# Check Go version
go version  # Must be 1.21+

# Check dependencies
go mod download

# Run lint for errors
make lint

See Also: Configuration | Contributing Guide