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Brakebear

Apply network constraints (bandwidth, latency, loss) to Docker containers using Linux traffic control.

Repository
brakebear

Overview​

Brakebear is a network traffic control tool that applies real-world network constraints to Docker containers for testing and simulation purposes. It leverages Linux kernel networking mechanisms (HTB, IFB, Netem, and network namespaces) to enforce per-container bandwidth limiting, latency simulation, jitter injection, and packet loss emulation without stopping the containers.

The tool provides granular control over network conditions, supporting both IPv4 and IPv6 dual-stack networks with intelligent exclusion capabilities for private networks, specific CIDR ranges, DNS hostnames, TCP/UDP ports, and Docker networks.

Features​

  • Bandwidth Management: Set configurable upload/download rate limits (e.g., "1mbps", "500kbps")
  • Network Emulation: Introduce latency, jitter, and packet loss to simulate real-world conditions
  • Docker Integration: Automatic discovery and monitoring of running containers
  • Dual-Stack Support: Works with both IPv4 and IPv6 networks
  • Smart Filtering: Exclude traffic by:
    • Private networks
    • CIDR ranges
    • DNS hostnames
    • Specific TCP/UDP ports
    • Docker networks
  • Live Application: Apply constraints to active containers without requiring restarts
  • Automatic Cleanup: Removes traffic control rules when containers terminate
  • Technical Foundation: Uses HTB queueing, IFB interfaces, Netem for emulation, and Linux network namespaces

Use Cases​

  • Resilience Testing: Test application behavior under degraded network conditions
  • Performance Validation: Simulate slow connections, high-latency environments, or packet loss scenarios
  • Ethereum Client Testing: Validate client behavior in adverse network conditions
  • Multi-Client Deployments: Test network issues in complex distributed systems
  • Development & Debugging: Debug network-sensitive applications in controlled environments