rcwatch

A lightweight service watchdog daemon written in C++.

rcwatch monitors configured services, detects unexpected process termination, and automatically restarts failed services according to configurable restart policies.

Features

• Process health monitoring
• Automatic service restart
• Privilege dropping for monitoring processes
• IPC-based watcher/supervisor architecture
• Restart rate limiting
• Configurable restart windows
• Fixed, Linear, and Exponential backoff support
• Syslog-based logging
• Unit-tested core components

---

Architecture

rcwatch uses a simple supervisor/watcher model.

             +----------------+
             |   Supervisor   |
             |  (privileged)  |
             +--------+-------+
                      ^
                      |
                   Pipe IPC
                      |
                      v
             +--------+-------+
             |    Watcher     |
             | (unprivileged) |
             +----------------+

Watcher

• Runs with reduced privileges
• Periodically checks service health
• Reports failed services to the supervisor

Supervisor

• Receives failure notifications
• Applies restart policies
• Restarts services when allowed

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Build

git clone https://github.com/mateofz/rcwatch.git
cd rcwatch/src
make

./rcwatch rcwatch.conf

---

Configuration

Example:

service
service_name sshd
pid_file /var/run/sshd.pid

start_cmd /path/to/start/script/file
stop_cmd /path/to/stop/script/file
restart_cmd /path/to/restart/script/file

check_interval 10

max_restart 5
restart_window 60

backoff_method Fixed

delay_time 5
end_service

Parameters

Option	Description
service_name	Service identifier
pid_file	PID file path
start_cmd	Service start command
stop_cmd	Service stop command
restart_cmd	Service restart command
check_interval	Health check interval (seconds)
max_restart	Maximum restart attempts
restart_window	Restart window (seconds)
backoff_method	Fixed / Linear / Exponential
delay_time	Delay between restart attempts

---

Testing

Current test coverage includes:

• Configuration parser
• IPC pipe communication
• Process state detection

Run tests:

cd test/test_config_manager
make run

cd ../test_ipc_pipe
make run

cd ../test_process
make run

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Project Structure

src/
├── config_manager.cpp
├── process.cpp
├── privilege.cpp
├── restart_manager.cpp
├── logger.cpp
├── rcwatch.cpp
└── ipc/

test/
├── test_config_manager/
├── test_ipc_pipe/
└── test_process/

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Design Goals

• Minimal dependencies
• Unix-oriented design
• Separation of privileges
• Simple and maintainable codebase
• Educational implementation of service supervision concepts

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Future Improvements

• SIGHUP configuration reload
• Daemonization support
• Shared-memory configuration updates
• Integration tests
• Makefile/CMake build system
• Service state persistence
• Structured logging

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License

GPL-3