Logging and Metrics

Glass Box includes a custom logging system and real-time metrics collection, both of which can stream data to connected SSE clients.

ServerLogger

ServerLogger is a thread-safe singleton that runs on its own virtual thread. It processes log entries from a BlockingQueue, ensuring that logging never blocks the request-handling threads.

Initialization

The logger is initialized once at startup in Main.java:

ServerLogger.initialize(null, Loglevel.DEBUG);

After the SSE handler is available (post-config), the handler is attached:

ServerLogger.getInstance().setSseHandler(sseHandler);

Usage

Log a message from anywhere in the codebase:

ServerLogger.getInstance().log(Loglevel.INFO, "Request processed", LogDestination.EVERYWHERE);

Log Levels

Log levels control which messages are displayed. Messages below the configured threshold are suppressed on the server console (but may still be sent to SSE clients).

Level	Severity	Use Case
DEBUG	0	Detailed diagnostic information
INFO	1	General operational messages
WARN	2	Potential issues that don't prevent operation
ERROR	3	Errors that affect a single request
FATAL	4	Critical failures

The log level is set in the YAML config:

logLevel: DEBUG   # Show all messages
logLevel: INFO    # Hide DEBUG messages
logLevel: WARN    # Only warnings and above

Log Destinations

Each log entry has a destination that controls where it is delivered:

Destination	Behavior
SERVER	Printed to the server console only
CLIENT	Broadcast to SSE clients only
EVERYWHERE	Both console and SSE clients

Log Entry Format

Log entries broadcast via SSE are serialized as JSON:

{
  "level": "INFO",
  "message": "GET /api/todos from /127.0.0.1:54321",
  "timestamp": 1700000000000
}

Stats

The Stats singleton tracks server metrics using atomic counters for thread safety.

Available Metrics

Metric	Type	Description
uptime	long	Milliseconds since server start
totalRequests	long	Total HTTP requests processed
activeConnections	long	Current number of SSE clients
cpuUsage	double	System CPU load (0.0 to 1.0)
memoryUsage	double	Used memory in GB

CPU and memory metrics are collected using the OSHI library for cross-platform system monitoring.

Stats JSON Format

Stats are broadcast to SSE clients as the stats event:

{
  "uptime": 120000,
  "totalRequests": 42,
  "activeConnections": 3,
  "cpuUsage": 0.15,
  "memoryUsage": 2.4
}

How Stats Are Updated

• Request count — incremented by HTTPHandler after each successful request parse
• Active connections — updated by SSEHandler when clients connect or disconnect
• CPU and memory — polled on demand when stats are requested by an SSE broadcast cycle