Implement MCP logging and OpenTelemetry tracing for sampling workflows

[Copilot]

Overview

This PR implements structured logging via the Model Context Protocol (MCP) specification and distributed tracing via OpenTelemetry (OTEL) for sampling workflows, addressing issue #[feature].

What's Changed

🔔 MCP Logging Implementation

Implemented dual logging system that ensures visibility while supporting MCP clients:

New Features:

• MCPLogger class that sends notifications/message events per MCP spec
• Always logs to console for visibility during development and debugging
• Additionally sends MCP notifications when server is available
• Supports all MCP log levels: debug, info, notice, warning, error, critical, alert, emergency
• Structured logging support (objects and strings)
• Hierarchical logger names with child() method

Example Usage:

import { createLogger } from "./packages/core/src/utils/logger.ts";

const logger = createLogger("my-agent", server);
await logger.info("Processing started");
await logger.warning({ resource: "memory", usage: 85 });
await logger.error("Operation failed");

📊 OpenTelemetry Tracing

Implemented distributed tracing for sampling workflows with configurable export destinations:

Configuration via Environment Variables:

export MCPC_TRACING_ENABLED=true
export MCPC_TRACING_EXPORT=console  # or 'otlp' or 'none'
export MCPC_TRACING_OTLP_ENDPOINT=http://localhost:4318/v1/traces

Trace Hierarchy:

• Root span for entire sampling loop
• Child spans for each iteration
• Automatic error tracking and exception recording
• Compatible with Jaeger, Zipkin, Grafana Tempo, and other OTLP backends

🔧 Integration Points

Modified Components:

• compose.ts: Server lifecycle events and tool matching warnings now use MCP logging
• base-sampling-executor.ts: Iteration progress logging and automatic span creation for tracing
• logging-plugin.ts: Composition logging now uses MCP notifications

Before:

console.log(`Iteration ${i}:`, data);
console.warn("Tool not found");

After:

await this.logger.debug({ iteration: i, data });
await this.logger.warning("Tool not found");

📦 Dependencies

Added OpenTelemetry packages to packages/core/deno.json:

• @opentelemetry/api@^1.9.0
• @opentelemetry/sdk-trace-base@^1.29.0
• @opentelemetry/sdk-trace-node@^1.29.0
• @opentelemetry/exporter-trace-otlp-http@^0.56.0
• @opentelemetry/resources@^1.29.0
• @opentelemetry/semantic-conventions@^1.29.0

📚 Documentation

Added comprehensive guide at docs/LOGGING_AND_TRACING.md covering:

• MCP logging usage and best practices
• OpenTelemetry configuration and setup
• Integration with observability platforms
• Code examples and patterns
• Updated main README with documentation link

Backward Compatibility

✅ All changes are backward compatible:

• Console logging is always enabled for visibility
• MCP notifications are sent in addition to console logs when server is available
• Tracing is opt-in via environment variables
• No breaking changes to existing APIs
• Examples continue to work unchanged

Testing

• ✅ Logger verified with and without server (always logs to console)
• ✅ Type checking passes for all modified files
• ✅ Code formatted with deno fmt
• ✅ Error handling for environment access in different runtimes

References

• MCP Logging Specification
• OpenTelemetry Documentation
• OpenTelemetry JavaScript

Fixes #12

Original prompt

---

This section details on the original issue you should resolve

<issue_title>[feature] implement logging, possibly OTEL tracing when sampling</issue_title>
<issue_description>https://modelcontextprotocol.io/legacy/tools/debugging#implementing-logging

https://github.com/open-telemetry/opentelemetry-specification</issue_description>

<agent_instructions>Please implement MCP logging as an alternative to current console logs

And in sampling workflow, implement both MCP logging and otel tracing </agent_instructions>

Comments on the Issue (you are @copilot in this section)

@yaonyan https://modelcontextprotocol.io/specification/2025-03-26/server/utilities/logging

Fixes #12

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💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

[yaonyan]

Make sure console logs are always enabled @copilot

[Copilot]

Make sure console logs are always enabled @copilot

Done! Console logs are now always enabled. The logger now outputs to console regardless of whether an MCP server is available, and additionally sends MCP notifications when the server is present. See commit f46d250.

[yaonyan]

modified, then qualified