turnstone/app/mcp_server.py

"""Turnstone MCP server — log search and diagnostics via stdio transport.

Works with both Claude Code and Copilot CLI (both use MCP stdio).

Run directly:  python -m app.mcp_server
Or via:        python app/mcp_server.py

Configure TURNSTONE_DB env var to override the default DB path.
"""
from __future__ import annotations

import logging
import os
import sqlite3
import sys
from pathlib import Path

from mcp.server.fastmcp import FastMCP

# All logging must go to stderr — stdout is reserved for MCP JSON-RPC
logging.basicConfig(
    stream=sys.stderr,
    level=logging.INFO,
    format="%(levelname)s %(message)s",
)
logger = logging.getLogger(__name__)

# Allow running as a script from the project root
sys.path.insert(0, str(Path(__file__).parent.parent))

from app.services.search import (
    build_fts_index,
    format_results,
    list_sources,
    search,
)

_DEFAULT_DB = Path(__file__).parent.parent / "data" / "turnstone.db"
DB_PATH = Path(os.environ.get("TURNSTONE_DB", _DEFAULT_DB))

mcp = FastMCP(
    "turnstone",
    instructions=(
        "Turnstone is a diagnostic intelligence layer for server, service, and device logs. "
        "Call list_log_sources first to understand what data is available and identify "
        "source_id values for filtering. Use search_logs for targeted FTS queries. "
        "Use diagnose for symptom-driven investigation — it runs layered searches and "
        "returns evidence ranked by severity and relevance."
    ),
)

_index_ready = False


def _ensure_index() -> None:
    """Build FTS index on first use; skip if already present."""
    global _index_ready
    if _index_ready:
        return

    try:
        conn = sqlite3.connect(str(DB_PATH))
        count = conn.execute("SELECT COUNT(*) FROM log_fts").fetchone()[0]
        conn.close()
        if count > 0:
            _index_ready = True
            logger.info("FTS index present (%d entries)", count)
            return
    except sqlite3.OperationalError:
        pass

    logger.info("Building FTS index for %s — this may take a minute...", DB_PATH)
    build_fts_index(DB_PATH)
    _index_ready = True
    logger.info("FTS index ready")


@mcp.tool()
def search_logs(
    query: str,
    severity: str | None = None,
    source: str | None = None,
    pattern: str | None = None,
    since: str | None = None,
    until: str | None = None,
    limit: int = 20,
    include_repeats: bool = False,
) -> str:
    """Search log entries using full-text search with optional filters.

    Args:
        query: FTS5 search expression. Supports AND, OR, NOT, phrase quotes, prefix*.
               Example: '"connection refused" OR "connection lost"'
        severity: Filter by level — EMERGENCY, ALERT, CRITICAL, ERROR, WARN, NOTICE, INFO, DEBUG.
        source: Partial match on source_id. Format is 'corpus:host:service'.
                Example: 'example-node:caddy' matches all Caddy entries from example-node.
        pattern: Filter by named pattern tag applied at glean time.
                 Known tags: auth_failure, connection_lost, oom, segfault, disk_full,
                 timeout, caddy_tls_error, caddy_config_error, caddy_auth_error,
                 caddy_upstream_error, service_restart, service_update,
                 power_failure, network_interface, ip_change.
        since: Earliest timestamp, ISO 8601 (e.g. 2026-05-06T18:00:00).
        until: Latest timestamp, ISO 8601.
        limit: Result count cap (default 20, max 100).
        include_repeats: Include deduplicated repeat log lines (default False).

    Returns:
        Formatted log entries ranked by FTS relevance, or a no-results message.
    """
    _ensure_index()
    results = search(
        DB_PATH,
        query=query,
        severity=severity,
        source_filter=source,
        pattern_filter=pattern,
        since=since,
        until=until,
        limit=min(limit, 100),
        include_repeats=include_repeats,
    )
    return format_results(results)


@mcp.tool()
def diagnose(
    symptom: str,
    source: str | None = None,
    since: str | None = None,
    until: str | None = None,
) -> str:
    """Investigate a symptom or problem description across the log corpus.

    Runs layered searches — broad relevance first, then CRITICAL/ERROR filtered —
    and merges results deduplicated by entry ID, sorted chronologically.
    Use this for open-ended questions like "why did auth break?" or
    "what happened during the network outage?".

    Args:
        symptom: Plain-language description of the problem or symptom.
        source: Limit to a host or service (partial match on source_id).
        since: Earliest timestamp, ISO 8601.
        until: Latest timestamp, ISO 8601.

    Returns:
        Consolidated log evidence sorted by time, formatted for analysis.
    """
    _ensure_index()

    common = dict(source_filter=source, since=since, until=until, include_repeats=False)

    broad = search(DB_PATH, query=symptom, limit=15, **common)
    critical = search(DB_PATH, query=symptom, severity="CRITICAL", limit=5, **common)
    errors = search(DB_PATH, query=symptom, severity="ERROR", limit=10, **common)

    seen: set[str] = set()
    combined = []
    for r in broad + critical + errors:
        if r.entry_id not in seen:
            seen.add(r.entry_id)
            combined.append(r)

    combined.sort(key=lambda r: (r.timestamp_iso or "\xff", r.sequence))
    return format_results(combined[:20])


@mcp.tool()
def list_log_sources() -> str:
    """List all log sources in the corpus with entry counts and time ranges.

    Call this before searching to understand what data is available and to
    identify source_id values for use in the source= filter parameter.

    Returns:
        Each source on its own block with entry count, error count, and time range.
    """
    sources = list_sources(DB_PATH)
    if not sources:
        return "No log sources found. Has the corpus been gleaned? Run: python scripts/glean_corpus.py"

    lines = [f"Corpus: {DB_PATH}", f"Sources ({len(sources)} total):\n"]
    for s in sources:
        err_note = f"  — {s['error_count']:,} errors" if s["error_count"] else ""
        lines.append(
            f"  {s['source_id']}\n"
            f"    entries: {s['entry_count']:,}{err_note}\n"
            f"    range:   {s['earliest'] or 'unknown'} → {s['latest'] or 'unknown'}"
        )
    return "\n".join(lines)


if __name__ == "__main__":
    if not DB_PATH.exists():
        logger.error("Database not found: %s", DB_PATH)
        logger.error("Run: python scripts/glean_corpus.py <corpus_dir> <db_path>")
        sys.exit(1)
    logger.info("Starting Turnstone MCP server (DB: %s)", DB_PATH)
    mcp.run()