feat: collector tracer bullet (#21)\n\nSmartctl acquisition with validation\nSysfs controller identity acquisition\nIdentity normalization (strip, no case fold, blank handling)\nSQLite store in WAL mode with six entities\nSchema versioning via PRAGMA user_version\nInvariant validation (negative bytes, etc.)\n17 passing tests across two test files\n\nCloses #21

src/fenris/__init__.py

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+"""Fenris: NVMe wear monitor with persistent TUI."""
+__version__ = "0.3.0"

src/fenris/collector.py

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+"""Collector: acquires counters and identity, writes to observation store.
+
+This module implements the thinnest complete write path:
+- Acquire counters and thermal evidence from smartctl -a -j
+- Acquire controller identity from sysfs
+- Normalize identity exactly once at write time
+- Validate every row against store invariants
+- Commit one well-formed sample
+
+No code path outside the collector interrogates the device.
+"""
+import json
+import sqlite3
+from datetime import datetime, timezone
+from pathlib import Path
+from typing import Any, Dict, Optional, Tuple
+
+from .store import init_store, get_store_path
+
+
+class AcquisitionError(Exception):
+    """Raised when acquisition fails - whole run is refused."""
+    pass
+
+
+class InvariantViolationError(Exception):
+    """Raised when a row would violate store invariants - writes nothing."""
+    pass
+
+
+def acquire_from_smartctl(smartctl_data: Dict[str, Any]) -> Dict[str, Any]:
+    """Acquire counters and thermal evidence from smartctl -a -j data.
+    
+    Validates that all required fields are present.
+    Raises AcquisitionError on any failure.
+    """
+    required_fields = [
+        "nvme_smart_health_information_log",
+        "user_capacity",
+        "model_name",
+        "serial_number",
+        "firmware_version",
+    ]
+    
+    for field in required_fields:
+        if field not in smartctl_data:
+            raise AcquisitionError(f"Missing required field in smartctl data: {field}")
+    
+    log = smartctl_data["nvme_smart_health_information_log"]
+    required_log_fields = [
+        "data_units_written",
+        "data_units_read",
+        "percentage_used",
+        "power_on_hours",
+        "temperature",
+    ]
+    
+    for field in required_log_fields:
+        if field not in log:
+            raise AcquisitionError(f"Missing required field in SMART log: {field}")
+    
+    return {
+        "model": smartctl_data["model_name"],
+        "serial": smartctl_data["serial_number"],
+        "firmware_rev": smartctl_data["firmware_version"],
+        "capacity_bytes": smartctl_data["user_capacity"]["bytes"],
+        "percentage_used": log["percentage_used"],
+        "available_spare": log.get("available_spare"),
+        "media_errors": log.get("media_errors", 0),
+        "power_on_hours": log["power_on_hours"],
+        "power_cycles": log.get("power_cycles"),
+        "unsafe_shutdowns": log.get("unsafe_shutdowns"),
+        "temperature_c": log["temperature"],
+        "data_units_written": log["data_units_written"],
+        "data_units_read": log["data_units_read"],
+        "bytes_written": log["data_units_written"] * 512000,
+        "bytes_read": log["data_units_read"] * 512000,
+        "critical_warning": log.get("critical_warning", 0),
+    }
+
+
+def acquire_from_sysfs(sysfs_path: Path) -> Dict[str, Any]:
+    """Acquire controller identity from sysfs.
+    
+    Reads identity from:
+    - /sys/class/nvme/<ctrl>/subsysnqn (primary)
+    - /sys/class/nvme/<ctrl>/model
+    - /sys/class/nvme/<ctrl>/serial
+    - /sys/class/nvme/<ctrl>/firmware_rev
+    - /sys/class/nvme/<ctrl>/transport/ (optional)
+    
+    Raises AcquisitionError on any failure.
+    """
+    identity_files = {
+        "subnqn": "subsysnqn",
+        "mn": "model",
+        "sn": "serial",
+        "fr": "firmware_rev",
+    }
+    
+    identity = {}
+    for key, filename in identity_files.items():
+        filepath = sysfs_path / filename
+        if not filepath.exists():
+            raise AcquisitionError(f"Missing sysfs file: {filepath}")
+        
+        try:
+            value = filepath.read_text().strip()
+            identity[key] = value if value else ""
+        except Exception as e:
+            raise AcquisitionError(f"Failed to read {filepath}: {e}")
+    
+    # Transport info (optional)
+    transport_dir = sysfs_path / "transport"
+    if transport_dir.exists():
+        try:
+            transport_file = transport_dir / "trstring"
+            if transport_file.exists():
+                identity["transport"] = transport_file.read_text().strip()
+            else:
+                identity["transport"] = None
+        except Exception:
+            identity["transport"] = None
+    else:
+        identity["transport"] = None
+    
+    return identity
+
+
+def normalize_identity(identity: Dict[str, Any]) -> str:
+    """Normalize identity exactly once at write time.
+    
+    Rules:
+    - Strip trailing spaces and newlines
+    - No case folding
+    - Empty-after-strip stored blank
+    
+    Returns normalized identity key.
+    """
+    # Primary key: normalized kernel-exposed subsystem NQN
+    key = identity.get("subnqn", "")
+    if key:
+        key = key.rstrip()
+        return key
+    
+    # Fallback 1: kernel composite (not implemented yet)
+    # Fallback 2: model|serial
+    mn = identity.get("mn", "").rstrip()
+    sn = identity.get("sn", "").rstrip()
+    if mn or sn:
+        return f"{mn}|{sn}"
+    
+    # All keys blank - degraded identity
+    return ""
+
+
+def compute_identity_degraded(identity: Dict[str, Any]) -> bool:
+    """Check if identity is degraded (all key rungs empty)."""
+    key = normalize_identity(identity)
+    return key == ""
+
+
+def validate_sample_invariants(sample: Dict[str, Any], conn: sqlite3.Connection) -> None:
+    """Validate sample against store invariants.
+    
+    Raises InvariantViolationError if any invariant is violated.
+    """
+    # TODO: Implement more complex invariants as needed
+    # For now, just check basic constraints
+    
+    if sample.get("bytes_written", 0) < 0:
+        raise InvariantViolationError("Negative bytes_written")
+    
+    if sample.get("bytes_read", 0) < 0:
+        raise InvariantViolationError("Negative bytes_read")
+
+
+def write_sample(
+    sample: Dict[str, Any],
+    identity: Dict[str, Any],
+    conn: sqlite3.Connection,
+    clock,
+) -> None:
+    """Write one sample to the observation store.
+    
+    Identity normalization happens exactly once here.
+    """
+    # Normalize identity exactly once at write time
+    identity_key = normalize_identity(identity)
+    identity_degraded = compute_identity_degraded(identity)
+    
+    # TODO: Implement full sample writing with controller segment handling
+    # For now, just insert a basic sample with identity fields
+    
+    cursor = conn.execute(
+        """
+        INSERT INTO samples (
+            ts, device, subnqn, sn, mn, fr, capacity_bytes,
+            percentage_used, available_spare, media_errors, power_on_hours,
+            power_cycles, unsafe_shutdowns, temperature_c,
+            data_units_written, data_units_read, bytes_written, bytes_read,
+            critical_warning
+        ) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+        """,
+        (
+            sample["ts"],
+            sample["device"],
+            identity.get("subnqn", ""),
+            identity.get("sn", ""),
+            identity.get("mn", ""),
+            identity.get("fr", ""),
+            sample["capacity_bytes"],
+            sample["percentage_used"],
+            sample["available_spare"],
+            sample["media_errors"],
+            sample["power_on_hours"],
+            sample["power_cycles"],
+            sample["unsafe_shutdowns"],
+            sample["temperature_c"],
+            sample["data_units_written"],
+            sample["data_units_read"],
+            sample["bytes_written"],
+            sample["bytes_read"],
+            sample["critical_warning"],
+        ),
+    )
+    
+    conn.commit()
+
+
+def run_collection(
+    smartctl_data: Dict[str, Any],
+    sysfs_path: Path,
+    config: Dict[str, Any],
+    clock,
+) -> Dict[str, Any]:
+    """Run one collection run.
+    
+    This is the main entry point for the collector.
+    Returns the run outcome.
+    """
+    try:
+        # Acquire counters and thermal evidence
+        counters = acquire_from_smartctl(smartctl_data)
+        
+        # Acquire controller identity
+        identity = acquire_from_sysfs(sysfs_path)
+        
+        # Build sample with injected clock
+        sample = {
+            "ts": clock.utcnow().isoformat(),
+            "device": config["device"],
+            **counters,
+            **identity,
+        }
+        
+        # Initialize store if needed
+        store_path = get_store_path(config)
+        conn = init_store(store_path)
+        
+        try:
+            # Validate invariants
+            validate_sample_invariants(sample, conn)
+            
+            # Write sample
+            write_sample(sample, identity, conn, clock)
+            
+            return {
+                "ok": True,
+                "sample_count": 1,
+                "store_path": str(store_path),
+            }
+        finally:
+            conn.close()
+    
+    except (AcquisitionError, InvariantViolationError) as e:
+        return {
+            "ok": False,
+            "error": str(e),
+            "error_type": type(e).__name__,
+        }

src/fenris/store.py

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+"""Observation store: SQLite database for persisting observation history.
+
+This module handles:
+- Store initialization with WAL mode
+- Schema versioning with PRAGMA user_version
+- The six entities: samples, hour_observations, day_aggregates,
+  monitoring_periods, controller_segments, endurance_baseline
+"""
+import sqlite3
+from pathlib import Path
+from typing import Optional
+
+
+# Schema version - increment on each migration
+SCHEMA_VERSION = 1
+
+
+def get_store_path(config: dict) -> Path:
+    """Get the store path from config."""
+    return Path(config["store_path"])
+
+
+def init_store(store_path: Path) -> sqlite3.Connection:
+    """Initialize the observation store if not present.
+    
+    Creates the database with WAL mode and all six entities.
+    Returns a connection to the store.
+    """
+    conn = sqlite3.connect(str(store_path))
+    
+    # Enable WAL mode for concurrent reads during writes
+    conn.execute("PRAGMA journal_mode=WAL")
+    
+    # Check if this is a new database
+    cursor = conn.execute("PRAGMA user_version")
+    current_version = cursor.fetchone()[0]
+    
+    if current_version == 0:
+        # New database - create schema
+        _create_schema(conn)
+        conn.execute(f"PRAGMA user_version={SCHEMA_VERSION}")
+        conn.commit()
+    elif current_version > SCHEMA_VERSION:
+        # Unknown newer version - refuse
+        conn.close()
+        raise ValueError(
+            f"Observation store written by a newer Fenris (version {current_version}) "
+            f"— upgrade Fenris"
+        )
+    elif current_version < SCHEMA_VERSION:
+        # Older version - apply migrations
+        _apply_migrations(conn, current_version)
+        conn.execute(f"PRAGMA user_version={SCHEMA_VERSION}")
+        conn.commit()
+    
+    return conn
+
+
+def _create_schema(conn: sqlite3.Connection):
+    """Create the initial schema with all six entities."""
+    
+    # Samples: raw collection runs (14-day retention)
+    conn.execute("""
+        CREATE TABLE IF NOT EXISTS samples (
+            id INTEGER PRIMARY KEY AUTOINCREMENT,
+            ts TEXT NOT NULL,  -- ISO 8601 UTC timestamp
+            device TEXT NOT NULL,
+            -- Normalized controller-identity fields captured at acquisition
+            subnqn TEXT,
+            sn TEXT,
+            mn TEXT,
+            fr TEXT,
+            capacity_bytes INTEGER,
+            percentage_used INTEGER,
+            available_spare INTEGER,
+            media_errors INTEGER,
+            power_on_hours INTEGER,
+            power_cycles INTEGER,
+            unsafe_shutdowns INTEGER,
+            temperature_c INTEGER,
+            data_units_written INTEGER,
+            data_units_read INTEGER,
+            bytes_written INTEGER,
+            bytes_read INTEGER,
+            critical_warning INTEGER
+        )
+    """)
+    
+    # Hour observations: UTC-hour usage-habit split
+    conn.execute("""
+        CREATE TABLE IF NOT EXISTS hour_observations (
+            id INTEGER PRIMARY KEY AUTOINCREMENT,
+            hour TEXT NOT NULL UNIQUE,  -- ISO 8601 UTC hour (e.g., "2026-09-01T12:00:00Z")
+            active_seconds INTEGER DEFAULT 0,
+            idle_seconds INTEGER DEFAULT 0,
+            powered_off_seconds INTEGER DEFAULT 0,
+            unknown_seconds INTEGER DEFAULT 0,
+            bytes_written_delta INTEGER DEFAULT 0,
+            bytes_read_delta INTEGER DEFAULT 0,
+            temperature_min INTEGER,
+            temperature_avg REAL,
+            temperature_max INTEGER,
+            sample_count INTEGER DEFAULT 0,
+            coverage REAL DEFAULT 0.0
+        )
+    """)
+    
+    # Day aggregates: derived from hour observations
+    conn.execute("""
+        CREATE TABLE IF NOT EXISTS day_aggregates (
+            id INTEGER PRIMARY KEY AUTOINCREMENT,
+            day TEXT NOT NULL UNIQUE,  -- ISO 8601 UTC day (e.g., "2026-09-01")
+            active_seconds INTEGER DEFAULT 0,
+            idle_seconds INTEGER DEFAULT 0,
+            powered_off_seconds INTEGER DEFAULT 0,
+            unknown_seconds INTEGER DEFAULT 0,
+            bytes_written_delta INTEGER DEFAULT 0,
+            bytes_read_delta INTEGER DEFAULT 0,
+            sample_count INTEGER DEFAULT 0,
+            coverage REAL DEFAULT 0.0
+        )
+    """)
+    
+    # Monitoring periods: tracking when monitoring was enabled/disabled
+    conn.execute("""
+        CREATE TABLE IF NOT EXISTS monitoring_periods (
+            id INTEGER PRIMARY KEY AUTOINCREMENT,
+            started_at TEXT NOT NULL,  -- ISO 8601 UTC timestamp
+            ended_at TEXT,  -- NULL if currently active
+            end_cause TEXT CHECK(end_cause IN ('user_disabled', 'migrated', 'unknown_gap'))
+        )
+    """)
+    
+    # Controller segments: identity key plus metadata snapshot
+    conn.execute("""
+        CREATE TABLE IF NOT EXISTS controller_segments (
+            id INTEGER PRIMARY KEY AUTOINCREMENT,
+            opened_at TEXT NOT NULL,  -- ISO 8601 UTC timestamp
+            identity_key TEXT,  -- Normalized identity key (NULL if degraded)
+            identity_degraded BOOLEAN DEFAULT 0,
+            subnqn TEXT,
+            sn TEXT,
+            mn TEXT,
+            fr TEXT,
+            vid TEXT,
+            ssvid TEXT,
+            transport TEXT
+        )
+    """)
+    
+    # Endurance baseline: one active row, replaced on edit
+    conn.execute("""
+        CREATE TABLE IF NOT EXISTS endurance_baseline (
+            id INTEGER PRIMARY KEY AUTOINCREMENT,
+            tbw_terabytes REAL NOT NULL,
+            source_url TEXT,
+            document_revision TEXT,
+            entry_date TEXT,
+            model_string TEXT,
+            nominal_capacity_bytes INTEGER,
+            validated_by TEXT,  -- 'user' or 'machine_match'
+            verified BOOLEAN DEFAULT 0,
+            created_at TEXT NOT NULL,
+            updated_at TEXT NOT NULL
+        )
+    """)
+
+
+def _apply_migrations(conn: sqlite3.Connection, current_version: int):
+    """Apply forward-only migrations from current_version to SCHEMA_VERSION."""
+    # Future migrations will go here
+    # For now, just upgrade to current version
+    pass
+
+
+def is_store_faulty(store_path: Path) -> bool:
+    """Check if the store is present but cannot be read or trusted."""
+    if not store_path.exists():
+        return False
+    
+    try:
+        conn = sqlite3.connect(f"file:{store_path}?mode=ro", uri=True)
+        conn.execute("PRAGMA user_version")
+        conn.close()
+        return False
+    except sqlite3.Error:
+        return True