feat: add bounded business state observability

internal/storage/mysql/operational_metrics.go

@@ -0,0 +1,126 @@
+package mysql
+
+import (
+	"context"
+	"database/sql"
+	"errors"
+	"time"
+)
+
+const operationalMetricSampleLimit = 10000
+
+// OperationalSnapshot 是进程观测使用的有限数据库快照。
+// Counts 只包含固定状态的有界计数；达到上限时 Truncated 为 true，不能解释为精确总量。
+type OperationalSnapshot struct {
+	// TaskStates 是 Pulse 任务按状态的有界计数。
+	TaskStates map[string]uint64
+	// TaskOldestAgeSeconds 是运行中任务中最早 available_at 的年龄。
+	TaskOldestAgeSeconds float64
+	// DeliveryStates 是结果交付按状态的有界计数。
+	DeliveryStates map[string]uint64
+	// DeliveryOldestAgeSeconds 是待处理交付中最早 available_at 的年龄。
+	DeliveryOldestAgeSeconds float64
+	// WorkflowStates 是 Weave 实例按状态的有界计数。
+	WorkflowStates map[string]uint64
+	// WorkflowOldestAgeSeconds 是未终结流程中最早 updated_at 的年龄。
+	WorkflowOldestAgeSeconds float64
+	// Truncated 表示至少一个状态达到有界采样上限。
+	Truncated bool
+}
+
+var (
+	operationalTaskStates     = []string{"WAITING", "LEASED", "RUNNING", "NEEDS_REVIEW", "SUCCEEDED", "FAILED", "CANCELLED"}
+	operationalDeliveryStates = []string{"PENDING", "LEASED", "ACKED", "EXPIRED"}
+	operationalWorkflowStates = []string{"RUNNING", "WAITING", "CANCELLING", "NEEDS_REVIEW", "SUCCEEDED", "FAILED", "CANCELLED"}
+)
+
+// ReadOperationalSnapshot performs only bounded, indexed reads. It is intended
+// for a background sampler with a short context deadline, never for a request.
+func ReadOperationalSnapshot(ctx context.Context, db *sql.DB) (OperationalSnapshot, error) {
+	if db == nil {
+		return OperationalSnapshot{}, errors.New("database is required")
+	}
+	now, err := readDatabaseNow(ctx, db)
+	if err != nil {
+		return OperationalSnapshot{}, err
+	}
+	tasks, taskTruncated, err := boundedStateCounts(ctx, db, "pulse_tasks", "ix_task_observe_state_available", operationalTaskStates)
+	if err != nil {
+		return OperationalSnapshot{}, err
+	}
+	deliveries, deliveryTruncated, err := boundedStateCounts(ctx, db, "orbit_deliveries", "ix_delivery_observe_state_available", operationalDeliveryStates)
+	if err != nil {
+		return OperationalSnapshot{}, err
+	}
+	workflows, workflowTruncated, err := boundedStateCounts(ctx, db, "weave_instances", "ix_workflow_observe_state_updated", operationalWorkflowStates)
+	if err != nil {
+		return OperationalSnapshot{}, err
+	}
+	taskAge, err := oldestAge(ctx, db, "pulse_tasks", "ix_task_observe_state_available", []string{"WAITING", "LEASED", "RUNNING", "NEEDS_REVIEW"}, "available_at", now)
+	if err != nil {
+		return OperationalSnapshot{}, err
+	}
+	deliveryAge, err := oldestAge(ctx, db, "orbit_deliveries", "ix_delivery_observe_state_available", []string{"PENDING", "LEASED"}, "available_at", now)
+	if err != nil {
+		return OperationalSnapshot{}, err
+	}
+	workflowAge, err := oldestAge(ctx, db, "weave_instances", "ix_workflow_observe_state_updated", []string{"RUNNING", "WAITING", "CANCELLING", "NEEDS_REVIEW"}, "updated_at", now)
+	if err != nil {
+		return OperationalSnapshot{}, err
+	}
+	return OperationalSnapshot{
+		TaskStates: tasks, TaskOldestAgeSeconds: taskAge,
+		DeliveryStates: deliveries, DeliveryOldestAgeSeconds: deliveryAge,
+		WorkflowStates: workflows, WorkflowOldestAgeSeconds: workflowAge,
+		Truncated: taskTruncated || deliveryTruncated || workflowTruncated,
+	}, nil
+}
+
+func readDatabaseNow(ctx context.Context, db *sql.DB) (time.Time, error) {
+	var now time.Time
+	if err := db.QueryRowContext(ctx, "SELECT UTC_TIMESTAMP(6)").Scan(&now); err != nil {
+		return time.Time{}, err
+	}
+	return now.UTC(), nil
+}
+
+func boundedStateCounts(ctx context.Context, db *sql.DB, table, index string, states []string) (map[string]uint64, bool, error) {
+	counts := make(map[string]uint64, len(states))
+	truncated := false
+	for _, state := range states {
+		query := "SELECT COUNT(*) FROM (SELECT id FROM " + table + " FORCE INDEX (" + index + ") WHERE state=? LIMIT ?) AS bounded"
+		var n uint64
+		if err := db.QueryRowContext(ctx, query, state, operationalMetricSampleLimit+1).Scan(&n); err != nil {
+			return nil, false, err
+		}
+		if n > operationalMetricSampleLimit {
+			n = operationalMetricSampleLimit
+			truncated = true
+		}
+		counts[state] = n
+	}
+	return counts, truncated, nil
+}
+
+func oldestAge(ctx context.Context, db *sql.DB, table, index string, states []string, column string, now time.Time) (float64, error) {
+	placeholders := "?"
+	args := make([]any, 0, len(states))
+	args = append(args, states[0])
+	for _, state := range states[1:] {
+		placeholders += ",?"
+		args = append(args, state)
+	}
+	query := "SELECT " + column + " FROM " + table + " FORCE INDEX (" + index + ") WHERE state IN (" + placeholders + ") ORDER BY " + column + ",id LIMIT 1"
+	var occurred time.Time
+	if err := db.QueryRowContext(ctx, query, args...).Scan(&occurred); err != nil {
+		if err == sql.ErrNoRows {
+			return 0, nil
+		}
+		return 0, err
+	}
+	age := now.Sub(occurred.UTC()).Seconds()
+	if age < 0 {
+		return 0, nil
+	}
+	return age, nil
+}