2 files changed, 113 insertions, 0 deletions
diff --git a/internal/transporthealth/monitor.go b/internal/transporthealth/monitor.go
new file mode 100644
index 0000000..48369ee
--- /dev/null
+++ b/internal/transporthealth/monitor.go
@@ -0,0 +1,83 @@
+package transporthealth
+
+import (
+	"context"
+	"log"
+	"sync"
+	"time"
+)
+
+type Checker interface {
+	Check(context.Context) error
+}
+
+type Monitor struct {
+	checker  Checker
+	interval time.Duration
+	timeout  time.Duration
+
+	mu        sync.RWMutex
+	ready     bool
+	checkedAt time.Time
+}
+
+func New(checker Checker, interval, timeout time.Duration) *Monitor {
+	if interval < time.Minute {
+		interval = 15 * time.Minute
+	}
+	if timeout <= 0 {
+		timeout = 90 * time.Second
+	}
+	return &Monitor{checker: checker, interval: interval, timeout: timeout}
+}
+
+func (m *Monitor) Run(ctx context.Context) {
+	m.Probe(ctx)
+	ticker := time.NewTicker(m.interval)
+	defer ticker.Stop()
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case <-ticker.C:
+			m.Probe(ctx)
+		}
+	}
+}
+
+func (m *Monitor) Probe(ctx context.Context) {
+	probeCtx, cancel := context.WithTimeout(ctx, m.timeout)
+	defer cancel()
+	if err := m.checker.Check(probeCtx); err != nil {
+		m.MarkFailure(err)
+		log.Printf("transport probe failed: %v", err)
+		return
+	}
+	m.MarkSuccess()
+	log.Printf("transport probe succeeded")
+}
+
+func (m *Monitor) Ready() bool {
+	m.mu.RLock()
+	ready := m.ready
+	checkedAt := m.checkedAt
+	m.mu.RUnlock()
+	if !ready || checkedAt.IsZero() {
+		return false
+	}
+	return time.Since(checkedAt) <= 2*m.interval+m.timeout
+}
+
+func (m *Monitor) MarkSuccess() {
+	m.mu.Lock()
+	m.ready = true
+	m.checkedAt = time.Now()
+	m.mu.Unlock()
+}
+
+func (m *Monitor) MarkFailure(error) {
+	m.mu.Lock()
+	m.ready = false
+	m.checkedAt = time.Now()
+	m.mu.Unlock()
+}
diff --git a/internal/transporthealth/monitor_test.go b/internal/transporthealth/monitor_test.go
new file mode 100644
index 0000000..c5eb98d
--- /dev/null
+++ b/internal/transporthealth/monitor_test.go
@@ -0,0 +1,30 @@
+package transporthealth
+
+import (
+	"context"
+	"errors"
+	"testing"
+	"time"
+)
+
+type checkerFunc func(context.Context) error
+
+func (f checkerFunc) Check(ctx context.Context) error {
+	return f(ctx)
+}
+
+func TestProbeTracksReadiness(t *testing.T) {
+	var checkErr error
+	monitor := New(checkerFunc(func(context.Context) error { return checkErr }), time.Minute, time.Second)
+
+	monitor.Probe(context.Background())
+	if !monitor.Ready() {
+		t.Fatal("successful probe did not mark transport ready")
+	}
+
+	checkErr = errors.New("transport unavailable")
+	monitor.Probe(context.Background())
+	if monitor.Ready() {
+		t.Fatal("failed probe left transport ready")
+	}
+}