feat: add generic phased background shutdown to managed services

scripts/testdata/phasedMySQL_test.go

@@ -0,0 +1,85 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"example.com/mysqlAcceptance/internal/config"
+	"example.com/mysqlAcceptance/internal/svc"
+	"git.yuntuo.hk/k2safe/go-omni/lifecycle"
+	"git.yuntuo.hk/k2safe/go-omni/logx"
+	"io"
+	"testing"
+	"time"
+)
+
+func TestGeneratedMySQLBackgroundDrain(t *testing.T) {
+	cfg, err := config.Load("etc/config.yaml")
+	if err != nil {
+		t.Fatal(err)
+	}
+	logger, err := logx.New(logx.Config{Writer: io.Discard})
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer logger.Close()
+	parent, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	c, err := svc.New(parent, logger, cfg)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer c.Close()
+	stop := make(chan struct{})
+	finished := make(chan error, 1)
+	c.OnStop("writer", func(context.Context) error { close(stop); return nil })
+	c.OnDrain("writer", func(context.Context) error { return <-finished })
+	go func() {
+		<-stop
+		result := func() (err error) {
+			ctx, end := context.WithTimeout(c.WorkContext(), 3*time.Second)
+			defer end()
+			conn, err := c.DB.Conn(ctx)
+			if err != nil {
+				return err
+			}
+			defer func() { err = errors.Join(err, conn.Close()) }()
+			for _, query := range []string{"CREATE TEMPORARY TABLE omni_phase_records (id INT)", "INSERT INTO omni_phase_records VALUES (42)"} {
+				if _, err = conn.ExecContext(ctx, query); err != nil {
+					return err
+				}
+			}
+			var n int
+			if err = conn.QueryRowContext(ctx, "SELECT id FROM omni_phase_records").Scan(&n); err != nil {
+				return err
+			}
+			if n != 42 {
+				return errors.New("final background write missing")
+			}
+			_, err = conn.ExecContext(ctx, "DROP TEMPORARY TABLE omni_phase_records")
+			return err
+		}()
+		// Completion follows release of the borrowed connection, including failures.
+		finished <- result
+	}()
+	cancel()
+	if err = c.Finish(nil); err != nil {
+		t.Fatal(err)
+	}
+	if err = c.DB.PingContext(context.Background()); err == nil {
+		t.Fatal("pool not closed after worker finished")
+	}
+
+	held, err := svc.New(context.Background(), logger, cfg)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer held.DB.Close() // This test owns recovery and has no outstanding work.
+	cause := errors.New("worker completion unproven")
+	held.OnDrain("unjoined", func(context.Context) error { return cause })
+	if err = held.Finish(nil); !errors.Is(err, cause) || !errors.Is(err, lifecycle.ErrResourcesRetained) {
+		t.Fatal(err)
+	}
+	if err = held.DB.Health(context.Background()); err != nil {
+		t.Fatal("unjoined worker lost shared database", err)
+	}
+}