X δbtail: tests: Run much faster with live ZODB cache

        $ time go test -failfast -short -run 'ΔBTail/rebuild' >x

before:

        real    0m43,071s
        user    0m57,487s
        sys     0m4,869s

after:

        real    0m17,852s
        user    0m23,068s
        sys     0m1,825s

wcfs/go.mod

@@ -10,7 +10,7 @@ require (
 	github.com/pkg/errors v0.9.1
 	github.com/stretchr/testify v1.7.0
 	lab.nexedi.com/kirr/go123 v0.0.0-20210302025843-863c4602a230
-	lab.nexedi.com/kirr/neo/go v0.0.0-20210326102715-dc35035cdc18
+	lab.nexedi.com/kirr/neo/go v0.0.0-20210503113049-7fba56df234c
 )
 
 // we use kirr/go-fuse@y/nodefs-cancel

wcfs/go.sum

@@ -191,3 +191,5 @@ lab.nexedi.com/kirr/neo/go v0.0.0-20210322184934-2888bbbcbe4b h1:JmC5mk3Mts39k6l
 lab.nexedi.com/kirr/neo/go v0.0.0-20210322184934-2888bbbcbe4b/go.mod h1:llI3hcJJMACe+rYuXUfS5dljjwIrlBMfJ1ZeRcey96A=
 lab.nexedi.com/kirr/neo/go v0.0.0-20210326102715-dc35035cdc18 h1:ysqIq6WqSMhCPbSRt3RnI1geV+chVkneXV7Wxn9zsEc=
 lab.nexedi.com/kirr/neo/go v0.0.0-20210326102715-dc35035cdc18/go.mod h1:llI3hcJJMACe+rYuXUfS5dljjwIrlBMfJ1ZeRcey96A=
+lab.nexedi.com/kirr/neo/go v0.0.0-20210503113049-7fba56df234c h1:+M4xtOKZqy7oC6L9CzdXi77PNI9KnohOEnEsHlmAPPE=
+lab.nexedi.com/kirr/neo/go v0.0.0-20210503113049-7fba56df234c/go.mod h1:llI3hcJJMACe+rYuXUfS5dljjwIrlBMfJ1ZeRcey96A=

wcfs/wcfs.go

@@ -2366,7 +2366,10 @@ func _main() (err error) {
 	at0 := zstor.AddWatch(zwatchq)
 	defer zstor.DelWatch(zwatchq)
 
-	zdb := zodb.NewDB(zstor)
+	// TODO consider using zodbCacheControl for all connections
+	// ( in addition to zhead, historic connections - that are used to access @rev -
+	//   also need to traverse BigFile.blktab btree )
+	zdb := zodb.NewDB(zstor, &zodb.DBOptions{})
 	defer xclose(zdb)
 	zhead, err := zopen(ctx, zdb, &zodb.ConnOptions{
 		At: at0,

wcfs/zblk_test.go

@@ -44,7 +44,7 @@ func TestZBlk(t *testing.T) {
 	assert := require.New(t)
 	ctx := context.Background()
 	stor, err := zodb.Open(ctx, "testdata/zblk.fs", &zodb.OpenOptions{ReadOnly: true}); X(err)
-	db := zodb.NewDB(stor)
+	db := zodb.NewDB(stor, &zodb.DBOptions{})
 	defer func() {
 		err := db.Close();	X(err)
 		err  = stor.Close();	X(err)

wcfs/δbtail_test.go

@@ -1097,6 +1097,15 @@ type tTreeCommit struct {
 	// XXX do we also need δkv ?
 }
 
+// tZODBCacheEverything is workaround for ZODB/go not implementing real
+// live cache for now: Objects get dropped on PDeactivate if cache
+// control does not say we need the object to stay in the cache.
+// XXX place
+type tZODBCacheEverything struct{}
+func (_ *tZODBCacheEverything) PCacheClassify(_ zodb.IPersistent) zodb.PCachePolicy {
+	return zodb.PCachePinObject | zodb.PCacheKeepState
+}
+
 // testΔBTail verifies ΔBTail on sequence of tree topologies coming from testq.
 func testΔBTail(t *testing.T, testq chan ΔBTestEntry) {
 	X := exc.Raiseif
@@ -1117,7 +1126,12 @@ func testΔBTail(t *testing.T, testq chan ΔBTestEntry) {
 		err := zstor.Close(); X(err)
 	}()
 
-	db := zodb.NewDB(zstor)
+	db := zodb.NewDB(zstor, &zodb.DBOptions{
+		// We need objects to be cached, because otherwise it is too
+		// slow to run the test for many testcases, especially
+		// xverifyΔBTail_rebuild.
+		CacheControl: &tZODBCacheEverything{},
+	})
 	defer func() {
 		err := db.Close(); X(err)
 	}()