From 0920a47f25089b2ef01b21fb9b36b4841b5872de Mon Sep 17 00:00:00 2001
From: Roman Vanicek <roman.vanicek@ivasoft.cz>
Date: Tue, 19 Mar 2024 22:59:54 +0100
Subject: [PATCH] Allow reduction of mounted snapshots to conserve RAM

---
 main.go | 44 +++++++++++++++++++++++++++++++-------------
 1 file changed, 31 insertions(+), 13 deletions(-)

diff --git a/main.go b/main.go
index d8338e8..4245fff 100644
--- a/main.go
+++ b/main.go
@@ -35,12 +35,13 @@ import (
 )
 
 type ofsVolume struct {
-	Volume         *volume.Volume
-	Fs             string
-	Opts           string
-	Env            []string
-	Asap           bool
-	MountSnapshots bool
+	Volume          *volume.Volume
+	Fs              string
+	Opts            string
+	Env             []string
+	Asap            bool
+	MountSnapshots  bool
+	SnapshotsFilter string
 }
 
 type ofsVolumeRt struct {
@@ -104,6 +105,8 @@ func (d *ofsDriver) Create(r *volume.CreateRequest) error {
 			v.Asap = true
 		case "mountSnapshots":
 			v.MountSnapshots = val == "yes"
+		case "snapshotsFilter":
+			v.SnapshotsFilter = val
 		default:
 			env[key] = val
 		}
@@ -349,20 +352,35 @@ func (d *ofsDriver) Mount(r *volume.MountRequest) (*volume.MountResponse, error)
 										if existingMountDirs, err := getMountedSnaphots(snapshotsPath, false); err == nil {
 											log.WithFields(log.Fields{"name": r.Name, "existingMountDirs": existingMounts}).Trace("Existing snapshot mount dirs")
 
-											// Remove left-over dirs of expired snapshots (ie. appears during downtime)
-											for i, path := range setMinus(setMinus(existingMountDirs, expectedSnapshots), existingMounts) {
-												if err := os.Remove(path); err != nil {
-													log.WithFields(log.Fields{"name": r.Name, "snapshot": i}).Warn("Failed to remove directory of an off-line expired snapshot.")
+											// PERF: We allow mounting just subset of snapshots for performance reasons (required RAM)
+											var filteredSnapshots map[string]bool
+											if len(strings.TrimSpace(v.SnapshotsFilter)) != 0 {
+												if a, err := generateSnapshotsFromRulesForNow(strings.TrimSpace(v.SnapshotsFilter)); err != nil {
+													filteredSnapshots = a
+													log.WithFields(log.Fields{"name": r.Name, "invalidFilter": a}).Trace("Snapshots filter.")
+												} else {
+													filteredSnapshots = expectedSnapshots
+													log.WithFields(log.Fields{"name": r.Name, "invalidFilter": v.SnapshotsFilter}).Warn("Failed to parse snapshots filter. Will mount all snapshots.")
 												}
+											} else {
+												filteredSnapshots = expectedSnapshots
 											}
 
-											// Remove mounts of expired snapshots
-											for i, path := range setMinus(existingMounts, expectedSnapshots) {
+											// Unmount snapshots that are no longer in filteredSnapshots to conserve RAM
+											// Note: We cannot remove the directory as other machines may have different
+											//	filteredSnapshots and may be using them.
+											for i, path := range setMinus(existingMounts, setIntersect(expectedSnapshots, filteredSnapshots)) {
 												if err := exec.Command("umount", path).Run(); err != nil {
 													log.WithFields(log.Fields{"name": r.Name, "snapshot": i}).Warn("Failed to unmount an expired snapshot.")
 												} else {
 													log.WithFields(log.Fields{"name": r.Name, "snapshot": i}).Debug("Snapshot unmounted.")
 												}
+											}
+
+											// Remove left-over dirs of expired snapshots
+											// Note: That is directories that no other machine would use as the snapshots are not
+											//	mounted due to filteredSnapshots but because they are not even in expectedSnapshots.
+											for i, path := range setMinus(existingMountDirs, expectedSnapshots) {
 												if err := os.Remove(path); err != nil {
 													log.WithFields(log.Fields{"name": r.Name, "snapshot": i}).Warn("Failed to remove directory of an expired snapshot.")
 												}
@@ -379,7 +397,7 @@ func (d *ofsDriver) Mount(r *volume.MountRequest) (*volume.MountResponse, error)
 											}
 
 											// Add new mounts
-											for i, name := range setMinus(setIntersect(existingSnapshots, expectedSnapshots), existingMounts) {
+											for i, name := range setMinus(setIntersect(existingSnapshots, setIntersect(expectedSnapshots, filteredSnapshots)), existingMounts) {
 												dest := filepath.Join(snapshotsPath, i)
 												if err := os.Mkdir(dest, os.ModePerm); err == nil || os.IsExist(err) {
 													// Note: There is a missing "mount" argument so the mount continues running in a background process