From 2bf252c5a68b16269ff2135df7e09bc9df657355 Mon Sep 17 00:00:00 2001
From: Bert De Jonghe <Bert.DeJonghe@openvstorage.com>
Date: Wed, 24 May 2017 15:28:05 +0200
Subject: [PATCH 1/2] fixes #690

---
 ocaml/src/alba_eviction.ml | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/ocaml/src/alba_eviction.ml b/ocaml/src/alba_eviction.ml
index 8a310fda..2941780d 100644
--- a/ocaml/src/alba_eviction.ml
+++ b/ocaml/src/alba_eviction.ml
@@ -233,5 +233,10 @@ let lru_collect_some_garbage alba_client redis_client key =
 
   >>= fun sizes ->
 
-  R.zrem redis_client key items >>= fun _ ->
-  Lwt.return (List.fold_left Int64.add 0L sizes)
+  (if List.length items > 0
+   then
+     R.zrem redis_client key items
+   else
+     Lwt.return 0)
+
+  >>= fun _ -> Lwt.return (List.fold_left Int64.add 0L sizes)

From 6e5186dbcf3b52026e4a5183d537069d7133322a Mon Sep 17 00:00:00 2001
From: Bert De Jonghe <Bert.DeJonghe@openvstorage.com>
Date: Fri, 26 May 2017 16:40:47 +0200
Subject: [PATCH 2/2] prevent spinning fast if no work found; fallback to
 random eviction if it takes too long

---
 ocaml/src/maintenance.ml | 25 ++++++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

diff --git a/ocaml/src/maintenance.ml b/ocaml/src/maintenance.ml
index 9f8f1f46..dbe5af1a 100644
--- a/ocaml/src/maintenance.ml
+++ b/ocaml/src/maintenance.ml
@@ -2091,7 +2091,7 @@ class client ?(retry_timeout = 60.)
                       let percentage = percentage_from_fill_ratio fill_ratio in
                       (* collect precentage of objects *)
                       let target = Int64.div total_disk_size 100L |> Int64.mul percentage in
-                      let rec inner acc =
+                      let rec inner acc retrycnt =
                         if acc > target
                         then Lwt.return ()
                         else
@@ -2100,10 +2100,29 @@ class client ?(retry_timeout = 60.)
                               alba_client
                               client
                               key >>= fun size ->
-                            inner (Int64.add acc size)
+                            if size > 0L
+                            then
+                              (* part of the job done, try to do more *)
+                              inner (Int64.add acc size) 0
+                            else
+                              let retrycnt = retrycnt + 1 in
+                              if retrycnt >= 5
+                              then
+                                begin
+                                  Lwt_log.info
+                                    "redis based lru eviction has too many retries, fallback to random"
+                                  >>= fun () ->
+                                  do_random_eviction fill_ratio
+                                end
+                              else
+                                begin
+                                  (* wait a little here to increase chance to have work *)
+                                  Lwt_unix.sleep 1. >>= fun () ->
+                                  inner (Int64.add acc size) retrycnt
+                                end
                           end
                       in
-                      inner 0L)
+                      inner 0L 0)
                   )
                   (fun exn ->
                    Lwt_log.info_f