Do not crash when free space cannot be calculated (#803)

If the compaction daemon cannot calculate the free space
for a volume, do not crash CouchDB. Instead, log a warning
that free space could not be calculated and continue.

Compaction of the database is not necessarily prevented -
just that the disk space for this specific volume
won't be taken into account when deciding whether
to automatically compact or not.

This is primarily to cope with edge cases arising from
ERL-343, whereby disksup:get_disk_data() returns invalid
paths for volumes containing whitespace.

Fixes #732

1 files changed, 28 insertions, 16 deletions

diff --git a/src/couch/src/couch_compaction_daemon.erl b/src/couch/src/couch_compaction_daemon.erl
index 8f95eb21e..024b867d0 100644
--- a/src/couch/src/couch_compaction_daemon.erl
+++ b/src/couch/src/couch_compaction_daemon.erl
@@ -509,34 +509,46 @@ free_space(Path) ->
             length(filename:split(PathA)) > length(filename:split(PathB))
         end,
         disksup:get_disk_data()),
-    free_space_rec(abs_path(Path), DiskData).
+    {ok, AbsPath} = abs_path(Path),
+    free_space_rec(AbsPath, DiskData).
 
 free_space_rec(_Path, []) ->
     undefined;
 free_space_rec(Path, [{MountPoint0, Total, Usage} | Rest]) ->
-    MountPoint = abs_path(MountPoint0),
-    case MountPoint =:= string:substr(Path, 1, length(MountPoint)) of
-    false ->
-        free_space_rec(Path, Rest);
-    true ->
-        trunc(Total - (Total * (Usage / 100))) * 1024
+    case abs_path(MountPoint0) of
+    {ok, MountPoint} ->
+        case MountPoint =:= string:substr(Path, 1, length(MountPoint)) of
+        false ->
+            free_space_rec(Path, Rest);
+        true ->
+            trunc(Total - (Total * (Usage / 100))) * 1024
+        end;
+    {error, Reason} ->
+        couch_log:warning("Compaction daemon - unable to calculate free space"
+            " for `~s`: `~s`",
+            [MountPoint0, Reason]),
+        free_space_rec(Path, Rest)
     end.
 
 abs_path(Path0) ->
-    {ok, Info} = file:read_link_info(Path0),
-    case Info#file_info.type of
-        symlink ->
-            {ok, Path} = file:read_link(Path0),
-            abs_path(Path);
-        _ ->
-            abs_path2(Path0)
+    case file:read_link_info(Path0) of
+    {ok, Info} ->
+        case Info#file_info.type of
+            symlink ->
+                {ok, Path} = file:read_link(Path0),
+                abs_path(Path);
+            _ ->
+                abs_path2(Path0)
+        end;
+    {error, Reason} ->
+        {error, Reason}
     end.
 
 abs_path2(Path0) ->
     Path = filename:absname(Path0),
     case lists:last(Path) of
     $/ ->
-        Path;
+        {ok, Path};
     _ ->
-        Path ++ "/"
+        {ok, Path ++ "/"}
     end.