[couchdb] branch feat/log-file-truncation created (now 60910d4)

[ja...@apache.org]

This is an automated email from the ASF dual-hosted git repository.

jan pushed a change to branch feat/log-file-truncation
in repository https://gitbox.apache.org/repos/asf/couchdb.git.


      at 60910d4  feat(couch_file): log file path when a file was truncated from under us

This branch includes the following new commits:

     new 60910d4  feat(couch_file): log file path when a file was truncated from under us

The 1 revisions listed above as "new" are entirely new to this
repository and will be described in separate emails.  The revisions
listed as "add" were already present in the repository and have only
been added to this reference.

[couchdb] 01/01: feat(couch_file): log file path when a file was truncated from under us

[ja...@apache.org]

This is an automated email from the ASF dual-hosted git repository.

jan pushed a commit to branch feat/log-file-truncation
in repository https://gitbox.apache.org/repos/asf/couchdb.git

commit 60910d4105d2a4741a89b75403bfb9bb4759e532
Author: Jan Lehnardt <ja...@apache.org>
AuthorDate: Wed Apr 14 11:39:29 2021 +0200

    feat(couch_file): log file path when a file was truncated from under us
---
 src/couch/src/couch_file.erl | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/src/couch/src/couch_file.erl b/src/couch/src/couch_file.erl
index b1e3555..2948d68 100644
--- a/src/couch/src/couch_file.erl
+++ b/src/couch/src/couch_file.erl
@@ -711,10 +711,21 @@ read_raw_iolist_int(Fd, {Pos, _Size}, Len) -> % 0110 UPGRADE CODE
     read_raw_iolist_int(Fd, Pos, Len);
 read_raw_iolist_int(#file{fd = Fd} = File, Pos, Len) ->
     {Pos, TotalBytes} = get_pread_locnum(File, Pos, Len),
-    {ok, <<RawBin:TotalBytes/binary>>} = file:pread(Fd, Pos, TotalBytes),
-    {remove_block_prefixes(Pos rem ?SIZE_BLOCK, RawBin), Pos + TotalBytes}.
-
+    case catch file:pread(Fd, Pos, TotalBytes) of
+        {ok, <<RawBin:TotalBytes/binary>>} ->
+            {remove_block_prefixes(Pos rem ?SIZE_BLOCK, RawBin), Pos + TotalBytes};
+        Else ->
+            % This clause matches when the file we are working with got truncated
+            % outside of CouchDB after we opened it. To find affected files, we
+            % need to log the file path.
+            %
+            % Technically, this should also go into read_multi_raw_iolists_int/2,
+            % but that doesn’t seem to be in use anywhere.
+            {_Fd, Filepath} = get(couch_file_fd),
+            throw({file_truncate_error, Else, Filepath})
+    end.
 
+% TODO: check if this is really unused
 read_multi_raw_iolists_int(#file{fd = Fd} = File, PosLens) ->
     LocNums = lists:map(fun({Pos, Len}) ->
         get_pread_locnum(File, Pos, Len)