Hi Stefan,
Thanks for the additional info. I’m happy to try a yocto build here.
Best
Jan
—
> On 2. Mar 2023, at 12:24, Stefan Kral <stefan.k...@emlix.com> wrote:
>
> Hi,
>
> I can give you some background context: our CouchDB instance is running
> on a embedded device (with minimal attack vector, so we have no pressure
> to mitigate CVEs). CouchDB has been chosen because of its write append
> and power fail safe property (and because of the easy scriptable
> curl/json interface).
>
> Currently there is a production system running on a SMB1 share (mounted
> in a Linux host) which works well (at least for our uses cases). SMB1 is
> not logner the default on the Windows remote side. And SMB2/3 has an
> issue with opening a renamend but not closed filedescriptor. The
> question is, wether we can solve this issue with minimal changes.
>
>> 1. How did you verify that the gen_server:call/3 call never returns?
>> 2. Do you get any pertinent lines (especially crashes) in your
>> couch.log?
>
> by adding:
>
>> + ?LOG_DEBUG("before gen_server:call", []),
>> ok = gen_server:call(Db#db.main_pid, {db_updated, NewDb3}, infinity),
>> + ?LOG_DEBUG("after gen_server:call", []),
>
> the log gives:
>
>> [Thu, 02 Mar 2023 10:36:24 GMT] [debug] [<0.391.0>] Compaction process
>> spawned for db "asdf"
>> [Thu, 02 Mar 2023 10:36:24 GMT] [debug] [<0.84.0>] New task status for
>> <0.391.0>: [{changes_done,1},
>> {database,<<"asdf">>},
>> {progress,100},
>> {started_on,1677753384},
>> {total_changes,1},
>> {type,database_compaction},
>> {updated_on,1677753384}]
>> [Thu, 02 Mar 2023 10:36:24 GMT] [debug] [<0.366.0>] CouchDB swapping files
>> .../asdf.couch and .../asdf.couch.compact.
>> [Thu, 02 Mar 2023 10:36:24 GMT] [debug] [<0.366.0>] before gen_server:call
>
> then long time nothing...
>
> refreshing the db in the futon web gui gives: no response
>
> and the log continues with:
>
>> [Thu, 02 Mar 2023 11:02:54 GMT] [error] [<0.144.0>] ** Generic server
>> couch_compaction_daemon terminating
>> ** Last message in was {'EXIT',<0.145.0>,
>> {timeout,
>> {gen_server,call,[couch_server,get_server]}}}
>> ** When Server state == {state,<0.145.0>}
>> ** Reason for termination ==
>> ** {compaction_loop_died,
>> {timeout,{gen_server,call,[couch_server,get_server]}}}
>>
>> [Thu, 02 Mar 2023 11:02:54 GMT] [error] [<0.144.0>] {error_report,<0.31.0>,
>> {<0.144.0>,crash_report,
>> [[{initial_call,
>> {couch_compaction_daemon,init,['Argument__1']}},
>> {pid,<0.144.0>},
>> {registered_name,couch_compaction_daemon},
>> {error_info,
>> {exit,
>> {compaction_loop_died,
>> {timeout,
>> {gen_server,call,[couch_server,get_server]}}},
>> [{gen_server,terminate,7,
>> [{file,"gen_server.erl"},{line,804}]},
>> {proc_lib,init_p_do_apply,3,
>> [{file,"proc_lib.erl"},{line,237}]}]}},
> ...
>
>
>> 3. Can you share your environment where you get to compile 1.6.1
>> successfully, so we can try and reproduce this?
>
> I could prepare you a yocto setup to build a toolchain and packages for
> an qemu/docker imgage, if you are familar with that build system...
>
>> 4. Could it be that your SMB implementation doesn’t allow for opening
>> and closing files in this quick succession (with our without a rename
>> in the mix)?
>
> For testing it desn't need to run on SMB share, the timeout issue
> occures with the given fd-swap patch on a default (Linux) setup.
>
> And a strace log does not show any underlying FS issues.
>
>
> Best,
> Stefan
>
> Am 28.02.23 um 16:47 schrieb Jan Lehnardt:
>> first off, CouchDB 1.6.1 is no longer supported by this project AND it
>> has a long list of CVEs[1] against it. You REALLY should be operating
>> on a newer version.
>>
>> Secondly, just to understand your motivation: you think closing and
>> opening the fds after the file:rename/2 call will make things work
>> for your SMB operation?
>>
>> If yes, the only think I could spot that is substantially different, is
>> that the NewFd position is advanced implicitly by the underlying
>> file:pread/3 in [2] and your SwappedFd doesn’t get the same treatment,
>> but I don’t know why that should block the gen server call, as that only
>> does some refcounting updates[3]. While this includes stopping the
>> gen_server[4], I don’t see how the Pid this operates on should be any
>> different under your patch.
>>
>> So:
>>
>> 1. How did you verify that the gen_server:call/3 call never returns?
>> 2. Do you get any pertinent lines (especially crashes) in your couch.log?
>> 3. Can you share your environment where you get to compile 1.6.1
>> successfully, so we can try and reproduce this?
>> 4. Could it be that your SMB implementation doesn’t allow for opening and
>> closing files in this quick succession (with our without a rename in
>> the mix)?
>>
>>
>> [1]: https://docs.couchdb.org/en/stable/cve/index.html
>> [2]:
>> https://github.com/apache/couchdb/blob/1.6.x/src/couchdb/couch_db_updater.erl#L179
>> [3]:
>> https://github.com/apache/couchdb/blob/1.6.x/src/couchdb/couch_db.erl#L1122-L1130
>> [4]:
>> https://github.com/apache/couchdb/blob/1.6.x/src/couchdb/couch_ref_counter.erl#L84
>>
>>
>> Best
>> Jan
>> —
>> Professional Support for Apache CouchDB:
>> https://neighbourhood.ie/couchdb-support/
>>
>> 24/7 Observation for your CouchDB Instances:
>> https://opservatory.app
>>
>>
>>> On 28. Feb 2023, at 10:19, Stefan Kral <stefan.k...@emlix.com> wrote:
>>>
>>> Hi,
>>>
>>> I'm experimenting with a CouchDB setup on a SMB mount point. I know this
>>> is not supported, but I ran into a (maybe simple) problem I don't
>>> understand. Maybe someone of you can give a hint easily (that would be
>>> amazing).
>>>
>>> Given the following patch (I need to close/reopen the file descriptors
>>> after renaming) for the function
>>> https://github.com/apache/couchdb/blob/1.6.x/src/couchdb/couch_db_updater.erl#L176
>>>
>>>> 1 --- a/src/couchdb/couch_db_updater.erl
>>>> 2 +++ b/src/couchdb/couch_db_updater.erl
>>>> 3 @@ -202,8 +202,18 @@ handle_call({compact_done, CompactFilepath}, _From,
>>>> #db{filepath=Path}=Db) ->
>>>> 4 RootDir = couch_config:get("couchdb", "database_dir", "."),
>>>> 5 couch_file:delete(RootDir, Filepath),
>>>> 6 ok = file:rename(CompactFilepath, Filepath),
>>>> 7 +
>>>> 8 + ok = couch_file:close(NewDb#db.updater_fd),
>>>> 9 + ok = couch_file:close(NewDb#db.fd),
>>>> 10 + {ok, SwappedFd} = couch_file:open(Filepath),
>>>> 11 + SwappedReaderFd = open_reader_fd(Filepath, Db#db.options),
>>>> 12 + SwappedDb = NewDb2#db{
>>>> 13 + fd = SwappedReaderFd,
>>>> 14 + updater_fd = SwappedFd
>>>> 15 + },
>>>> 16 + unlink(SwappedFd),
>>>> 17 close_db(Db),
>>>> 18 - NewDb3 = refresh_validate_doc_funs(NewDb2),
>>>> 19 + NewDb3 = refresh_validate_doc_funs(SwappedDb),
>>>> 20 ok = gen_server:call(Db#db.main_pid, {db_updated, NewDb3},
>>>> infinity),
>>>> 21 couch_db_update_notifier:notify({compacted, NewDb3#db.name}),
>>>> 22 ?LOG_INFO("Compaction for db \"~s\" completed.", [Db#db.name]),
>>>
>>> then the gen_server:call() of line 20 never returns.
>>>
>>> Is there a major issue with this approach or just a minor mistake in my
>>> implementation?
>>>
>>>
>>> Thank you for having a look,
>>> Stefan
>>
>>
