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ccdff3ebbf44fc386fc146cf34530d4b95e28bc2
rsync/TODO
Paul Green a577af9067 Added a TODO item about temporary file names bumping up against the 
maximum name length.  (I have an unfinished patch that will address
this).
2003-01-27 16:33:47 +00:00

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-*- indented-text -*-
BUGS ---------------------------------------------------------------
rsync-url barfs on upload
rsync foo rsync://localhost/transfer/
Fix the parser.
There seems to be a bug with hardlinks
mbp/2 build$ ls -l /tmp/a /tmp/b -i
/tmp/a:
total 32
2568307 -rw-rw-r-- 3 mbp mbp 29 Mar 25 17:30 a1
2568307 -rw-rw-r-- 3 mbp mbp 29 Mar 25 17:30 a2
2568307 -rw-rw-r-- 3 mbp mbp 29 Mar 25 17:30 a3
2568310 -rw-rw-r-- 5 mbp mbp 29 Mar 25 17:30 a4
2568310 -rw-rw-r-- 5 mbp mbp 29 Mar 25 17:30 a5
2568310 -rw-rw-r-- 5 mbp mbp 29 Mar 25 17:30 b1
2568310 -rw-rw-r-- 5 mbp mbp 29 Mar 25 17:30 b2
2568310 -rw-rw-r-- 5 mbp mbp 29 Mar 25 17:30 b3
/tmp/b:
total 32
2568309 -rw-rw-r-- 3 mbp mbp 29 Mar 25 17:30 a1
2568309 -rw-rw-r-- 3 mbp mbp 29 Mar 25 17:30 a2
2568309 -rw-rw-r-- 3 mbp mbp 29 Mar 25 17:30 a3
2568311 -rw-rw-r-- 5 mbp mbp 29 Mar 25 17:30 a4
2568311 -rw-rw-r-- 5 mbp mbp 29 Mar 25 17:30 a5
2568311 -rw-rw-r-- 5 mbp mbp 29 Mar 25 17:30 b1
2568311 -rw-rw-r-- 5 mbp mbp 29 Mar 25 17:30 b2
2568311 -rw-rw-r-- 5 mbp mbp 29 Mar 25 17:30 b3
mbp/2 build$ rm -r /tmp/b && ./rsync -avH /tmp/a/ /tmp/b
building file list ... done
created directory /tmp/b
./
a1
a4
a2 => a1
a3 => a2
wrote 350 bytes read 52 bytes 804.00 bytes/sec
total size is 232 speedup is 0.58
mbp/2 build$ rm -r /tmp/b
mbp/2 build$ ls -l /tmp/b
ls: /tmp/b: No such file or directory
mbp/2 build$ rm -r /tmp/b && ./rsync -avH /tmp/a/ /tmp/b
rm: cannot remove `/tmp/b': No such file or directory
mbp/2 build$ rm -f -r /tmp/b && ./rsync -avH /tmp/a/ /tmp/b
building file list ... done
created directory /tmp/b
./
a1
a4
a2 => a1
a3 => a2
wrote 350 bytes read 52 bytes 804.00 bytes/sec
total size is 232 speedup is 0.58
mbp/2 build$ ls -l /tmp/b
total 32
-rw-rw-r-- 3 mbp mbp 29 Mar 25 17:30 a1
-rw-rw-r-- 3 mbp mbp 29 Mar 25 17:30 a2
-rw-rw-r-- 3 mbp mbp 29 Mar 25 17:30 a3
-rw-rw-r-- 5 mbp mbp 29 Mar 25 17:30 a4
-rw-rw-r-- 5 mbp mbp 29 Mar 25 17:30 a5
-rw-rw-r-- 5 mbp mbp 29 Mar 25 17:30 b1
-rw-rw-r-- 5 mbp mbp 29 Mar 25 17:30 b2
-rw-rw-r-- 5 mbp mbp 29 Mar 25 17:30 b3
mbp/2 build$ ls -l /tmp/a
total 32
-rw-rw-r-- 3 mbp mbp 29 Mar 25 17:30 a1
-rw-rw-r-- 3 mbp mbp 29 Mar 25 17:30 a2
-rw-rw-r-- 3 mbp mbp 29 Mar 25 17:30 a3
-rw-rw-r-- 5 mbp mbp 29 Mar 25 17:30 a4
-rw-rw-r-- 5 mbp mbp 29 Mar 25 17:30 a5
-rw-rw-r-- 5 mbp mbp 29 Mar 25 17:30 b1
-rw-rw-r-- 5 mbp mbp 29 Mar 25 17:30 b2
-rw-rw-r-- 5 mbp mbp 29 Mar 25 17:30 b3
Progress indicator can produce corrupt output when transferring directories:
main/binary-arm/
main/binary-arm/admin/
main/binary-arm/base/
main/binary-arm/comm/8.56kB/s 0:00:52
main/binary-arm/devel/
main/binary-arm/doc/
main/binary-arm/editors/
main/binary-arm/electronics/s 0:00:53
main/binary-arm/games/
main/binary-arm/graphics/
main/binary-arm/hamradio/
main/binary-arm/interpreters/
main/binary-arm/libs/6.61kB/s 0:00:54
main/binary-arm/mail/
main/binary-arm/math/
main/binary-arm/misc/
lchmod
I don't think we handle this properly on systems that don't have the
call. Are there any such?
Cross-test versions
Part of the regression suite should be making sure that we don't
break backwards compatibility: old clients vs new servers and so
on. Ideally we would test the cross product of versions.
It might be sufficient to test downloads from well-known public
rsync servers running different versions of rsync. This will give
some testing and also be the most common case for having different
versions and not being able to upgrade.
--no-blocking-io might be broken
in the same way as --no-whole-file; somebody needs to check.
Do not rely on having a group called "nobody"
http://www.linuxbase.org/spec/refspecs/LSB_1.1.0/gLSB/usernames.html
On Debian it's "nogroup"
Temporary file names can exceed max name length
Rsync creates temporary file names that are 10 characters longer
than the length of the file being transferred. This creates
problems for operating systems have fairly short maximum lengths
(e.g., 32 characters for Stratus VOS). Even on operating systems
with long max lengths it can still be a problem as it is perfectly
reasonable to be using files with long names.
DAEMON --------------------------------------------------------------
server-imposed bandwidth limits
rsyncd over ssh
There are already some patches to do this.
BitKeeper uses a server whose login shell is set to bkd. That's
probably a reasonable approach.
FEATURES ------------------------------------------------------------
--dry-run is too dry
Mark Santcroos points out that -n fails to list files which have
only metadata changes, though it probably should.
There may be a Debian bug about this as well.
use chroot
If the platform doesn't support it, then don't even try.
If running as non-root, then don't fail, just give a warning.
(There was a thread about this a while ago?)
http://lists.samba.org/pipermail/rsync/2001-August/thread.html
http://lists.samba.org/pipermail/rsync/2001-September/thread.html
--files-from
Avoids traversal. Better option than a pile of --include statements
for people who want to generate the file list using a find(1)
command or a script.
supplementary groups
Perhaps allow supplementary groups to be specified in rsyncd.conf;
then make the first one the primary gid and all the rest be
supplementary gids.
File list structure in memory
Rather than one big array, perhaps have a tree in memory mirroring
the directory tree.
This might make sorting much faster! (I'm not sure it's a big CPU
problem, mind you.)
It might also reduce memory use in storing repeated directory names
-- again I'm not sure this is a problem.
Performance
Traverse just one directory at a time. Tridge says it's possible.
At the moment rsync reads the whole file list into memory at the
start, which makes us use a lot of memory and also not pipeline
network access as much as we could.
Handling duplicate names
We need to be careful of duplicate names getting into the file list.
See clean_flist(). This could happen if multiple arguments include
the same file. Bad.
I think duplicates are only a problem if they're both flowing
through the pipeline at the same time. For example we might have
updated the first occurrence after reading the checksums for the
second. So possibly we just need to make sure that we don't have
both in the pipeline at the same time.
Possibly if we did one directory at a time that would be sufficient.
Alternatively we could pre-process the arguments to make sure no
duplicates will ever be inserted. There could be some bad cases
when we're collapsing symlinks.
We could have a hash table.
The root of the problem is that we do not want more than one file
list entry referring to the same file. At first glance there are
several ways this could happen: symlinks, hardlinks, and repeated
names on the command line.
If names are repeated on the command line, they may be present in
different forms, perhaps by traversing directory paths in different
ways, traversing paths including symlinks. Also we need to allow
for expansion of globs by rsync.
At the moment, clean_flist() requires having the entire file list in
memory. Duplicate names are detected just by a string comparison.
We don't need to worry about hard links causing duplicates because
files are never updated in place. Similarly for symlinks.
I think even if we're using a different symlink mode we don't need
to worry.
Unless we're really clever this will introduce a protocol
incompatibility, so we need to be able to accept the old format as
well.
Memory accounting
At exit, show how much memory was used for the file list, etc.
Also we do a wierd exponential-growth allocation in flist.c. I'm
not sure this makes sense with modern mallocs. At any rate it will
make us allocate a huge amount of memory for large file lists.
Hard-link handling
At the moment hardlink handling is very expensive, so it's off by
default. It does not need to be so.
Since most of the solutions are rather intertwined with the file
list it is probably better to fix that first, although fixing
hardlinks is possibly simpler.
We can rule out hardlinked directories since they will probably
screw us up in all kinds of ways. They simply should not be used.
At the moment rsync only cares about hardlinks to regular files. I
guess you could also use them for sockets, devices and other beasts,
but I have not seen them.
When trying to reproduce hard links, we only need to worry about
files that have more than one name (nlinks>1 && !S_ISDIR).
The basic point of this is to discover alternate names that refer to
the same file. All operations, including creating the file and
writing modifications to it need only to be done for the first name.
For all later names, we just create the link and then leave it
alone.
If hard links are to be preserved:
Before the generator/receiver fork, the list of files is received
from the sender (recv_file_list), and a table for detecting hard
links is built.
The generator looks for hard links within the file list and does
not send checksums for them, though it does send other metadata.
The sender sends the device number and inode with file entries, so
that files are uniquely identified.
The receiver goes through and creates hard links (do_hard_links)
after all data has been written, but before directory permissions
are set.
At the moment device and inum are sent as 4-byte integers, which
will probably cause problems on large filesystems. On Linux the
kernel uses 64-bit ino_t's internally, and people will soon have
filesystems big enough to use them. We ought to follow NFS4 in
using 64-bit device and inode identification, perhaps with a
protocol version bump.
Once we've seen all the names for a particular file, we no longer
need to think about it and we can deallocate the memory.
We can also have the case where there are links to a file that are
not in the tree being transferred. There's nothing we can do about
that. Because we rename the destination into place after writing,
any hardlinks to the old file are always going to be orphaned. In
fact that is almost necessary because otherwise we'd get really
confused if we were generating checksums for one name of a file and
modifying another.
At the moment the code seems to make a whole second copy of the file
list, which seems unnecessary.
We should have a test case that exercises hard links. Since it
might be hard to compare ./tls output where the inodes change we
might need a little program to check whether several names refer to
the same file.
Handling IPv6 on old machines
The KAME IPv6 patch is nice in theory but has proved a bit of a
nightmare in practice. The basic idea of their patch is that rsync
is rewritten to use the new getaddrinfo()/getnameinfo() interface,
rather than gethostbyname()/gethostbyaddr() as in rsync 2.4.6.
Systems that don't have the new interface are handled by providing
our own implementation in lib/, which is selectively linked in.
The problem with this is that it is really hard to get right on
platforms that have a half-working implementation, so redefining
these functions clashes with system headers, and leaving them out
breaks. This affects at least OSF/1, RedHat 5, and Cobalt, which
are moderately improtant.
Perhaps the simplest solution would be to have two different files
implementing the same interface, and choose either the new or the
old API. This is probably necessary for systems that e.g. have
IPv6, but gethostbyaddr() can't handle it. The Linux manpage claims
this is currently the case.
In fact, our internal sockets interface (things like
open_socket_out(), etc) is much narrower than the getaddrinfo()
interface, and so probably simpler to get right. In addition, the
old code is known to work well on old machines.
We could drop the rather large lib/getaddrinfo files.
Other IPv6 stuff:
Implement suggestions from http://www.kame.net/newsletter/19980604/
and ftp://ftp.iij.ad.jp/pub/RFC/rfc2553.txt
If a host has multiple addresses, then listen try to connect to all
in order until we get through. (getaddrinfo may return multiple
addresses.) This is kind of implemented already.
Possibly also when starting as a server we may need to listen on
multiple passive addresses. This might be a bit harder, because we
may need to select on all of them. Hm.
Define a syntax for IPv6 literal addresses. Since they include
colons, they tend to break most naming systems, including ours.
Based on the HTTP IPv6 syntax, I think we should use
rsync://[::1]/foo/bar [::1]::bar
which should just take a small change to the parser code.
Errors
If we hang or get SIGINT, then explain where we were up to. Perhaps
have a static buffer that contains the current function name, or
some kind of description of what we were trying to do. This is a
little easier on people than needing to run strace/truss.
"The dungeon collapses! You are killed." Rather than "unexpected
eof" give a message that is more detailed if possible and also more
helpful.
If we get an error writing to a socket, then we should perhaps
continue trying to read to see if an error message comes across
explaining why the socket is closed. I'm not sure if this would
work, but it would certainly make our messages more helpful.
What happens if a directory is missing -x attributes. Do we lose
our load? (Debian #28416) Probably fixed now, but a test case would
be good.
File attributes
Device major/minor numbers should be at least 32 bits each. See
http://lists.samba.org/pipermail/rsync/2001-November/005357.html
Transfer ACLs. Need to think of a standard representation.
Probably better not to even try to convert between NT and POSIX.
Possibly can share some code with Samba.
Empty directories
With the current common --include '*/' --exclude '*' pattern, people
can end up with many empty directories. We might avoid this by
lazily creating such directories.
zlib
Perhaps don't use our own zlib.
Advantages:
- will automatically be up to date with bugfixes in zlib
- can leave it out for small rsync on e.g. recovery disks
- can use a shared library
- avoids people breaking rsync by trying to do this themselves and
messing up
Should we ship zlib for systems that don't have it, or require
people to install it separately?
Apparently this will make us incompatible with versions of rsync
that use the patched version of rsync. Probably the simplest way to
do this is to just disable gzip (with a warning) when talking to old
versions.
logging
Perhaps flush stdout after each filename, so that people trying to
monitor progress in a log file can do so more easily. See
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=48108
At the connections that just get a list of modules are not logged,
but they should be.
If a child of the rsync daemon dies with a signal, we should notice
that when we reap it and log a message.
Keep stderr and stdout properly separated (Debian #23626)
After we get the @RSYNCD greeting from the server, we know it's
version but we have not yet sent the command line, so we could just
remove the -z option if the server is too old.
For ssh invocation it's not so simple, because we actually use the
command line to start the remote process. However, we only actually
do compression in token.c, and we could therefore once we discover
the remote version emit an error if it's too old. I'm not sure if
that's a good tradeoff or not.
proxy authentication
Allow RSYNC_PROXY to be http://user:pass@proxy.foo:3128/, and do
HTTP Basic Proxy-Authentication.
Multiple schemes are possible, up to and including the insanity that
is NTLM, but Basic probably covers most cases.
SOCKS
Add --with-socks, and then perhaps a command-line option to put them
on or off. This might be more reliable than LD_PRELOAD hacks.
FAT support
rsync to a FAT partition on a Unix machine doesn't work very well at
the moment. I think we get errors about invalid filenames and
perhaps also trying to do atomic renames.
I guess the code to do this is currently #ifdef'd on Windows;
perhaps we ought to intelligently fall back to it on Unix too.
Better statistics:
<Rasmus> mbp: hey, how about an rsync option that just gives you the
summary without the list of files? And perhaps gives more
information like the number of new files, number of changed,
deleted, etc. ? <mbp> Rasmus: nice idea <mbp> there is --stats
<mbp> but at the moment it's very tridge-oriented <mbp> rather than
user-friendly <mbp> it would be nice to improve it <mbp> that would
also work well with --dryrun
TDB:
Rather than storing the file list in memory, store it in a TDB.
This *might* make memory usage lower while building the file list.
Hashtable lookup will mean files are not transmitted in order,
though... hm.
This would neatly eliminate one of the major post-fork shared data
structures.
chmod:
On 12 Mar 2002, Dave Dykstra <dwd@bell-labs.com> wrote: > If we
would add an option to do that functionality, I would vote for one >
that was more general which could mask off any set of permission bits
and > possibly add any set of bits. Perhaps a chmod-like syntax if it
could be > implemented simply.
I think that would be good too. For example, people uploading files
to a web server might like to say
rsync -avzP --chmod a+rX ./ sourcefrog.net:/home/www/sourcefrog/
Ideally the patch would implement as many of the gnu chmod semantics
as possible. I think the mode parser should be a separate function
that passes back something like (mask,set) description to the rest
of the program. For bonus points there would be a test case for the
parser.
Possibly also --chown
(Debian #23628)
--diff
Allow people to specify the diff command. (Might want to use wdiff,
gnudiff, etc.)
Just diff the temporary file with the destination file, and delete
the tmp file rather than moving it into place.
Interaction with --partial.
Security interactions with daemon mode?
(Suggestion from david.e.sewell)
Incorrect timestamps (Debian #100295)
A bit hard to believe, but apparently it happens.
Check "refuse options works"
We need a test case for this...
Was this broken when we changed to popt?
PERFORMANCE ----------------------------------------------------------
MD4 file_sum
If we're doing a local transfer, or using -W, then perhaps don't
send the file checksum. If we're doing a local transfer, then
calculating MD4 checksums uses 90% of CPU and is unlikely to be
useful.
Indeed for transfers over zlib or ssh we can also rely on the
transport to have quite strong protection against corruption.
Perhaps we should have an option to disable this, analogous to
--whole-file, although it would default to disabled. The file
checksum takes up a definite space in the protocol -- we can either
set it to 0, or perhaps just leave it out.
MD4
Perhaps borrow an assembler MD4 from someone?
Make sure we call MD4 with properly-sized blocks whenever possible
to avoid copying into the residue region?
String area code
Test whether this is actually faster than just using malloc(). If
it's not (anymore), throw it out.
PLATFORMS ------------------------------------------------------------
Win32
Don't detach, because this messes up --srvany.
http://sources.redhat.com/ml/cygwin/2001-08/msg00234.html
DEVELOPMENT ----------------------------------------------------------
Splint
Build rsync with SPLINT to try to find security holes. Add
annotations as necessary. Keep track of the number of warnings
found initially, and see how many of them are real bugs, or real
security bugs. Knowing the percentage of likely hits would be
really interesting for other projects.
Torture test
Something that just keeps running rsync continuously over a data set
likely to generate problems.
Cross-testing
Run current rsync versions against significant past releases.
Memory debugger
jra recommends Valgrind:
http://devel-home.kde.org/~sewardj/
Release script
Update spec files
Build tar file; upload
Send announcement to mailing list and c.o.l.a.
Make freshmeat announcement
Update web site
TESTING --------------------------------------------------------------
Cross-test versions
Part of the regression suite should be making sure that we don't
break backwards compatibility: old clients vs new servers and so on.
Ideally we would test both up and down from the current release to
all old versions.
We might need to omit broken old versions, or versions in which
particular functionality is broken
It might be sufficient to test downloads from well-known public
rsync servers running different versions of rsync. This will give
some testing and also be the most common case for having different
versions and not being able to upgrade.
Test on kernel source
Download all versions of kernel; unpack, sync between them. Also
sync between uncompressed tarballs. Compare directories after
transfer.
Use local mode; ssh; daemon; --whole-file and --no-whole-file.
Use awk to pull out the 'speedup' number for each transfer. Make
sure it is >= x.
Test large files
Sparse and non-sparse
Mutator program
Insert bytes, delete bytes, swap blocks, ...
configure option to enable dangerous tests
If tests are skipped, say why.
Test daemon feature to disallow particular options.
Pipe program that makes slow/jerky connections.
Versions of read() and write() that corrupt the stream, or abruptly
fail
Separate makefile target to run rough tests -- or perhaps just run
them every time?
Test "refuse options" works
What about for --recursive?
If you specify an unrecognized option here, you should get an error.
DOCUMENTATION --------------------------------------------------------
Update README
Keep list of open issues and todos on the web site
Update web site from CVS
Perhaps redo manual as SGML
The man page is getting rather large, and there is more information
that ought to be added.
TexInfo source is probably a dying format.
Linuxdoc looks like the most likely contender. I know DocBook is
favoured by some people, but it's so bloody verbose, even with emacs
support.
BUILD FARM -----------------------------------------------------------
Add machines
Cygwin (on different versions of Win32?)
HP-UX variants (via HP?)
SCO
LOGGING --------------------------------------------------------------
Perhaps flush stdout after each filename, so that people trying to
monitor progress in a log file can do so more easily. See
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=48108
At the connections that just get a list of modules are not logged,
but they should be.
If a child of the rsync daemon dies with a signal, we should notice
that when we reap it and log a message.
Keep stderr and stdout properly separated (Debian #23626)
Use a separate function for reporting errors; prefix it with
"rsync:" or "rsync(remote)", or perhaps even "rsync(local
generator): ".
verbose output
Indicate whether files are new, updated, or deleted
At end of transfer, show how many files were or were not transferred
correctly.
-vv
Explain *why* every file is transferred or not (e.g. "local mtime
123123 newer than 1283198")
debugging of daemon
Add an rsyncd.conf parameter to turn on debugging on the server.
NICE -----------------------------------------------------------------
--no-detach and --no-fork options
Very useful for debugging. Also good when running under a
daemon-monitoring process that tries to restart the service when the
parent exits.
hang/timeout friendliness
internationalization
Change to using gettext(). Probably need to ship this for platforms
that don't have it.
Solicit translations.
Does anyone care? Before we bother modifying the code, we ought to
get the manual translated first, because that's possibly more useful
and at any rate demonstrates desire.
rsyncsh
Write a small emulation of interactive ftp as a Pythonn program
that calls rsync. Commands such as "cd", "ls", "ls *.c" etc map
fairly directly into rsync commands: it just needs to remember the
current host, directory and so on. We can probably even do
completion of remote filenames.
RELATED PROJECTS -----------------------------------------------------
http://rsync.samba.org/rsync-and-debian/
rsyncable gzip patch
Exhaustive, tortuous testing
Cleanups?
rsyncsplit as alternative to real integration with gzip?
reverse rsync over HTTP Range
Goswin Brederlow suggested this on Debian; I think tridge and I
talked about it previous in relation to rproxy.
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