* Re: Random crash when sending USR2 + QUIT signals to Unicorn process
2017-07-13 19:34 0% ` Eric Wong
@ 2017-07-14 10:21 0% ` Pere Joan Martorell
0 siblings, 0 replies; 6+ results
From: Pere Joan Martorell @ 2017-07-14 10:21 UTC (permalink / raw)
To: Eric Wong; +Cc: unicorn-public, Philip Cunningham, Jonathan del Strother
2017-07-13 21:34 GMT+02:00 Eric Wong <e@80x24.org>:
> +Cc: Philip and Jonathan since they encountered this three years
> ago, but we never heard back from them:
>
> https://bogomips.org/unicorn-public/?q=T_NODE+d:..20170713
>
>
> Pere Joan Martorell <pere.joan@camaloon.com> wrote:
>> > /home/deployer/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/unicorn-5.3.0/lib/unicorn/http_request.rb:80:in `parse': method `hash' called on unexpected T_NODE object (0x0055b15b973508 flags=0xaa31b) (NotImplementedError)
>
>> Any idea what is happening?
>
> This is most likely a bug in a C extension not using write
> barriers correctly (perhaps via undocumented C-API functions in
> Ruby).
>
> I don't think I've seen this on ruby-core bug reports in a few years:
>
> https://public-inbox.org/ruby-core/?q=T_NODE
>
> Fwiw, Appendix D on Generational GC in the Ruby source is
> worth reading to any C extension authors:
>
> https://80x24.org/mirrors/ruby.git/plain/doc/extension.rdoc
>
> There are probably build warnings when using some dangerous methods/macros,
> maybe you can check build logs for const warnings.
>
>
> Can you share the list of RubyGems you have loaded and maybe try
> upgrading/replacing/eliminating the ones with C extensions
> one-by-one until the error stops?
Thank you very much for your fast reply. I'm not using Bundler to
manage my dependencies, but I checked it and there's not any conflict
between gem versions.
Seems that I solved the issue removing some of the gems. This was my gem list:
cuba -v 3.8.0
slim -v 3.0.8
cutest -v 1.2.3
rack-test -v 0.6.3
sequel -v 4.46.0
pg -v 0.20.0
shotgun -v 0.9.2
shield -v 2.1.1
sequel_pg -v 1.6.19
unicorn -v 5.3.0
capistrano-rbenv -v 2.1.1
And I finally removed these gems:
cutest -v 1.2.3
rack-test -v 0.6.3
shotgun -v 0.9.2
sequel_pg -v 1.6.19
I suspect that the conflicting gem was 'sequel_pg' (sequel_pg
overwrites the inner loop of the Sequel postgres adapter row fetching
code with a C version. The C version is significantly faster than the
pure ruby version that Sequel uses by default), but given I didn't
remove these gems one by one I can't completely ensure that.
If the problem reemerges I'll keep you informed.
Thanks!! :)
>
> Also, perhaps the output of "pmap $PID_OF_WORKER" if you're on
> Linux (or equivalent command if you're on another OS).
>
> Anyways, I didn't notice anything suspicious in your config.
>
> I'll do another self-audit of the unicorn + kgio + raindrops
> extensions, too, but judging from the lack of reports and how
> much they get used; I suspect the bug is elsewhere (more eyes
> welcome, of course).
>
> Thanks for the report and any more info you can provide!
^ permalink raw reply [relevance 0%]
* Re: Random crash when sending USR2 + QUIT signals to Unicorn process
2017-07-13 18:48 0% Random crash when sending USR2 + QUIT signals to Unicorn process Pere Joan Martorell
@ 2017-07-13 19:34 0% ` Eric Wong
2017-07-14 10:21 0% ` Pere Joan Martorell
0 siblings, 1 reply; 6+ results
From: Eric Wong @ 2017-07-13 19:34 UTC (permalink / raw)
To: Pere Joan Martorell
Cc: unicorn-public, Philip Cunningham, Jonathan del Strother
+Cc: Philip and Jonathan since they encountered this three years
ago, but we never heard back from them:
https://bogomips.org/unicorn-public/?q=T_NODE+d:..20170713
Pere Joan Martorell <pere.joan@camaloon.com> wrote:
> > /home/deployer/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/unicorn-5.3.0/lib/unicorn/http_request.rb:80:in `parse': method `hash' called on unexpected T_NODE object (0x0055b15b973508 flags=0xaa31b) (NotImplementedError)
> Any idea what is happening?
This is most likely a bug in a C extension not using write
barriers correctly (perhaps via undocumented C-API functions in
Ruby).
I don't think I've seen this on ruby-core bug reports in a few years:
https://public-inbox.org/ruby-core/?q=T_NODE
Fwiw, Appendix D on Generational GC in the Ruby source is
worth reading to any C extension authors:
https://80x24.org/mirrors/ruby.git/plain/doc/extension.rdoc
There are probably build warnings when using some dangerous methods/macros,
maybe you can check build logs for const warnings.
Can you share the list of RubyGems you have loaded and maybe try
upgrading/replacing/eliminating the ones with C extensions
one-by-one until the error stops?
Also, perhaps the output of "pmap $PID_OF_WORKER" if you're on
Linux (or equivalent command if you're on another OS).
Anyways, I didn't notice anything suspicious in your config.
I'll do another self-audit of the unicorn + kgio + raindrops
extensions, too, but judging from the lack of reports and how
much they get used; I suspect the bug is elsewhere (more eyes
welcome, of course).
Thanks for the report and any more info you can provide!
^ permalink raw reply [relevance 0%]
* Random crash when sending USR2 + QUIT signals to Unicorn process
@ 2017-07-13 18:48 0% Pere Joan Martorell
2017-07-13 19:34 0% ` Eric Wong
0 siblings, 1 reply; 6+ results
From: Pere Joan Martorell @ 2017-07-13 18:48 UTC (permalink / raw)
To: unicorn-public
Hi, I'm experimenting with a Rack application and Unicorn and I have a
random error occurring when upgrading my app. When upgrading (sending
a USR2 + QUIT signals), 10% of the times unicorn master process and
its 2 worker processes start and after serving the first request they
crash.
This the stderror.log:
> 91.126.37.106 - - [13/Jul/2017:18:21:09 +0000] "GET /login HTTP/1.0" 200 1571 0.0473
> I, [2017-07-13T18:21:14.351677 #21426] INFO -- : executing ["/home/deployer/.rbenv/versions/2.4.1/bin/unicorn", "-c", "/home/deployer/apps/suppliers/current/config/unicorn.rb", "-E", "deployment", "-D", {12=>#<Kgio::UNIXServer:fd 12>}] (in /home/deployer/apps/suppliers/releases/20170713180855)
> I, [2017-07-13T18:21:14.351881 #21426] INFO -- : forked child re-executing...
> I, [2017-07-13T18:21:14.441075 #21426] INFO -- : inherited addr=/home/deployer/apps/suppliers/current/tmp/sockets/unicorn.socket fd=12
> I, [2017-07-13T18:21:14.441414 #21426] INFO -- : Refreshing Gem list
> I, [2017-07-13T18:21:14.576843 #21426] INFO -- : worker=0 spawning...
> I, [2017-07-13T18:21:14.577589 #21426] INFO -- : worker=1 spawning...
> I, [2017-07-13T18:21:14.578117 #21426] INFO -- : master process ready
> I, [2017-07-13T18:21:14.578866 #21430] INFO -- : worker=0 spawned pid=21430
> I, [2017-07-13T18:21:14.579053 #21430] INFO -- : worker=0 ready
> I, [2017-07-13T18:21:14.579649 #21432] INFO -- : worker=1 spawned pid=21432
> I, [2017-07-13T18:21:14.579790 #21432] INFO -- : worker=1 ready
> I, [2017-07-13T18:21:16.449066 #21369] INFO -- : reaped #<Process::Status: pid 21373 exit 0> worker=0
> I, [2017-07-13T18:21:16.449174 #21369] INFO -- : reaped #<Process::Status: pid 21375 exit 0> worker=1
> I, [2017-07-13T18:21:16.449207 #21369] INFO -- : master complete
> /home/deployer/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/unicorn-5.3.0/lib/unicorn/http_request.rb:80:in `parse': method `hash' called on unexpected T_NODE object (0x0055b15b973508 flags=0xaa31b) (NotImplementedError)
> from /home/deployer/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/unicorn-5.3.0/lib/unicorn/http_request.rb:80:in `read'
> from /home/deployer/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/unicorn-5.3.0/lib/unicorn/http_server.rb:606:in `process_client'
> from /home/deployer/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/unicorn-5.3.0/lib/unicorn/http_server.rb:702:in `worker_loop'
> from /home/deployer/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/unicorn-5.3.0/lib/unicorn/http_server.rb:549:in `spawn_missing_workers'
> from /home/deployer/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/unicorn-5.3.0/lib/unicorn/http_server.rb:142:in `start'
> from /home/deployer/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/unicorn-5.3.0/bin/unicorn:126:in `<top (required)>'
> from /home/deployer/.rbenv/versions/2.4.1/bin/unicorn:22:in `load'
> from /home/deployer/.rbenv/versions/2.4.1/bin/unicorn:22:in `<main>'
> /home/deployer/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/unicorn-5.3.0/lib/unicorn/http_request.rb:80:in `parse': method `hash' called on unexpected T_NODE object (0x0055b15b973508 flags=0xaa31b) (NotImplementedError)
> from /home/deployer/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/unicorn-5.3.0/lib/unicorn/http_request.rb:80:in `read'
> from /home/deployer/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/unicorn-5.3.0/lib/unicorn/http_server.rb:606:in `process_client'
> from /home/deployer/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/unicorn-5.3.0/lib/unicorn/http_server.rb:702:in `worker_loop'
> from /home/deployer/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/unicorn-5.3.0/lib/unicorn/http_server.rb:549:in `spawn_missing_workers'
> from /home/deployer/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/unicorn-5.3.0/lib/unicorn/http_server.rb:142:in `start'
> from /home/deployer/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/unicorn-5.3.0/bin/unicorn:126:in `<top (required)>'
> from /home/deployer/.rbenv/versions/2.4.1/bin/unicorn:22:in `load'
> from /home/deployer/.rbenv/versions/2.4.1/bin/unicorn:22:in `<main>'
> E, [2017-07-13T18:21:29.147001 #21426] ERROR -- : reaped #<Process::Status: pid 21432 exit 1> worker=1
> I, [2017-07-13T18:21:29.147127 #21426] INFO -- : worker=1 spawning...
> I, [2017-07-13T18:21:29.150907 #21439] INFO -- : worker=1 spawned pid=21439
> I, [2017-07-13T18:21:29.151109 #21439] INFO -- : worker=1 ready
> E, [2017-07-13T18:21:29.153360 #21426] ERROR -- : reaped #<Process::Status: pid 21430 exit 1> worker=0
> I, [2017-07-13T18:21:29.153424 #21426] INFO -- : worker=0 spawning...
> I, [2017-07-13T18:21:29.154226 #21442] INFO -- : worker=0 spawned pid=21442
> I, [2017-07-13T18:21:29.154383 #21442] INFO -- : worker=0 ready
This is the configuration of unicorn:
> DEPLOY_TO = "/home/deployer/apps/suppliers" # The path in which capistrano caches deployed versions of the source
> CURRENT = "#{DEPLOY_TO}/current" # The current, deployed release
> UNICORN_PID = "#{CURRENT}/tmp/pids/unicorn.pid" # Unicorn server process id file
> UNICORN_STDOUT = "#{CURRENT}/log/unicorn.stdout.log" # Log file for messages on standard output
> UNICORN_STDERR = "#{CURRENT}/log/unicorn.stderr.log" # Log file for messages on standard error
> UNICORN_SOCKET = "#{CURRENT}/tmp/sockets/unicorn.socket" # Server socket
>
> # Set unicorn options
> working_directory CURRENT
> worker_processes 2
> preload_app true
> timeout 30
>
> # Set up socket location
> listen UNICORN_SOCKET, :backlog => 64
>
> # Logging
> stderr_path UNICORN_STDERR
> stdout_path UNICORN_STDOUT
>
> # Set master PID location
> pid UNICORN_PID
Any idea what is happening?
Thanks!
^ permalink raw reply [relevance 0%]
* Re: [ANN] unicorn 5.3.0 - Rack HTTP server for fast clients and Unix
2017-04-01 8:08 10% [ANN] unicorn 5.3.0 " Eric Wong
@ 2017-04-02 2:14 14% ` Eric Wong
0 siblings, 0 replies; 6+ results
From: Eric Wong @ 2017-04-02 2:14 UTC (permalink / raw)
To: ruby-talk, unicorn-public
Cc: Jeremy Evans, Simon Eskildsen, Dylan Thacker-Smith
Eric Wong <e@80x24.org> wrote:
> Anyways, this is a largish release with several new features,
> and no backwards incompatibilities.
Oops :x Just released Rainbows! 5.1.1 to fix one incompatibility
introduced with unicorn 5.3.0 :x
https://bogomips.org/rainbows-public/20170402021109.GA29200@dcvr/
Anyways, I no longer promote Rainbows! and there's almost no
users, so I hope the impact is small.
^ permalink raw reply [relevance 14%]
* [ANN] unicorn 5.3.0 - Rack HTTP server for fast clients and Unix
@ 2017-04-01 8:08 10% Eric Wong
2017-04-02 2:14 14% ` Eric Wong
0 siblings, 1 reply; 6+ results
From: Eric Wong @ 2017-04-01 8:08 UTC (permalink / raw)
To: ruby-talk, unicorn-public
Cc: Jeremy Evans, Simon Eskildsen, Dylan Thacker-Smith
unicorn is an HTTP server for Rack applications designed to only serve
fast clients on low-latency, high-bandwidth connections and take
advantage of features in Unix/Unix-like kernels. Slow clients should
only be served by placing a reverse proxy capable of fully buffering
both the the request and response in between unicorn and slow clients.
* https://bogomips.org/unicorn/
* public list: unicorn-public@bogomips.org
* mail archives: https://bogomips.org/unicorn-public/
* git clone git://bogomips.org/unicorn.git
* https://bogomips.org/unicorn/NEWS.atom.xml
* nntp://news.public-inbox.org/inbox.comp.lang.ruby.unicorn
Changes:
unicorn 5.3.0
A couple of portability fixes from Dylan Thacker-Smith and
Jeremy Evans since 5.3.0.pre1 over a week ago, but this looks
ready for a stable release, today.
When I started this over 8 years ago, I wondered if this would
just end up being an April Fools' joke. Guess not. I guess I
somehow tricked people into using a terribly marketed web server
that cannot talk directly to untrusted clients :x Anyways,
unicorn won't be able to handle slow clients 8 years from now,
either, or 80 years from now. And I vow never to learn to use
new-fangled things like epoll, kqueue, or threads :P
Anyways, this is a largish release with several new features,
and no backwards incompatibilities.
Simon Eskildsen contributed heavily using TCP_INFO under Linux
to implement the (now 5 year old) check_client_connection feature:
https://bogomips.org/unicorn/Unicorn/Configurator.html#method-i-check_client_connection
https://bogomips.org/unicorn-public/?q=s:check_client_connection&d:..20170401&x=t
This also led to FreeBSD and OpenBSD portability improvements in
one of our dependencies, raindrops:
https://bogomips.org/raindrops-public/20170323024829.GA5190@dcvr/T/#u
Jeremy Evans contributed several new features. First he
implemented after_worker_exit to aid debugging:
https://bogomips.org/unicorn/Unicorn/Configurator.html#method-i-after_worker_exit
https://bogomips.org/unicorn-public/?q=s:after_worker_exit&d:..20170401&x=t#t
And then security-related features to isolate workers. Workers
may now chroot to drop access to the master filesystem, and the
new after_worker_ready configuration hook now exists to aid with
chroot support in workers:
https://bogomips.org/unicorn/Unicorn/Configurator.html#method-i-after_worker_ready
https://bogomips.org/unicorn/Unicorn/Worker.html#method-i-user
https://bogomips.org/unicorn-public/?q=s:after_worker_ready&d:..20170401&x=t#t
https://bogomips.org/unicorn-public/?q=s:chroot&d:..20170401&x=t#t
Additionally, workers may run in a completely different VM space
(nullifying preload_app and any CoW savings) with the new
worker_exec option:
https://bogomips.org/unicorn/Unicorn/Configurator.html#method-i-worker_exec
https://bogomips.org/unicorn-public/?q=s:worker_exec&d:..20170401&x=t#t
There are also several improvements to FreeBSD and OpenBSD
support with the addition of these features.
shortlog of changes since v5.2.0 (2016-10-31):
Dylan Thacker-Smith (1):
Check for Socket::TCP_INFO constant before trying to get TCP_INFO
Eric Wong (30):
drop rb_str_set_len compatibility replacement
TUNING: document THP caveat for Linux users
tee_input: simplify condition for IO#write
remove response_start_sent
http_request: freeze constant strings passed IO#write
Revert "remove response_start_sent"
t/t0012-reload-empty-config.sh: access ivars directly if needed
t0011-active-unix-socket.sh: fix race condition in test
new test for check_client_connection
revert signature change to HttpServer#process_client
support "struct tcp_info" on non-Linux and Ruby 2.2+
unicorn_http: reduce rb_global_variable calls
oob_gc: rely on opt_aref_with optimization on Ruby 2.2+
http_request: reduce insn size for check_client_connection
freebsd: avoid EINVAL when setting accept filter
test-lib: expr(1) portability fix
tests: keep disabled tests defined
test_exec: SO_KEEPALIVE value only needs to be true
doc: fix links to raindrops project
http_request: support proposed Raindrops::TCP states on non-Linux
ISSUES: expand on mail archive info + subscription disclaimer
test_ccc: use a pipe to synchronize test
doc: remove private email support address
input: update documentation and hide internals.
http_server: initialize @pid ivar
gemspec: remove olddoc from build dependency
doc: add version annotations for new features
unicorn 5.3.0.pre1
doc: note after_worker_exit is also 5.3.0+
test_exec: SO_KEEPALIVE value only needs to be true (take #2)
Jeremy Evans (7):
Add after_worker_exit configuration option
Fix code example in after_worker_exit documentation
Add support for chroot to Worker#user
Add after_worker_ready configuration option
Add worker_exec configuration option
Don't pass a block for fork when forking workers
Check for SocketError on first ccc attempt
Simon Eskildsen (1):
check_client_connection: use tcp state on linux
--
Yes, this release is real despite the date.
^ permalink raw reply [relevance 10%]
* [ANN] unicorn 5.3.0.pre1 - Rack HTTP server for fast clients and Unix
@ 2017-03-24 0:28 10% Eric Wong
0 siblings, 0 replies; 6+ results
From: Eric Wong @ 2017-03-24 0:28 UTC (permalink / raw)
To: ruby-talk, unicorn-public; +Cc: Jeremy Evans, Simon Eskildsen
unicorn is an HTTP server for Rack applications designed to only serve
fast clients on low-latency, high-bandwidth connections and take
advantage of features in Unix/Unix-like kernels. Slow clients should
only be served by placing a reverse proxy capable of fully buffering
both the the request and response in between unicorn and slow clients.
* https://bogomips.org/unicorn/
* public list: unicorn-public@bogomips.org
* mail archives: https://bogomips.org/unicorn-public/
* git clone git://bogomips.org/unicorn.git
* https://bogomips.org/unicorn/NEWS.atom.xml
* nntp://news.public-inbox.org/inbox.comp.lang.ruby.unicorn
This is a pre-release RubyGem intended for testing.
Changes:
unicorn 5.3.0.pre1
A largish release with several new features.
Simon Eskildsen contributed heavily using TCP_INFO under Linux
to implement the (now 5 year old) check_client_connection feature:
https://bogomips.org/unicorn/Unicorn/Configurator.html#method-i-check_client_connection
https://bogomips.org/unicorn-public/?q=s:check_client_connection&d:..20170324&x=t
This also led to FreeBSD and OpenBSD portability improvements in
one of our dependencies, raindrops:
https://bogomips.org/raindrops-public/20170323024829.GA5190@dcvr/T/#u
Jeremy Evans contributed several new features. First he
implemented after_worker_exit to aid debugging:
https://bogomips.org/unicorn/Unicorn/Configurator.html#method-i-after_worker_exit
https://bogomips.org/unicorn-public/?q=s:after_worker_exit&d:..20170324&x=t#t
And then security-related features to isolate workers. Workers
may now chroot to drop access to the master filesystem, and the
new after_worker_ready configuration hook now exists to aid with
chroot support in workers:
https://bogomips.org/unicorn/Unicorn/Configurator.html#method-i-after_worker_ready
https://bogomips.org/unicorn/Unicorn/Worker.html#method-i-user
https://bogomips.org/unicorn-public/?q=s:after_worker_ready&d:..20170324&x=t#t
https://bogomips.org/unicorn-public/?q=s:chroot&d:..20170324&x=t#t
Additionally, workers may run in a completely different VM space
(nullifying preload_app and any CoW savings) with the new
worker_exec option:
https://bogomips.org/unicorn/Unicorn/Configurator.html#method-i-worker_exec
https://bogomips.org/unicorn-public/?q=s:worker_exec&d:..20170324&x=t#t
There are also several improvements to FreeBSD and OpenBSD
support with the addition of these features.
34 changes since 5.2.0 (2016-10-31):
Eric Wong (27):
drop rb_str_set_len compatibility replacement
TUNING: document THP caveat for Linux users
tee_input: simplify condition for IO#write
remove response_start_sent
http_request: freeze constant strings passed IO#write
Revert "remove response_start_sent"
t/t0012-reload-empty-config.sh: access ivars directly if needed
t0011-active-unix-socket.sh: fix race condition in test
new test for check_client_connection
revert signature change to HttpServer#process_client
support "struct tcp_info" on non-Linux and Ruby 2.2+
unicorn_http: reduce rb_global_variable calls
oob_gc: rely on opt_aref_with optimization on Ruby 2.2+
http_request: reduce insn size for check_client_connection
freebsd: avoid EINVAL when setting accept filter
test-lib: expr(1) portability fix
tests: keep disabled tests defined
test_exec: SO_KEEPALIVE value only needs to be true
doc: fix links to raindrops project
http_request: support proposed Raindrops::TCP states on non-Linux
ISSUES: expand on mail archive info + subscription disclaimer
test_ccc: use a pipe to synchronize test
doc: remove private email support address
input: update documentation and hide internals.
http_server: initialize @pid ivar
gemspec: remove olddoc from build dependency
doc: add version annotations for new features
Jeremy Evans (6):
Add after_worker_exit configuration option
Fix code example in after_worker_exit documentation
Add support for chroot to Worker#user
Add after_worker_ready configuration option
Add worker_exec configuration option
Don't pass a block for fork when forking workers
Simon Eskildsen (1):
check_client_connection: use tcp state on linux
--
5.3.0 in a week, maybe?
^ permalink raw reply [relevance 10%]
Results 1-6 of 6 | reverse | options above
-- pct% links below jump to the message on this page, permalinks otherwise --
2017-03-24 0:28 10% [ANN] unicorn 5.3.0.pre1 - Rack HTTP server for fast clients and Unix Eric Wong
2017-04-01 8:08 10% [ANN] unicorn 5.3.0 " Eric Wong
2017-04-02 2:14 14% ` Eric Wong
2017-07-13 18:48 0% Random crash when sending USR2 + QUIT signals to Unicorn process Pere Joan Martorell
2017-07-13 19:34 0% ` Eric Wong
2017-07-14 10:21 0% ` Pere Joan Martorell
Code repositories for project(s) associated with this public inbox
https://yhbt.net/unicorn.git/
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).