[erlang-questions] 'ssl_otp_session_cache' ets table
Bogdan Andu
bog495@REDACTED
Thu Nov 6 08:53:53 CET 2014
Hi,
on my production servers I have relayd (on OpenBSD) daemon as a reverse
proxy to some webservers
where one can fine tune some connection parameters, as well as some ssl
parameters.
I give a snippet from a relayd.conf configuration file on one of my
production server:
.............
#
# Relay and protocol for HTTP layer 7 loadbalancing and SSL acceleration
#
http protocol www_ssl_prot {
header append "$REMOTE_ADDR" to "X-Forwarded-For"
header append "$SERVER_ADDR:$SERVER_PORT" to "X-Forwarded-By"
header change "Connection" to "close"
response header change "Server" to "Apache 0.1"
# Various TCP performance options
tcp { nodelay, sack, socket buffer 65536, backlog 128 }
ssl { no sslv2, no sslv3, tlsv1, ciphers "HIGH" }
ssl session cache disable
}
the last directive tells relayd not to use ssl cache.
This configuration is working for years and relayd was restarted once by
accident - my fault.
SO, y question is:
can we have this configurable in Erlang, in other words, we might be able
to start an erlang vm such as:
erl -ssl session_cache 'disable' -name x@REDACTED ....
The ssl option session_cache can be set to disabled by default and can take
values either disable or enabled.
Just to let you know...
The statistics of a node running from yesterday when I opened this thread
of discussion, using a single client:
Node: 'n1@REDACTED' (Connected) (17/6.2) unix (openbsd 5.4.0) CPU:2 SMP
+A:10
Time: local time 09:48:48, up for 000:20:27:49, 0ms latency,
Processes: total 681 (RQ 0) at 610275 RpI using 11526.4k (11805.8k
allocated)
Memory: Sys 94835.5k, Atom 407.7k/419.5k, Bin 176.4k, Code 9934.7k, Ets
80739.2k
...........
So, can be this made configurable?
On Wed, Nov 5, 2014 at 8:52 PM, Ingela Andin <ingela.andin@REDACTED> wrote:
> Hi!
>
> 2014-11-05 14:15 GMT+01:00 Tony Rogvall <tony@REDACTED>:
>
>> I think the ssl session times is the problem here, and the lack of a
>> maximum size.
>>
>> You can change the session time in the ssl environment: session_lifetime
>> The default is set to 24 hours (in seconds) (if I read it correctly, in
>> ssl_manager.erl)
>>
>
> Default values are always hard. It is the maximum recommended time for a
> session to live
> according to the spec.
>
>
>> I guess that a session_cache_size could be a nice thing to have,
>> limiting the growth of the session cache.
>>
>>
> Yes I agree.
>
>
>> In other words you have to estimate the life time of your clients and
>> try to find a reasonable session_lifetime to match that, without blowing
>> up
>> the system.
>>
>> Maybe the ssl_session_cache_api could be used to implement a strategy
>> with a max size
>> cache. Retire session least recently used, while performing the update?
>> There is a time_stamp in the session that that could be used for this
>> purpose.
>>
>> OTP: Why is a fixed limit not implemented in the standard
>> ssl_session_cache?
>> Could this be a target for DOS attacks?
>>
>
>
> We are aware of the problem, and it is on our todo list. One reason it has
> not had top priority is that on the server side there are often other
> mechanisms
> like firewalls and webbserver settings that limits the problem. And the
> reason why it was not implemented in the first place is that
> implementations by nature
> are iterative and at first you are faced with a lot of bigger problems to
> solve and then you need to iterate and fine tune and fix things that you
> now have a better understanding of.
>
> In current master there is a change to the session table that limits the
> growth on the client side if the client behaves inappropriate. It also
> splits the session table into
> a server and a client table which is a better implementation as the same
> Erlang node can be both a client and a server at the same time. So if
> someone feels like contributing a max limit please base it on the master
> branch, otherwise I suspect someone compiling about it did raise the
> priority level a little.
>
>
> Regards Ingela Erlang/OTP team - Ericsson AB
>
>
>
>> /Tony
>>
>> > On 5 nov 2014, at 13:08, Bogdan Andu <bog495@REDACTED> wrote:
>> >
>> >
>> >
>> > Hi,
>> >
>> > I performed a series of test regarding the an Erlang SSL server.
>> >
>> > In this setup a major role is played by the table called
>> 'ssl_otp_session_cache', and of course the processes using it.
>> >
>> > The problem is that the size of table increases constantly and, because
>> an ets table does not automatically deallocate memory unless the object are
>> deleted from that table, the size of table remains the same even if there
>> no ssl connections to server.
>> >
>> > For example, with a single client running 'ad infinitum' the table
>> increases at a rate of 5 MBytes/hour. In 12 hours there are allocate around
>> 60 MB of memory only for this table.
>> >
>> > Some info about this:
>> > $ erl -sname console@REDACTED -remsh n1@REDACTED -setcookie operator
>> > Erlang/OTP 17 [erts-6.2] [source] [64-bit] [smp:2:2] [async-threads:10]
>> [kernel-poll:false]
>> >
>> > Eshell V6.2 (abort with ^G)
>> >
>> >
>> > (n1@REDACTED)1> ets:i().
>> > id name type size mem owner
>> >
>> ----------------------------------------------------------------------------
>> > 12 cookies set 0 291 auth
>> > 4111 code set 410 26132 code_server
>> > 8208 code_names set 58 7459 code_server
>> > 12307 httpc_manager__session_cookie_db bag 0 291
>> httpc_manager
>> > 16404 ssl_otp_cacertificate_db set 0 291
>> ssl_manager
>> > 20501 ssl_otp_ca_file_ref set 0 291 ssl_manager
>> > 24598 ssl_otp_pem_cache set 3 360 ssl_manager
>> > 28695 ssl_otp_session_cache ordered_set 138057 8421893
>> ssl_manager
>> > 32797 dets duplicate_bag 2 308 dets
>> > 40990 ign_requests set 0 291
>> inet_gethost_native
>> > 45087 ign_req_index set 0 291
>> inet_gethost_native
>> > 2261635104 shell_records ordered_set 0 81
>> <0.30638.37>
>> > ac_tab ac_tab set 33 2216
>> application_controller
>> > code_map code_map set 100 2791 <0.72.0>
>> > config config set 12 892 <0.72.0>
>> > dets_owners dets_owners set 1 298 dets
>> > dets_registry dets_registry set 1 299 dets
>> > file_io_servers file_io_servers set 1 344 file_server_2
>> > global_locks global_locks set 0 291
>> global_name_server
>> > global_names global_names set 0 291
>> global_name_server
>> > global_names_ext global_names_ext set 0 291
>> global_name_server
>> > global_pid_ids global_pid_ids bag 0 291
>> global_name_server
>> > global_pid_names global_pid_names bag 0 291
>> global_name_server
>> > httpc_manager__handler_db httpc_manager__handler_db set 0 291
>> httpc_manager
>> > httpc_manager__session_db httpc_manager__session_db set 0 291
>> httpc_manager
>> > inet_cache inet_cache bag 0 291 inet_db
>> > inet_db inet_db set 29 600 inet_db
>> > inet_hosts_byaddr inet_hosts_byaddr bag 0 291 inet_db
>> > inet_hosts_byname inet_hosts_byname bag 0 291 inet_db
>> > inet_hosts_file_byaddr inet_hosts_file_byaddr bag 0 291
>> inet_db
>> > inet_hosts_file_byname inet_hosts_file_byname bag 0 291
>> inet_db
>> > models models set 3 28952 <0.72.0>
>> > sys_dist sys_dist set 1 334 net_kernel
>> > ok
>> > (n1@REDACTED)5> ets:info(ssl_otp_session_cache).
>> > undefined
>> > (n1@REDACTED)7> (8421893*8)/1024.
>> > 65796.0390625
>> > (n1@REDACTED)8> memory().
>> > [{total,92699464},
>> > {processes,8964000},
>> > {processes_used,8963152},
>> > {system,83735464},
>> > {atom,429569},
>> > {atom_used,421768},
>> > {binary,199040},
>> > {code,10411520},
>> > {ets,69163032}]
>> >
>> > The memory allocated to table 'ssl_otp_session_cache' is roughly 64 MB
>> in 12 hours.
>> >
>> > On an OpenBSD platform such process gets killed immediately it hits
>> some memory and/or CPU limits.
>> >
>> > To make this test on OpenBSD I had to put 'infinit' to memory,
>> otherwise the Erlang VM would be killed.
>> >
>> > How can one control , tweak or configure this table such that it does
>> not accumulate such data at such high rate.
>> >
>> > I seems the table being created private, and there is no way to
>> ets:delete_all_objects/1 from table manually.
>> >
>> > I know that this table caches some SSL data related to clients, but the
>> client has the same IP address,
>> > and I wonder why is neccesary to store a lot of SSL connection info
>> about the same client when only the ephemeral peer port
>> > differs?
>> >
>> > How the size of this table can be held in reasonable limits and the
>> rate it's size increases ?
>> >
>> > Please if somebody shed some light on these issues.
>> >
>> > Thank you,
>> >
>> > Bogdan
>> >
>> >
>> > _______________________________________________
>> > erlang-questions mailing list
>> > erlang-questions@REDACTED
>> > http://erlang.org/mailman/listinfo/erlang-questions
>>
>> "Installing applications can lead to corruption over time. Applications
>> gradually write over each other's libraries, partial upgrades occur, user
>> and system errors happen, and minute changes may be unnoticeable and
>> difficult to fix"
>>
>>
>>
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>
>
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