<div dir="ltr">Hi!<br><div class="gmail_extra"><br><div class="gmail_quote">2014-11-05 14:15 GMT+01:00 Tony Rogvall <span dir="ltr"><<a href="mailto:tony@rogvall.se" target="_blank">tony@rogvall.se</a>></span>:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">I think the ssl session times is the problem here, and the lack of a maximum size.<br>
<br>
You can change the session time in the ssl environment: session_lifetime<br>
The default is set to 24 hours (in seconds) (if I read it correctly, in ssl_manager.erl)<br></blockquote><div><br></div><div>Default values are always hard. It is the maximum recommended time for a session to live</div><div>according to the spec.</div><div><br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<br>
I guess that a session_cache_size could be a nice thing to have,<br>
limiting the growth of the session cache.<br>
<br></blockquote><div><br></div><div>Yes I agree.</div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
In other words you have to estimate the life time of your clients and<br>
try to find a reasonable session_lifetime to match that, without blowing up<br>
the system.<br>
<br>
Maybe the ssl_session_cache_api could be used to implement a strategy with a max size<br>
cache. Retire session least recently used, while performing the update?<br>
There is a time_stamp in the session that that could be used for this purpose.<br>
<br>
OTP: Why is a fixed limit not implemented in the standard ssl_session_cache?<br>
Could this be a target for DOS attacks?<br></blockquote><div><br></div><div><br></div><div>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</div><div>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</div><div>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. </div><div><br></div><div>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 </div><div>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. </div><div><br></div><div><br></div><div>Regards Ingela Erlang/OTP team - Ericsson AB</div><div> </div><div><br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<br>
/Tony<br>
<div><div><br>
> On 5 nov 2014, at 13:08, Bogdan Andu <<a href="mailto:bog495@gmail.com" target="_blank">bog495@gmail.com</a>> wrote:<br>
><br>
><br>
><br>
> Hi,<br>
><br>
> I performed a series of test regarding the an Erlang SSL server.<br>
><br>
> In this setup a major role is played by the table called 'ssl_otp_session_cache', and of course the processes using it.<br>
><br>
> 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.<br>
><br>
> 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.<br>
><br>
> Some info about this:<br>
> $ erl -sname console@www-apps -remsh n1@www-apps -setcookie operator<br>
> Erlang/OTP 17 [erts-6.2] [source] [64-bit] [smp:2:2] [async-threads:10] [kernel-poll:false]<br>
><br>
> Eshell V6.2 (abort with ^G)<br>
><br>
><br>
> (n1@www-apps)1> ets:i().<br>
> id name type size mem owner<br>
> ----------------------------------------------------------------------------<br>
> 12 cookies set 0 291 auth<br>
> 4111 code set 410 26132 code_server<br>
> 8208 code_names set 58 7459 code_server<br>
> 12307 httpc_manager__session_cookie_db bag 0 291 httpc_manager<br>
> 16404 ssl_otp_cacertificate_db set 0 291 ssl_manager<br>
> 20501 ssl_otp_ca_file_ref set 0 291 ssl_manager<br>
> 24598 ssl_otp_pem_cache set 3 360 ssl_manager<br>
> 28695 ssl_otp_session_cache ordered_set 138057 8421893 ssl_manager<br>
> 32797 dets duplicate_bag 2 308 dets<br>
> 40990 ign_requests set 0 291 inet_gethost_native<br>
> 45087 ign_req_index set 0 291 inet_gethost_native<br>
> 2261635104 shell_records ordered_set 0 81 <0.30638.37><br>
> ac_tab ac_tab set 33 2216 application_controller<br>
> code_map code_map set 100 2791 <0.72.0><br>
> config config set 12 892 <0.72.0><br>
> dets_owners dets_owners set 1 298 dets<br>
> dets_registry dets_registry set 1 299 dets<br>
> file_io_servers file_io_servers set 1 344 file_server_2<br>
> global_locks global_locks set 0 291 global_name_server<br>
> global_names global_names set 0 291 global_name_server<br>
> global_names_ext global_names_ext set 0 291 global_name_server<br>
> global_pid_ids global_pid_ids bag 0 291 global_name_server<br>
> global_pid_names global_pid_names bag 0 291 global_name_server<br>
> httpc_manager__handler_db httpc_manager__handler_db set 0 291 httpc_manager<br>
> httpc_manager__session_db httpc_manager__session_db set 0 291 httpc_manager<br>
> inet_cache inet_cache bag 0 291 inet_db<br>
> inet_db inet_db set 29 600 inet_db<br>
> inet_hosts_byaddr inet_hosts_byaddr bag 0 291 inet_db<br>
> inet_hosts_byname inet_hosts_byname bag 0 291 inet_db<br>
> inet_hosts_file_byaddr inet_hosts_file_byaddr bag 0 291 inet_db<br>
> inet_hosts_file_byname inet_hosts_file_byname bag 0 291 inet_db<br>
> models models set 3 28952 <0.72.0><br>
> sys_dist sys_dist set 1 334 net_kernel<br>
> ok<br>
> (n1@www-apps)5> ets:info(ssl_otp_session_cache).<br>
> undefined<br>
> (n1@www-apps)7> (8421893*8)/1024.<br>
> 65796.0390625<br>
> (n1@www-apps)8> memory().<br>
> [{total,92699464},<br>
> {processes,8964000},<br>
> {processes_used,8963152},<br>
> {system,83735464},<br>
> {atom,429569},<br>
> {atom_used,421768},<br>
> {binary,199040},<br>
> {code,10411520},<br>
> {ets,69163032}]<br>
><br>
> The memory allocated to table 'ssl_otp_session_cache' is roughly 64 MB in 12 hours.<br>
><br>
> On an OpenBSD platform such process gets killed immediately it hits some memory and/or CPU limits.<br>
><br>
> To make this test on OpenBSD I had to put 'infinit' to memory, otherwise the Erlang VM would be killed.<br>
><br>
> How can one control , tweak or configure this table such that it does not accumulate such data at such high rate.<br>
><br>
> I seems the table being created private, and there is no way to ets:delete_all_objects/1 from table manually.<br>
><br>
> I know that this table caches some SSL data related to clients, but the client has the same IP address,<br>
> and I wonder why is neccesary to store a lot of SSL connection info about the same client when only the ephemeral peer port<br>
> differs?<br>
><br>
> How the size of this table can be held in reasonable limits and the rate it's size increases ?<br>
><br>
> Please if somebody shed some light on these issues.<br>
><br>
> Thank you,<br>
><br>
> Bogdan<br>
><br>
><br>
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