[erlang-questions] Erlang accepting SSL connection is really slow (comparing to C++)

Morgan Segalis <>
Tue Apr 10 19:16:54 CEST 2012


Hi Ali,

It is indeed.
Cipher    : DHE-RSA-AES256-SHA

What would be the fastest Cipher, knowing that I don't really care about 128 or 256 encoding.
And How can I change the Cipher on the SSL options ?

Le 10 avr. 2012 à 18:50, Ali Sabil a écrit :

> Hi Morgan,
> 
> Did you check which cipher is being used in your c++ server vs the
> erlang server? DHE ciphers are notably slow.
> 
> You can check which cipher suite is being used with:
>    openssl s_client -host HOST -port PORT
> 
> On Tue, Apr 10, 2012 at 6:19 PM, Morgan Segalis <> wrote:
>> Hi Loïc,
>> 
>> That's what I was afraid of.
>> 
>> Then what would be the best workaround in order to outcome this slowness of Erlang's SSL ?
>> Using a C++ Driver ? would that be even possible to pass a Socket to the driver for it to upgrade it into a SSL one ?
>> 
>> Thanks.
>> 
>> Le 10 avr. 2012 à 17:56, Loïc Hoguin a écrit :
>> 
>>> Hello!
>>> 
>>> On 04/10/2012 05:27 PM, SEGALIS Morgan wrote:
>>> [...]
>>>> While it will take 10 second to a ssl accepting bit of C++ code to accept
>>>> all of them (which don't even have multiple accept pending), in Erlang this
>>>> is quite different. It will accept at most 20 connections a second
>>>> (according to netstat info, whilst C++ accept more like 1K connection per
>>>> seconds)
>>>> 
>>>> While the 10K connections are awaiting for acceptance, I'm manually trying
>>>> to connect as well.
>>>> 
>>>>     openssl s_client -ssl3 -ign_eof -connect myserver.com:4242
>>>> 
>>>> 3 cases happen when I do :
>>>> 
>>>>  - Connection simply timeout
>>>>  - Connection will connect after waiting for it 30 sec. at least
>>>>  - Connection will occur almost directly
>>> 
>>> The OTP SSL code is just very slow, and AFAIK the reason for this is that it's done in full Erlang. Here's a quick and dirty comparison between HTTP and HTTPS in Cowboy, where only the transport used differs:
>>> 
>>> HTTP:
>>> 
>>> % siege -b -c 100 http://localhost:8080/
>>> ** SIEGE 2.70
>>> ** Preparing 100 concurrent users for battle.
>>> The server is now under siege...^C
>>> Lifting the server siege...      done.
>>> Transactions:                49266 hits
>>> Availability:               100.00 %
>>> Elapsed time:                 5.94 secs
>>> Data transferred:             0.56 MB
>>> Response time:                        0.01 secs
>>> Transaction rate:          8293.94 trans/sec
>>> Throughput:                   0.09 MB/sec
>>> Concurrency:                 99.36
>>> Successful transactions:       49266
>>> Failed transactions:             0
>>> Longest transaction:          0.06
>>> Shortest transaction:         0.00
>>> 
>>> HTTPS:
>>> 
>>> % siege -b -c 100 https://localhost:8443/
>>> ** SIEGE 2.70
>>> ** Preparing 100 concurrent users for battle.
>>> The server is now under siege...^C
>>> Lifting the server siege...      done.
>>> Transactions:                  698 hits
>>> Availability:               100.00 %
>>> Elapsed time:                 4.50 secs
>>> Data transferred:             0.01 MB
>>> Response time:                        0.59 secs
>>> Transaction rate:           155.11 trans/sec
>>> Throughput:                   0.00 MB/sec
>>> Concurrency:                 92.15
>>> Successful transactions:         698
>>> Failed transactions:             0
>>> Longest transaction:          1.14
>>> Shortest transaction:         0.07
>>> 
>>> This is on a Zenbook UX31E which is a damn good machine but it still shows a huge difference between both of them. And the more you try to accept at the same time, the longest time it can take to accept.
>>> 
>>> --
>>> Loïc Hoguin
>>> Erlang Cowboy
>>> Nine Nines
>> 
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>> 
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