Requests are not concurrent with SPDY and proxy_cache modules

[vgallissot]

Hi all, 

I'm experiencing a strange behaviour on my SPDY tests. 

I use nginx as a reverse proxy of a node.Js application. 

I enabled spdy module and proxy_cache (nginx.conf file bellow) and I
actually see no difference in requests speed. Requests are well handed by
SPDY protocol (one TCP connection and multiple streams catched with
tcpdump), but they should be concurrent and they actually are sequentials
like without SPDY support. 

Here are two screenshots of the waterfalls to see the behaviour
1) With proxy_cache support and SPDY not enabled : 
https://lut.im/9QKXlT5T/LVFNWqxN

2) With proxy_cache support and SPDY enabled : 
https://lut.im/DmJ2wqFp/43ZOyhTE

Here is the configuration file I use to test on my laptop : 
8------------------------------------------------------------------------------------------------------------------------------------>
...
    ####### tests SPDY
    keepalive_requests 1000;
    keepalive_timeout 10;

    client_body_timeout 10;
    client_header_timeout 10;
    types_hash_max_size 2048;

    server_tokens off;

    server_names_hash_bucket_size 128;
    server_name_in_redirect off;

    proxy_http_version 1.1;

    fastcgi_buffers 256 4k;

    gzip_static on;
    gzip_disable "MSIE [1-6]\.(?!.*SV1)";
    gzip_vary on;
    gzip_http_version 1.1;

    ssl_session_timeout 5m;
    ssl_session_cache shared:SSL:20m;
    ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
    ssl_ciphers
'ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:DHE-DSS-AES128-GCM-SHA256:kEDH+AESGCM:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA:ECDHE-ECDSA-AES128-SHA:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA:ECDHE-ECDSA-AES256-SHA:DHE-RSA-AES128-SHA256:DHE-RSA-AES128-SHA:DHE-DSS-AES128-SHA256:DHE-RSA-AES256-SHA256:DHE-DSS-AES256-SHA:DHE-RSA-AES256-SHA:AES128-GCM-SHA256:AES256-GCM-SHA384:AES128:AES256:AES:DES-CBC3-SHA:HIGH:!aNULL:!eNULL:!EXPORT:!DES:!RC4:!MD5:!PSK';
    ssl_prefer_server_ciphers   on;
    ssl_ecdh_curve secp384r1;
    ssl_dhparam /etc/nginx/ssl/dhparam.pem;

    upstream node_servers {
        keepalive 64;
        server node-server1;
        server node-server2;
    }

    # cache options
    proxy_buffering           on;
    proxy_cache_path /etc/nginx/cache/ levels=1:1:2 keys_zone=nodes:256m
inactive=2048m max_size=4096m;
    proxy_ignore_client_abort off;
    proxy_intercept_errors    on;
    proxy_ignore_headers X-Accel-Expires Expires Cache-Control;

    proxy_cache_methods       GET;
    spdy_keepalive_timeout 10s; # inactivity timeout after which the SPDY
connection is closed
    spdy_recv_timeout        4s; # timeout if nginx is currently expecting
data from the client but nothing arrives
    server {
        listen 127.0.0.1:443 ssl spdy;
        listen [::1]:443 ssl spdy;

        server_name beta.mydomain.com;

        ssl_certificate     /etc/nginx/ssl/cert.pem;
        ssl_certificate_key /etc/nginx/ssl/key.pem;
        
        add_header  Alternate-Protocol "443:npn-spdy/3.1";
        location / {
            proxy_set_header Host $http_host;
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
            proxy_set_header X-Forwarded-Proto $scheme;
            proxy_redirect off;
            proxy_pass http://node_servers;
            proxy_cache nodes;
            proxy_cache_valid any 1h;
            proxy_cache_min_uses 10;
            add_header X-Nginx-Cached $upstream_cache_status;
        }
    }
...
<------------------------------------------------------------------------------------------------------------------------------------8

More infos : nginx-1.8.0-4.fc22.x86_64

So my question is : can those two modules work together or am I missing
something in the conf ?

Thank you

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,259906,259906#msg-259906