{"id":910,"date":"2014-12-05T11:15:52","date_gmt":"2014-12-05T16:15:52","guid":{"rendered":"https:\/\/www.softwareab.net\/wordpress\/?p=910"},"modified":"2014-12-05T11:18:49","modified_gmt":"2014-12-05T16:18:49","slug":"backport-websockets-apache-2-2-x86","status":"publish","type":"post","link":"https:\/\/www.softwareab.net\/wordpress\/backport-websockets-apache-2-2-x86\/","title":{"rendered":"Backport Websockets to Apache 2.2 (x86!)"},"content":{"rendered":"

Hello all – today’s post is on backporting Websockets to an ancient PE2650 running CentOS 6.6. Yup…i686 in all its glory. Read on for our solution!<\/p>\n

<\/p>\n

The problem? We have a Shiny<\/a> app that uses Websockets<\/a>. But we are proxying access to the Shiny app (via the R Server<\/a>) from a front-end Apache. And – as we all know – on CentOS standard yum repositories only go up to Apache 2.2 (2.2.15 currently). And Websockets is supported – via mod_proxy_wstunnel<\/a> – only in Apache 2.4.<\/p>\n

Hmmm. So what to do? Backport the fix in, of course!<\/p>\n

Here are our steps:<\/p>\n

    \n
  1. See following resources; we modify them heavily to meet our CentOS 6.6 i686 environment:\n
      \n
    • http:\/\/serverfault.com\/questions\/290121\/configuring-apache2-to-proxy-websocket<\/li>\n
    • https:\/\/issues.apache.org\/bugzilla\/show_bug.cgi?id=49053<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n

      Continue to the next step.<\/p>\n

    • \nInstall Apache for CentOS:<\/p>\n
      sudo yum install httpd\r\nchkconfig httpd24-httpd on\r\nservice httpd24-httpd start\r\n<\/code><\/pre>\n
      Continue to the next step.\n<\/li>\n
    • \nInstall necessary packages to base CentOS and setup firewall to permit HTTPS. Note that we are *not* running as root<\/code>:<\/p>\n
      sudo yum install -y patch autoconf libtool\r\nsudo yum install -y httpd mod_ssl mod_proxy_html\r\nsudo iptables -I INPUT 2 -p tcp -m state --state NEW -m tcp \\\r\n  -m multiport --dports 80,443 -m comment --comment \"HTTP\/HTTPS\" -j ACCEPT\r\nsudo service iptables reload\r\nsudo service iptables save<\/code><\/pre>\n
      Note that libtool<\/code> is version 2.0 while Apache source (specifically, apr-utils<\/code>) was built for libtool<\/code> version 1. We will address that problem below.<\/p>\n
      On the firewall: Be sure to do the same for the VM Security Group if running virtually.<\/p>\n
      Continue to the next step.\n<\/li>\n
    • \nCreate the dev tree to do your work. We’re running our builds locally:<\/p>\n
      mkdir -p ~\/proj\/websockets\r\ncd ~\/proj\/websockets<\/code><\/pre>\n
      Continue to the next step.\n<\/li>\n
    • \nDownload packages and patches to build Apache 2.2.15 (which matches the CentOS Apache distro):<\/p>\n
      wget https:\/\/archive.apache.org\/dist\/httpd\/httpd-2.2.15.tar.gz\r\nwget https:\/\/archive.apache.org\/dist\/apr\/apr-util-1.5.4.tar.gz\r\nwget https:\/\/archive.apache.org\/dist\/apr\/apr-1.5.1.tar.gz\r\nwget http:\/\/people.apache.org\/~rjung\/patches\/expat-libtool2.patch\r\nwget https:\/\/gist.github.com\/vitkin\/6661683\/raw\/873dd8b4de4ad1ff69757ffe48fc574374aedc57\/apache-2.2-wstunnel.patch<\/code><\/pre>\n
      Continue to the next step.\n<\/li>\n
    • \nExtract files and apply patches:<\/p>\n
      tar zxf httpd-2.2.15.tar.gz\r\ncd httpd-2.2.15\r\npatch -p1 -i ..\/apache-2.2-wstunnel.patch\r\ncd srclib\/apr\r\ntar xzf ..\/..\/..\/apr-1.5.1.tar.gz\r\ncd ..\/apr-util\/\r\ntar xzf ..\/..\/..\/apr-util-1.5.4.tar.gz\r\npatch -p1 -i ..\/..\/..\/expat-libtool2.patch\r\ncd ..\/..\/..<\/code><\/pre>\n
      Continue to the next step.\n<\/li>\n
    • \nConfigure and build system. Note we build all the dependent modules as our production environment requires them.<\/p>\n
      .\/buildconf\r\n.\/configure --enable-proxy=shared --enable-proxy_ajp=shared \\\r\n  --enable-proxy_balancer=shared --enable-proxy_connect=shared \\\r\n  --enable-proxy_ftp=shared --enable-proxy_http=shared \\\r\n  --enable-proxy_wstunnel=shared\r\nmake<\/code><\/pre>\n
      Continue to the next step.\n<\/li>\n
    • \nInstall the compiled mod_proxy over the base (saving the original for the first run). You can run these commands as-is any number of times.<\/p>\n
      [ ! -d \/usr\/lib\/httpd\/modules\/bak ] && sudo mkdir \/usr\/lib\/httpd\/modules\/bak\r\nl_lib=\/usr\/lib\/httpd\/modules; l_lib_loc=modules\/proxy\/.libs\r\nl_sos=''; for i in $(ls $l_lib_loc\/*.so); do l_sos=\"$l_sos $(basename $i)\"; done\r\nfor i in $l_sos; do [ ! -f $l_lib\/bak\/$i ] && sudo cp $l_lib\/$i $l_lib\/bak\/; done\r\nfor i in $l_sos; do yes | sudo cp $l_lib_loc\/$i $l_lib\/; sudo chmod 755 $l_lib\/$i; done<\/code><\/pre>\n
      service httpd restart
      \nContinue to the next step.\n<\/li>\n
    • \nModify your Apache config file; here we create a new file to hold our Websockets process:<\/p>\n
      # \/etc\/httpd\/conf.d\/z-websockets-demo.conf\r\nLoadModule proxy_wstunnel_module modules\/mod_proxy_wstunnel.so\r\n\r\n<VirtualHost *:80>\r\n  ServerName websockets-demo.hlsdev.com\r\n  ProxyRequests Off\r\n  ProxyPreserveHost Off\r\n  <Proxy *>\r\n    Order allow,deny\r\n    Allow from all\r\n  <\/Proxy>\r\n\r\n  # websockets?\r\n  ProxyPassMatch ^\/(.*\/__sockjs__\/[0-9]+\/.*) ws:\/\/backend.example.local:3838\/$1\r\n  ProxyPass \/  http:\/\/backend.example.local:3838\/ max=1 disablereuse=on keepalive=on\r\n  ProxyPassReverse \/ http:\/\/backend.example.local:3838\/\r\n  CustomLog \/var\/log\/httpd\/demo.log combined\r\n  ErrorLog  \/var\/log\/httpd\/demo_error.log\r\n<\/VirtualHost><\/code><\/pre>\n
      In the above: the Websockets support is provided by two additional lines. The first line loads the Websockets Tunneling code (which is an add-on to standard ws-proxy module):<\/p>\n
      LoadModule proxy_wstunnel_module modules\/mod_proxy_wstunnel.so<\/code><\/pre>\n
      The second line performs the check for the \u201cwebsocketized\u201d application using the ProxyPassMatch command. The regular expression checks for __socksjs__ followed by an all-numeric identifier. If found, then the proxy will send the request to the \u201cws:\/\/\u201d destination, which automagically invokes the ws_tunnel code.\n<\/li>\n<\/ol>\n
      That is all. The proxy now works.<\/p>\n","protected":false},"excerpt":{"rendered":"
      Hello all – today’s post is on backporting Websockets to an ancient PE2650 running CentOS 6.6. Yup…i686 in all its glory. Read on for our solution!<\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[77,1],"tags":[42,18,79],"yoast_head":"\nBackport Websockets to Apache 2.2 (x86!) - softwareab<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.softwareab.net\/wordpress\/backport-websockets-apache-2-2-x86\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Backport Websockets to Apache 2.2 (x86!) - softwareab\" \/>\n<meta property=\"og:description\" content=\"Hello all – today’s post is on backporting Websockets to an ancient PE2650 running CentOS 6.6. Yup…i686 in all its glory. 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