cluster: cluster tag configuration

Each <cluster> contains a set of virtual hosts served by a collection of <server>s. The cluster provides load-balancing and distributed sessions for scalability and reliability.

• See the index for a list of all the tags.
• See Web Application configuration for web.xml (Servlet) configuration.
• See Server tags for ports, threads, and JVM configuration.
• See Resource configuration for resources: classloader, databases, connectors, and resources.
• See Log configuration for access log configuration, java.util.logging, and stdout/stderr logging.

<access-log> configures a HTTP access log for all virtual hosts in the cluster. See access-log in the <host> tag for more information.

<cache> configures the proxy cache (requires Resin Professional). The proxy cache improves performance by caching the output of servlets, jsp and php pages. For database-heavy pages, this caching can improve performance and reduce database load by several orders of magnitude.

The proxy cache uses a combination of a memory cache and a disk-based cache to save large amounts of data with little overhead.

Management of the proxy cache uses the ProxyCacheMXBean.

element cache {
  disk-size?
  & enable?
  & enable-range?
  & entries?
  & path?
  & max-entry-size?
  & memory-size?
  & rewrite-vary-as-private?
}

<resin xmlns="http://caucho.com/ns/resin">
    <cluster id="web-tier">
        <cache entries="16384" disk-size="2G" memory-size="256M"/>

        <server id="a" address="192.168.0.10"/>

        <host host-name="www.foo.com">
    </cluster>
</resin>

<cluster> configures a set of identically-configured servers. The cluster typically configures a set of <server>s, each with some ports, and a set of virtual <host>s.

Only one <cluster> is active in any on server. At runtime, the <cluster> is selected by the <server> with id matching the -server-id on the command line.

element cluster {
  attribute id { string }
  & environment resources
  & access-log?
  & cache?
  & connection-error-page?
  & ear-default*
  & error-page*
  & host*
  & host-default*
  & host-deploy*
  & ignore-client-disconnect?
  & invocation-cache-size?
  & invocation-cache-max-url-length?
  & machine*
  & persistent-store?
  & ping*
  & redeploy-mode?
  & resin:choose*
  & resin:import*
  & resin:if*
  & rewrite-dispatch?
  & root-directory?
  & server*
  & server-default*
  & server-header?
  & session-cookie?
  & session-sticky-disable?
  & url-character-encoding?
  & url-length-max?
  & web-app-default*
}

<resin xmlns="http://caucho.com/ns/resin">
    <cluster id="web-tier">
        <server-default>
            <http port="8080"/>
        </server-default>

        <server id="a" address="192.168.0.10"/>
        <server id="b" address="192.168.0.11"/>

        <host host-name="www.foo.com">
          ...
        </host>
    </cluster>
</resin>

<cluster-default> defines default cluster configuration for all clusters in the <resin> server.

<resin xmlns="http://caucho.com/ns/resin">
    <cluster-default>
        <cache entries="16384" memory-size="64M"/>
    </cluster-default>

    <cluster id="web-tier">
        ...
    </cluster>

    <cluster id="app-tier">
        ...
    </cluster>
</resin>

<connection-error-page> specifies an error page to be used by IIS when it can't contact an app-tier Resin. This directive only applies to IIS.

element connection-error-page {
  string
}

<ear-default> configures defaults for .ear resource, i.e. enterprise applications.

<error-page> defines a web page to be displayed when an error occurs outside of a virtual host or web-app. Note, this is not a default error-page, i.e. if an error occurs inside a <host> or <web-app>, the error-page for that host or web-app will be used instead.

See webapp: error-page.

element error-page {
  (error-code | exception-type)?
  & location?
}

<host> configures a virtual host. Virtual hosts must be configured explicitly.

• See host tags for configuration details.

<host host-name="www.foo.com">
  <host-alias>foo.com</host-alias>
  <host-alias>web.foo.com</host-alias>

  <root-directory>/opt/www/www.foo.com</root-directory>

  <web-app id="/" document-directory="webapps/ROOT">
    
  </web-app>
  ...
</host>

<host regexp="([^.]+)\.foo\.com">
  <host-name>${host.regexp[1]}.foo.com</host-name>

  <root-directory>/var/www/hosts/www.${host.regexp[1]}.com</root-directory>

  ...
</host>

It is recommended that any <host> using a regexp include a <host-name> to set the canonical name for the host.

Defaults for a virtual host.

The host-default can contain any of the host configuration tags. It will be used as defaults for any virtual host.

Configures a deploy directory for virtual host.

The host-deploy will add an EL variable ${name}, referring to the name of the host jar file.

ignore-client-disconnect configures whether Resin should ignore disconnection exceptions from the client, or if it should send those exceptions to the application.

element ignore-client-disconnect {
  r_boolean-Type
}

Configures the number of entries in the invocation cache. The invocation cache is used to store pre-calculated servlet and filter chains from the URLs. It's also used as the basis for proxy caching.

element invocation-cache-size {
  r_int-Type
}

Configures the longest entry cacheable in the invocation cache. It is used to avoid certain types of denial-of-service attacks.

element invocation-cache-max-url-length {
  r_int-Type
}

Defines the cluster-aware persistent store used for sharing distributed sessions. The allowed types are "jdbc", "cluster" and "file". The "file" type is only recommended in single-server configurations.

The <persistent-store> configuration is in the <server> level because it needs to share update information across the active cluster and the <cluster> definition is at the <server> level. Sessions activate the persistent store with the <use-persistent-store> tag of the <session-config>.

See Persistent sessions for more details.

element persistent-store {
  type
  & init?
}

element persistent-store {
  type { "cluster "}

  element init {
    always-load?
    & always-save?
    & max-idle-time?
    & triplicate?
    & wait-for-acknowledge?
  }
}

<resin xmlns="http://caucho.com/ns/resin">
<cluster>
  <server id="a" address="192.168.0.1" port="6800"/>
  <server id="b" address="192.168.0.2" port="6800"/>

  <persistent-store type="cluster">
    <init>
      <triplicate>true</triplicate>
    </init>
  </persistent-store>

  <web-app-default>
    <session-config use-persistent-store="true"/>
  </web-app-default>
</cluster>
</resin>

<resin xmlns="http://caucho.com/ns/resin">
<cluster>
  <server id="a" address="192.168.0.1" port="6800"/>
  <server id="b" address="192.168.0.2" port="6800"/>

  <persistent-store type="jdbc">
    <init>
      <data-source>jdbc/session</data-source>

      <max-idle-time>24h</max-idle-time>
    </init>
  </persistent-store>

  <web-app-default>
    <session-config use-persistent-store="true"/>
  </web-app-default>
</cluster>
</resin>

Starts a thread that periodically makes a request to the server, and restarts Resin if it fails. This facility is used to increase server reliability - if there is a problem with the server (perhaps from a deadlock or an exhaustion of resources), the server is restarted.

A failure occurs if a request to the url returns an HTTP status that is not 200.

Since the local process is restarted, it does not make sense to specify a url that does not get serviced by the instance of Resin that has the ping configuration. Most configurations use url's that specify 'localhost' as the host.

This pinging only catches some problems because it's running in the same process as Resin itself. If the entire JDK freezes, this thread will freeze as well. Assuming the JDK doesn't freeze, the PingThread will catch errors like deadlocks.

<resin xmlns="http://caucho.com/ns/resin"
       xmlns:resin="http://caucho.com/ns/resin/core">
    <cluster id="app-tier">
        <ping url="http://localhost/"/>
        ...
    </cluster>
</resin>

<resin xmlns="http://caucho.com/ns/resin"
       xmlns:resin="http://caucho.com/ns/resin/core">
    ...
    <cluster id="app-tier">
        <ping>
            <url>http://localhost:8080/index.jsp</url>
            <url>http://localhost:8080/webapp/index.jsp</url>
            <url>http://virtualhost/index.jsp</url>
            <url>http://localhost:443/index.jsp</url>

            <sleep-time>5m</sleep-time>
            <try-count>5</try-count>
    
            <!-- a very busy server -->
            <socket-timeout>30s</socket-timeout>
        </ping>
      ...
    </cluster>
</resin>

The class that corresponds to <ping> is PingThread.

<resin xmlns="http://caucho.com/ns/resin"
       xmlns:resin="http://caucho.com/ns/resin/core">
  ...
  <cluster id="web-tier">
    <ping resin:type="com.caucho.server.admin.PingMailer">
      <url>http://localhost:8080/index.jsp</url>
      <url>http://localhost:8080/webapp/index.jsp</url>

      <mail-to>fred@hogwarts.com</mail-to>
      <mail-from>resin@hogwarts.com</mail-from>
      <mail-subject>Resin ping has failed for server ${'${'}server.name}</mail-subject>
    </ping>
    ...
  </server>
</resin>

  <system-property mail.smtp.host="127.0.0.1"/>
  <system-property mail.smtp.port="25"/>

All Environment tags are available to the <cluster>. For example, resources like <database>.

<resin xmlns="http://caucho.com/ns/resin">
    <cluster id="app-tier">
        <database jndi-name="jdbc/test">
            <driver type="org.postgresql.Driver">
                <url>jdbc:postgresql://localhost/test</url>
                <user>caucho</user>
            </driver>
        </database>

        <server id="a" ...>
          ...

        <host host-name="www.foo.com">
          ...
    </cluster>
</resin>

<rewrite-dispatch> defines a set of rewriting rules for dispatching and forwarding URLs. Applications can use these rules to redirect old URLs to their new replacements.

See rewrite-dispatch for more details.

<resin xmlns="http://caucho.com/ns/resin">
    <cluster id="web-tier">

        <rewrite-dispatch>
            <redirect regexp="^http://www.foo.com"
                      target="http://bar.com/foo"/>
        </rewrite-dispatch>
  
    </cluster>
</resin>

<root-directory> configures the root directory for files within the cluster. All paths in the <cluster> will be relative to the root directory.

element root-directory {
  r_path-Type
}

<resin xmlns="http://caucho.com/ns/resin">
    <cluster id="app-tier">
        <root-directory>/var/www/app-tier</root-directory>

        <server id="a" ...>

        <host host-name="www.foo.com">
    </cluster>
</resin>

The <server> tag configures a JVM instance in the cluster. Each <server> is uniquely identified by its id attribute. The id will match the -server-id command line argument.

See the full server configuration for more details of the <server> tag and its children.

The current server is managed with a ServerMXBean. The ObjectName is resin:type=Server.

Peer servers are managed with ServerConnectorMXBean. The ObjectName is resin:type=ServerConnector,name=server-id.

element server {
  attribute id { string }
  & address?
  & bind-ports-after-start?
  & cluster-port*
  & group-name?
  & http*
  & java-exe?
  & jvm-arg?
  & jvm-classpath?
  & keepalive-connection-time-max?
  & keepalive-max?
  & keepalive-select-enable?
  & keepalive-timeout?
  & load-balance-connect-timeout?
  & load-balance-idle-time?
  & load-balance-recover-time?
  & load-balance-socket-timeout?
  & load-balance-warmup-time?
  & load-balance-weight?
  & memory-free-min?
  & ping?
  & port?
  & protocol?
  & shutdown-wait-max?
  & socket-timeout?
  & thread-max?
  & thread-executor-task-max?
  & thread-idle-max?
  & thread-idle-min?
  & user-name?
  & watchdog-jvm-arg*
  & watchdog-port?
}

<resin xmlns="http://caucho.com/ns/resin">
    <cluster id="web-tier">
        <server id="a" address="192.168.0.10" port="6800">
          <http port="8080"/>
        </server>

        <server id="b" address="192.168.0.11" port="6800">
          <http port="8080"/>
        </server>

        <server id="c" address="192.168.0.12" port="6800">
          <http port="8080"/>
        </server>

        <host id="">
          ...
    </cluster>
</resin>

Defines default values for all <server> instances. See <server> configuration for more details.

<resin xmlns="http://caucho.com/ns/resin">
    <cluster id="web-tier">
        <server-default>
            <server-port>6800</server-port>

            <http port="8080"/>
        </server-default>

        <server id="a" address="192.168.0.10"/>
        <server id="b" address="192.168.0.11"/>
        <server id="c" address="192.168.0.12"/>

        <host id="">
          ...
    </cluster>
</resin>

Configures the HTTP Server: header which Resin sends back to any HTTP client.

element server-header {
  string
}

<resin xmlns="http://caucho.com/ns/resin">
    <cluster id="web-tier">
        <server-header>MyServer/1.0</server-header>
    </cluster>
</resin>

Configures the cookie used for servlet sessions.

element session-cookie {
  string
}

Disables sticky sessions from the load balancer.

element session-sticky-disable {
  r_boolean-Type
}

Configures the URL prefix used for session rewriting.

element session-cookie {
  string
}

Defines an alternative session cookie to be used for a SSL connection. Having two separate cookies increases security.

element ssl-session-cookie {
  string
}

<resin xmlns="http://caucho.com/ns/resin">
    <cluster id="web-tier">
        <ssl-session-cookie>SSLJSESSIONID</ssl-session-cookie>
        ...
    </cluster>
</resin>

Defines the character encoding for decoding URLs.

The HTTP specification does not define the character-encoding for URLs, so the server must make assumptions about the encoding.

element url-character-encoding {
  string
}

<web-app-default> defines default values for any web-app in the cluster.

<resin xmlns="http://caucho.com/ns/resin">
    <cluster id="app-tier">

        <web-app-default>
            <servlet servlet-name="resin-php"
                     servlet-class="com.caucho.quercus.servlet.QuercusServlet"/>

            <servlet-mapping url-pattern="*.php"
                             servlet-name="resin-php"/>
        </web-app-default>

        <host id="">
          ...
    </cluster>
</resin>