Fusion Server

Version 4.2
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      System Requirements

      Requirements for Fusion installation are detailed below.

      Lucidworks recommends not virus scanning the fusion/data folder. Virus scanning can cause slow performance, and it can cause downtime if it quarantines an index file identified as a possible virus.
      Fusion does not support installation under a directory whose name contains a space.

      Supported Operating Systems

      Certain systems may place limits on open files or processes that may be used by a process or user (for example, Unix systems may use ulimit and the limits.conf file). Fusion may require increasing these limits. We recommend setting these to "unlimited" or the maximum allowed by the system. If "unlimited" is not an option, we suggest a minimum limit of 65535 on the number of open files, and a minimum limit of 16384 on the number of processes for the Fusion user.

      Supported for production use of Fusion services

      Operating system:


      See Java requirements below.

      Also supported for trial and development use of Fusion services

      Operating system:

      • Windows 7, 8, 8.1, and 10 64-bit (x64 only)

      • Mac OS X 10.8 and above

      For information about the embedded versions of Solr, ZooKeeper, and so forth, see the Release Notes.


      See Java requirements below.

      Hardware requirements

      Fusion and Solr nodes

      Here are some minimum recommendations for different Fusion deployments. These are for the nodes that run Fusion (including ones that also run Solr and/or ZooKeeper, if those cluster arrangements are used), as well as for external (non-Fusion) nodes for SolrCloud nodes:

      Deployment type Memory CPU


      16 GB

      4 cores

      Small Production*

      32 GB

      8 cores

      Large Production**

      64+ GB

      8+ cores

      * Small production environments will have 2+ nodes with these specs, on which both Fusion and Solr are installed. (3+ nodes are recommended.)

      ** Large production environments will have 3+ nodes with these specs.

      ZooKeeper nodes

      Here are some minimum recommendations for the nodes that run ZooKeeper. These nodes can be more lightweight than the nodes that run Fusion and/or Solr. With the exception of small development/testing deployments, ZooKeeper nodes should only run ZooKeeper (not Fusion or Solr). Because ZooKeeper synchronizes all its operations to disk, we recommend using a disk with high throughput and low latency for your ZooKeeper nodes.

      Deployment type Memory CPU


      4 GB

      4 cores

      Small Production

      4+ GB

      4+ cores

      Large Production

      4+ GB

      4+ cores

      Fusion components

      You can run Fusion components on different nodes. Different Fusion components require different amounts of resources. Below are the minimum recommended memory requirements; consult Lucidworks for specific recommendations tailored to your unique use case, data load, and production needs.

      Fusion component Minimum RAM


      2 GB

      API service

      1 GB

      Fusion UI

      512 MB


      2 GB

      Spark master

      512 MB

      Spark worker

      1 GB

      Java requirements

      Fusion is a Java-based application and requires a pre-installed JDK to start. The JRE alone is not sufficient:

      • Oracle JDK 1.8, 64-bit (x64 only)

      • OpenJDK JDK 1.8, 64-bit (x64/x86_64 only)

        Java 8 is recommended for Lucidworks Fusion 4.2. In some cases, Java 9 can be used without issue. Java 10 and later is not supported by Lucidworks Fusion 4.2.

      Future releases of Lucidworks Fusion will support and/or require the use of Java 11.

      Java 11 licensing requirements

      Starting with Java 11, Oracle has changed the license requirements for commercial or production use of the Oracle Java JDK. In particular, such use may require purchase of a subscription.

      Oracle also offers a Java JDK under an open source license as the OpenJDK. This is available for commercial use at no additional cost. If you have been using the OpenJDK to run Lucidworks Fusion, then the licensing change will not affect you.

      If you have been using the Oracle JDK at no cost to run Lucidworks Fusion, and wish to continue using a free Java runtime after moving to Java 11 or later, you should use the OpenJDK versions of Java.

      If you have a commercial license for Oracle Java, you might be able to continue using Oracle JDK under the same license.

      For additional details, see Oracle JDK Releases for Java 11 and Later on the Oracle blog.

      Checking your Java version

      Fusion scripts execute both the java and javac commands, which are usually aliases for the current Java installation. To check which version of Java is invoked, run the following commands from a shell or terminal window:

      java -version
      javac -version
      echo $JAVA_HOME     // Unix
      echo %JAVA_HOME%    // Windows

      JavaScript pipeline stages

      Fusion’s JavaScript pipeline stages are application-specific custom JavaScript programs. The first time a pipeline is run, the JDK compiles the JavaScript using the Nashorn JavaScript engine.

      Cluster Requirements

      Supported Solr Versions

      Fusion includes an embedded instance of Solr; see the Release Notes to find out which Solr version is included in each Fusion release.

      Fusion Server 4.2 is certified with Solr 7.5.0 (included).

      We strongly recommend that you use Network Time Protocol (NTP) on a SolrCloud cluster to ensure that nodes use synchronized time. While this is not strictly required, reasoning about log contents and database entries becomes impossible without it. Information and instructions on how to install and run NTP are available at www.ntp.org.

      Supported ZooKeeper Versions

      Fusion includes an embedded instance of ZooKeeper; see the release history to find out which version of ZooKeeper is included in each Fusion release. For demo, trial, and some testing deployments, you can use the embedded ZooKeeper. For production deployments, we recommend using an external ZooKeeper cluster.

      ZooKeeper 3.4.11 is supported for external ZooKeeper instances.

      A ZooKeeper cluster must have 3+ nodes configured as an ensemble, and it must have an odd number of nodes. We recommend three ZooKeeper nodes in a ZooKeeper cluster/ensemble. Only for very large SolrCloud clusters (50+ nodes) might you need more ZooKeeper nodes.

      Recommended HTTP Clients

      The Fusion API can be accessed from any HTTP client, and allows you to build user interfaces and applications that work with any browser. However, the Fusion Administration UI, Dashboards, and built-in Search UI are supported only with:

      • Chrome latest version

      • Firefox latest version and latest Extended Support Release (ESR)

      • Internet Explorer 11