Project: Alluxio (Runtime / Cloud Native Storage)
File: Configuration.md

layout: global title: Configuration Settings An Alluxio cluster can be configured by setting the values of Alluxio within `${ALLUXIO_HOME}/conf/alluxio-site.properties`. When different client applications (Alluxio Shell CLI, Spark jobs, MapReduce jobs) or Alluxio workers connect to an Alluxio master, they will initialize their own Alluxio configuration properties with the default values supplied by the masters based on the master-side `${ALLUXIO_HOME}/conf/alluxio-site.properties` files. As a result, cluster admins can set default client-side settings (e.g., `alluxio.user.*`), or network transport settings (e.g., `alluxio.security.authentication.type`) in `${ALLUXIO_HOME}/conf/alluxio-site.properties` on all the masters, which will be distributed and become cluster-wide default values when clients and workers connect. For example, the property `alluxio.user.file.writetype.default` defaults to `ASYNC_THROUGH`, which first writes to Alluxio and then asynchronously writes to the UFS. In an Alluxio cluster where data persistence is preferred and all jobs need to write to both the UFS and Alluxio, the administrator can add `alluxio.user.file.writetype.default=CACHE_THROUGH` in each master's `alluxio-site.properties` file. After restarting the cluster, all jobs will automatically set `alluxio.user.file.writetype.default` to `CACHE_THROUGH`. Clients can ignore or overwrite the cluster-wide default values by following the approaches described in to overwrite the same properties. Alluxio properties can be configured from multiple sources. A property's final value is determined by the following priority list, from highest priority to lowest: : When an Alluxio cluster starts, each server process including master and worker searches for `alluxio-site.properties` within the following directories in the given order, stopping when a match is found: `${CLASSPATH}`, `${HOME}/.alluxio/`, `/etc/alluxio/`, and `${ALLUXIO_HOME}/conf` : An Alluxio client may initialize its configuration based on the cluster-wide default configuration served by the masters. If no user-specified configuration is found for a property, Alluxio will fall back to its . To check the value of a specific configuration property and the source of its value, users can run the following command: ```shell $ ./bin/alluxio conf get alluxio.worker.rpc.port 29998 $ ./bin/alluxio conf get --source alluxio.worker.rpc.port DEFAULT ``` To list all of the configuration properties with sources: ```shell $ ./bin/alluxio conf get --source alluxio.conf.dir=/Users/bob/alluxio/conf (SYSTEM_PROPERTY) alluxio.debug=false (DEFAULT) ... ``` Users can also specify the `--master` option to list all of the cluster-wide configuration properties served by the masters. Note that with the `--master` option, `bin/alluxio conf get` will query the master which requires the master process to be running. Otherwise, without `--master` option, this command only checks the local configuration. ```shell $ ./bin/alluxio conf get --master --source alluxio.conf.dir=/Users/bob/alluxio/conf (SYSTEM_PROPERTY) alluxio.debug=false (DEFAULT) ... ``` Alluxio also supports Java 11. To run Alluxio on Java 11, configure the `JAVA_HOME` environment variable to point to a Java 11 installation directory. If you only want to use Java 11 for Alluxio, you can set the `JAVA_HOME` environment variable in the `alluxio-env.sh` file. Setting the `JAVA_HOME` in `alluxio-env.sh` will not affect the Java version which may be used by other applications running in the same environment. The server-side configuration checker helps discover configuration errors and warnings. Suspected configuration errors are reported through the web UI, `info doctor` CLI, and master logs. The web UI shows the result of the server configuration check. Users can also run the `info doctor` command to get the same results. ```shell $ ./bin/alluxio info doctor configuration ``` Configuration warnings can also be found in the master logs.