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Configuration Settings

docs/en/operation/Configuration.md

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An Alluxio cluster can be configured by setting the values of Alluxio [configuration properties]({{ '/en/reference/Properties-List.html' | relativize_url }}) within ${ALLUXIO_HOME}/conf/alluxio-site.properties.

The two major components to configure are:

Alluxio properties mostly fall into three categories:

  • properties prefixed with alluxio.user affect Alluxio client operations (e.g. compute applications)
  • properties prefixed with alluxio.master affect the Alluxio master processes
  • properties prefixed with alluxio.worker affect the Alluxio worker processes

Configure Applications

Customizing how an application interacts with Alluxio is specific to each application. The following are recommendations for some common applications.

Alluxio Shell Commands

Alluxio shell users can put JVM system properties -Dproperty=value after the fs command and before the subcommand to specify Alluxio user properties from the command line. For example, the following Alluxio shell command sets the write type to CACHE_THROUGH when copying files to Alluxio:

console
$ ./bin/alluxio fs -Dalluxio.user.file.writetype.default=CACHE_THROUGH \
  copyFromLocal README.md /README.md

Note that, as a part of Alluxio deployment, the Alluxio shell will also take the configuration in ${ALLUXIO_HOME}/conf/alluxio-site.properties when it is run from Alluxio installation at ${ALLUXIO_HOME}.

Spark

To customize Alluxio client-side properties in Spark applications, Spark users can use pass Alluxio properties as JVM system properties. See examples for [configuring the Spark service]({{ '/en/compute/Spark.html' | relativize_url }}#basic-setup) or for [individual Spark jobs]({{ '/en/compute/Spark.html' | relativize_url }}#customize-alluxio-user-properties-for-individual-spark-jobs).

Hadoop MapReduce

See examples to configure Alluxio properties for [the MapReduce service]({{ '/en/compute/Hadoop-MapReduce.html' | relativize_url }}#customize-alluxio-user-properties-for-all-mapreduce-jobs) or for [individual MapReduce jobs]({{ '/en/compute/Hadoop-MapReduce.html' | relativize_url }}#customize-alluxio-user-properties-for-individual-mapreduce-jobs).

Hive

Hive can be configured to use customized Alluxio client-side properties for the entire service. See [examples]({{ '/en/compute/Hive.html' | relativize_url }}#customize-alluxio-user-properties).

Presto

Presto can be configured to use customized Alluxio client-side properties for the entire service. See [examples]({{ '/en/compute/Presto.html' | relativize_url }}#customize-alluxio-user-properties).

Configure an Alluxio Cluster

alluxio-site.properties Files (Recommended)

Alluxio admins can create and edit the properties file conf/alluxio-site.properties to configure Alluxio masters or workers. If this file does not exist, it can be copied from the template file under ${ALLUXIO_HOME}/conf:

console
$ cp conf/alluxio-site.properties.template conf/alluxio-site.properties

Make sure that this file is distributed to ${ALLUXIO_HOME}/conf on every Alluxio master and worker before starting the cluster. Restarting Alluxio processes is the safest way to ensure any configuration updates are applied.

Environment Variables

Alluxio supports defining a few frequently used configuration settings through environment variables, including:

<table class="table table-striped"> <tr><th>Environment Variable</th><th>Description</th></tr> {% for env_var in site.data.table.en.env_vars %} <tr> <td markdown="span">`{{env_var.name}}`</td> <td markdown="span">{{env_var.description}}</td> </tr> {% endfor %} </table>

For example, the following example will set up:

  • an Alluxio master at localhost
  • the root mount point as an HDFS cluster with a namenode also running at localhost
  • defines the maximum heap space of the VM to be 30g
  • enable Java remote debugging at port 7001
console
$ export ALLUXIO_MASTER_HOSTNAME="localhost"
$ export ALLUXIO_MASTER_MOUNT_TABLE_ROOT_UFS="hdfs://localhost:9000"
$ export ALLUXIO_MASTER_JAVA_OPTS="-Xmx30g"
$ export ALLUXIO_MASTER_ATTACH_OPTS="-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=7001"

Users can either set these variables through the shell or in conf/alluxio-env.sh. If this file does not exist yet, it can be copied from the template file under ${ALLUXIO_HOME}/conf:

console
$ cp conf/alluxio-env.sh.template conf/alluxio-env.sh

Cluster Defaults

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 Configure Applications to overwrite the same properties.

Path Defaults

Alluxio administrators can set default client-side configurations for specific Alluxio filesystem paths. Filesystem client operations have options which are derived from client side configuration properties. Only client-side configuration properties can be set as path defaults.

For example, the createFile operation has an option to specify write type. By default, the write type is the value of the configuration key alluxio.user.file.writetype.default. The administrator can set default value of alluxio.user.file.write.type.default to MUST_CACHE for all paths with prefix /tmp by running:

console
$ bin/alluxio fsadmin pathConf add --property alluxio.user.file.writetype.default=MUST_CACHE /tmp`

After executing this command any create operations on paths with prefix /tmp will use the MUST_CACHE write type by default unless the application configuration overrides the cluster defaults.

Path defaults will be automatically propagated to long-running clients if they are updated. If the administrator updates path defaults using the following:

console
$ bin/alluxio fsadmin pathConf add --property alluxio.user.file.writetype.default=THROUGH /tmp

All write operations that occur on a path with the prefix /tmp prefix will use the THROUGH write type by default.

See [fsadmin pathConf]({{ '/en/operation/Admin-CLI.html' | relativize_url }}#pathconf) on how to show, add, update, and remove path defaults.

Configuration Sources

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:

  1. JVM system properties (i.e., -Dproperty=key)
  2. Environment variables
  3. Property files: 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
  4. Path default values
  5. Cluster default values: 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 [default property value]({{ '/en/reference/Properties-List.html' | relativize_url }}).

To check the value of a specific configuration property and the source of its value, users can run the following command:

console
$ ./bin/alluxio getConf alluxio.worker.rpc.port
29998
$ ./bin/alluxio getConf --source alluxio.worker.rpc.port
DEFAULT

To list all of the configuration properties with sources:

console
$ ./bin/alluxio getConf --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, getConf will query the master which requires the master process to be running. Otherwise, without --master option, this command only checks the local configuration.

console
$ ./bin/alluxio getConf --master --source
alluxio.conf.dir=/Users/bob/alluxio/conf (SYSTEM_PROPERTY)
alluxio.debug=false (DEFAULT)
...

Java 11 Configuration

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.

Server Configuration Checker

The server-side configuration checker helps discover configuration errors and warnings. Suspected configuration errors are reported through the web UI, fsadmin doctor CLI, and master logs.

The web UI shows the result of the server configuration check.

![webUi]({{ '/img/screenshot_configuration_checker_webui.png' | relativize_url }})

Users can also run the fsadmin doctor command to get the same results.

console
$ ./bin/alluxio fsadmin doctor configuration

Configuration warnings can also be found in the master logs.

![masterLogs]({{ '/img/screenshot_configuration_checker_masterlogs.png' | relativize_url }})