Ozone - Object store for Hadoop ============================== Introduction ------------ Ozone is an object store for Hadoop. It is a redundant, distributed object store build by leveraging primitives present in HDFS. Ozone supports REST API for accessing the store. Getting Started --------------- Ozone is a work in progress and currently lives in its own branch. To use it, you have to build a package by yourself and deploy a cluster. ### Building Ozone To build Ozone, please checkout the hadoop sources from github. Then checkout the ozone branch, HDFS-7240 and build it. - `git checkout HDFS-7240` - `mvn clean package -DskipTests=true -Dmaven.javadoc.skip=true -Pdist -Dtar -DskipShade` skipShade is just to make compilation faster and not really required. This will give you a tarball in your distribution directory. This is the tarball that can be used for deploying your hadoop cluster. Here is an example of the tarball that will be generated. * `~/apache/hadoop/hadoop-dist/target/${project.version}.tar.gz` At this point we have an option to setup a physical cluster or run ozone via docker. Running Ozone via Docker ------------------------ This assumes that you have a running docker setup on the machine. Please run these following commands to see ozone in action. Go to the directory where the docker compose files exist. - `cd dev-support/compose/ozone` Tell docker to start ozone, this will start a KSM, SCM and a single datanode in the background. - `docker-compose up -d` Now let us run some work load against ozone, to do that we will run corona. This will log into the datanode and run bash. - `docker-compose exec datanode bash` - `cd hadoop/bin` Now you can run the oz command shell or corona the ozone load generator. This is the command to run corona. - `./hdfs corona -mode offline -validateWrites -numOfVolumes 1 -numOfBuckets 10 -numOfKeys 100` You can checkout the KSM UI to see the requests information. - `http://localhost:9874/` If you need more datanode you can scale up: - `docker-compose scale datanode=3` Running Ozone using a real cluster ---------------------------------- Please proceed to setup a hadoop cluster by creating the hdfs-site.xml and other configuration files that are needed for your cluster. ### Ozone Configuration Ozone relies on its own configuration file called `ozone-site.xml`. It is just for convenience and ease of management -- you can add these settings to `hdfs-site.xml`, if you don't want to keep ozone settings separate. This document refers to `ozone-site.xml` so that ozone settings are in one place and not mingled with HDFS settings. * _*ozone.enabled*_ This is the most important setting for ozone. Currently, Ozone is an opt-in subsystem of HDFS. By default, Ozone is disabled. Setting this flag to `true` enables ozone in the HDFS cluster. Here is an example, ``` ozone.enabled True ``` * _*ozone.metadata.dirs*_ Ozone is designed with modern hardware in mind. It tries to use SSDs effectively. So users can specify where the metadata must reside. Usually you pick your fastest disk (SSD if you have them on your nodes). KSM, SCM and datanode will write the metadata to these disks. This is a required setting, if this is missing Ozone will fail to come up. Here is an example, ``` ozone.metadata.dirs /data/disk1/meta ``` * _*ozone.scm.names*_ Ozone is build on top of container framework (See Ozone Architecture TODO). Storage container manager(SCM) is a distributed block service which is used by ozone and other storage services. This property allows datanodes to discover where SCM is, so that datanodes can send heartbeat to SCM. SCM is designed to be highly available and datanodes assume there are multiple instances of SCM which form a highly available ring. The HA feature of SCM is a work in progress. So we configure ozone.scm.names to be a single machine. Here is an example, ``` ozone.scm.names scm.hadoop.apache.org ``` * _*ozone.scm.datanode.id*_ Each datanode that speaks to SCM generates an ID just like HDFS. This is an optional setting. Please note: This path will be created by datanodes if it doesn't exist already. Here is an example, ``` ozone.scm.datanode.id /data/disk1/scm/meta/node/datanode.id ``` * _*ozone.scm.block.client.address*_ Storage Container Manager(SCM) offers a set of services that can be used to build a distributed storage system. One of the services offered is the block services. KSM and HDFS would use this service. This property describes where KSM can discover SCM's block service endpoint. There is corresponding ports etc, but assuming that we are using default ports, the server address is the only required field. Here is an example, ``` ozone.scm.block.client.address scm.hadoop.apache.org ``` * _*ozone.ksm.address*_ KSM server address. This is used by Ozonehandler and Ozone File System. ``` ozone.ksm.address ksm.hadoop.apache.org ``` Here is a quick summary of settings needed by Ozone. | Setting | Value | Comment | |--------------------------------|------------------------------|------------------------------------------------------------------| | ozone.enabled | True | This enables SCM and containers in HDFS cluster. | | ozone.metadata.dirs | file path | The metadata will be stored here. | | ozone.scm.names | SCM server name | Hostname:port or or IP:port address of SCM. | | ozone.scm.block.client.address | SCM server name and port | Used by services like KSM | | ozone.scm.client.address | SCM server name and port | Used by client side | | ozone.scm.datanode.address | SCM server name and port | Used by datanode to talk to SCM | | ozone.ksm.address | KSM server name | Used by Ozone handler and Ozone file system. | Here is a working example of`ozone-site.xml`. ``` ozone.enabled True ozone.metadata.dirs /data/disk1/ozone/meta ozone.scm.names 127.0.0.1 ozone.scm.client.address 127.0.0.1:9860 ozone.scm.block.client.address 127.0.0.1:9863 ozone.scm.datanode.address 127.0.0.1:9861 ozone.ksm.address 127.0.0.1:9874 ``` ### Starting Ozone Ozone is designed to run concurrently with HDFS. The simplest way to [start HDFS](../hadoop-common/ClusterSetup.html) is to run `start-dfs.sh` from the `$HADOOP/sbin/start-dfs.sh`. Once HDFS is running, please verify it is fully functional by running some commands like - *./hdfs dfs -mkdir /usr* - *./hdfs dfs -ls /* Once you are sure that HDFS is running, start Ozone. To start ozone, you need to start SCM and KSM. Currently we assume that both KSM and SCM is running on the same node, this will change in future. - `./hdfs --daemon start scm` - `./hdfs --daemon start ksm` if you would like to start HDFS and Ozone together, you can do that by running a single command. - `$HADOOP/sbin/start-ozone.sh` This command will start HDFS and then start the ozone components. Once you have ozone running you can use these ozone [shell](./OzoneCommandShell.html) commands to create a volume, bucket and keys. ### Diagnosing issues Ozone tries not to pollute the existing HDFS streams of configuration and logging. So ozone logs are by default configured to be written to a file called `ozone.log`. This is controlled by the settings in `log4j.properties` file in the hadoop configuration directory. Here is the log4j properties that are added by ozone. ``` # # Add a logger for ozone that is separate from the Datanode. # #log4j.debug=true log4j.logger.org.apache.hadoop.ozone=DEBUG,OZONE,FILE # Do not log into datanode logs. Remove this line to have single log. log4j.additivity.org.apache.hadoop.ozone=false # For development purposes, log both to console and log file. log4j.appender.OZONE=org.apache.log4j.ConsoleAppender log4j.appender.OZONE.Threshold=info log4j.appender.OZONE.layout=org.apache.log4j.PatternLayout log4j.appender.OZONE.layout.ConversionPattern=%d{ISO8601} [%t] %-5p \ %X{component} %X{function} %X{resource} %X{user} %X{request} - %m%n # Real ozone logger that writes to ozone.log log4j.appender.FILE=org.apache.log4j.DailyRollingFileAppender log4j.appender.FILE.File=${hadoop.log.dir}/ozone.log log4j.appender.FILE.Threshold=debug log4j.appender.FILE.layout=org.apache.log4j.PatternLayout log4j.appender.FILE.layout.ConversionPattern=%d{ISO8601} [%t] %-5p \ (%F:%L) %X{function} %X{resource} %X{user} %X{request} - \ %m%n ``` If you would like to have a single datanode log instead of ozone stuff getting written to ozone.log, please remove this line or set this to true. ` log4j.additivity.org.apache.hadoop.ozone=false` On the SCM/KSM side, you will be able to see - `hadoop-hdfs-ksm-hostname.log` - `hadoop-hdfs-scm-hostname.log` Please file any issues you see under [Object store in HDFS (HDFS-7240)](https://issues.apache.org/jira/browse/HDFS-7240) as this is still a work in progress.