mirror of
https://github.com/ceph/ceph
synced 2024-12-24 20:33:27 +00:00
203 lines
9.9 KiB
ReStructuredText
203 lines
9.9 KiB
ReStructuredText
========================
|
|
Using Hadoop with CephFS
|
|
========================
|
|
|
|
The Ceph file system can be used as a drop-in replacement for the Hadoop File
|
|
System (HDFS). This page describes the installation and configuration process
|
|
of using Ceph with Hadoop.
|
|
|
|
Dependencies
|
|
============
|
|
|
|
* CephFS Java Interface
|
|
* Hadoop CephFS Plugin
|
|
|
|
.. important:: Currently requires Hadoop 1.1.X stable series
|
|
|
|
Installation
|
|
============
|
|
|
|
There are three requirements for using CephFS with Hadoop. First, a running
|
|
Ceph installation is required. The details of setting up a Ceph cluster and
|
|
the file system are beyond the scope of this document. Please refer to the
|
|
Ceph documentation for installing Ceph.
|
|
|
|
The remaining two requirements are a Hadoop installation, and the Ceph file
|
|
system Java packages, including the Java CephFS Hadoop plugin. The high-level
|
|
steps are two add the dependencies to the Hadoop installation ``CLASSPATH``,
|
|
and configure Hadoop to use the Ceph file system.
|
|
|
|
CephFS Java Packages
|
|
--------------------
|
|
|
|
* CephFS Hadoop plugin (`hadoop-cephfs.jar <http://ceph.com/download/hadoop-cephfs.jar>`_)
|
|
|
|
Adding these dependencies to a Hadoop installation will depend on your
|
|
particular deployment. In general the dependencies must be present on each
|
|
node in the system that will be part of the Hadoop cluster, and must be in the
|
|
``CLASSPATH`` searched for by Hadoop. Typically approaches are to place the
|
|
additional ``jar`` files into the ``hadoop/lib`` directory, or to edit the
|
|
``HADOOP_CLASSPATH`` variable in ``hadoop-env.sh``.
|
|
|
|
The native Ceph file system client must be installed on each participating
|
|
node in the Hadoop cluster.
|
|
|
|
Hadoop Configuration
|
|
====================
|
|
|
|
This section describes the Hadoop configuration options used to control Ceph.
|
|
These options are intended to be set in the Hadoop configuration file
|
|
`conf/core-site.xml`.
|
|
|
|
+---------------------+--------------------------+----------------------------+
|
|
|Property |Value |Notes |
|
|
| | | |
|
|
+=====================+==========================+============================+
|
|
|fs.default.name |Ceph URI |ceph://[monaddr:port]/ |
|
|
| | | |
|
|
| | | |
|
|
+---------------------+--------------------------+----------------------------+
|
|
|ceph.conf.file |Local path to ceph.conf |/etc/ceph/ceph.conf |
|
|
| | | |
|
|
| | | |
|
|
| | | |
|
|
+---------------------+--------------------------+----------------------------+
|
|
|ceph.conf.options |Comma separated list of |opt1=val1,opt2=val2 |
|
|
| |Ceph configuration | |
|
|
| |key/value pairs | |
|
|
| | | |
|
|
+---------------------+--------------------------+----------------------------+
|
|
|ceph.root.dir |Mount root directory |Default value: / |
|
|
| | | |
|
|
| | | |
|
|
+---------------------+--------------------------+----------------------------+
|
|
|ceph.mon.address |Monitor address |host:port |
|
|
| | | |
|
|
| | | |
|
|
| | | |
|
|
+---------------------+--------------------------+----------------------------+
|
|
|ceph.auth.id |Ceph user id |Example: admin |
|
|
| | | |
|
|
| | | |
|
|
| | | |
|
|
+---------------------+--------------------------+----------------------------+
|
|
|ceph.auth.keyfile |Ceph key file | |
|
|
| | | |
|
|
| | | |
|
|
| | | |
|
|
+---------------------+--------------------------+----------------------------+
|
|
|ceph.auth.keyring |Ceph keyring file | |
|
|
| | | |
|
|
| | | |
|
|
| | | |
|
|
+---------------------+--------------------------+----------------------------+
|
|
|ceph.object.size |Default file object size |Default value (64MB): |
|
|
| |in bytes |67108864 |
|
|
| | | |
|
|
| | | |
|
|
+---------------------+--------------------------+----------------------------+
|
|
|ceph.data.pools |List of Ceph data pools |Default value: default Ceph |
|
|
| |for storing file. |pool. |
|
|
| | | |
|
|
| | | |
|
|
+---------------------+--------------------------+----------------------------+
|
|
|ceph.localize.reads |Allow reading from file |Default value: true |
|
|
| |replica objects | |
|
|
| | | |
|
|
| | | |
|
|
+---------------------+--------------------------+----------------------------+
|
|
|
|
Support For Per-file Custom Replication
|
|
---------------------------------------
|
|
|
|
The Hadoop file system interface allows users to specify a custom replication
|
|
factor (e.g. 3 copies of each block) when creating a file. However, object
|
|
replication factors in the Ceph file system are controlled on a per-pool
|
|
basis, and by default a Ceph file system will contain only a single
|
|
pre-configured pool. Thus, in order to support per-file replication with
|
|
Hadoop over Ceph, additional storage pools with non-default replications
|
|
factors must be created, and Hadoop must be configured to choose from these
|
|
additional pools.
|
|
|
|
Additional data pools can be specified using the ``ceph.data.pools``
|
|
configuration option. The value of the option is a comma separated list of
|
|
pool names. The default Ceph pool will be used automatically if this
|
|
configuration option is omitted or the value is empty. For example, the
|
|
following configuration setting will consider the pools ``pool1``, ``pool2``, and
|
|
``pool5`` when selecting a target pool to store a file. ::
|
|
|
|
<property>
|
|
<name>ceph.data.pools</name>
|
|
<value>pool1,pool2,pool5</value>
|
|
</property>
|
|
|
|
Hadoop will not create pools automatically. In order to create a new pool with
|
|
a specific replication factor use the ``ceph osd pool create`` command, and then
|
|
set the ``size`` property on the pool using the ``ceph osd pool set`` command. For
|
|
more information on creating and configuring pools see the `RADOS Pool
|
|
documentation`_.
|
|
|
|
.. _RADOS Pool documentation: ../../rados/operations/pools
|
|
|
|
Once a pool has been created and configured the metadata service must be told
|
|
that the new pool may be used to store file data. A pool is be made available
|
|
for storing file system data using the ``ceph mds add_data_pool`` command.
|
|
|
|
First, create the pool. In this example we create the ``hadoop1`` pool with
|
|
replication factor 1. ::
|
|
|
|
ceph osd pool create hadoop1 100
|
|
ceph osd pool set hadoop1 size 1
|
|
|
|
Next, determine the pool id. This can be done by examining the output of the
|
|
``ceph osd dump`` command. For example, we can look for the newly created
|
|
``hadoop1`` pool. ::
|
|
|
|
ceph osd dump | grep hadoop1
|
|
|
|
The output should resemble::
|
|
|
|
pool 3 'hadoop1' rep size 1 min_size 1 crush_ruleset 0...
|
|
|
|
where ``3`` is the pool id. Next we will use the pool id reference to register
|
|
the pool as a data pool for storing file system data. ::
|
|
|
|
ceph mds add_data_pool 3
|
|
|
|
The final step is to configure Hadoop to consider this data pool when
|
|
selecting the target pool for new files. ::
|
|
|
|
<property>
|
|
<name>ceph.data.pools</name>
|
|
<value>hadoop1</value>
|
|
</property>
|
|
|
|
Pool Selection Rules
|
|
~~~~~~~~~~~~~~~~~~~~
|
|
|
|
The following rules describe how Hadoop chooses a pool given a desired
|
|
replication factor and the set of pools specified using the
|
|
``ceph.data.pools`` configuration option.
|
|
|
|
1. When no custom pools are specified the default Ceph data pool is used.
|
|
2. A custom pool with the same replication factor as the default Ceph data
|
|
pool will override the default.
|
|
3. A pool with a replication factor that matches the desired replication will
|
|
be chosen if it exists.
|
|
4. Otherwise, a pool with at least the desired replication factor will be
|
|
chosen, or the maximum possible.
|
|
|
|
Debugging Pool Selection
|
|
~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
Hadoop will produce log file entry when it cannot determine the replication
|
|
factor of a pool (e.g. it is not configured as a data pool). The log message
|
|
will appear as follows::
|
|
|
|
Error looking up replication of pool: <pool name>
|
|
|
|
Hadoop will also produce a log entry when it wasn't able to select an exact
|
|
match for replication. This log entry will appear as follows::
|
|
|
|
selectDataPool path=<path> pool:repl=<name>:<value> wanted=<value>
|