Hadoop CDC and processes notification with Apache Falcon, Apache ActiveMQ, and Apache Camel

Some weeks (months ? ;)) ago, I started to work on Apache Falcon. First of all, I would like to thanks all Falcon guys: they are really awesome and do a great job (special thanks to Srikanth, Venkatesh, Swetha).

This blog post is a preparation to a set of “recipes documentation” that I will propose in Apache Falcon.

Falcon is in incubation at Apache. The purpose is to provide a data processing and management solution for Hadoop designed for data motion, coordination of data pipelines, lifecycle management, and data discovery. Falcon enables end consumers to quickly onboard their data and its associated processing and management tasks on Hadoop clusters.

A interesting feature provided by Falcon is notifications of the activities in the Hadoop cluster “outside” of the cluster 😉
In this article, we will see how to get two kinds of notification in Camel routes “outside” of the Hadoop cluster:

a Camel route will be notified and triggered when a process is executed in the Hadoop cluster
a Camel route will be notified and triggered when a HDFS location changes (a first CDC feature)

Requirements

If you already have your Hadoop cluster, or you know to install/prepare it, you can skip this step.

In this section, I will create a “real fake” Hadoop cluster on one machine. It’s not really a pseudo-distributed as I will use multiple datanodes and tasktrackers, but all on one machine (of course, it doesn’t make sense, but it’s just for demo purpose ;)).

In addition of Hadoop common components (HDFS namenode/datanodes and M/R jobtracker/tasktracker), Falcon requires Oozie (for scheduling) and ActiveMQ.

By default, Falcon embeds ActiveMQ, but for the demo (and provide screenshots to the ActiveMQ WebConsole), I will use a standalone ActiveMQ instance.

Hadoop “fake” cluster preparation

For the demo, I will “fake” three machines.

I create a demo folder on my machine, and I uncompress hadoop-1.1.2-bin.tar.gz tarball in node1, node2, node3 folders:

$ mkdir demo$ cd demo$ tar zxvf ~/hadoop-1.1.2-bin.tar.gz$ cp -r hadoop-1.1.2 node1$ cp -r hadoop-1.1.2 node2$ cp -r hadoop-1.1.2 node3$ mkdir storage

I also create a storage folder where I will put the nodes’ files. This folder is just for convenience, as it’s easier to restart from scratch, just be deleting the storage folder content.

Node1 will hosts:

the HDFS namenode
a HDFS datanode
the M/R jobtracker
a M/R tasktracker

So, the node1/conf/core-site.xml file contains the location of the namenode:

<?xml version="1.0"><?xml-stylesheet type="text/xsl" href="configuration.xsl"?><!-- node1 conf/core-site.xml --><configuration>  <property>     <name>fs.default.name</name>     <value>hdfs://localhost</value>  </property></configuration>

In the node1/conf/hdfs-site.xml file, we define the storage location for the namenode and the datanode (in the storage folder), and the default replication:

<?xml version="1.0"?><?xml-stylesheet type="text/xsl" href="configuration.xsl"?><!-- node1 conf/hdfs-site.xml --><configuration>  <property>    <name>dfs.name.dir</name>    <value>/home/jbonofre/demo/storage/node1/namenode</value>  </property>  <property>    <name>dfs.data.dir</name>    <value>/home/jbonofre/demo/storage/node1/datanode</value>  </property>  <property>    <name>dfs.replication</name>    <value>3</value>  </property></configuration>

Finally, in node1/conf/mapred-site.xml file, we define the location of the job tracker:

<?xml version="1.0"?><?xml-stylesheet type="text/xsl" href="configuration.xsl"?><!-- node1 conf/mapred-site.xml --><configuration>  <property>    <name>mapred.job.tracker</name>    <value>localhost:8021</value>  </property></configuration>

Node1 is not ready.

Node2 hosts a datanode and a tasktracker. As for node1, the node2/conf/core-site.xml file contains the location of the namenode:

<?xml version="1.0"><?xml-stylesheet type="text/xsl" href="configuration.xsl"?><!-- node2 conf/core-site.xml --><configuration>  <property>     <name>fs.default.name</name>     <value>hdfs://localhost</value>  </property></configuration>

The node2/conf/hdfs-site.xml file contains:

the storage location of the datanode
the network location of the namenode (from node1)
the port numbers used by the datanode (core, IPC, and HTTP in order to be able to start multiple datanodes on the same machine)

<?xml version="1.0"?><?xml-stylesheet type="text/xsl" href="configuration.xsd"?><!-- node2 conf/hdfs-site.xml --><configuration>  <property>    <name>dfs.data.dir</name>    <value>/home/jbonofre/demo/storage/node2/datanode</value>  </property>  <property>    <name>dfs.datanode.address</name>    <value>localhost:50110</value>  </property>  <property>    <name>dfs.datanode.ipc.address</name>    <value>localhost:50120</value>  </property>  <property>    <name>dfs.datanode.http.address</name>    <value>localhost:50175</value>  </property></configuration>

The node2/conf/mapred-site.xml file contains the network location of the jobtracker, and the HTTP port number used by the tasktracker (in order to be able to run multiple tasktracker on the same machine):

<?xml version="1.0"?><?xml-stylesheet type="text/xsl" href="configuration.xsl"?><!-- node2 conf/mapred-site.xml --><configuration>  <property>    <name>mapred.job.tracker</name>    <value>localhost:8021</value>  </property>  <property>    <name>mapred.task.tracker.http.address</name>    <value>localhost:50160</value>  </property></configuration>

Node3 is very similar to node2: it hosts a datanode and a tasktracker. So the configuration is very similar to node2 (just the storage location, and the datanode and tasktracker port numbers are different).

Here’s the node3/conf/core-site.xml file:

<?xml version="1.0"?><?xml-stylesheet type="text/xsl" href="configuration.xsl"?><!-- node3 conf/core-site.xml --><configuration>  <property>    <name>fs.default.name</name>    <value>hdfs://localhost</value>  </property></configuration>

Here’s the node3/conf/hdfs-site.xml:

<?xml version="1.0"?><?xml-stylesheet type="text/xsl" href="configuration.xsl"?><!-- node3 conf/hdfs-site.xml --><configuration>  <property>    <name>dfs.data.dir</name>    <value>/home/jbonofre/demo/storage/node3/datanode</value>  </property>  <property>    <name>dfs.datanode.address</name>    <value>localhost:50210</value>  </property>  <property>    <name>dfs.datanode.ipc.address</name>    <value>localhost:50220</value>  </property>  <property>    <name>dfs.datanode.http.address</name>    <value>localhost:50275</value>  </property></configuration>

Here’s the node3/conf/mapred-site.xml file:

<?xml version="1.0"?><?xml-stylesheet type="text/xsl" href="configuration.xsl"?><!-- node2 conf/mapred-site.xml --><configuration>  <property>    <name>mapred.job.tracker</name>    <value>localhost:8021</value>  </property>  <property>    <name>mapred.task.tracker.http.address</name>    <value>localhost:50260</value>  </property></configuration>

Our “fake” cluster configuration is now ready.

We can format the namenode on node1:

$ cd node1/bin$ ./hadoop namenode -format14/03/06 17:26:38 INFO namenode.NameNode: STARTUP_MSG: /************************************************************STARTUP_MSG: Starting NameNodeSTARTUP_MSG:   host = vostro/127.0.0.1STARTUP_MSG:   args = [-format]STARTUP_MSG:   version = 1.1.2STARTUP_MSG:   build = https://svn.apache.org/repos/asf/hadoop/common/branches/branch-1.1 -r 1440782; compiled by 'hortonfo' on Thu Jan 31 02:03:24 UTC 2013************************************************************/14/03/06 17:26:39 INFO util.GSet: VM type       = 64-bit14/03/06 17:26:39 INFO util.GSet: 2% max memory = 17.78 MB14/03/06 17:26:39 INFO util.GSet: capacity      = 2^21 = 2097152 entries14/03/06 17:26:39 INFO util.GSet: recommended=2097152, actual=209715214/03/06 17:26:39 INFO namenode.FSNamesystem: fsOwner=jbonofre14/03/06 17:26:39 INFO namenode.FSNamesystem: supergroup=supergroup14/03/06 17:26:39 INFO namenode.FSNamesystem: isPermissionEnabled=true14/03/06 17:26:39 INFO namenode.FSNamesystem: dfs.block.invalidate.limit=10014/03/06 17:26:39 INFO namenode.FSNamesystem: isAccessTokenEnabled=false accessKeyUpdateInterval=0 min(s), accessTokenLifetime=0 min(s)14/03/06 17:26:39 INFO namenode.NameNode: Caching file names occuring more than 10 times 14/03/06 17:26:40 INFO common.Storage: Image file of size 114 saved in 0 seconds.14/03/06 17:26:40 INFO namenode.FSEditLog: closing edit log: position=4, editlog=/home/jbonofre/demo/storage/node1/namenode/current/edits14/03/06 17:26:40 INFO namenode.FSEditLog: close success: truncate to 4, editlog=/home/jbonofre/demo/storage/node1/namenode/current/edits14/03/06 17:26:40 INFO common.Storage: Storage directory /home/jbonofre/demo/storage/node1/namenode has been successfully formatted.14/03/06 17:26:40 INFO namenode.NameNode: SHUTDOWN_MSG: /************************************************************SHUTDOWN_MSG: Shutting down NameNode at vostro/127.0.0.1************************************************************/

We are now ready to start the namenode on node1:

$ cd node1/bin$ ./hadoop namenode &

We start the datanode on node1:

$ cd node1/bin$ ./hadoop datanode &

We start the jobtracker on node1:

$ cd node1/bin$ ./hadoop jobtracker &

We start the tasktracker on node1:

$ cd node1/bin$ ./hadoop tasktracker &

Node1 is fully started with the namenode, a datanode, the jobtracker, and a tasktracker.

We start a datanode and a tasktracker on node2:

$ cd node2/bin$ ./hadoop datanode &$ ./hadoop tasktracker &

And finally, we start a datanode and a tasktracker on node3:

$ cd node3/bin$ ./hadoop datanode &$ ./hadoop tasktracker &

We access to the HDFS web console (http://localhost:50070) to verify that the namenode is able to see the 3 live datanodes:

We also access to the MapReduce web console (http://localhost:50030) to verify that the jobtracker is able to see the 3 live tasktrackers:

Oozie

Falcon delegates scheduling of jobs (plannification, re-execution, etc) to Oozie.

Oozie is a workflow scheduler system to manage hadoop jobs, using Quartz internally.

It uses a “custom” Oozie distribution: Falcon adds some addition EL extensions on top of a “regular” Oozie.

Falcon provides a script to create the Falcon custom Oozie distribution: we provide the Hadoop and Oozie version that we need.

We can clone Falcon sources from git and call the src/bin/package.sh with the Hadoop and Oozie target versions that we want:

$ git clone https://git-wip-us.apache.org/repos/asf/incubator-falcon falcon$ cd falcon$ src/bin/package.sh 1.1.2 4.0.0

The package.sh script creates target/oozie-4.0.0-distro.tar.gz in the Falcon sources folder.

In the demo folder, I uncompress oozie-4.0.0-distro.tar.gz tarball:

$ cp ~/oozie-4.0.0-distro.tar.gz$ tar zxvf oozie-4.0.0-distro.tar.gz

We now have a oozie-4.0.0-falcon folder.

Oozie requires a special configuration on the namenode (so on node1). We have to update the node1/conf/core-site.xml file to define the system user “proxied” by Oozie:

<?xml version="1.0"?><?xml-stylesheet type="text/xsl" href="configuration.xsl"?><!-- node1 conf/core-site.xml --><configuration>  <property>    <name>fs.default.name</name>    <value>hdfs://localhost</value>  </property>  <property>    <name>hadoop.proxyuser.jbonofre.hosts</name>    <value>localhost</value>  </property>  <property>    <name>hadoop.proxyuser.jbonofre.groups</name>    <value>localhost</value>  </property></configuration>

NB: don’t forget to restart the namenode to include these changes.

Now, we can prepare the Oozie webapplication. Due to license restriction, it’s up to you to add ExtJS library for Oozie webconsole. To enable it, first, we create a oozie-4.0.0-falcon/libext folder and put ext-2.2.zip archive:

$ cd oozie-4.0.0-falcon$ mkdir libext$ cd libext$ wget "http://extjs.com/deploy/ext-2.2.zip"

We have to populate the libext folder with different additional jar files:

the Hadoop jar files:

$ cp node1/hadoop-core-1.1.2.jar oozie-4.0.0-falcon/libext$ cp node1/hadoop-client-1.1.2.jar oozie-4.0.0-falcon/libext$ cp node1/hadoop-tools-1.1.2.jar oozie-4.0.0-falcon/libext$ cp node1/lib/commons-beanutils-1.7.0.jar oozie-4.0.0-falcon/libext$ cp node1/lib/commons-beanutils-core-1.8.0.jar oozie-4.0.0-falcon/libext$ cp node1/lib/commons-codec-1.4.jar oozie-4.0.0-falcon/libext$ cp node1/lib/commons-collections-3.2.1.jar oozie-4.0.0-falcon/libext$ cp node1/lib/commons-configuration-1.6.jar oozie-4.0.0-falcon/libext$ cp node1/lib/commons-digester-1.8.jar oozie-4.0.0-falcon/libext$ cp node1/lib/commons-el-1.0.jar oozie-4.0.0-falcon/libext$ cp node1/lib/commons-io-2.1.jar oozie-4.0.0-falcon/libext$ cp node1/lib/commons-lang-2.4.jar oozie-4.0.0-falcon/libext$ cp node1/lib/commons-logging-api-1.0.4.jar oozie-4.0.0-falcon/libext$ cp node1/lib/commons-logging-1.1.1.jar oozie-4.0.0-falcon/libext$ cp node1/lib/commons-math-2.1.jar oozie-4.0.0-falcon/libext$ cp node1/lib/commons-net-3.1.jar oozie-4.0.0-falcon/libext

the Falcon Oozie extender:

$ cp falcon-0.5-incubating-SNAPSHOT/oozie/libext/falcon-oozie-el-extension-0.5-incubating-SNAPSHOT.jar oozie-4.0.0-falcon/libext

jar files required for hcatalog, pig from oozie-sharelib-4.0.0-falcon.tar.gz:

$ cd oozie-4.0.0-falcon$ tar zxvf oozie-sharelib-4.0.0-falcon.tar.gz$ cp share/lib/hcatalog/hcatalog-core-0.5.0-incubating.jar libext$ cp share/lib/hcatalog/hive-* libext$ cp share/lib/pig/hsqldb-1.8.0.7.jar libext$ cp share/lib/pig/jackson-* libext$ cp share/lib/hcatalog/libfb303-0.7.0.jar libext$ cp share/lib/hive/log4j-1.2.16.jar libext$ cp libtools/oro-2.0.8.jar libext$ cp share/lib/hcatalog/webhcat-java-client-0.5.0-incubating.jar libext$ cp share/lib/pig/xmlenc-0.52.jar libext$ cp share/lib/pig/guava-11.0.2.jar libext$ cp share/lib/hcatalog/oozie-* libext

We are now ready to setup Oozie.

First, we “assemble” the oozie webapplication (war):

$ cd oozie-4.0.0-falcon/bin$ ./oozie-setup.sh prepare-war  setting CATALINA_OPTS="$CATALINA_OPTS -Xmx1024m"INFO: Adding extension: /home/jbonofre/demo/oozie-4.0.0-falcon/libext/ant-1.6.5.jar...New Oozie WAR file with added 'ExtJS library, JARs' at /home/jbonofre/demo/oozie-4.0.0-falcon/oozie-server/webapps/oozie.warINFO: Oozie is ready to be started

Now, we “upload” the oozie shared libraries on our HDFS, including the falcon shared lib:

$ cd oozie-4.0.0/bin$ ./oozie-setup.sh sharelib create -fs hdfs://localhost -locallib ../oozie-sharelib-4.0.0-falcon.tar.gz  setting CATALINA_OPTS="$CATALINA_OPTS -Xmx1024m"the destination path for sharelib is: /user/jbonofre/share/lib

If we browse the HDFS, we can see the folders created by Oozie.

Finally, we create the Oozie database (where it stores the jobs definition, etc).

$ cd oozie-4.0.0-falcon/bin$ ./oozie-setup.sh db create -run  setting CATALINA_OPTS="$CATALINA_OPTS -Xmx1024m"Validate DB ConnectionDONECheck DB schema does not existDONECheck OOZIE_SYS table does not existDONECreate SQL schemaDONECreate OOZIE_SYS tableDONEOozie DB has been created for Oozie version '4.0.0'The SQL commands have been written to: /tmp/ooziedb-4527318150729236810.sql

The Oozie configuration is done, we start it:

$ cd oozie-4.0.0-falcon/bin$ ./oozied.sh startSetting OOZIE_HOME:          /home/jbonofre/demo/oozie-4.0.0-falconSetting OOZIE_CONFIG:        /home/jbonofre/demo/oozie-4.0.0-falcon/confSourcing:                    /home/jbonofre/demo/oozie-4.0.0-falcon/conf/oozie-env.sh  setting CATALINA_OPTS="$CATALINA_OPTS -Xmx1024m"Setting OOZIE_CONFIG_FILE:   oozie-site.xmlSetting OOZIE_DATA:          /home/jbonofre/demo/oozie-4.0.0-falcon/dataSetting OOZIE_LOG:           /home/jbonofre/demo/oozie-4.0.0-falcon/logsSetting OOZIE_LOG4J_FILE:    oozie-log4j.propertiesSetting OOZIE_LOG4J_RELOAD:  10Setting OOZIE_HTTP_HOSTNAME: vostro.nanthrax.netSetting OOZIE_HTTP_PORT:     11000Setting OOZIE_ADMIN_PORT:     11001Setting OOZIE_HTTPS_PORT:     11443Setting OOZIE_BASE_URL:      http://vostro.nanthrax.net:11000/oozieSetting CATALINA_BASE:       /home/jbonofre/demo/oozie-4.0.0-falcon/oozie-serverSetting OOZIE_HTTPS_KEYSTORE_FILE:     /home/jbonofre/.keystoreSetting OOZIE_HTTPS_KEYSTORE_PASS:     passwordSetting CATALINA_OUT:        /home/jbonofre/demo/oozie-4.0.0-falcon/logs/catalina.outSetting CATALINA_PID:        /home/jbonofre/demo/oozie-4.0.0-falcon/oozie-server/temp/oozie.pidUsing   CATALINA_OPTS:        -Xmx1024m -Dderby.stream.error.file=/home/jbonofre/demo/oozie-4.0.0-falcon/logs/derby.logAdding to CATALINA_OPTS:     -Doozie.home.dir=/home/jbonofre/demo/oozie-4.0.0-falcon -Doozie.config.dir=/home/jbonofre/demo/oozie-4.0.0-falcon/conf -Doozie.log.dir=/home/jbonofre/demo/oozie-4.0.0-falcon/logs -Doozie.data.dir=/home/jbonofre/demo/oozie-4.0.0-falcon/data -Doozie.config.file=oozie-site.xml -Doozie.log4j.file=oozie-log4j.properties -Doozie.log4j.reload=10 -Doozie.http.hostname=vostro.nanthrax.net -Doozie.admin.port=11001 -Doozie.http.port=11000 -Doozie.https.port=11443 -Doozie.base.url=http://vostro.nanthrax.net:11000/oozie -Doozie.https.keystore.file=/home/jbonofre/.keystore -Doozie.https.keystore.pass=password -Djava.library.path=Using CATALINA_BASE:   /home/jbonofre/demo/oozie-4.0.0-falcon/oozie-serverUsing CATALINA_HOME:   /home/jbonofre/demo/oozie-4.0.0-falcon/oozie-serverUsing CATALINA_TMPDIR: /home/jbonofre/demo/oozie-4.0.0-falcon/oozie-server/tempUsing JRE_HOME:        /opt/jdk/1.7.0_51Using CLASSPATH:       /home/jbonofre/demo/oozie-4.0.0-falcon/oozie-server/bin/bootstrap.jarUsing CATALINA_PID:    /home/jbonofre/demo/oozie-4.0.0-falcon/oozie-server/temp/oozie.pid

We access to the Oozie webconsole on http://localhost:11000/oozie/:

ActiveMQ

By default, Falcon embeds ActiveMQ, so generally speaking, you don’t have to install ActiveMQ. However, for the demo, I would like to show how to use a external and standalone ActiveMQ.

I uncompress the apache-activemq-5.7.0-bin.tar.gz tarball in the demo folder:

$ cd demo$ tar zxvf ~/apache-activemq-5.7.0-bin.tar.gz

The default ActiveMQ configuration is fine, we can just start the broker on the default port (61616):

$ cd demo/apache-activemq-5.7.0/bin$ ./activemq console

All the Falcon pre-requirements are done.

Falcon installation

Falcon can be deployed:

standalone: it’s the “regular” deployment mode when you have only one hadoop cluster. It’s the deployment mode that I will use for this CDC demo.
distributed: it’s the deployment to use when you have multiple hadoop clusters, especially if you want to use the Falcon replication feature.

For the installation, we uncompress the falcon-0.5-incubating-SNAPSHOT-bin.tar.gz tarball in the demo folder:

$ cd demo$ tar zxvf ~/falcon-0.5-incubating-SNAPSHOT-bin.tar.gz

Before starting Falcon, we disable the default embedded ActiveMQ broker in the conf/falcon-env.sh file:

# conf/falcon-env.sh...export FALCON_OPTS="-Dfalcon.embeddedmq=false"...

We start the falcon server:

$ cd falcon-0.5-incubating-SNAPSHOT/bin$ ./falcon-start Could not find installed hadoop and HADOOP_HOME is not set.Using the default jars bundled in /home/jbonofre/demo/falcon-0.5-incubating-SNAPSHOT/hadooplibs//home/jbonofre/demo/falcon-0.5-incubating-SNAPSHOT/binfalcon started using hadoop version:  Hadoop 1.1.2

The falcon server starts actually a Jetty container with jersey to expose the Falcon REST API.

You can check if the falcon server started correctly using bin/falcon-status or bin/falcon:

$ bin/falcon-statusFalcon server is running (on http://localhost:15000/)$ bin/falcon admin -statusFalcon server is running (on http://localhost:15000/)$ bin/falcon admin -versionFalcon server build version: {"properties":[{"key":"Version","value":"0.5-incubating-SNAPSHOT-r5445e109bc7fbfea9295f3411a994485b65d1477"},{"key":"Mode","value":"embedded"}]}

Falcon usage: the entities

In Falcon, the configuration is defined by “entity”. Falcon supports three types of entity:

cluster entity defines the hadoop cluster (location of the namenode, location of the jobtracker), related falcon module (Oozie, ActiveMQ), and the location of the Falcon working directories (on HDFS)
feed entity defines a location on HDFS
process entity defines a hadoop job scheduled by Oozie

An entity is described using XML. You can do different actions on an entity:

Submit: register an entity in Falcon. Submitted entity are not scheduled, meaning it would simply be in the configuration store of Falcon.
List: provide the list of all entities registered in the configuration store of Falcon.
Dependency: provide the dependency of an entity. For example, a feed would show process that are dependent on the feed and the clusters that it depends on.
Schedule: feeds or processes that are already submitted and present in the configuration store can be scheduled. Upon schedule, Falcon system wraps the required repeatable action as a bundle of oozie coordinators and executes them on the Oozie scheduler.
Suspend: this action is applicable only on scheduled entity. This triggers suspend on the oozie bundle that was scheduled earlier through the schedule function. No further instances are executed on a suspended process/feed.
Resume: put a suspended process/feed back to active, which in turn resumes applicable oozie bundle.
Status: to display the current status of an entity.
Definition: dump the entity definition from the configuration store.
Delete: remote an entity from the Falcon configuration store.
Update: update operation allows an already submitted/scheduled entity to be updated. Cluster update is currently not allowed. Feed update can cause cascading update to all the processes already scheduled. The following set of actions are performed in Oozie to realize an update.
- Suspend the previously scheduled Oozie coordinator. This is prevent any new action from being triggered.
- Update the coordinator to set the end time to “now”
- Resume the suspended coordinators
- Schedule as per the new process/feed definition with the start time as “now”

Cluster

The cluster entity defines the configuration of the hadoop cluster and components used by Falcon.

We will store the entity descriptors in the entity folder:

$ mkdir entity

For the cluster, we create entity/local.xml file:

<?xml version="1.0" encoding="UTF-8"?><cluster colo="local" description="Local cluster" name="local" xmlns="uri:falcon:cluster:0.1">  <interfaces>    <interface type="readonly" endpoint="hftp://localhost:50010" version="1.1.2"/>    <interface type="write" endpoint="hdfs://localhost:8020" version="1.1.2"/>    <interface type="execute" endpoint="localhost:8021" version="1.1.2"/>    <interface type="workflow" endpoint="http://localhost:11000/oozie/" version="4.0.0"/>    <interface type="messaging" endpoint="tcp://localhost:61616" version="5.7.0"/>  </interfaces>  <locations>    <location name="staging" path="/falcon/staging"/>    <location name="temp" path="/falcon/temp"/>    <location name="working" path="/falcon/working"/>  </locations>  <properties></properties></cluster>

A cluster contains different interfaces and locations used by Falcon. A cluster is referenced by feeds and processes entities (using the cluster name). A cluster can’t be scheduled (it doesn’t make sense).

The colo specifies a kind of cluster grouping. It’s used in distributed deployment mode, so not useful in our demo (as we have only one cluster).
The readonly interface specifies the Hadoop’s HFTP protocol, only used in the case of feed replication between clusters (again, not use in our demo).
The write interface specifies the write access to hdfs, containing the fs.default.name value. Falcon uses this interface to write system data to hdfs and feeds referencing this cluster are written to hdfs using this interface.
The execute interface specifies the location of the jobtracker, containing the mapred.job.tracker value. Falcon uses this interface to submit the processes as jobs in the jobtracker defined here.
The workflow interface specifies the interface for worklow engine (the Oorie URL). Falcon uses this interface to schedule the processes referencing this cluster on workflow engine defined here.
Optionally, you can have a registry interface (defininng thrift URL) to specify the metadata catalog, such as Hive Metastore (or HCatalog). We don’t use it in our demo.
The messaging interface specifies the interface for sending feed availability messages. It’s the URL of the ActiveMQ broker.

A cluster has a list of locations with a name (working, temp, staging) and a path on HDFS. Falcon would use the location to do intermediate processing of entities in hdfs and hence Falcon should have read/write/execute permission on these locations.

Optionally, a cluster may have a list of properties. It’s a list of key-value pairs used in Falcon and propagated to the workflow engine. For instance, you can specify the JMS broker connection factory:

<property name="brokerImplClass" value="org.apache.activemq.ActiveMQConnectionFactory" />

Now, that we have the XML description, we can register our cluster in Falcon. We use the Falcon client commandline to do submit our cluster definition:

$ cd falcon-0.5-incubating-SNAPSHOT$ bin/falcon entity -submit -type cluster -file ~/demo/local.xmldefault/Submit successful (cluster) local

We can check that our local cluster is actually present in the Falcon configuration store:

$ bin/falcon entity -list -type cluster(cluster) local(null)

We can see our cluster “local”, for now without any dependency (null).

If we take a look on hdfs, we can see that the falcon directory has been created:

$ cd node1$ bin/hadoop fs -ls /Found 3 itemsdrwxr-xr-x   - jbonofre supergroup          0 2014-03-08 07:48 /falcondrwxr-xr-x   - jbonofre supergroup          0 2014-03-06 17:32 /tmpdrwxr-xr-x   - jbonofre supergroup          0 2014-03-06 18:05 /user

Feed

A feed entity is a location on the cluster. It also defines additional attributes like frequency, late-arrival handling, and retention policies. A feed can be scheduled, meaning that Falcon will create processes to deal with retention and replication on the cluster.

As other entity, a feed is described using a XML. We create entity/output.xml file:

<?xml version="1.0" encoding="UTF-8"?><feed description="RandomProcess output feed" name="output" xmlns="uri:falcon:feed:0.1">  <group>output</group>   <frequency>minutes(1)</frequency>  <timezone>UTC</timezone>  <late-arrival cut-off="minutes(5)"/>  <clusters>    <cluster name="local">       <validity start="2012-07-20T03:00Z" end="2099-07-16T00:00Z"/>       <retention limit="hours(10)" action="delete"/>    </cluster>  </clusters>  <locations>    <location type="data" path="/data/output"/>  </locations>  <ACL owner="jbonofre" group="supergroup" permission="0x644"/>  <schema location="none" provider="none"/></feed>

The locations element define the feed storage. It’s paths on HDFS or table names for Hive. A location is define on a cluster, identified by name. In our example, we use the “local” cluster that we submitted before.

The group element defines a list of comma separated groups. A group is a logical grouping of feeds. A group is said available if all the feeds belonging to a group are available. The frequency of all the feeds which belong to the same group must be same.

The frequency element specifies the frequency by which this feed is generated (for instance, it can generated every hour, every 5 minutes, daily, weekly, etc). Falcon uses this frequency to check if the feed has changed or not (the size has changed). In our example, we define a frequency of every minute. Falcon creates a job in Oozie to monitor the feed.
Falcon system can handle late arrival of input data and appropriately re-trigger processing for the affected instance. From the perspective of late handling, there are two main configuration parameters late-arrival cut-off and late-inputs section in feed and process entity definition that are central. These configurations govern how and when the late processing happens. In the current implementation (oozie based) the late handling is very simple and basic. The falcon system looks at all dependent input feeds for a process and computes the max late cut-off period. Then it uses a scheduled messaging framework, like the one available in Apache ActiveMQ to schedule a message with a cut-off period, then after a cut-off period the message is dequeued and Falcon checks for changes in the feed data which is recorded in HDFS in late data file by Falcons “record-size” action, if it detects any changes then the workflow will be rerun with the new set of feed data.

The retention element specifies how long the feed is retained on the cluster and the action to be taken on the feed after the expiration of the retention period. In our example, we delete the feed after a retention of 10 days.

The validity of a feed on cluster specifies duration for which this feed is valid on this cluster (considered for scheduling by Falcon).

The ACL defines the permission on the feed (owner/group/permission).

The schema allows you to specific the “format” of the feed (for instance csv). In our case, we don’t define any schema.

We can now submit the feed (register the feed) into Falcon:

$ cd falcon-0.5-incubating-SNAPSHOT$ bin/falcon entity -submit -type feed -file ~/demo/entity/output.xmldefault/Submit successful (feed) output

Process

A process entity defines a job in the cluster.

Like other entity, a process is described with XML (entity/process.xml):

<?xml version="1.0" encoding="UTF-8"?><process name="my-process" xmlns="uri:falcon:process:0.1">    <clusters>        <cluster name="local">            <validity start="2013-11-15T00:05Z" end="2030-11-15T01:05Z"/>        </cluster>    </clusters>    <parallel>1</parallel>    <order>FIFO</order>    <frequency>minutes(5)</frequency>    <timezone>UTC</timezone>    <inputs>        <!-- In the workflow, the input paths will be available in a variable 'inpaths' -->        <input name="inpaths" feed="input" start="now(0,-5)" end="now(0,-1)"/>    </inputs>    <outputs>        <!-- In the workflow, the output path will be available in a variable 'outpath' -->        <output name="outpath" feed="output" instance="now(0,0)"/>    </outputs>    <properties>        <!-- In the workflow, these properties will be available with variable - key -->        <property name="queueName" value="default"/>        <!-- The schedule time available as a property in workflow -->        <property name="time" value="${instanceTime()}"/>    </properties>    <workflow engine="oozie" path="/app/mr"/>    <late-process policy="periodic" delay="minutes(1)">       <late-input input="inpaths" workflow-path="/app/mr"/>    </late-process></process>

The cluster element defines where the process will be executed. Each cluster has a validity period, telling the times between which the job should run on the cluster. For the demo, we set a large validity period.

The parallel element defines how many instances of the process can run concurrently. We set a value of 1 here to ensure that only one instance of the process can run at a time.

The order element defines the order in which the ready instances are picked up. The possible values are FIFO(First In First Out), LIFO(Last In First Out), and ONLYLAST(Last Only). It’s not really used in our case.

The frequency element defines how frequently the process should run. In our case, minutes(5) means that the job will run every 5 minutes.

The inputs element defines the input data for the process. The process job will start executing only after the schedule time and when all the inputs are available. There can be 0 or more inputs and each of the input maps to a feed. The path and frequency of input data is picked up from feed definition. Each input should also define start and end instances in terms of EL expressions and can optionally specify specific partition of input that the process requires. The components in partition should be subset of partitions defined in the feed.
For each input, Falcon will create a property with the input name that contains the comma separated list of input paths. This property can be used in process actions like pig scripts and so on.

The outputs element defines the output data that is generated by the process. A process can define 0 or more outputs. Each output is mapped to a feed and the output path is picked up from feed definition. The output instance that should be generated is specified in terms of EL expression.
For each output, Falcon creates a property with output name that contains the path of output data. This can be used in workflows to store in the path.

The properties element contains key value pairs that are passed to the process. These properties are optional and can be used to parameterize the process.

The workflow element defines the workflow engine that should be used and the path to the workflow on hdfs. The workflow definition on hdfs contains the actual job that should run and it should confirm to the workflow specification of the engine specified. The libraries required by the workflow should be in lib folder inside the workflow path.
The properties defined in the cluster and cluster properties(nameNode and jobTracker) will also be available for the workflow.
Currently, Falcon supports three workflow engines:

oozie enables users to provide a Oozie workflow definition (in XML).
pig enables users to embed a Pig script as a process
hive enables users to embed a Hive script as a process. This would enable users to create materialized queries in a declarative way.

NB: I proposed to support a new type of workflow: MapReduce, to be able to directly execute MapReduce job.

In this demo, we use the oozie workflow engine.

We create a Oozie workflow.xml:

<?xml version="1.0" encoding="UTF-8"?><workflow-app xmlns="uri:oozie:workflow:0.2" name="map-reduce-wf">    <start to="mr-node"/>    <action name="mr-node">        <map-reduce>            <job-tracker>${jobTracker}</job-tracker>            <name-node>${nameNode}</name-node>            <prepare>                <delete path="${outpath}"/>            </prepare>            <configuration>                <property>                    <name>mapred.job.queue.name</name>                    <value>${queueName}</value>                </property>                <property>                    <name>mapred.mapper.class</name>                    <value>org.apache.hadoop.mapred.lib.IdentityMapper</value>                </property>                <property>                    <name>mapred.reducer.class</name>                    <value>org.apache.hadoop.mapred.lib.IdentityReducer</value>                </property>                <property>                    <name>mapred.map.tasks</name>                    <value>1</value>                </property>                <property>                    <name>mapred.input.dir</name>                    <value>${inpaths}</value>                </property>                <property>                    <name>mapred.output.dir</name>                    <value>${outpath}</value>                </property>            </configuration>        </map-reduce>        <ok to="end"/>        <error to="fail"/>    </action>    <kill name="fail">        <message>Map/Reduce failed, error message[${wf:errorMessage(wf:lastErrorNode())}]</message>    </kill>    <end name="end"/></workflow-app>

This workflow is very simple: it uses IdentityMapper and IdentityReducer (provided in Hadoop core) to copy input data as output data.

We upload this workflow.xml on HDFS (in the location specified in the Falcon process workflow element):

$ cd node1$ bin/hadoop fs -mkdir /app/mr$ bin/hadoop fs -put ~/demo/workflow.xml /app/mr

The late-process allows the process to react with the input feed changes and trigger an action (here, we re-execute the oozie workflow).

We are now ready to submit the process in Falcon:

$ cd falcon-*$ bin/falcon entity -submit -type process -file ~/entity/process.xml

The process is ready to be scheduled.

Before scheduling the process, we create the input data. The input data is a simple file (containing a string) that we upload to HDFS:

$ cat > file1This is a test file$ node1/bin/hadoop fs -mkdir /data/input$ node1/bin/hadoop fs -put file1 /data/input

We can now trigger the process:

$ cd falcon*$ bin/falcon entity -schedule -type process -name my-processdefault/my-process(process) scheduled successfully

We can see the different jobs in Oozie (accessing http://localhost:11000/oozie):

On the other hand, we see new topics and queues created in ActiveMQ:

Especially, in ActiveMQ, we have two topics:

Falcon publishes messages in the FALCON.my-process topic for each execution of the process
Falcon publishes messages in the FALCON.ENTITY.TOPIC topic for each change on the feeds

It’s where our Camel routes subscribe.

Camel routes in Karaf

Now that we have our Falcon platform ready, we just have to create Camel routes (hosted in Karaf container), subscribing on the Falcon topics in ActiveMQ.

We uncompress a Karaf container, and install the Camel features (camel-spring, activemq-camel):

$ tar zxvf apache-karaf-2.3.1.tar.gz$ cd apache-karaf-2.3.1$ bin/karafkaraf@root> features:chooseurl cameladding feature url mvn:org.apache.camel.karaf/apache-camel/LATEST/xml/featureskaraf@root> features:install camel-springkaraf@root> features:chooseurl activemqkaraf@root> features:install activemq-camel

We create a falcon-route.xml route file containing the Camel routes (using Spring DSL):

<?xml version="1.0" encoding="UTF-8"?><beans xmlns="http://www.springframework.org/schema/beans"       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"       xsi:schemaLocation="         http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd         http://camel.apache.org/schema/spring http://camel.apache.org/schema/spring/camel-spring.xsd">  <camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">    <route id="process-listener">       <from uri="jms:topic:FALCON.my-process"/>       <to uri="log:process-listener"/>    </route>    <route id="feed-listener">       <from uri="jms:topic:FALCON.ENTITY.TOPIC"/>       <to uri="log:feed-listener"/>    </route>  </camelContext>  <bean id="jms" class="org.apache.camel.component.jms.JmsComponent">    <property name="connectionFactory">      <bean class="org.apache.activemq.ActiveMQConnectionFactory">        <property name="brokerURL" value="tcp://localhost:61616"/>      </bean>    </property>  </bean></beans>

In the Camel context, we create two routes, both connecting on the ActiveMQ broker, and listening on the two topics.

We drop the falcon-routes.xml in the deploy folder, and we can see it active:

karaf@root> la|grep -i falcon[ 114] [Active     ] [            ] [Started] [   80] falcon-routes.xml (0.0.0)karaf@root> camel:route-list  Context        Route              Status    -------        -----              ------    camel          feed-listener      Started   camel          process-listener   Started

The routes subscribed on the topics and just send to the log (it’s very very simple).

So, we just have to take a look on the log (log:tail):

2014-03-19 11:25:43,273 | INFO  | LCON.my-process] | process-listener                 | rg.apache.camel.util.CamelLogger  176 | 74 - org.apache.camel.camel-core - 2.13.0.SNAPSHOT | Exchange[ExchangePattern: InOnly, BodyType: java.util.HashMap, Body: {brokerUrl=tcp://localhost:61616, timeStamp=2014-03-19T10:24Z, status=SUCCEEDED, logFile=hdfs://localhost:8020/falcon/staging/falcon/workflows/process/my-process/logs/instancePaths-2013-11-15-06-05.csv, feedNames=output, runId=0, entityType=process, nominalTime=2013-11-15T06:05Z, brokerTTL=4320, workflowUser=null, entityName=my-process, feedInstancePaths=hdfs://localhost:8020/data/output, operation=GENERATE, logDir=null, workflowId=0000026-140319105443372-oozie-jbon-W, cluster=local, brokerImplClass=org.apache.activemq.ActiveMQConnectionFactory, topicName=FALCON.my-process}]2014-03-19 11:25:43,693 | INFO  | ON.ENTITY.TOPIC] | feed-listener                    | rg.apache.camel.util.CamelLogger  176 | 74 - org.apache.camel.camel-core - 2.13.0.SNAPSHOT | Exchange[ExchangePattern: InOnly, BodyType: java.util.HashMap, Body: {brokerUrl=tcp://localhost:61616, timeStamp=2014-03-19T10:24Z, status=SUCCEEDED, logFile=hdfs://localhost:8020/falcon/staging/falcon/workflows/process/my-process/logs/instancePaths-2013-11-15-06-05.csv, feedNames=output, runId=0, entityType=process, nominalTime=2013-11-15T06:05Z, brokerTTL=4320, workflowUser=jbonofre, entityName=my-process, feedInstancePaths=hdfs://localhost:8020/data/output, operation=GENERATE, logDir=hdfs://localhost:8020/falcon/staging/falcon/workflows/process/my-process/logs/job-2013-11-15-06-05/, workflowId=0000026-140319105443372-oozie-jbon-W, cluster=local, brokerImplClass=org.apache.activemq.ActiveMQConnectionFactory, topicName=FALCON.ENTITY.TOPIC}]

And we can see our notifications:

on the process-listener logger, we can see that my-process (entityName) has been executed with SUCCEEDED (status) at 2014-03-19T10:24Z (timeStamp). We also have the location of the job execution log on HDFS.
on the feed-listener logger, we can see quite the same messages. This message comes from the late-arrival, so it means that the input field changed.

For sure, the Camel routes are very simple now (just a log), but there is no limit: you bring all the powerful from ESB and BigData all together.
Once the Camel routes get the messages on ActiveMQ coming from Falcon, you can implement the integration process of your choice (sending e-mails, using Camel EIPs, calling beans, etc).

What’s next ?

I’m working on different enhancements on the late-arrival/CDC feature:

The late-arrival messages in the FALCON.ENTITY.TOPIC should be improved: the message should contain a message with the feed changed, the location of the feed, eventually the size gap.
We should provide a more straight forward CDC feature which doesn’t require a process to monitor a feed. Just scheduling a feed should be enough with the late cut-off.
In addition of the oozie, pig, and hive workflow engine, we should provide a “pure” MapReduce jar workflow engine.
The package.sh should be improved to provide a more “ready” to use Falcon Oozie custom distribution.

I’m working on this different enhancements and improvements.

On the other hand, I will propose a set of documentation improvements, especially some kind of “recipe documentation” like this one.

Stay tuned, I’m preparing a new blog about Falcon, this time about the replication between two Hadoop clusters.

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