https://www.java.net/forum/topic/jxta/jxta-community-forum/hadoop-port-jxta-p2p-framework
——————————————————————————————————————————————————————————————————————
Hi,
I started few months ack a port of Hadoop DFS to JXTA to use it to share files across all my PCs and ensure automated replication.
Current version is 0.6.0 and is quite stable. Still have to finalize the Windows poirt but workds fine on other platforms.
Source : https://github.com/besn0847/Jxtadoop
Info : http://fbe-big-data.blogspot.fr/
Binaries : http://sourceforge.net/projects/jxtadoop/
Feel free to comment / criticize ...
Franck
——————————————————————————————————————————
Description
Hadoop is designed to work in large datacenters with thousands of servers connected to each others in the Hadoop cloud. This project focuses on the Distributed File System part of Hadoop (HDFS).
The goal of this project is to provide an alternative to direct IP
connectivity required for Hadoop. Instead, the DFS layer has been
modified to use a Peer-2-Peer framework which allows direct connectivity
in datacenters as well as indirect connectivity to bypass firewall
constraints.
The typical use case is the use of servers in various DMZs with hundreds
of gigabytes of data not used which can be leveraged to provide a
massive storage cloud for Hadoop.
The first release of Jxtadoop focused on providing the data storage layer with P2P capabilities based on the JXTA framework.
——————————————————————————————————————————————————————
History
Genesis
This project started about 1 year and half ago when i thought about creating a private Hadoop cloud to leverage existing servers not located in the same sites. The initial goal was to create a private storage cloud using HDFS.
This cloud was setup using OpenVpn between all the sites but this was not ideal because :
- Using a VPN involves to have all the traffic flowing to one central place even if the nodes are on the same local LAN;
- This solution requires to install a VPN on remote server which couldn't be easily controlled;
Hence the decision to look into an alternative to direct IP connectivity requested by Hadoop nodes.
Concept
The concept is quite simple : the IP connectivity layer is replaced by a P2P one which can handle either direct connections (thru use of multicast) or indirect connections (thru the use of relays & rendez-vous).
——————————————————————————————————————————————————
Peer-to-Peer
This wiki section describes the peer-to-peer layer chosen for Jxtadoop.
Multiple peer-to-peer frameworks exist today and some of them are based on Java. Jxta is a framework designed since 2001 and its current version is 2.7 dating back to H1 2011. This is one of the most comprehensive P2P Java framework even though it is quite complex and is not currently active.
More information can be found at :
I also recommend the reading of Jérôme Verstrynge book : Practical JXTA II (http://amzn.to/zIQ8NH) which is a very good introduction.
Few reasons drove the choice of JXTA :
- JXTA is a longstanding P2P framework (10 years) with recent updates in 2011
- JXTA is developped in Java making seamless integration with Hadoop
- JXTA can cope with LAN and enable direct communications through use of multicasting
- For none direct communications (firewalls, NAT, internet...), JXTA provides the rendez-vous and peers infrastructure to enable those communications
- JXTA provides sockets capabilities which can replace the Hadoop sockets without requiring in-depth Hadoop code rework
- Communications in JXTA can be fully authorized and encrypted to secure communications out of the corporate LAN
- JXTA provides PeerGroup concepts which can be used to isolate datanodes ...
However if you want to support this project and start diving into JXTA you need to know that support it pretty limited, the document is quite poor and the community is small. So your investment can be quite important.
————————————————————————————————————————————————————————
Architecture
The JXTA P2P layer has been implemented aside the Namenode and Datanodes. This layer uses with the basic JXTA features. There is one PeerGroup dedicated for NN and DN RPC and DATA communications.
Security features will be added in the future along with multiple peer groups to isolate and secure RPC comms from DATA comms.
At this P2P level, a monitor is implemented to identify datanode when they connect and disconnect. A notification is then sent to the Namenode which will update the datanode hosts map accordingly.
This has been designed that way since many storage nodes could be connected and disconnected quite often.
On top of this P2P layer, JXTA sockets have been used to minimize the rework at the Namenode and DataNode level.
For the first version the following components have been removed : Balancer, Secondary Namenode and Jetty server.
Code Changes
The following code changes have been made to Hadoop DFS 0.20.2. The next version will be based on Hadoop 1.0.0.
P2P Infrastructure
JXTA layer deployed with a unique peergroup for all comms :
. NN-to-DN : RPC
. DN-to-DN : RPC + data comms
Hadoop RPC Server
The RPC server classes have been modified to support JXTA sockets.
Hadoop Data Block Server
The socket server used to exchange data blocks has been modified to support JXTA sockets.
Components Removal
The following components have been removed from the first version :
. Balancer
. Secondary Namenode
. Http Web Server
Local Buffering
When the used FsShell has a colocated Datanode, the file is loaded to
the local DN only. The replication will then take place in the backend.
Datanodes Notifications
If a Datanode disconnects from the P2P cloud, a notification is
raised by the peer monitor and sent to the Namenode which will remove it
from the hosts map.
Full list of modified classes
Roadmap
This is the roadmap page
2012-01-26
Future work (thoughts)
- Re-include the removed components (balancer, secondary namenode, jetty server)
- Re-work the code to use the Hadoop 1.0.0 branch
Last edit: Jxtadoop Admin 2012-01-28
Instructions
Instructions to start the Namenode & Datanodes
Namenode
1/ Set the JAVA_HOME environment variable
2/ Unzip the jxtadoop-datanode-x.y.z.zip to the target directory
+ chmod the executable in bin/ directory
3/ Edit the etc/hdfs-p2p.xml and set the following 2 properties :
hadoop.p2p.rpc.rdv
hadoop.p2p.rpc.relay
Note that this 2 properties are mandatory even if the same multicast network
to avoid issues with multiple namenodes running in the same network.
4/ Initiliaze the namenode :
> bin/hadoop namenode -format
5/ Start up the namenode
> bin/start-namenode.sh
Datanode
1/ Set the JAVA_HOME environment variable
2/ Unzip the jxtadoop-datanode-x.y.z.zip to the target directory
+ chmod the executable in bin/ directory
3/ Edit the etc/hdfs-p2p.xml and set the following 2 properties :
hadoop.p2p.rpc.rdv
hadoop.p2p.rpc.relay
4/ Start up the namenode
> bin/start-datanode.sh
DFSClient
You can use the DFSClient as per Hadoop. For example
bin/hadoop fs -mkdir /test
bin/hadoop fs -chmod 777 /test
bin/hadoop fs -put ~/tmp/myfile /test
bin/hadoop fs get /test/myfile /tmp
Contact
Mail to : jxtadoop@besnard.mobi
Known issues
i1/ The JXTA layer may generate P2P exceptions upon sockets closure;