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JActor Cluster Platform
JActor Cluster Platform
JActor Cluster Platform
JActor Cluster Platform
JActor Cluster Platform
JActor Cluster Platform
JActor Cluster Platform
JActor Cluster Platform
JActor Cluster Platform
JActor Cluster Platform
JActor Cluster Platform
JActor Cluster Platform
JActor Cluster Platform
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JActor Cluster Platform

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http://jactorconsulting.com/

http://jactorconsulting.com/

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Transcript

  • 1. Distributed, Robust Software Made Easy Introducing theJActor Cluster Platform Bill La Forge, CTO JActor Consulting Pvt. Ltd laforge49@gmail.com http://jactorconsulting.com
  • 2. The Jactor Cluster Platform● Discovers new nodes (JVMs) running in the cluster and detects when a node is no longer active.● Prevents more than one cluster from being active due to a network failure by requiring a quorum of hosts to be present.● Creates and manages Server objects across multiple nodes.● Determines the least busy node in the cluster or on a given host for running a Server.● Provides basic tools for monitoring and configuring the cluster.
  • 3. The Jactor Cluster is a Platform● To port a Java application to the JActor Cluster Platform, you need to write an adapter class, a subclass of Server, for starting and stopping your application and which provides access, as needed, to other servers running in the cluster.● The Apache SSHD Project has already been ported to the JActor Cluster Platform to provide remote console access.● The next port will likely be OSGi.
  • 4. Running the JActor Cluster Platform● Just set the CLASSPATH and run the main function of agilewiki.jaconfig.JACNode on all the hosts of the cluster.● There is a single, optional argument: the port number used to communicate with other nodes in the cluster. It has a default value of 8880.● If no port number is specified, an operator console is also started up.● To run a server, its class file or a jar containing it must be included in the CLASSPATH.● To change the basic configuration, simply subclass JACNode and override the appropriate methods.
  • 5. The Config Database● The config database holds key/value pairs of strings.● This is a fully replicated, eventually consistent database (NOSQL). Every node in the cluster has its own copy.● There is no log file, and no operational complications. If a database copy gets corrupted, it gets rebuilt when the node is restarted.● The database holds the cluster configuration, as well as encrypted operator passwords.● Application servers may subscribe to database change notifications.
  • 6. Cluster Commands (1)● help lists the cluster commands.● halt exits the local node.● who lists the operators that are logged in across the cluster.● broadcast sends a message to all users.● write {name} {msg} sends the msg to an operator.
  • 7. Cluster Commands (2)● localServers lists all the local servers.● startup {server class name} {args string} starts a local server.● server {server name} {command line} sends a command to a local server.● server {server name} help lists the commands of a server.
  • 8. Cluster Commands (3)● channels lists the addresses of the other nodes in the cluster.● heap lists the memory usage of all the nodes in the cluster.● servers lists all the servers running in the cluster.● to {node address} {command line} sends a command to another node.
  • 9. Config Commands● server config values lists all the assignments.● server config assign {name} {value} assigns a value to a name.● server config assign {name} removes an assignment.● server config changePassword changes your password.● server config setPassword {operator name} assigns the operators password.● server config clearPassword {operator name} removes the operators password.
  • 10. Quorum● A cluster is not active unless it has a quorum of hosts. This prevents multiple clusters from running with inconsistent state due to a networking failure.● The value quorum.totalHostCount must be set in the config database. The quorum is calculated as totalHostCount / 2 + 1.● Example: server config assign quorum.totalHostCount 5 requires a quorum of 3.● With a totalHostCount of 5, the cluster will remain active even if 2 hosts are down.
  • 11. Cluster Manager Server● The clusterManager server runs on only one node in the cluster, and only when the server is active.● The clusterManager is used to startup servers which subclass ClusterServer.● The config database is used to drive clusterManager. It looks for assignments of the form clusterManager. {server name} = {server class name} {args string}● Servers started by clusterManager are restarted when the node where they are running goes down.
  • 12. Host Manager Server● A hostManager server runs on one node on every host in the cluster, even if the cluster is not active.● The hostManager is used to startup servers which subclass HostServer. These servers are run on every host in the cluster.● The config database is used to drive the hostManager servers, which look for assignments of the form hostManager.{server name} = {server class name} {args string}
  • 13. SSH Server● The ssh server integrates Apache SSHD and supports operator login via an ssh client like PuTTY.● To have the ssh run on every host in the cluster, just enter this command: server config assign hostManager.ssh org.agilewiki.config.SSHHostServer {ssh port number}● To list all the ssh servers in the cluster, enter this command: server hostManager.ssh all● The all command lists the port number and the number of operators using each ssh server.

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