This chapter includes the following sections:
Parent topic: Using Coherence Clusters
This section includes the following topics:
Parent topic: Starting and Stopping Cluster Members
The com.tangosol.net.DefaultCacheServer
class is used to start a cache server. A cache server can be started from the command line or can be started programmatically. The following arguments are used when starting a cache server:
the name of a cache configuration file that is found on the classpath or the path to a Grid ARchive (GAR). If both are provided, the GAR takes precedence. A GAR includes the artifacts that comprise a Coherence application and adheres to a specific directory structure. A GAR can be left as a directory or can be archived with a .gar
extension. See Building a Coherence GAR Module in Administering Oracle Coherence.
An optional application name for the GAR. If no name is provided, the archive name is used (the directory name or the file name without the .gar
extension). The name provides an application scope that is used to separate applications on a cluster.
the number of seconds between checks for stopped services. Stopped services are only automatically started if they are set to be automatically started (as configured by an <autostart>
element in the cache configuration file). The default value if no argument is provided is 5 seconds.
Parent topic: Starting Cache Servers
Cache servers are typically started from the command line. Use the Java -cp
option to indicate the location of the coherence.jar
file and the location where the tangosol-coherence-override.xml
and coherence-cache-config.xml
files are located. The location of the configuration files must precede the coherence.jar
file on the classpath; otherwise, the default configuration files that are located in the coherence.jar
file are used to start the cache server instance. See Understanding Configuration.
The following example starts a cache server member, uses any configuration files that are placed in the COHERENCE_HOME
\config
directory, and checks for service restarts every 2 seconds.
java -server -Xms512m -Xmx512m -cp COHERENCE_HOME\config;COHERENCE_HOME\lib\coherence.jar com.tangosol.net.DefaultCacheServer 2
The following example starts a cache server member and uses the Coherence application artifacts that are packaged in the MyGar.gar
file. The default name (MyGAR
) is used as the application name.
java -server -Xms512m -Xmx512m -cp COHERENCE_HOME\config;COHERENCE_HOME\lib\coherence.jar com.tangosol.net.DefaultCacheServer D:\example\MyGAR.gar
Note:
The cache configuration file that is packaged in a GAR file takes precedence over a cache configuration file that is located on the classpath.
The COHERENCE_HOME
\bin\cache-server
script is provided as a convenience and can start a cache server instance. The script is available for both Windows (cache-server.cmd
) and UNIX-based platforms (cache-server.sh
). The script sets up a basic environment and then runs the DefaultCacheServer
class. The scripts are typically modified as required for a particular cluster.
Tip:
During testing, it is sometimes useful to create multiple scripts with different names that uniquely identify each cache server. For example: cahe-server-a
, cache-server-b
, and so on.
Lastly, a cache server can be started on the command line by using the java -jar
command with the coherence.jar
library. Cache servers are typically started this way for testing and demonstration purposes. For example:
java -jar COHERENCE_HOME\lib\coherence.jar
Parent topic: Starting Cache Servers
An application can use or extend the DefaultCacheServer
class as required when starting a cache server. For example, an application may want to do some application-specific setup or processing before starting a cache server and its services.
The following example starts a cache server using the main
method:
String[] args = new String[]{"my-cache-config.xml", "5"}; DefaultCacheServer.main(args);
The DefaultCacheServer(ConfigurableCacheFactory)
constructor uses a factory class to create a cache server instance that uses a specified cache configuration file. The following example uses the ExtensibleConfigurableCacheFactory
implementation and creates a DefaultCacheServer
instance and also uses the startAndMonitor(long)
method to start a cache server as in the previous example:
ExtensibleConfigurableCacheFactory.Dependencies deps = ExtensibleConfigurableCacheFactory.DependenciesHelper.newInstance("my-cache-co nfig.xml"); ExtensibleConfigurableCacheFactory factory; factory = new ExtensibleConfigurableCacheFactory(deps); DefaultCacheServer dcs = new DefaultCacheServer(factory); dcs.startAndMonitor(5000);
The static method startDaemon()
method starts a cache server on a dedicated daemon thread and is intended for use within managed containers.
Two additional static start methods (start()
and start(ConfigurableCacheFactory)
) are also available to start a cache server and return control. However, the cache factory class is typically used instead of these methods, which remain for backward compatibility.
Applications that require even more fine-grained control can subclass the DefaultCacheServer
class and override its methods to perform any custom processing as required.
Parent topic: Starting Cache Servers
This section includes the following topics:
Parent topic: Starting and Stopping Cluster Members
Cache clients that use the partition cache service (distributed caches) should not maintain any partitioned data. Cache clients that have storage disabled perform better and use less resources. Partitioned data should only be distributed among cache server instances.
Local storage is disabled on a per-process basis using the coherence.distributed.localstorage
system property. This allows cache clients and servers to use the same configuration descriptors. For example:
java -cp COHERENCE_HOME\config;COHERENCE_HOME\lib\coherence.jar -Dcoherence.distributed.localstorage=false com.MyApp
Parent topic: Starting Cache Clients
Applications that use the com.tangosol.net.CacheFactory
class to get an instance of a cache become cluster members and are considered cache clients. The following example demonstrates the most common way of starting a cache client:
CacheFactory.ensureCluster();
NamedCache cache = CacheFactory.getCache("cache_name");
When starting an application that is a cache client, use the Java -cp
option to indicate the location of the coherence.jar
file and the location where the tangosol-coherence-override.xml
and coherence-cache-config.xml
files are located. The location of the configuration files must precede the coherence.jar
file on the classpath; otherwise, the default configuration files that are located in the coherence.jar
file are used to start the cache server instance. See Understanding Configuration.
The following example starts an application that is a cache client, uses any configuration files that are placed in the COHERENCE_HOME
\config
directory, and disables storage on the member.
java -cp COHERENCE_HOME\config;COHERENCE_HOME\lib\coherence.jar -Dcoherence.distributed.localstorage=false com.MyApp
The COHERENCE_HOME
\bin\coherence
script is provided for testing purposes and can start a cache client instance. The script is available for both Windows (coherence.cmd
) and UNIX-based platforms (coherence.sh
). The script sets up a basic environment, sets storage to be disabled, and then runs the CacheFactory
class, which returns a prompt. The prompt is used to enter commands for interacting with a cache and a cluster. The scripts are typically modified as required for a particular cluster. The class can also be started directly from the command line instead of using the script. For example:
java -cp COHERENCE_HOME\config;COHERENCE_HOME\lib\coherence.jar -Dcoherence.distributed.localstorage=false com.tangosol.net.CacheFactory
If a Coherence application is packaged as a GAR, the GAR can be loaded by the CacheFactory
instance using the server
command at the prompt after the client member starts.
server [<path-to-gar>] [<app-name>]
The following example loads the Coherence application artifacts that are packaged in the MyGar.gar
file. The default name (MyGAR
) is used as the application name.
Map (?) server D:\example\MyGAR.gar
Parent topic: Starting Cache Clients
This section includes the following topics:
Parent topic: Starting and Stopping Cluster Members
Cluster members are most often shutdown using the kill
command when on the UNIX platform and Ctrl+c
when on the Windows platform. These commands initiate the standard JVM shutdown hook which is invoked upon normal JVM termination.
Note:
Issuing the kill -9
command triggers an abnormal JVM termination and the shutdown hook does not run. However, a graceful shutdown is generally not required if a service is known to be node-safe (as seen using JMX management) before termination.
The action a cluster member takes when receiving a shutdown command is configured in the operational override file within the <shutdown-listener>
element. The following options are available:
none
— perform no explicit shutdown actions. This is the suggested value for production unless testing has verified that the behavior on external shutdown is exactly what is desired.
force
— (default) perform a hard-stop on the node by calling Cluster.stop()
. This is the default out-of-box action.
graceful
— perform a normal shutdown by calling Cluster.shutdown(
)
true
— same as force
false
— same as none
The following example sets the shutdown hook to none
.
<?xml version='1.0'?> <coherence xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.oracle.com/coherence/coherence-operational-config" xsi:schemaLocation="http://xmlns.oracle.com/coherence/coherence-operational-config coherence-operational-config.xsd"> <cluster-config> <shutdown-listener> <enabled system-property="coherence.shutdownhook">none</enabled> </shutdown-listener> </cluster-config> </coherence>
The coherence.shutdownhook
system property is used to specify the shutdown hook behavior instead of using the operational override file. For example:
-Dcoherence.shutdownhook=none
Parent topic: Stopping Cluster Members
The DefaultCacheServer
class provides two methods that are used to shutdown a cache server:
Note:
Shutdown is supposed to be called in a standalone application where it shuts down the instance which the DefaultCacheServer
class itself maintains as a static member.
shutdown()
– This is a static method that is used to shut down a cache server that was started on a different thread using the DefaultCacheServer.main()
or DefaultCacheServer.start()
methods.
shutdownServer()
– This method is called on a DefaultCacheServer
instance which an application keeps hold of.
Parent topic: Stopping Cluster Members
Rolling restarts are commonly performed when a cache server or its host computer must be updated or when upgrading a cache server to a new patch set release or patch set update release. However, the technique can also be used whenever you want to restart a cache server that is currently managing a portion of cached data.
Note:
When upgrading a cluster, a rolling restart can only be used to upgrade patch set releases or patch set update releases, but not major or minor releases. See Release Number Format in Administering Oracle Fusion Middleware.
This section includes the following topics:
Parent topic: Starting and Stopping Cluster Members
A rolling restart requires initial consideration and setup prior to starting a cluster. A rolling restart cannot be performed on a cluster that does not meet the following prerequisites:
The cache servers in a cluster must provide enough capacity to handle the shutdown of a single cache server (n minus 1 where n is the number of cache servers in the cluster). An out-of-memory exception or data eviction can occur during a redistribution of data if the cache servers are running at capacity. See Cache Size Calculation Recommendations in Administering Oracle Coherence.
Remote JMX management must be enabled on all cache servers and at least two cache servers must contain an operational MBean server. Ensure that you can connect to the MBean servers using an MBean browser such as JConsole. See Using JMX to Manage Oracle Coherence in Managing Oracle Coherence.
If a cache service is configured to use asynchronous backups, then use the shutdown
method to perform an orderly shut down instead of the stop
method or kill -9
. Otherwise, a member may shutdown before asynchronous backups are complete. The shutdown
method guarantees that all updates are complete.
Parent topic: Performing a Rolling Restart
Use these instructions to restart a cache server. If you are restarting the host computer, then make sure all cache server processes are shutdown before shutting down the computer.
To restart a cache server:
StatusHA
attribute for any cluster member to ensure that the attribute's value is MACHINE-SAFE
. The MACHINE-SAFE
state indicates that all the cache servers running on any given computer could be stopped without data loss. If the attribute is not MACHINE-SAFE
, then additional cache servers, possibly on different computers, must be started before performing a restart. See ServiceMBean in Managing Oracle Coherence.StatusHA
attribute and wait for the state to return to MACHINE-SAFE
.StatusHA
attribute and wait for the state to return to MACHINE-SAFE
.Parent topic: Performing a Rolling Restart