JMS Channels
Contents
Placement in NetarchiveSuite software
Every channel is named after the set of applications instances that are expected to receive messages sent to it. All channel names are constructed privately in the dk.netarkivet.distribute.ChannelID
class. To get a channel, you must use one of the public methods in dk.netarkivet.distribute.Channels
.
Channel Behavior
There are used to types of channels:
- Queue where only one listener takes a message from the queue. For example a queue where request for doing a harvest is only received by one harvester.
- Topic where all listeners takes a copy of the message. For example a batch job which has to be executed by all bitarchive applications.
The type of channel is not affecting the channel name directly. It is indicated by the Channel Prefix, since only channel names starting withALL
are topics, while the rest are queues.
The channel type for different queues is given in a table in the next section.
Naming Conventions
The structure of channel names are as follows:
<Environment Name>_<Channel Prefix>_<Replica Annotation>[_<Machine>][_<Application Instance>]
- Environment Name value must be the same for all channels on all JVMs belonging to a single NetarchiveSuite installation. It identifies the environment for the queue, e.g.: "DEV", "TEST", "RELEASETEST", "CLOVER", "PROD" or initials on developer running personal environment for e.g. sanity tests. It is read from the setting
settings.common.environmentName
of the NetarchiveSuite installation. - Channel Prefix** is constructed by a convention for channel behavior together with denotation of the concerned application(s). For example THE_SCHED uses the convention THE for SCHED denoting the scheduler of the harvester.
. The conventions for channel behavior are: - THE - communicate with singleton in the system.
- THIS - communicate with one uniquely identified instance of a number of distributed listeners.
- ANY - has all instances listening to the same queue.
- ALL - is used for topics only, i.e. topics are sent to all listeners on the channel.
- Use Replica Id** will result in a channel name with the replica identifier in question (which must match possible replicas in settings). In case of no use of replica id the COMMON will be used.
- Use IP Node will result in a channel name with the IP address of the machine whether the application in question is placed. It is read directly from the running system.
. In case of no use of IP Node, nothing will be written. - Use Application Instance Id is used, if only one process is expected to listen to the queue. It will result in a channel name with an identification of the individual application instance. It consists of the application abbreviation (uppercase letters of application name) and the application instance identifier from the settings. It is read from the common settings:
settings.common.applicationName
andsettings.common.applicationInstanceId
.
. In case of no use of Application Instance Id, nothing will be written. - Channel Type is only here to complete the picture. Please refer to the section on channel behavior.
Channel names are constructed as described in the below table (columns described after the table).Channel Prefix
Use Replica Id
(for Replica Annotation)Use IP Node
(for Machine)Use Application Instance Identification
Channel Type
Example
THE_SCHED
No
No
No
Queue
PROD_THE_SCHED_COMMON
ANY_HIGHPRIORITY_HACO
No
No
No
Queue
PROD_ANY_HIGHPRIORITY_HACO_COMMON
ANY_LOWPRIORITY_HACO
No
No
No
Queue
PROD_ANY_LOWPRIORITY_HACO_COMMON
THIS_REPOS_CLIENT
No
Yes
Yes
Queue
PROD_THIS_REPOS_CLIENT_COMMON_130_226_258_7_HCA_HIGH
THE_REPOS
No
No
No
Queue
PROD_THE_REPOS_COMMON
THE_BAMON
Yes
No
No
Queue
PROD_THE_BAMON_TWO
ALL_BA
Yes
No
No
Topic
PROD_ALL_BA_TWO
ANY_BA
Yes
No
No
Queue
PROD_ANY_BA_TWO
THIS_INDEX_CLIENT
No
Yes
Yes
Queue
PROD_THIS_INDEX_CLIENT_COMMON_130_226_258_7_ISA
INDEX_SERVER
No
No
No
Queue
PROD_INDEX_SERVER_COMMON
MONITOR
No
No
No
Queue
PROD_MONITOR_COMMON
ERROR
No
No
No
Queue
PROD_ERROR_COMMON
THE_CR
Yes
No
No
Queue
PROD_THE_CR_THREE
The examples are using values
- Environment name
PROD
- Possible replica identifiers
ONE
orTWO
- IP on machine
130.226.258.7
- Application instances
HCA_HIGH
(for HarvestControllerApplication with instance idHIGH
)ISA
(for IndexServerApplication with instance id""
)
Design Notes
Note that creation of channel names for the ANY xxx_HACO-queues are designed in a way so extension to more priorities is easy.