Configuring a Multi-site (WAN) System
Configuring a Multi-site (WAN) System
Plan and configure your multi-site topology, and configure the regions that will be shared between systems.
Before you start, you should understand how to configure membership and communication in peer-to-peer systems using locators. See Configuring Peer-to-Peer Discovery and Configuring Peer Communication. WAN replication is not supported when using multicast for discovery.
WAN deployments increase the messaging demands on a GemFire system. To avoid hangs related to WAN messaging, always set conserve-sockets=false for GemFire members that participate in a WAN deployment. See Controlling Socket Use and Making Sure You Have Enough Sockets.
Use the following steps to configure a multi-site system:
- Plan the topology of your multi-site system. See Multi-site (WAN) Topologies for a description of different multi-site topologies.
- Configure membership and communication for each distributed system in your multi-site system. You must use locators for peer discovery in a WAN configuration. See Configuring Peer-to-Peer Discovery. Start each distributed system using a unique distributed-system-id and identify remote clusters using remote-locators.
- Configure the gateway senders that you will use to distribute region events to remote systems.See Configure Gateway Senders.
- Create the data regions that you want to participate in the multi-site system, specifying the gateway sender(s) that each region should use for WAN distribution. Configure the same regions in the target clusters to apply the distributed events. See Create Data Regions for Multi-site Communication.
- Configure gateway receivers in each GemFire cluster that will receive region events from another cluster. See Configure Gateway Receivers.
- Start distributed system member processes in the correct order (locators first, followed by data nodes) to ensure efficient discovery of WAN resources. See Starting Up Your System.
- (Optional.) Deploy custom conflict resolvers to handle resolve potential conflicts that are detected when applying events from over a WAN. See Resolving Conflicting Events.
- (Optional.) Deploy WAN filters to determine which events are distributed over the WAN, or to modify events as they are distributed over the WAN. See Filtering Events for Multi-Site (WAN) Distribution.
- (Optional.) Configure persistence, conflation, and/or dispatcher threads for gateway sender queues using the instructions in Configuring Event Queues.
Configure Gateway Senders
Each gateway sender configuration includes:
- A unique ID for the gateway sender configuration.
- The distributed system ID of the remote site to which the sender propagates region events.
- A property that specifies whether the gateway sender is a serial gateway sender or a parallel gateway sender.
- Optional properties that configure the gateway sender queue. These queue properties determine features such the amount of memory used by the queue, whether the queue is persisted to disk, and how one or more gateway sender threads dispatch events from the queue.
- For each GemFire system, choose the members that will
host a gateway sender configuration and distribute region events to remote sites:
- You must deploy a parallel gateway sender configuration on each GemFire member that hosts a region that uses the sender.
- You may choose to deploy a serial gateway sender configuration on one or more GemFire members in order to provide high availability. However, only one instance of a given serial gateway sender configuration distributes region events at any given time.
- Configure each gateway sender on a GemFire member using
gfsh, cache.xml or Java API:
gfsh configuration command
gfsh>create gateway-sender --id="sender2" --parallel=true ----remote-distributed-system-id="2" gfsh>create gateway-sender --id="sender3" --parallel=true ----remote-distributed-system-id="3"
These example cache.xml entries configure two parallel gateway senders to distribute region events to two remote GemFire clusters (clusters "2" and "3"):
<cache> <gateway-sender id="sender2" parallel="true" remote-distributed-system-id="2"/> <gateway-sender id="sender3" parallel="true" remote-distributed-system-id="3"/> ... </cache>
This example code shows how to configure a parallel gateway sender using the GemFire API:
// Create or obtain the GemFire cache Cache cache = new CacheFactory().create(); // Configure and create the gateway sender GatewaySenderFactory gateway = cache.createGatewaySenderFactory(); gateway.setParallel(true); GatewaySender sender = gateway.create("sender2", "2"); sender.start();
- gfsh configuration command
- Depending on your applications, you may need to
configure additional features in each gateway sender. Things you need to consider are:
- The maximum amount of memory each gateway
sender queue can use. When the queue exceeds the configured amount of memory, the
contents of the queue overflow to disk. For
gfsh>create gateway-sender --id=sender2 --parallel=true --remote-distributed-system-id=2 --maximum-queue-memory=150In cache.xml:
<gateway-sender id="sender2" parallel="true" remote-distributed-system-id="2" maximum-queue-memory="150"/>
- Whether to enable disk persistence, and
whether to use a named disk store for persistence or for overflowing queue events.
See Persisting an Event Queue. For example:
gfsh>create gateway-sender --id=sender2 --parallel=true --remote-distributed-system-id=2 \ --maximum-queue-memory=150 --enable-persistence=true --disk-store-name=cluster2StoreIn cache.xml:
<gateway-sender id="sender2" parallel="true" remote-distributed-system-id="2" enable-persistence="true" disk-store-name="cluster2Store" maximum-queue-memory="150"/>
- The number of dispatcher threads to use for
processing events from each each gateway queue. The
dispatcher-threads attribute of the gateway sender specifies
the number of threads that process the queue (default of 5). For example:
gfsh>create gateway-sender --id=sender2 --parallel=true --remote-distributed-system-id=2 \ --dispatcher-threads=2 --order-policy=partitionIn cache.xml:
<gateway-sender id="sender2" parallel="false" remote-distributed-system-id="2" dispatcher-threads="2" order-policy="partition"/>Note: When multiple dispatcher threads are configured for a serial queue, each thread operates on its own copy of the gateway sender queue. Queue configuration attributes such as maximum-queue-memory are repeated for each dispatcher thread that you configure.
- For serial gateway senders (parallel=false) that use multiple dispatcher-threads, also configure the ordering policy to use for dispatching the events. See Configuring Dispatcher Threads and Order Policy for Event Distribution.
- Determine whether you should conflate events in the queue. See Conflating Events in a Queue.
- The maximum amount of memory each gateway sender queue can use. When the queue exceeds the configured amount of memory, the contents of the queue overflow to disk. For example:
Create Data Regions for Multi-site Communication
After you define gateway senders, configure regions to use the gateway sender to distribute region events :
gfsh>create region --name=customer --gateway-sender-id=sender2,sender3or to modify an existing region:
gfsh>alter region --name=customer --gateway-sender-id=sender2,sender3
Use the gateway-sender-ids region attribute to add gateway senders to a region. To assign multiple gateway senders, use a comma-separated list. For example:
<region-attributes gateway-sender-ids="sender2,sender3"> </region-attributes>
Java API Configuration
This example shows adding two gateway senders (configured in the earlier example) to a partitioned region:
RegionFactory rf = cache.createRegionFactory(RegionShortcut.PARTITION); rf.addCacheListener(new LoggingCacheListener()); rf.addGatewaySenderId("sender2"); rf.addGatewaySenderId("sender3"); custRegion = rf.create("customer");Note: When using the Java API, you must configure a parallel gateway sender before you add its id to a region. This ensures that the sender distributes region events that were persisted before new cache operations take place. If the gateway sender id does not exist when you add it to a region, you receive an IllegalStateException.
Configure Gateway Receivers
Always configure a gateway receiver in each GemFire cluster that will receive and apply region events from another cluster.
A gateway receiver configuration can be applied to multiple GemFire servers for load balancing and high availability. However, each GemFire member that hosts a gateway receiver must also define all of the regions for which the receiver may receive an event. If a gateway receiver receives an event for a region that the local member does not define, GemFire throws an exception. See Create Data Regions for Multi-site Communication.
A gateway receiver configuration specifies a range of possible port numbers on which to listen. The GemFire server picks an unused port number from the specified range to use for the receiver process. You can use this functionality to easily deploy the same gateway receiver configuration to multiple members.
gfsh>create gateway-receiver --start-port=1530 --end-port=1551
The following configuration defines a gateway receiver that listens on an unused port in the range from 1530 to 1550:
<cache> <gateway-receiver start-port="1530" end-port="1551" hostname-for-senders="gateway1.mycompany.com"/> ... </cache>
// Create or obtain the GemFire cache Cache cache = new CacheFactory().create(); // Configure and create the gateway receiver GatewayReceiverFactory gateway = cache.createGatewayReceiverFactory(); gateway.setStartPort(1530); gateway.setEndPort(1551); gateway.setHostnameForSenders("gateway1.mycompany.com"); GatewayReceiver receiver = gateway.create(); receiver.start();Note: When using the Java API, you must create any region that might receive events from a remote site before you start the gateway receiver. Otherwise, batches of events could arrive from remote sites before the regions for those events have been created. If this occurs, the local site will throw exceptions because the receiving region does not exist yet. If you define regions in cache.xml, the correct startup order is handled automatically.