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Data Grid Guide to Cross-Site Replication

Red Hat Data Grid 8.2

Back up data across global Data Grid clusters

Red Hat Customer Content Services

Abstract

Data Grid can form global clusters to replicate your data across geographic locations. This guide explains how to configure backup locations for caches and perform cross-site operations. You can also learn how to monitor and troubleshoot global clusters.

Red Hat Data Grid

Data Grid is a high-performance, distributed in-memory data store.

Schemaless data structure: Flexibility to store different objects as key-value pairs.
Grid-based data storage: Designed to distribute and replicate data across clusters.
Elastic scaling: Dynamically adjust the number of nodes to meet demand without service disruption.
Data interoperability: Store, retrieve, and query data in the grid from different endpoints.

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Documentation for Data Grid is available on the Red Hat customer portal.

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Access the Data Grid Software Downloads on the Red Hat customer portal.

Note

You must have a Red Hat account to access and download Data Grid software.

Making open source more inclusive

Red Hat is committed to replacing problematic language in our code, documentation, and web properties. We are beginning with these four terms: master, slave, blacklist, and whitelist. Because of the enormity of this endeavor, these changes will be implemented gradually over several upcoming releases. For more details, see our CTO Chris Wright’s message.

Chapter 1. Data Grid Cross-Site Replication

Cross-site replication allows you to back up data from one Data Grid cluster to another. Learn the concepts to understand how Data Grid cross-site replication works before you configure your clusters.

1.1. Cross-Site Replication

Data Grid clusters running in different locations can discover and communicate with each other.

Sites are typically data centers in various geographic locations. Cross-site replication bridges Data Grid clusters in sites to form global clusters, as in the following diagram:

LON is a datacenter in London, England.
NYC is a datacenter in New York City, USA.

Note

Data Grid can form global clusters across two or more sites.

For example, configure a third Data Grid cluster running in San Francisco, SFO, as backup location for LON and NYC.

1.1.1. Site Masters

Site masters are the nodes in Data Grid clusters that are responsible for sending and receiving requests from backup locations.

If a node is not a site master, it must forward backup requests to a local site master. Only site masters can send requests to backup locations.

For optimal performance, you should configure all nodes as site masters. This increases the speed of backup requests because each node in the cluster can backup to remote sites directly without having to forward backup requests to site masters.

Note

Diagrams in this document illustrate Data Grid clusters with one site master because this is the default for the JGroups RELAY2 protocol. Likewise, a single site master is easier to illustrate because each site master in a cluster communicates with each site master in the remote cluster.

1.2. Adding Backups to Caches

Name remote sites as backup locations in your cache definitions.

For example, the following diagram shows three caches, "customers", "eu-orders", and "us-orders":

In LON, "customers" names NYC as a backup location.
In NYC, "customers" names LON as a backup location.
"eu-orders" and "us-orders" do not have backups and are local to the respective cluster.

1.3. Backup strategies

Data Grid replicates data between clusters at the same time that writes to caches occur. For example, if a client writes "k1" to LON, Data Grid backs up "k1" to NYC at the same time.

To back up data to a different cluster, Data Grid can use either a synchronous or asynchronous strategy.

Synchronous strategy

When Data Grid replicates data to backup locations, it writes to the cache on the local cluster and the cache on the remote cluster concurrently. With the synchronous strategy, Data Grid waits for both write operations to complete before returning.

You can control how Data Grid handles writes to the cache on the local cluster if backup operations fail. Data Grid can do the following:

Ignore the failed backup and silently continue the write to the local cluster.
Log a warning message or throw an exception and continue the write to the local cluster.
Handle failed backup operations with custom logic.

Synchronous backups also support two-phase commits with caches that participate in optimistic transactions. The first phase of the backup acquires a lock. The second phase commits the modification.

Important

Two-phase commit with cross-site replication has a significant performance impact because it requires two round-trips across the network.

Asynchronous strategy

When Data Grid replicates data to backup locations, it does not wait until the operation completes before writing to the local cache.

Asynchronous backup operations and writes to the local cache are independent of each other. If backup operations fail, write operations to the local cache continue and no exceptions occur. When this happens Data Grid also retries the write operation until the remote cluster disconnects from the cross-site view.

Synchronous vs asynchronous backups

Synchronous backups offer the strongest guarantee of data consistency across sites. If strategy=sync, when cache.put() calls return you know the value is up to date in the local cache and in the backup locations.

The trade-off for this consistency is performance. Synchronous backups have much greater latency in comparison to asynchronous backups.

Asynchronous backups, on the other hand, do not add latency to client requests so they have no performance impact. However, if strategy=async, when cache.put() calls return you cannot be sure of that the value in the backup location is the same as in the local cache.

1.4. Automatically Taking Backups Offline

You can configure backup locations to go offline automatically when the remote sites become unavailable. This prevents Data Grid nodes from continuously attempting to replicate data to offline backup locations, which results in error messages and consumes resources.

Timeout for backup operations

Backup configurations include timeout values for operations to replicate data. If operations do not complete before the timeout occurs, Data Grid records them as failures.

<!-- Operations to replicate data to NYC are recorded as failures if they do not complete after 10 seconds. -->
<backup site="NYC" strategy="ASYNC" timeout="10000">
	<!-- Configuration for backup locations goes here. -->
</backup>

Number of failures

You can specify the number of consecutive failures that can occur before backup locations go offline.

For example, the following configuration for NYC sets five as the number of failed operations before it goes offline:

<!-- If a cluster attempts to replicate data to NYC and five consecutive operations fail, NYC automatically goes offline. -->
<backup site="NYC" strategy="ASYNC" timeout="10000">
  <take-offline after-failures="5"/>
</backup>

Time to wait

You can also specify how long to wait before taking sites offline when backup operations fail. If a backup request succeeds before the wait time runs out, Data Grid does not take the site offline.

<!-- If a cluster attempts to replicate data to NYC and there are more than five consecutive failures and 15 seconds elapse after the first failed operation, NYC automatically goes offline. -->
<backup site="NYC" strategy="ASYNC" timeout="10000">
  <take-offline after-failures="5"
                min-wait="15000"/>
</backup>

Tip

Set a negative or zero value for the after-failures attribute if you want to use only a minimum time to wait to take sites offline.

<take-offline after-failures="-1" min-wait="10000"/>

1.5. State Transfer

State transfer is an administrative operation that synchronizes data between sites.

For example, LON goes offline and NYC starts handling client requests. When you bring LON back online, the Data Grid cluster in LON does not have the same data as the cluster in NYC.

To ensure the data is consistent between LON and NYC, you can push state from NYC to LON.

State transfer is bidirectional. For example, you can push state from NYC to LON or from LON to NYC.
Pushing state to offline sites brings them back online.
State transfer overwrites only data that exists on both sites, the originating site and the receiving site. Data Grid does not delete data.
For example, "k2" exists on LON and NYC. "k2" is removed from NYC while LON is offline. When you bring LON back online, "k2" still exists at that location. If you push state from NYC to LON, the transfer does not affect "k2" on LON.

Tip

To ensure contents of the cache are identical after state transfer, remove all data from the cache on the receiving site before pushing state.

Use the clear() method or the clearcache command from the CLI.

State transfer does not overwrite updates to data that occur after you initiate the push.
For example, "k1,v1" exists on LON and NYC. LON goes offline so you push state transfer to LON from NYC, which brings LON back online. Before state transfer completes, a client puts "k1,v2" on LON.
In this case the state transfer from NYC does not overwrite "k1,v2" because that modification happened after you initiated the push.

1.5.1. Automatic State Transfer

By default you must manually perform cross-site state transfer operations with the CLI or via JMX or REST.

However, when using the asynchronous backup strategy, Data Grid can automatically perform cross-site state transfer operations. When it detects that a backup location has come back online, and the network connection is stable, Data Grid initiates bi-directional state transfer between backup locations. For example, Data Grid simultaneously transfers state from LON to NYC and NYC to LON.

Note

To avoid temporary network disconnects triggering state transfer operations, there are two conditions that backup locations must meet to go offline. The status of a backup location must be offline and it must not be included in the cross-site view with JGroups RELAY2.

Reference

1.6. Client Connections Across Sites

Clients can write to Data Grid clusters in either an Active/Passive or Active/Active configuration.

Active/Passive

The following diagram illustrates Active/Passive where Data Grid handles client requests from one site only:

In the preceding image:

Client connects to the Data Grid cluster at LON.
Client writes "k1" to the cache.
The site master at LON, "n1", sends the request to replicate "k1" to the site master at NYC, "nA".

With Active/Passive, NYC provides data redundancy. If the Data Grid cluster at LON goes offline for any reason, clients can start sending requests to NYC. When you bring LON back online you can synchronize data with NYC and then switch clients back to LON.

Active/Active

The following diagram illustrates Active/Active where Data Grid handles client requests at two sites:

In the preceding image:

Client A connects to the Data Grid cluster at LON.
Client A writes "k1" to the cache.
Client B connects to the Data Grid cluster at NYC.
Client B writes "k2" to the cache.
Site masters at LON and NYC send requests so that "k1" is replicated to NYC and "k2" is replicated to LON.

With Active/Active both NYC and LON replicate data to remote caches while handling client requests. If either NYC or LON go offline, clients can start sending requests to the online site. You can then bring offline sites back online, push state to synchronize data, and switch clients as required.

Backup strategies

Important

With an Active/Active configuration, you should always use an asynchronous backup strategy (strategy=async).

If multiple clients attempt to write to the same entry concurrently, and the backup strategy is synchronous (strategy=sync), then deadlocks occur. However you can use the synchronous backup strategy with an Active/Passive configuration if both sites access different data sets, in which case there is no risk of deadlocks from concurrent writes.

1.6.1. Concurrent Writes and Conflicting Entries

Conflicting entries can occur with Active/Active site configurations if clients write to the same entries at the same time but at different sites.

For example, client A writes to "k1" in LON at the same time that client B writes to "k1" in NYC. In this case, "k1" has a different value in LON than in NYC. After replication occurs, there is no guarantee which value for "k1" exists at which site.

To ensure data consistency, Data Grid uses a vector clock algorithm to detect conflicting entries during backup operations, as in the following illustration:

            LON       NYC

k1=(n/a)    0,0       0,0

k1=2        1,0  -->  1,0   k1=2

k1=3        1,1  <--  1,1   k1=3

k1=5        2,1       1,2   k1=8

                 -->  2,1 (conflict)
(conflict)  1,2  <--

Vector clocks are timestamp metadata that increment with each write to an entry. In the preceding example, 0,0 represents the initial value for the vector clock on "k1".

A client puts "k1=2" in LON and the vector clock is 1,0, which Data Grid replicates to NYC. A client then puts "k1=3" in NYC and the vector clock updates to 1,1, which Data Grid replicates to LON.

However if a client puts "k1=5" in LON at the same time that a client puts "k1=8" in NYC, Data Grid detects a conflicting entry because the vector value for "k1" is not strictly greater or less between LON and NYC.

When it finds conflicting entries, Data Grid uses the Java compareTo(String anotherString) method to compare site names. To determine which key takes priority, Data Grid selects the site name that is lexicographically less than the other. Keys from a site named AAA take priority over keys from a site named AAB and so on.

Following the same example, to resolve the conflict for "k1", Data Grid uses the value for "k1" that originates from LON. This results in "k1=5" in both LON and NYC after Data Grid resolves the conflict and replicates the value.

Tip

Prepend site names with numbers as a simple way to represent the order of priority for resolving conflicting entries; for example, 1LON and 2NYC.

Note

Data Grid performs conflict resolution with the asynchronous backup strategy (strategy=async) only. However, you should not use the synchronous backup strategy with an Active/Active configuration because concurrent writes result in deadlocks.

Conflict resolution algorithms

Data Grid provides different algorithms for resolving conflicts in addition to an XSiteEntryMergePolicy SPI that lets you implement custom conflict resolution strategies.

Apart from the default conflict resolution strategy, which uses lexicographical comparison, you can use Data Grid conflict resolution algorithms to:

Always remove conflicting entries.
Keep write operations when write/remove conflicts occur.
Remove entries when write/remove conflicts occur.

Find all available algorithms and their descriptions in the org.infinispan.xsite.spi.XSiteMergePolicy enum.

Additional resources

1.7. Expiration with Cross-Site Replication

Expiration removes cache entries based on time. Data Grid provides two ways to configure expiration for entries:

lifespan: Sets the maximum amount of time that entries can exist.
When you set lifespan with cross-site replication, Data Grid clusters expire entries independently of remote sites.
max-idle: Specifies how long entries can exist based on read or write operations in a given time period.
When you set a max-idle with cross-site replication, Data Grid clusters send touch commands to coordinate idle timeout values with remote sites.

Note

Using maximum idle expiration in cross-site deployments can impact performance because the additional processing to keep max-idle values synchronized means some operations take longer to complete.

Chapter 2. Configuring Data Grid for Cross-Site Replication

Configuring Data Grid to replicate data across sites, you first set up cluster transport so Data Grid clusters can discover each other and site masters can communicate. You then add backup locations to cache definitions in your Data Grid configuration.

2.1. Configuring Cluster Transport for Cross-Site Replication

Add JGroups RELAY2 to your transport layer so that Data Grid clusters can communicate with backup locations.

Procedure

Open infinispan.xml for editing.
Add the RELAY2 protocol to a JGroups stack.

Configure Data Grid cluster transport to use the stack.

<infinispan>
  <jgroups>
    <!-- Extends the default UDP stack. -->
    <stack name="xsite" extends="udp">
      <!-- Adds RELAY2 for cross-site replication. -->
      <!-- Names the local site as LON. -->
      <!-- Specifies 1000 nodes as the maximum number of site masters. -->
      <relay.RELAY2 site="LON" xmlns="urn:org:jgroups" max_site_masters="1000"/>
      <!-- Uses the default TCP stack for inter-cluster communication. -->
      <!-- Names all sites that act as backup locations. -->
      <remote-sites default-stack="tcp">
         <remote-site name="LON"/>
         <remote-site name="NYC"/>
      </remote-sites>
    </stack>
  </jgroups>
  <cache-container name="default" statistics="true">
    <!-- Use the "xsite" stack for cluster transport. -->
    <transport cluster="${cluster.name}" stack="xsite"/>
  </cache-container>
</infinispan>

Save and close infinispan.xml.

Reference

2.1.1. JGroups RELAY2 Stacks

Data Grid clusters use JGroups RELAY2 for inter-cluster discovery and communication.

<jgroups>
   <!-- Uses the default JGroups UDP stack for intra-cluster traffic. -->
   <stack name="xsite" extends="udp">
      <!-- Adds RELAY2 to the stack for inter-cluster transport. -->
      <!-- Names the local site. Data in caches from the local site is replicated to backup locations. -->
      <!-- Configures a maximum of 1000 site masters for the local cluster. -->
      <relay.RELAY2 xmlns="urn:org:jgroups"
                    site="LON"
                    max_site_masters="1000"/>
      <!-- Specifies all site names and uses the default JGroups TCP stack for inter-cluster transport. -->
      <remote-sites default-stack="tcp">
         <!-- Names all sites that participate in cross-site replication. -->
         <remote-site name="LON"/>
         <remote-site name="NYC"/>
      </remote-sites>
   </stack>
</jgroups>

Tip

Set max_site_masters >= the number of nodes in the Data Grid cluster for optimal performance with backup requests.

2.1.2. Custom JGroups RELAY2 Stacks

The following configuration adds a custom RELAY2 stack that extends the default TCP stack:

<jgroups>
  <!-- Uses TCPPING instead of MPING for discovery. -->
   <stack name="relay-global" extends="tcp">
     <MPING stack.combine="REMOVE"/>
     <TCPPING initial_hosts="192.0.2.0[7800]"
              stack.combine="INSERT_AFTER"
              stack.position="TCP"/>
   </stack>
   <!-- Extends the default UDP stack with RELAY2. -->
   <!-- Specifies RELAY2 properties. -->
   <stack name="xsite" extends="udp">
      <relay.RELAY2 site="LON" xmlns="urn:org:jgroups"
                    max_site_masters="10"
                    can_become_site_master="true"/>
      <remote-sites default-stack="relay-global">
         <remote-site name="LON"/>
         <remote-site name="NYC"/>
      </remote-sites>
   </stack>
</jgroups>

You can also reference externally defined JGroups stack files, for example:

<infinispan>
  <jgroups>
     <stack-file name="relay-global" path="jgroups-relay.xml"/>
  </jgroups>
  <cache-container default-cache="replicatedCache">
    <transport stack="relay-global" />
    <replicated-cache name="replicatedCache"/>
  </cache-container>
</infinispan>

Where jgroups-relay.xml references a JGroups stack file such as:

<config xmlns="urn:org:jgroups"
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
      xsi:schemaLocation="urn:org:jgroups http://www.jgroups.org/schema/jgroups-4.1.xsd">

    <!-- Use TCP for inter-cluster transport. -->
    <TCP bind_addr="127.0.0.1"
         bind_port="7200"
         port_range="30"

         thread_pool.min_threads="0"
         thread_pool.max_threads="8"
         thread_pool.keep_alive_time="5000"
    />

    <!-- Use TCPPING for inter-cluster discovery. -->
    <TCPPING timeout="3000"
             initial_hosts="127.0.0.1[7200]"
             port_range="3"
             ergonomics="false"/>

    <!-- Provide other JGroups stack configuration as required. -->
</config>

Reference

2.2. Adding Backup Locations to Caches

Specify the names of remote sites so Data Grid can back up data to those locations.

Procedure

Add the backups element to your cache definition.
Specify the name of each remote site with the backup element.
As an example, in the LON configuration, specify NYC as the remote site.
Repeat the preceding steps so that each site is a backup for all other sites. For example, you cannot add LON as a backup for NYC without adding NYC as a backup for LON.

Note

Cache configurations can be different across sites and use different backup strategies. Data Grid replicates data based on cache names.

Example "customers" configuration in LON

<replicated-cache name="customers">
  <backups>
    <backup site="NYC" strategy="ASYNC" />
  </backups>
</replicated-cache>

Example "customers" configuration in NYC

<distributed-cache name="customers">
  <backups>
    <backup site="LON" strategy="SYNC" />
  </backups>
</distributed-cache>

Reference

Data Grid Configuration Schema

2.3. Backing Up to Caches with Different Names

By default, Data Grid replicates data between caches that have the same name.

Procedure

Use backup-for to replicate data from a remote site into a cache with a different name on the local site.

For example, the following configuration backs up the "customers" cache on LON to the "eu-customers" cache on NYC.

<distributed-cache name="eu-customers">
  <backups>
    <backup site="LON" strategy="SYNC" />
  </backups>
  <backup-for remote-cache="customers" remote-site="LON" />
</distributed-cache>

2.4. Configuring Cross-Site State Transfer

Change cross-site state transfer settings to optimize performance and specify whether operations happen manually or automatically.

Procedure

Use <state-transfer> to configure state transfer operations.

For example, the following configuration automatically performs cross-site state transfer with custom settings:

<distributed-cache name="eu-customers">
   <backups>
      <backup site="LON" strategy="ASYNC">
         <state-transfer chunk-size="64"
                         timeout="30000"
                         max-retries="30"
                         wait-time="2000"
                         mode="AUTO"/>
      </backup>
   </backups>
</distributed-cache>

2.5. Customizing the Conflict Resolution Algorithm

Configure Data Grid to use a different algorithm to resolve conflicting entries between backup locations.

Procedure

Open your Data Grid configuration for editing.
Specify one of the Data Grid algorithms or a custom implementation with the merge-policy attribute for the backups element.

Using Data Grid algorithms

Find all Data Grid algorithms and their descriptions in the org.infinispan.xsite.spi.XSiteMergePolicy enum.

The following example configuration uses the ALWAYS_REMOVE algorithm that deletes conflicting entries from both sites:

<distributed-cache name="eu-customers">
   <backups merge-policy="ALWAYS_REMOVE">
      <backup site="LON" strategy="ASYNC"/>
   </backups>
</distributed-cache>

Using custom implementations

Create a custom XSiteEntryMergePolicy implementation.

public interface XSiteEntryMergePolicy<K, V> {
   CompletionStage<SiteEntry<V>> merge(K key, SiteEntry<V> localEntry, SiteEntry<V> remoteEntry);
}

Specify the fully qualified class name as the value of the merge-policy attribute, as in the following example:

<distributed-cache name="eu-customers">
   <backups merge-policy="org.mycompany.MyCustomXSiteEntryMergePolicy">
      <backup site="LON" strategy="ASYNC"/>
   </backups>
</distributed-cache>

Additional resources

2.6. Verifying Cross-Site Views

After you configure Data Grid for cross-site replication, you should verify that Data Grid clusters successfully form cross-site views.

Procedure

Check log messages for ISPN000439: Received new x-site view messages.

For example, if the Data Grid cluster in LON has formed a cross-site view with the Data Grid cluster in NYC, it provides the following messages:

INFO  [org.infinispan.XSITE] (jgroups-5,${server.hostname}) ISPN000439: Received new x-site view: [NYC]
INFO  [org.infinispan.XSITE] (jgroups-7,${server.hostname}) ISPN000439: Received new x-site view: [NYC, LON]

2.7. Configuring Hot Rod Clients for Cross-Site Replication

Configure Hot Rod clients to use Data Grid clusters at different sites.

hotrod-client.properties

# Servers at the active site
infinispan.client.hotrod.server_list = LON_host1:11222,LON_host2:11222,LON_host3:11222

# Servers at the backup site
infinispan.client.hotrod.cluster.NYC = NYC_hostA:11222,NYC_hostB:11222,NYC_hostC:11222,NYC_hostD:11222

ConfigurationBuilder

ConfigurationBuilder builder = new ConfigurationBuilder();
builder.addServers("LON_host1:11222;LON_host2:11222;LON_host3:11222")
       .addCluster("NYC")
       .addClusterNodes("NYC_hostA:11222;NYC_hostB:11222;NYC_hostC:11222;NYC_hostD:11222")

Tip

Use the following methods to switch Hot Rod clients to the default cluster or to a cluster at a different site:

RemoteCacheManager.switchToDefaultCluster()
RemoteCacheManager.switchToCluster(${site.name})

Reference

Chapter 3. Performing Cross-Site Replication Operations

Bring sites online and offline. Transfer cache state to remote sites.

3.1. Performing Cross-Site Operations with the CLI

The Data Grid command line interface lets you remotely connect to Data Grid servers, manage sites, and push state transfer to backup locations.

Prerequisites

Start the Data Grid CLI.
Connect to a running Data Grid cluster.

3.1.1. Bringing Backup Locations Offline and Online

Take backup locations offline manually and bring them back online.

Procedure

Create a CLI connection to Data Grid.
Check if backup locations are online or offline with the site status command:
```
[//containers/default]> site status --cache=cacheName --site=NYC
```
Note
--site is an optional argument. If not set, the CLI returns all backup locations.
Manage backup locations as follows:
- Bring backup locations online with the bring-online command:
```
[//containers/default]> site bring-online --cache=customers --site=NYC
```
- Take backup locations offline with the take-offline command:
```
[//containers/default]> site take-offline --cache=customers --site=NYC
```

For more information and examples, run the help site command.

3.1.2. Configuring Cross-Site State Transfer Modes

You can configure cross-site state transfer operations to happen automatically when Data Grid detects that backup locations come online. Alternatively you can use the default mode, which is to manually perform state transfer through the CLI or via JMX or REST.

Procedure

Create a CLI connection to Data Grid.
Use the site command to configure state transfer modes, as in the following examples:
- Retrieve the current state transfer mode.
```
[//containers/default]> site state-transfer-mode get --cache=cacheName --site=NYC
"MANUAL"
```
- Configure automatic state transfer operations for a cache and backup location.

[//containers/default]> site state-transfer-mode set --cache=cacheName --site=NYC --mode=AUTO

Tip

Run the help site command for more information and examples.

3.1.3. Pushing State to Backup Locations

Transfer cache state to remote backup locations.

Procedure

Create a CLI connection to Data Grid.

Use the site command to push state transfer, as in the following example:

[//containers/default]> site push-site-state --cache=cacheName --site=NYC

For more information and examples, run the help site command.

Reference

Data Grid Command Line Interface

3.2. Performing Cross-Site Operations with the REST API

Data Grid servers provide a REST API that allows you to perform cross-site operations.

3.2.1. Getting Status of All Backup Locations

Retrieve the status of all backup locations with GET requests.

GET /v2/caches/{cacheName}/x-site/backups/

Data Grid responds with the status of each backup location in JSON format, as in the following example:

{
  "NYC": "online",
  "LON": "offline"
}

Table 3.1. Returned Status

Value	Description
`online`	All nodes in the local cluster have a cross-site view with the backup location.
`offline`	No nodes in the local cluster have a cross-site view with the backup location.
`mixed`	Some nodes in the local cluster have a cross-site view with the backup location, other nodes in the local cluster do not have a cross-site view. The response indicates status for each node.

3.2.2. Getting Status of Specific Backup Locations

Retrieve the status of a backup location with GET requests.

GET /v2/caches/{cacheName}/x-site/backups/{siteName}

Data Grid responds with the status of each node in the site in JSON format, as in the following example:

{
  "NodeA":"offline",
  "NodeB":"online"
}

Table 3.2. Returned Status

Value	Description
`online`	The node is online.
`offline`	The node is offline.
`failed`	Not possible to retrieve status. The remote cache could be shutting down or a network error occurred during the request.

3.2.3. Taking Backup Locations Offline

Take backup locations offline with POST requests and the ?action=take-offline parameter.

POST /v2/caches/{cacheName}/x-site/backups/{siteName}?action=take-offline

3.2.4. Bringing Backup Locations Online

Bring backup locations online with the ?action=bring-online parameter.

POST /v2/caches/{cacheName}/x-site/backups/{siteName}?action=bring-online

3.2.5. Pushing State to Backup Locations

Push cache state to a backup location with the ?action=start-push-state parameter.

POST /v2/caches/{cacheName}/x-site/backups/{siteName}?action=start-push-state

3.2.6. Canceling State Transfer

Cancel state transfer operations with the ?action=cancel-push-state parameter.

POST /v2/caches/{cacheName}/x-site/backups/{siteName}?action=cancel-push-state

3.2.7. Getting State Transfer Status

Retrieve status of state transfer operations with the ?action=push-state-status parameter.

GET /v2/caches/{cacheName}/x-site/backups?action=push-state-status

Data Grid responds with the status of state transfer for each backup location in JSON format, as in the following example:

{
   "NYC":"CANCELED",
   "LON":"OK"
}

Table 3.3. Returned Status

Value	Description
`SENDING`	State transfer to the backup location is in progress.
`OK`	State transfer completed successfully.
`ERROR`	An error occurred with state transfer. Check log files.
`CANCELLING`	State transfer cancellation is in progress.

3.2.8. Clearing State Transfer Status

Clear state transfer status for sending sites with the ?action=clear-push-state-status parameter.

POST /v2/caches/{cacheName}/x-site/local?action=clear-push-state-status

3.2.9. Modifying Take Offline Conditions

Sites go offline if certain conditions are met. Modify the take offline parameters to control when backup locations automatically go offline.

Procedure

Check configured take offline parameters with GET requests and the take-offline-config parameter.
```
GET /v2/caches/{cacheName}/x-site/backups/{siteName}/take-offline-config
```
The Data Grid response includes after_failures and min_wait fields as follows:
```
{
  "after_failures": 2,
  "min_wait": 1000
}
```
Modify take offline parameters in the body of PUT requests.
```
PUT /v2/caches/{cacheName}/x-site/backups/{siteName}/take-offline-config
```
If the operation successfully completes, the service returns 204 (No Content).

3.2.10. Canceling State Transfer from Receiving Sites

If the connection between two backup locations breaks, you can cancel state transfer on the site that is receiving the push.

Cancel state transfer from a remote site and keep the current state of the local cache with the ?action=cancel-receive-state parameter.

POST /v2/caches/{cacheName}/x-site/backups/{siteName}?action=cancel-receive-state

3.2.11. Getting Status of Backup Locations

Retrieve the status of all backup locations from Cache Managers with GET requests.

GET /rest/v2/cache-managers/{cacheManagerName}/x-site/backups/

Data Grid responds with status in JSON format, as in the following example:

{
   "SFO-3":{
      "status":"online"
   },
   "NYC-2":{
      "status":"mixed",
      "online":[
         "CACHE_1"
      ],
      "offline":[
         "CACHE_2"
      ]
   }
}

Table 3.4. Returned Status

Value	Description
`online`	All nodes in the local cluster have a cross-site view with the backup location.
`offline`	No nodes in the local cluster have a cross-site view with the backup location.
`mixed`	Some nodes in the local cluster have a cross-site view with the backup location, other nodes in the local cluster do not have a cross-site view. The response indicates status for each node.

3.2.12. Taking Backup Locations Offline

Take backup locations offline with the ?action=take-offline parameter.

POST /rest/v2/cache-managers/{cacheManagerName}/x-site/backups/{siteName}?action=take-offline

3.2.13. Bringing Backup Locations Online

Bring backup locations online with the ?action=bring-online parameter.

POST /rest/v2/cache-managers/{cacheManagerName}/x-site/backups/{siteName}?action=bring-online

3.2.14. Retrieving the State Transfer Mode

Check the state transfer mode with GET requests.

GET /rest/v2/caches/{cacheName}/x-site/backups/{site}/state-transfer-mode

3.2.15. Setting the State Transfer Mode

Configure the state transfer mode with the ?action=set parameter.

POST /rest/v2/caches/{cacheName}/x-site/backups/{site}/state-transfer-mode?action=set&mode={mode}

3.2.16. Starting State Transfer

Push state of all caches to remote sites with the ?action=start-push-state parameter.

POST /rest/v2/cache-managers/{cacheManagerName}/x-site/backups/{siteName}?action=start-push-state

3.2.17. Canceling State Transfer

Cancel ongoing state transfer operations with the ?action=cancel-push-state parameter.

POST /rest/v2/cache-managers/{cacheManagerName}/x-site/backups/{siteName}?action=cancel-push-state

3.3. Performing Cross-Site Operations with JMX

Data Grid provides JMX tooling to perform cross-site operations such as pushing state transfer and bringing sites online.

3.3.1. Configuring Data Grid to Register JMX MBeans

Data Grid can register JMX MBeans that you can use to collect statistics and perform administrative operations. You must enable statistics separately to JMX otherwise Data Grid provides 0 values for all statistic attributes.

Procedure

Modify your cache container configuration to enable JMX in one of the following ways:

Declarative: Add the <jmx enabled="true" /> element to the cache container.
Programmatic: Call the .jmx().enable() method.

Declarative

<cache-container>
  <jmx enabled="true" />
</cache-container>

Programmatic

GlobalConfiguration globalConfig = new GlobalConfigurationBuilder()
  .jmx().enable()
  .build();

3.3.2. Performing Cross-Site Operations

Perform cross-site operations via JMX clients.

Prerequisites

Configure Data Grid to register JMX MBeans

Procedure

Connect to Data Grid with any JMX client.
Invoke operations from the following MBeans:
- XSiteAdmin provides cross-site operations for caches.
- GlobalXSiteAdminOperations provides cross-site operations for Cache Managers.
  For example, to bring sites back online, invoke bringSiteOnline(siteName).

See the Data Grid JMX Components documentation for details about available cross-site operations.

Reference

Chapter 4. Monitoring and Troubleshooting Global Data Grid Clusters

Data Grid provides statistics for cross-site replication operations via JMX or the /metrics endpoint for Data Grid server.

Cross-site replication statistics are available at cache level so you must explicitly enable statistics for your caches. Likewise, if you want to collect statistics via JMX you must configure Data Grid to register MBeans.

Data Grid also includes an org.infinispan.XSITE logging category so you can monitor and troubleshoot common issues with networking and state transfer operations.

4.1. Enabling Data Grid Statistics

Configure Data Grid to export statistics for Cache Managers and caches.

Procedure

Modify your configuration to enable Data Grid statistics in one of the following ways:

Declarative: Add the statistics="true" attribute.
Programmatic: Call the .statistics() method.

Declarative

<!-- Enables statistics for the Cache Manager. -->
<cache-container statistics="true">
  <!-- Enables statistics for the named cache. -->
  <local-cache name="mycache" statistics="true"/>
</cache-container>

Programmatic

GlobalConfiguration globalConfig = new GlobalConfigurationBuilder()
  //Enables statistics for the Cache Manager.
  .cacheContainer().statistics(true)
  .build();

Configuration config = new ConfigurationBuilder()
  //Enables statistics for the named cache.
  .statistics().enable()
  .build();

4.2. Configuring Data Grid Metrics

Configure Data Grid to export gauges and histograms via the metrics endpoint.

Procedure

Turn gauges and histograms on or off in the metrics configuration as appropriate.

Declarative

<!-- Computes and collects statistics for the Cache Manager. -->
<cache-container statistics="true">
  <!-- Exports collected statistics as gauge and histogram metrics. -->
  <metrics gauges="true" histograms="true" />
</cache-container>

Programmatic

GlobalConfiguration globalConfig = new GlobalConfigurationBuilder()
  //Computes and collects statistics for the Cache Manager.
  .statistics().enable()
  //Exports collected statistics as gauge and histogram metrics.
  .metrics().gauges(true).histograms(true)
  .build();

4.2.1. Collecting Data Grid Metrics

Collect Data Grid metrics with monitoring tools such as Prometheus.

Prerequisites

Enable statistics. If you do not enable statistics, Data Grid provides 0 and -1 values for metrics.
Optionally enable histograms. By default Data Grid generates gauges but not histograms.

Procedure

Get metrics in Prometheus (OpenMetrics) format:
```
$ curl -v http://localhost:11222/metrics
```

Get metrics in MicroProfile JSON format:

$ curl --header "Accept: application/json" http://localhost:11222/metrics

Next steps

Configure monitoring applications to collect Data Grid metrics. For example, add the following to prometheus.yml:

static_configs:
    - targets: ['localhost:11222']

Reference

Prometheus Configuration
Enabling Data Grid Statistics

4.3. Configuring Data Grid to Register JMX MBeans

Procedure

Modify your cache container configuration to enable JMX in one of the following ways:

Declarative: Add the <jmx enabled="true" /> element to the cache container.
Programmatic: Call the .jmx().enable() method.

Declarative

<cache-container>
  <jmx enabled="true" />
</cache-container>

Programmatic

GlobalConfiguration globalConfig = new GlobalConfigurationBuilder()
  .jmx().enable()
  .build();

4.3.1. JMX MBeans for Cross-Site Replication

Data Grid provides JMX MBeans for cross-site replication that let you gather statistics and perform remote operations.

The org.infinispan:type=Cache component provides the following JMX MBeans:

XSiteAdmin exposes cross-site operations that apply to specific cache instances.
StateTransferManager provides statistics for state transfer operations.
InboundInvocationHandler provides statistics and operations for asynchronous and synchronous cross-site requests.

The org.infinispan:type=CacheManager component includes the following JMX MBean:

GlobalXSiteAdminOperations exposes cross-site operations that apply to all caches in a cache container.

For details about JMX MBeans along with descriptions of available operations and statistics, see the Data Grid JMX Components documentation.

Reference

Data Grid JMX Components

4.4. Collecting Logs and Troubleshooting Cross-Site Replication

Diagnose and resolve issues related to Data Grid cross-site replication. Use the Data Grid Command Line Interface (CLI) to adjust log levels at run-time and perform cross-site troubleshooting.

Procedure

Open a terminal in $RHDG_HOME.
Create a Data Grid CLI connection.
Adjust run-time logging levels to capture DEBUG messages if necessary.
For example, the following command enables DEBUG log messages for the org.infinispan.XSITE category:
```
[//containers/default]> logging set --level=DEBUG org.infinispan.XSITE
```
You can then check the Data Grid log files for cross-site messages in the ${rhdg.server.root}/log directory.
Use the site command to view status for backup locations and perform troubleshooting.

For example, check the status of the "customers" cache that uses "LON" as a backup location:

[//containers/default]> site status --cache=customers
{
  "LON" : "online"
}

Another scenario for using the Data Grid CLI to troubleshoot is when the network connection between backup locations is broken during a state transfer operation.

If this occurs, Data Grid clusters that receive state transfer continually wait for the operation to complete. In this case you should cancel the state transfer to the receiving site to return it to a normal operational state.

For example, cancel state transfer for "NYC" as follows:

[//containers/default]> site cancel-receive-state --cache=mycache --site=NYC`

Reference

4.4.1. Cross-Site Log Messages

Find user actions for log messages related to cross-site replication.

Log level	Identifier	Message	Description
DEBUG	ISPN000400	Node null was suspected	Data Grid prints this message when it cannot reach backup locations. Ensure that sites are online and check network status.
INFO	ISPN000439	Received new x-site view: ${site.name}	Data Grid prints this message when sites join and leave the global cluster.
INFO	ISPN100005	Site ${site.name} is online.	Data Grid prints this message when a site comes online.
INFO	ISPN100006	Site ${site.name} is offline.	Data Grid prints this message when a site goes offline. If you did not take the site offline manually, this message could indicate a failure has occurred. Check network status and try to bring the site back online.
WARN	ISPN000202	Problems backing up data for cache ${cache.name} to site ${site.name}:	Data Grid prints this message when issues occur with state transfer operations along with the exception. If necessary adjust Data Grid logging to get more fine-grained logging messages.
WARN	ISPN000289	Unable to send X-Site state chunk to ${site.name}.	Indicates that Data Grid cannot transfer a batch of cache entries during a state transfer operation. Ensure that sites are online and check network status.
WARN	ISPN000291	Unable to apply X-Site state chunk.	Indicates that Data Grid cannot apply a batch of cache entries during a state transfer operation. Ensure that sites are online and check network status.
WARN	ISPN000322	Unable to re-start x-site state transfer to site ${site.name}	Indicates that Data Grid cannot resume a state transfer operation to a backup location. Ensure that sites are online and check network status.
ERROR	ISPN000477	Unable to perform operation ${operation.name} for site ${site.name}	Indicates that Data Grid cannot successfully complete an operation on a backup location. If necessary adjust Data Grid logging to get more fine-grained logging messages.
FATAL	ISPN000449	XSite state transfer timeout must be higher or equals than 1 (one).	Results when the value of the `timeout` attribute is `0` or a negative number. Specify a value of at least `1` for the `timeout` attribute in the state transfer configuration for your cache definition.
FATAL	ISPN000450	XSite state transfer waiting time between retries must be higher or equals than 1 (one).	Results when the value of the `wait-time` attribute is `0` or a negative number. Specify a value of at least `1` for the `wait-time` attribute in the state transfer configuration for your cache definition.
FATAL	ISPN000576	Cross-site Replication not available for local cache.	Cross-site replication does not work with the local cache mode. Either remove the backup configuration from the local cache definition or use a distributed or replicated cache mode.

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Language and Page Formatting Options

Data Grid Guide to Cross-Site Replication

Back up data across global Data Grid clusters

Red Hat Data Grid

Data Grid documentation

Data Grid downloads

Making open source more inclusive

Chapter 1. Data Grid Cross-Site Replication

1.1. Cross-Site Replication

1.1.1. Site Masters

1.2. Adding Backups to Caches

1.3. Backup strategies

Synchronous strategy

Asynchronous strategy

Synchronous vs asynchronous backups

1.4. Automatically Taking Backups Offline

1.5. State Transfer

1.5.1. Automatic State Transfer

1.6. Client Connections Across Sites

Active/Passive

Active/Active

Backup strategies

1.6.1. Concurrent Writes and Conflicting Entries

Conflict resolution algorithms

1.7. Expiration with Cross-Site Replication

Chapter 2. Configuring Data Grid for Cross-Site Replication

2.1. Configuring Cluster Transport for Cross-Site Replication

2.1.1. JGroups RELAY2 Stacks

2.1.2. Custom JGroups RELAY2 Stacks

2.2. Adding Backup Locations to Caches

2.3. Backing Up to Caches with Different Names

2.4. Configuring Cross-Site State Transfer

2.5. Customizing the Conflict Resolution Algorithm

2.6. Verifying Cross-Site Views

2.7. Configuring Hot Rod Clients for Cross-Site Replication

Chapter 3. Performing Cross-Site Replication Operations

3.1. Performing Cross-Site Operations with the CLI

3.1.1. Bringing Backup Locations Offline and Online

3.1.2. Configuring Cross-Site State Transfer Modes

3.1.3. Pushing State to Backup Locations

3.2. Performing Cross-Site Operations with the REST API

3.2.1. Getting Status of All Backup Locations

3.2.2. Getting Status of Specific Backup Locations

3.2.3. Taking Backup Locations Offline

3.2.4. Bringing Backup Locations Online

3.2.5. Pushing State to Backup Locations

3.2.6. Canceling State Transfer

3.2.7. Getting State Transfer Status

3.2.8. Clearing State Transfer Status

3.2.9. Modifying Take Offline Conditions

3.2.10. Canceling State Transfer from Receiving Sites

3.2.11. Getting Status of Backup Locations

3.2.12. Taking Backup Locations Offline

3.2.13. Bringing Backup Locations Online

3.2.14. Retrieving the State Transfer Mode

3.2.15. Setting the State Transfer Mode

3.2.16. Starting State Transfer

3.2.17. Canceling State Transfer

3.3. Performing Cross-Site Operations with JMX

3.3.1. Configuring Data Grid to Register JMX MBeans

3.3.2. Performing Cross-Site Operations

Chapter 4. Monitoring and Troubleshooting Global Data Grid Clusters

4.1. Enabling Data Grid Statistics

4.2. Configuring Data Grid Metrics

4.2.1. Collecting Data Grid Metrics

4.3. Configuring Data Grid to Register JMX MBeans

4.3.1. JMX MBeans for Cross-Site Replication

4.4. Collecting Logs and Troubleshooting Cross-Site Replication

4.4.1. Cross-Site Log Messages

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