Friday, 05 June 2020
Infinispan introduced Cross Site Replication functionality in version 5.2 and Infinispan 7 extended it to support state transfer. With an increase of popularity, Infinispan 11 brings two major improvements to Cross Site Replication. Let’s take a look at them.
Infinispan uses JGroups' RELAY2 protocol to enable inter-site communication. Each site has Site Masters: these are nodes with special roles, and are responsible for the communication between sites.
RELAY2 can use more than one Site Master per site allowing load balancing of the inter-site requests. The new algorithm is now able to take advantage of multiple Site Masters.
max_site_masters configures the number of Site Masters, and it defaults to 1. To take advantage of the new algorithm, increase the number of Site Masters in RELAY2 configuration by changing
max_site_masters to a value higher than 1. A number greater than the number of nodes can be used, and it enables the Site Master role in all nodes.
<relay.RELAY2 site="<LOCAL_SITE_NAME>" max_site_masters="<PUT_VALUE_HERE>"/>
More information about RELAY2 is available in JGroups' Manual.
Infinispan is able to detect conflicts in asynchronous mode by taking advantage of vector clocks. A conflict happens when 2 or more sites update the same key at the same time. Let’s look at an example between 2 sites (LON and NYC):
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 <-- k1=5 2,1 <-> 2,1 k1=5
k1=2, with vector clock
1,0, and replicates it to NYC.
k1=3, with vector clock
1,1, and replicates it to LON.
However if LON puts
2,1), and NYC puts
k1=8in NYC (with vector clock
1,2) at the same time, Infinispan detects the conflict since none of the vector clocks are greater than the other.
Infinispan resolves the conflicts by comparing using the site names in lexicographical order. The site’s name lower in lexicographical order takes priority. In the example above, both LON and NYC end up with
k1=5 since LON < NYC.
You can choose the priority by prepending a number to the site name. For example, if you want updates from NYC to take priority over LON updates, you can prepend a number to the site name, example: 1NYC, 2LON and so on.
For more information check the Infinispan Documentation.
Tags: xsite cross site replication
Friday, 24 October 2014
Since the initial release of Cross-Site Replication, the state transfer between sites was really needed. When a new site is brought online, there was not way to synchronize the data between them. Finally, these days are over and it is possible synchronize geographically replicated sites. How to use is described in Infinispan’s Manual.
For the curious, the solution is described here.
Any question can be asked in the https://developer.jboss.org/en/infinispan/content?filterID=contentstatus%5Bpublished%5Dobjecttypeobjecttype%5Bthread%5D[forum], mailing list or directly with us in the IRC. If you found a bug please report it in here.
Happy coding, fellows.
Tags: state transfer cross site replication
Thursday, 27 March 2014
Dear Infinispan community, The Alpha2 release of Infinispan 7.0.0 is now available.
This release brings Cross-Site Replication State Transfer in a stable topology (i.e. no nodes leaving or joining during the state transfer) and several bug fixes.
Note: The LevelDB and Rest Cache Store artifacts published to the Maven repo for this version are broken. Please wait for the next Alpha release if you plan to use them. Sorry for the inconvenience.
Tags: alpha cross site replication
Wednesday, 19 September 2012
Besides other enhancements and fixes, this release brings the first implementation of the cross-site replication functionality in Infinispan. In other words, you can now use Infinispan for backing up your data across geographically distributed sites or migrate your data where your users are (follow the sun). More about the x-site replication functionality here. You can download the distribution or the maven artifact. If you have any questions please check our forums, our mailing lists or ping us directly on IRC!
Tags: xsite cross site replication