ES 1.6.2 Java client and ES 1.5.2 cluster

[Cleosson_Souza]

Hello,

I took a look at end of life and I understood that ES 1.6.2 Java client is compatible with ES 1.5.2 cluster
Is ES 1.6.2 Java client really compatible with ES 1.5.2 cluster ?
Is that compatibility official ?

Thanks
Cleosson

[Luca_Belluccini]

Hello @Cleosson_Souza

The compatibility is usually showed in the support matrix.

The EoL page shows until which version the product is maintained.

The official documentation for your client is at this link.

We strongly suggest to upgrade to a supported version of the Elastic Stack.

As noted at this page:

Please note that you are encouraged to use the same version on client and cluster sides. You may hit some incompatibility issues when mixing major versions.

As far as I recall, ES 1.6 client was based on the transport protocol and the client was actually "joining" the cluster as a client node and the communication is in binary protocol.
If the client node joins the cluster and receives the cluster state, it should work. But it is not guaranteed.