.. meta:: :title: Handling WAN Latency in Galera Cluster :description: :language: en-US :keywords: :copyright: Codership Oy, 2014 - 2021. All Rights Reserved. .. container:: left-margin .. container:: left-margin-top :doc:`The Library <../index>` .. container:: left-margin-content - :doc:`Documentation <../documentation/index>` .. cssclass:: here - :doc:`Knowledge Base <./index>` - :doc:`Training <../training/index>` .. cssclass:: sub-links - :doc:`Training Courses <../training/courses/index>` - :doc:`Tutorial Articles <../training/tutorials/index>` - :doc:`Training Videos <../training/videos/index>` - :doc:`FAQ <../faq>` - :ref:`search` Related Documents - :ref:`evs.join_retrans_period ` .. container:: top-links - `Home `_ - :doc:`Docs <../documentation/index>` .. cssclass:: here - :doc:`KB <./index>` .. cssclass:: nav-wider - :doc:`Training <../training/index>` - :doc:`FAQ <../faq>` .. cssclass:: library-article .. _`kb-best-wan-latency`: =============== WAN Latency =============== .. rst-class:: article-stats Length: 221 words; Published: June 24, 2015; Updated: October 22, 2019; Category: Performance; Type: Best Practices When using Galera Cluster over a :abbr:`WAN (Wide Area Network)`, remember that WAN links can have exceptionally high latency. You can check this by taking Round-Trip Time (RTT) measurements between cluster nodes. If there is a latency, you can correct for this by adjusting all of the temporal parameters. .. rst-class:: section-heading .. rubric:: Recommendations To take RTT measurements, use ``ping`` on each cluster node to ping the others. For example, if you were to log into the node at ``192.168.1.1``, you might execute something like the following from the command-line: .. code-block:: console $ ping -c 3 192.168.1.2 PING 192.168.1.2 (192.168.1.2) 58(84) bytes of data. 64 bytes from 192.168.1.2: icmp_seq=1 ttl=64 time=0.736 ms 64 bytes from 192.168.1.2: icmp_seq=2 ttl=64 time=0.878 ms 64 bytes from 192.168.1.2: icmp_seq=3 ttl=64 time=12.7 ms --- 192.168.1.2 --- 3 packets transmitted, 3 received, 0% packet loss, time 2002ms rtt min/avg/max/mdev = 0.736/4.788/12.752/5.631 ms Repeat this on each node in the cluster and note the highest value among them. Parameters that relate to periods and timeouts, such as :ref:`evs.join_retrans_period `, must all use values that exceed the highest RTT measurement in the cluster. .. code-block:: ini wsrep_provider_options="evs.join_retrans_period=PT0.5S" This allows the cluster to compensate for the latency issues of the :abbr:`WAN (Wide Area Network)` links between the cluster nodes. .. container:: bottom-links Related Documents - :ref:`evs.join_retrans_period `