-h3(#rolling-upgrades). Rolling upgrades procedure
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-Once you have more than one controller backend node, it's easy to take one at a time from the backend pool to upgrade it to a newer version of Arvados (which might involve applying database migrations) by adding its name to the @DISABLED_CONTROLLER@ variable in @local.params@. For example:
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-<pre><code>...
-DISABLED_CONTROLLER="controller1"
-...</code></pre>
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-Then, apply the configuration change to just the load-balancer:
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-<pre><code class="userinput">./installer.sh deploy controller.xarv1.example.com</code></pre>
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-This will allow you to do the necessary changes to the @controller1@ node without service disruption, as it will not be receiving any traffic until you remove it from the @DISABLED_CONTROLLER@ variable.
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-Next step is applying the @deploy@ command to @controller1@:
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-<pre><code class="userinput">./installer.sh deploy controller1.xarv1.example.com</code></pre>
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-After that, disable the other controller node by editing @local.params@:
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-<pre><code>...
-DISABLED_CONTROLLER="controller2"
-...</code></pre>
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-...applying the changes on the balancer node:
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-<pre><code class="userinput">./installer.sh deploy controller.xarv1.example.com</code></pre>
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-Then, deploy the changes to the recently disabled @controller2@ node:
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-<pre><code class="userinput">./installer.sh deploy controller2.xarv1.example.com</code></pre>
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-This won't cause a service interruption because the load balancer is already routing all traffic to the othe @controller1@ node.
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-And the last step is enabling both controller nodes by making the following change to @local.params@:
-
-<pre><code>...
-DISABLED_CONTROLLER=""
-...</code></pre>
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-...and running:
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-<pre><code class="userinput">./installer.sh deploy controller.xarv1.example.com</code></pre>
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-This should get all your @controller@ nodes correctly upgraded, and you can continue executing the @deploy@ command with the rest of the nodes individually, or just run:
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-<pre><code class="userinput">./installer.sh deploy</code></pre>
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-Only the nodes with pending changes might require certain services to be restarted. In this example, the @workbench@ node will have the remaining Arvados services upgraded and restarted. However, these services are not as critical as the ones on the @controller@ nodes.