title: Keeping Existing Sessions When Upgrading to Rails 5.2 (with Redis Session Store)
body: <p>I have recently finished a big upgrade of a Rails application. I took the App incrementally from <code>Rails 4.2.8</code> to <code>Rails 5.2.3</code>. Everything has gone smoothly, all our automated tests are passing, and we've begun user acceptance testing.</p>
  
  <p>So far the only issue that has been found is that logged in users are being signed out by this upgrade. We previously had the <code>redis-rails</code> gem (version <code>4.0.0</code>) installed to enable using Redis for our <code>session_store</code> and now we're using the built-in Redis store that comes with <code>Rails 5.2</code>.</p>
  
  <p>I have our configuration set up to use the same Redis connection and the same session_store key value as before, and I can't figure out why sessions are still being reset. It seems like perhaps <code>redis-rails 4.0.0</code> was not properly setting the session_store key value?</p>
  
  <p>Has anyone else dealt with this and successfully retained existing sessions when upgrading from <code>redis-rails</code> to <code>Rails 5.2</code>?</p>
  
  <p><em>Edit:</em>
  Other possibly-related gems that have been updated include <code>ruby 2.3.4 =&gt; 2.5.5</code>, <code>devise 4.0.3 =&gt; 4.6.2</code>, &amp; <code>redis 3.2.2 =&gt; 4.1.2</code></p>