<p>I am trying to detect Blackberry user agents in my app, which works fine in my development version. But nothing happens when I redeploy the app in production.</p>

<p>application_helper.rb</p>

<pre><code>  def blackberry_user_agent?
    request.env["HTTP_USER_AGENT"] &amp;&amp; request.env["HTTP_USER_AGENT"][/(Blackberry)/]
  end
</code></pre>

<p>application.html.erb</p>

<pre><code>&lt;% if blackberry_user_agent? -%&gt;
&lt;div class="message"&gt;
&lt;p&gt;Using a Blackberry? &lt;a href="http://mobile.site.ca/"&gt;Use the mobile optimized version&lt;/a&gt;.&lt;/p&gt;
&lt;/div&gt;
</code></pre>

<p>I've tried clearing the cache using rake tmp:cache:clear and restarted mongrel a few times. Apparently the HTTP_USER_AGENT is coming back nil in production. I am using Nginx with a mongrel cluster.</p>

Are you using Apache or nginx in front of your mongrel(s)?
Are you logging the user_agent? This is from my nginx.conf:
```
```
log_format main '$remote_addr - $remote_user [$time_local] $request '
                  '"$status" $body_bytes_sent "$http_referer" '
                  '"$http_user_agent" "http_x_forwarded_for"';
```
```