I have installed Umbraco 8.5.4 on three web servers. I have designated server1 to be master and server2 and server3 are replica servers. The issue is, when I publish content on server1 then it's not distributed to the two replica servers. I have read all the official documentation, and I can't figure out what is missing.

I set server1 to be the master server by following the guide in Advanced techniques with Flexible Load Balancing, and server2 and server3 are set as replica servers. I'm returning null in GetCurrentServerUmbracoApplicationUrl.

I have blocked umbraco backoffice on the replica servers by adding this rewrite rule in Web.config:

<rewrite>
  <rules>
    <!-- Restrict access to Umbraco -->
    <rule name="Restrict access" stopProcessing="true">
      <match url="umbraco(?!/api/)" />
      <conditions logicalGrouping="MatchAny" trackAllCaptures="false">
        <add input="{HTTP_HOST}" matchType="Pattern" pattern="IP1" ignoreCase="true" negate="true" />
      </conditions>
      <action type="CustomResponse" statusCode="404"
              subStatusCode="0"
              statusReason="Site is unavailable"
              statusDescription="Not available on replica instances" />
    </rule>
  </rules>
</rewrite>

Here IP1 is the IP address of server1.

When I look into the [umbracoServer] table in the database, then all three servers are added, and only server1 is master:

id address                 computerName               registeredDate           lastNotifiedDate         isActive  isMaster
1  http://IP1/umbraco      SERVER1//LM/W3SVC/2/ROOT   2020-09-30 11:05:50.370  2020-10-17 18:58:35.173  1         1
2  http://IP2/umbraco      SERVER2//LM/W3SVC/2/ROOT   2020-09-30 18:45:32.947  2020-10-16 14:31:49.897  0         0
3  http://IP3/umbraco      SERVER3//LM/W3SVC/2/ROOT   2020-09-30 19:39:22.090  2020-10-16 14:35:38.150  0         0

I am unsure if it's an issue, that isActive is false for server2 and server3.

I have not set up any file system synchronization besides this. I am actually unsure how to read the guide in file-system-replication. As I understand it each Umbraco instance will look into the database and figure out if new content has been published. Then they will read this content and build a local cache. I think that additional file system synchronization is only relevant for the /Media folder.

In /umbraco on server1 I will unpublish the content root and then publish with descendants. Now I expect this content to be synchronized to the replica servers. However when I access the front page on server2 and server3, then I just reach the "Welcome to your Umbraco installation" start page.

I can add log lines, if there is anything specific, that's relevant.

NB: Load balancing on the servers has not been set up yet. I access umbraco by remote desktop to each server and access them by their IP addresses.