ODM does not provide or implement a "gateway" directly, which typically is related to the infrastructure (hosted or on-prem) in which the product is deployed to.
504 Gateway Timeout error usually pertains to a load balancer network component or a proxy server and for an ODM installation that is non-container based (does not require "routes" to access), the URLs to access the consoles will indicate either a proxy server or load balancer and not the application server URL which has either host/IP and a port number.
However, in your case where the URL does specify the hostname:port of the app server , especially when using localhost , i.e. http(s)://localhost:port/<context root>
and still getting 504 Gateway timeout... it's important to understand if this is a hosted env within a managed provider VM.
Reviewing the application server logs and in particular the ffdc's generated when the incident occurs, you may see exceptions similar to these:
-java.io.IOException: ADMD0004E: The TCP socket: ip-10-1-51-48.us-east-2.compute.internal:7277 cannot be opened. Check if port is opened by remote process.
-Caused by: com.ibm.websphere.management.exception.ConnectorNotAvailableException: [SOAPException: faultCode=SOAP-ENV:Client; msg=Unable to find a valid IP for host ip-10-1-51-48.us-east-2.compute.internal]
-[SOAPException: faultCode=SOAP-ENV:Client; msg=Error opening socket: java.net.SocketException: Network is unreachable (connect failed);
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These errors should give a clear indication of the hosting env, in this case
the product is deployed and hosted within a managed provider as seen in the IP/ url-
ip-10-1-51-48.us-east-2.compute.internal.
In such cases, the Gateway is provided by your hosting provider, in this case Amazon AWS , even if you are using traditional WebSphere or Liberty AS (non-container based).
The hosting provider should be able to resolve such issues with the compute node or VM you are deployed which is important to identify in order to avoid any additional outages or downtime by not initially opening an IBM Support case, and create a support ticket with your hosting provider instead.
#OperationalDecisionManager(ODM)#Support#SupportMigration