Flow web authoring in Tableau server clustered environment fails with error "Unknown server error" and running published flow fails with error 'Failed to connect to ""'

Issue

Flow web authoring in Tableau server clustered environment fails with error:

"Unknown server error" and running published flow fails with error 'Failed to connect to ""'

Environment

Tableau Server 2021.3.1
Multi node cluster environment
Linux (Other)

Resolution

Make sure the gateway port for all nodes (IPs) are not blocked in Firewall rule or security rule of software used. Even if flow services are configured in one node, the nodes must be able to communicate with each other.

Cause

Nodes could not communicate with each other on gateway port (80)

Additional Information

Tableau Services Manager Ports
Configuring Tableau Server on Linux to work with a forward proxy

Troubleshooting steps:

+ Verify port 80 is open and nodes can communicate with each other.

+ If forward proxy is used verify all communications within a local Tableau Server cluster do not route to the proxy server by setting no_proxy and adding both the host name and the IP address for each computer.

+ Check if nodes can communicate with each other via flowprocessor port by running below steps:
a. Run "tsm topology list-ports" command in node1
b. Find flowprocessor:primary port in the result that indicates the service installed on that specific node.
c. Replace the port number from previous step in below telnet command and run it in other nodes in cluster:
telnet <node1hostname> <portnumber>

Example of nodes ip in cluster:
node1 ip: 10.22.234.32
node2 ip: 10.22.233.48
node3 ip: 10.22.233.227

Error in error.log in gateway in node1 (10.22.234.32) :
[proxy:error] [pid 80996:tid 140665983645440] (70007)The timeout specified has expired: AH00957: http: attempt to connect to 10.22.233.48:80 (ip-10-22-233-48) failed

[proxy:error] [pid 80996:tid 140666235426560] (70007)The timeout specified has expired: AH00957: http: attempt to connect to 10.22.233.227:80 (ip-10-22-233-227) failed

Error in error.log in gateway in node2 (10.22.233.48):
[proxy:error] [pid 39327:tid 140121915365120] (70007)The timeout specified has expired: AH00957: http: attempt to connect to 10.22.234.32:80 (ip-10-22-234-32.ap-south-3.comp.internal) failed

Error in error.log in gateway in node3 (10.22.233.227):
[proxy:error] [pid 24326:tid 140255000766208] (70007)The timeout specified has expired: AH00957: http: attempt to connect to 10.22.234.32:80 (ip-10-22-234-32.ap-south-3.comp.internal) failed