I notice the same problem with other software like Grafana.
So I would get more or less the same error message:
Jan 29 13:07:38 ubuntu-server grafana[12120]: logger=context xxxxx t=2025-01-29T13:07:38.456408785+01:00 level=error msg=“Error writing to response” err=“write tcp 127.0.0.1:3002->127.0.0.1:37254: write: broken pipe”
Port 3002 is the HTTP port of Grafana. Port 8080 in your case is the HTTP port of Dgraph.
The issue is most likely some connection issue between the service (Dgraph) and the Reverse Proxy, like Nginx or HAProxy.
You can check the connectivity via:
netstat -tnp | grep 8080
An error like broken pipe in this case suggests there is an issue between either the client (browser) or upstream server upstream server unexpectedly closed the connection, while the proxy was busy proxying the data.
Now the root cause is hard to say, it could be an issue in Nginx or HAProxy, it could also be the client that crashes. Or it could be the server that is restarting network or sysctl kernel configs that are reloaded. There are many reasons why such a network pipe can break during the transmission of data.