Read workers fail to connect to mysql server

[stephanievu]

What I Did

1. Rear & Write workers were configured to point to same DB:
   bash-3.2$ env | grep TWO_TASK
   TWO_TASK_READ=tcp(127.0.0.1:3306)/world?timeout=10s
   TWO_TASK=tcp(127.0.0.1:3306)/world?timeout=10s

2. I set readonly_children_pct=50 in hera.txt

What I Expected
When starting server, I expected all read & write workers to start successfully

What I Saw Instead
Hera Read workers fail to start
state.log:
08/08/2019 17:35:58: hera.w 0 2 0 0 0 0 0 0 0 0 0
08/08/2019 17:35:58: hera.r 2 0 0 0 0 0 0 0 0 0 0
08/08/2019 17:35:59: hera.w 0 2 0 0 0 0 0 0 0 0 0
08/08/2019 17:35:59: hera.r 2 0 0 0 0 0 0 0 0 0 0
08/08/2019 17:36:00: hera.w 0 2 0 0 0 0 0 0 0 0 0

Error in log:
10:52:51.876367 info: [R-WORKER 6 workerservice.go:103] DB heartbeat interval: 2m0s
10:52:51.876722 info: [R-WORKER 6 cmdprocessor.go:713] setup db connection.
10:52:51.932530 warn: [R-WORKER 5 adapter.go:75] recycling, got read-only conn
10:52:51.932706 warn: [R-WORKER 5 cmdprocessor.go:719] driver error cannot use read-only conn tcp(10.244.64.202:3306)/world
10:52:51.932728 warn: [R-WORKER 5 workerservice.go:117] Can't connect to DB: cannot use read-only conn tcp(10.244.64.202:3306)/world

[ModEtchFill]

We think the Oracle RAC read-write split won't work with MySQL. Oracle RAC has synchronous replication which most MySQL clusters don't.

In any case, we'll need to adjust the heartbeat checks for the r workers so they connect.

[ModEtchFill]

This may prevent use of Transparent Failover. We should test

[stephanievu]

I tested out with TAF enable, taf workers cannot connect to mysql DB server and taf workers stay in "init" status
Error in hera log:
11:34:05.763268 warn: [S0-WORKER 1 339228 cmdprocessor.go:812] driver error cannot use read-only conn tcp(10.180.128.159:3115)/clocschema?timeout=12s&tls=preferred&clientFoundRows=true
11:34:05.763286 warn: [S0-WORKER 1 339228 workerservice.go:130] Can't connect to DB: cannot use read-only conn tcp(10.180.128.159:3115)/clocschema?timeout=12s&tls=preferred&clientFoundRows=true