I think I am now 100% sure that there is no switch to the primary pool from the fall-back pool not 30 min later, not 10 (which I set in --set-reconnection-timer 10), not at all.
So, I gave it a check and it worked as it should.
What did I do for a try? Well I uses this config:
--server eu.minexpool.nl,optiminer.eu
--port 9998,9999
--user XQZoBeGPZJoLhTdkcF8bScsNH5Wyesd9g4.W033,XQZoBeGPZJoLhTdkcF8bScsNH5Wyesd9g4.W033
--pass x,x
--max-connection-attempts 5
--set-reconnection-timer 10
--set-short-stats-interval 30
--set-long-stats-interval 120
So you see I reduced stats output a bit and set the reconnection timer to 10 minutes.
And then got this output:
Stratum connection not reacting for too long time.
Lost connection to stratum server eu.minexpool.nl:9998 or server not reachable.
Trying to connect in 5 seconds
Stratum connection not reacting for too long time.
Lost connection to stratum server eu.minexpool.nl:9998 or server not reachable.
Trying to connect in 5 seconds
Stratum connection not reacting for too long time.
Lost connection to stratum server eu.minexpool.nl:9998 or server not reachable.
Trying to connect in 5 seconds
Stratum connection not reacting for too long time.
Lost connection to stratum server eu.minexpool.nl:9998 or server not reachable.
Trying to connect in 5 seconds
Stratum connection not reacting for too long time.
Lost connection to stratum server eu.minexpool.nl:9998 or server not reachable.
Trying to connect in 5 seconds
Too many attempts. Switching to failover pool optiminer.eu:9999
Connected to optiminer.eu:9999
Subscribed to stratum server
New target received: 0000333333333333340000000000000000000000000000000000000000000000
New job received: cf6f
Authorized worker: XQZoBeGPZJoLhTdkcF8bScsNH5Wyesd9g4.W033
Start Mining...
[Device 0] Average speed (30s): 1211.59 sol/s
Submitting share
Share accepted
New job received: cf70
Submitting share
Share accepted
[Device 0] Average speed (30s): 1203.9 sol/s
[Device 0] Average speed (30s): 1159.75 sol/s
New job received: cf71
---------------------------------------------
Average speed (120s): 1180.03 sol/s
---------------------------------------------
[Device 0] Average speed (30s): 1143.1 sol/s
[Device 0] Average speed (30s): 1128.57 sol/s
[Device 0] Average speed (30s): 1082.13 sol/s
[Device 0] Average speed (30s): 1108.65 sol/s
Submitting share
Share accepted
---------------------------------------------
Average speed (120s): 1112.11 sol/s
---------------------------------------------
[Device 0] Average speed (30s): 1128.52 sol/s
[Device 0] Average speed (30s): 1100.85 sol/s
New target received: 0001051eb854a875700000000000000000000000000000000000000000000000
New job received: cf72
New job received: cf73
[Device 0] Average speed (30s): 1124.74 sol/s
Submitting share
Share accepted
[Device 0] Average speed (30s): 1114.01 sol/s
Submitting share
Share accepted
---------------------------------------------
Average speed (120s): 1113.44 sol/s
---------------------------------------------
[Device 0] Average speed (30s): 1112.48 sol/s
[Device 0] Average speed (30s): 1113.21 sol/s
[Device 0] Average speed (30s): 1106.15 sol/s
Submitting share
Share accepted
[Device 0] Average speed (30s): 1142.23 sol/s
---------------------------------------------
Average speed (120s): 1121.17 sol/s
---------------------------------------------
[Device 0] Average speed (30s): 1121.42 sol/s
[Device 0] Average speed (30s): 1100.78 sol/s
[Device 0] Average speed (30s): 1121.37 sol/s
[Device 0] Average speed (30s): 1139.7 sol/s
Trying to reconnect to original pool.
Lost connection to stratum server optiminer.eu:9999 or server not reachable.
Trying to connect in 5 seconds
Stratum connection not reacting for too long time.
Lost connection to stratum server eu.minexpool.nl:9998 or server not reachable.
Trying to connect in 5 seconds
Too many attempts. Switching to failover pool optiminer.eu:9999
Connected to optiminer.eu:9999
Subscribed to stratum server
New target received: 0000333333333333340000000000000000000000000000000000000000000000
New job received: cf73
Authorized worker: XQZoBeGPZJoLhTdkcF8bScsNH5Wyesd9g4.W033
[Device 0] Average speed (30s): 1102.12 sol/s
[Device 0] Average speed (30s): 1107.46 sol/s
New job received: cf74
New job received: cf75
[Device 0] Average speed (30s): 1068.84 sol/s
You see that of cause the first connection to minexpool.nl failed because I configured the wrong port. After 5 attempts it connected to optiminer.eu and started mining. After about 10 minutes it tried to reconnect to minexpool.nl, but failed again (because the port is still not valid) and therefore swaped back to the first failover.
Overall this is exactly what it should do. Test system is an AMD A10 7850K integrated graphics, running Windows 10 Pro.