MidServers Load Balancer / Failover Cluster Behavior

[ZbigniewBednare]

Hello,

I'm looking for a help in figuring out how MidServers work in different scenarios described below (It is related to Discovery but also to API calls):

I have following 4 clusters already created
A) Load Balancing Cluster cl_lb_1 containing midserver_1 and midserver_2 Mid Servers
B) Load Balancing Cluster cl_lb_2 containing midserver_3 and midserver_4 Mid Servers
C) Failover Cluster cl_fo_1 containing midserver_1 and midserver_3 Mid Servers
D) Failover Cluster cl_fo_2 containing midserver_2 and midserver_4 Mid Servers

Scenario 1:
Midserver midserver_1 is going down / MidServer midserver_3 is idle
Questions:
1. midserver_3 will immediately take care of jobs that previously midserver_1 was working on as part of failover?
2. midserver_2 will immediately take care of jobs that previously midserver_1 was working on as part of load balancing ?
3. midserver_2 and midserver_3 will be working in load balancing mode ?  

Scenario 2:
Midserver midserver_1 is going down / MidServer midserver_3 is busy with other jobs as it is part of other load balancing cluster designed to process different data but with same capabilities etc ..
Questions:
1. midserver_3 will immediately take care of jobs that previously midserver_1 was working on as part of fail-over?
2. midserver_2 and midserver_3 will be working in load balancing mode ?  

Scenario 3:
Load Balancer Cluster1 with  Mid1 Mid2 MidServers
Load Balancer Cluster2 with Mid3 Mid4 MidServers
Failover Cluster Mid1 Mid3 with MidServers

Questions:
Can you tell me (Yes / No). If Mid1 Server will be down, and Mid3 Server will take care of Jobs assigned to Mid1 Server (as they are part of failover cluster) will Mid3 Server be loadbalancing jobs with Mid2 server which is part of Load Balancer Cluster1 where we have Mid1 (down) and Mid2 (up) Mid servers ?

Thank you in advance for your valuable help and support.

[Rahul Priyadars · Accepted solution]

Hi 

My 1 penny response on this.

Scenario 1:
Midserver midserver_1 is going down / MidServer midserver_3 is idle
Questions:
1. midserver_3 will immediately take care of jobs that previously midserver_1 was working on as part of failover? --> YES as a part of Failover

2. midserver_2 will immediately take care of jobs that previously midserver_1 was working on as part of load balancing ? --> now in this LB setup only one is available so all new job will route to Mid server 2 as part of LB

3. midserver_2 and midserver_3 will be working in load balancing mode ?  --> NO

Scenario 2:
Midserver midserver_1 is going down / MidServer midserver_3 is busy with other jobs as it is part of other load balancing cluster designed to process different data but with same capabilities etc ..
Questions:
1. midserver_3 will immediately take care of jobs that previously midserver_1 was working on as part of fail-over? As a part of Failover Configuration Yes
2. midserver_2 and midserver_3 will be working in load balancing mode ?  --> NO as MS1 and MS2 are load balanced 

Scenario 3:
Load Balancer Cluster1 with  Mid1 Mid2 MidServers
Load Balancer Cluster2 with Mid3 Mid4 MidServers
Failover Cluster Mid1 Mid3 with MidServers

Can you tell me (Yes / No). If Mid1 Server will be down, and Mid3 Server will take care of Jobs assigned to Mid1 Server (as they are part of failover cluster) will Mid3 Server be loadbalancing jobs with Mid2 server which is part of Load Balancer Cluster1 where we have Mid1 (down) and Mid2 (up) Mid servers ?--> NO

M1 M2 Makes LB configuration

M1 and M3 makes Fail-over Cluster Configuration

From Docs:

MID Servers in a fail-over cluster each have a configured order that the platform uses to determine which MID Server to use next in case of failure. MID Servers in a fail-over cluster work independently and do not load balance with other MID Servers in that cluster (although they might also be members of load balancing clusters). When a MID Server fails, the MID Server Cluster Management business rule selects the highest available MID Server in the order to take over the work.

I think you can test this scenario . 

Refer this for more details- https://docs.servicenow.com/bundle/london-servicenow-platform/page/product/mid-server/reference/mid-...

Regards

RP

[Runjay Patel]

Check out this video, it will clear all your doubts and help you to understand mid server in details. It will help you resolve below queries:

Link: https://youtu.be/RMXhYJxPMPU

1. Mid Server Installation step by steps
2. Mid Server Troubleshooting for all version.
3. I am unable to install mid server.
4. Unable to configure MID server.
5. Service Mapping Mid Servers.
6. How to log in to the Mid server using the Credential.
7. MID Server for multiple sub production instances.
8. Why do we use MID server? Purpose of using MID Server?
9. How to define a specific mid server for the discoverIpAddress () function?
10. Other issues.