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EFM Load Balancer Hooks Scripts

EFM 3.2 Load Balancer Hooks (script.load.balancer.attach & script.load.balancer.detach) gives great flexibility to control out side modules like connection poolers(or others) while performing switchover or failover or node stop/resume action. In this repository, EFM load balancer hooks script are created to control/modify PgPool Load balancer cluster. These scripts uses PgPool PCP unix command to attach/detach/promote database node in it.

PreRequisites:

  • Bash
  • PgPool Binaries for pcp command utilities

There are two scripts to handle the PgPool cluster.

  • efm_loadbalancer_attach.sh
  • efm_loadbalancer_detach.sh

Note: Scripts will execute PgPool pcp_ unix commands. Hence, PCP_ commands MUST be configured password-less connection to PgPool Cluster on PCP port 9898**

efm_loadbalancer_attach.sh

This script will be called by EFM after performing switchover or failover or standby node resume actions. Hence, this script takes action according to 2 rules to attach or promoate database node in PgPool cluster via PCP command

  • Rule 1: Node should be attached(pcp_attach_node) only if database is in Recovery
  • Rule 2: Node should be promoted(pcp_promote_node) only if database is NOT in Recovery.

efm_loadbalancer_detach.sh

This script will be called by EFM before performing switchover or failover or standby node stop actions. Hence, this script detachs any database node that becomes inactive and updates PgPool cluster via PCP command.

Important Points

  • Scripts should be edited to update ENVIRONMENT variables of 1) PG/EPAS database 2) PCP User/Port/Host and 3) Script Logging
  • Configure PCP password-less authentication so they are called by EFM user and they are not prompted for password.
  • All scripts should be placed in a location where **EFM user ** has access to it.

Sample Configuration files

Sample configuration files of EPAS, EFM & PgPool files are uploaded. Please go through it as a reference point when implementing it.

Sample EFM Attach Script Logging

[root@additional-dbs efm-scripts]# more efm_attach_20181027062933.log
-----------------------------------------------------------
EFM Attaching Nodes Rules :-
--------------------------
   Rule 1: Node should be attached if DB is in Recovery
   Rule 2: Node should be Promoted if DB is NOT in Recovery
-----------------------------------------------------------
EFM Attaching Node            : 172.31.41.249
DB Recovery Status[True/False]: f
Node ID in PgPool Cluster     : 0
-----------------------------------------------------------
pcp_promote_node -- Command Successful
--------------------------------------------
 Node IP: 172.31.41.249 Node ID: 0 after promote :
--------------------------------------------
172.31.41.249 5444 2 0.333333 up

Attaching Node-ID: 2 Node-IP: 172.31.34.34 NodeDBStatus[1-UP/0-DOWN] : 1

Attaching Node :
-----------------
pcp_attach_node -- Command Successful
--------------------------------------------
 Node IP: 172.31.34.34 Node ID: 2 after attach :
--------------------------------------------
172.31.34.34 5444 3 0.333333 down

*** Re-confirming DB Status to attach,due to delay when performing switchover/failover ***

Attaching Node-ID: 2 Node-IP: 172.31.34.34 NodeDBStatus[1-UP/0-DOWN] : 1

Attaching Node :
-----------------
pcp_attach_node -- Command Successful
--------------------------------------------
 Node IP: 172.31.34.34 Node ID: 2 after attach :
--------------------------------------------
172.31.34.34 5444 3 0.333333 down

*** Re-confirming DB Status to attach,due to delay when performing switchover/failover ***
Note: Check 'show pool_nodes;' if logs show node status as 'down/waiting'

Sample EFM Detach script logging

[root@masterdb efm-scripts]# more efm_detach_script_20181027062829.log
Dettach Node = ( DBNode=Down )
DB Status on 172.31.34.34: DOWN
Performing Detach operation

Node 172.31.34.34 Status before detach :
--------------------------------------------

Detaching Node :
-----------------
pcp_detach_node -- Command Successful

Node 172.31.34.34 Status after detach :
--------------------------------------------

References

Article posted on installation & configuration, Please visit: www.raghavt.com

Short video link demonstrating the integration of EFM & PgPool: https://youtu.be/pgZJiXa3SoY