I have made a setup of multi-master replication of PostgreSQL using BDR (Bi-Directional Replication) among 4 nodes (virtual machines).
Now i want to put a load-balancer for High Availability. For this i have installed and configured "HAProxy" on a different virtual machine, which is listening over 5432/tcp to connect. The haproxy configuration is as follows:
listen pgsql_bdr *:5432
server master 192.168.123.1:5432 check backup
server slave1 192.168.123.2:5432 check
server slave2 192.168.123.3:5432 check
server slave3 192.168.123.4:5432 check
The ip address of HAProxy server is 192.168.123.5
I have use the IP address of HAproxy server in my application to connect with the database (that must redirect the connection to actual database servers). But at that time i am getting following error:
Error connecting to the server: server closed the connection unexpectedly. This probably means the server terminated abnormally before or while processing the request.
And note that i have try to resolve the problem using 2 manner. 1st I disabled the firewall on all servers (HAProxy and all postgres servers) and also i try to replace configuration with the following:
listen pgsql_bdr 0.0.0.0:5432
listen pgsql_bdr 127.0.0.1:5432
listen pgsql_bdr localhost:5432
But all was not working in my case.
Please help me to solve the problem. what i am doing wrong in this scenario?
Thanks in advance!
Check your haproxy
/stats, I am guessing that all backends are marked down, due to wrong check - postgres probably won't respond with 200 -
option httpchk. Use pgsql-check
option pgsql-check user healcheckuser
Also I am not aware of BDR requirements/limitations, but it is common in slaves setups, to have some pooler e.g. pgbouncer - next to client, or in front of each backend, or whatever that is needed.
To check stats you can use stats socket:
# stats about all frontents and backends in a csv format echo "show stat" | socat unix-connect:/run/haproxy/admin.sock stdio # version, PID, current connections, session rates, tasks, etc echo "show info" | socat unix-connect:/run/haproxy/admin.sock stdio # sessions with the used backend/frontend, the source echo "show sess" | socat unix-connect:/run/haproxy/admin.sock stdio # informations about errors if there are any echo "show errors" | socat unix-connect:/run/haproxy/admin.sock stdio
As I tested with postgres 9.4, (some slaves, no BDR), haproxy 1.5.14, no checks
global log /dev/log local0 log /dev/log local1 notice chroot /var/lib/haproxy stats socket /run/haproxy/admin.sock mode 660 level admin stats timeout 30s user haproxy group haproxy daemon listen pgsql *:15432 mode tcp balance roundrobin server master dev1.db.fed:5432 server slave1 dev2.db.fed:5432
And I was able to connect without any issue:
[email protected]:/# echo "show sess" | socat unix-connect:/run/haproxy/admin.sock stdio 0x20d89f0: proto=tcpv4 src=10.163.74.109:46815 fe=pgsql be=pgsql srv=slave1 ts=08 age=3m8s calls=3 rq[f=848202h,i=0,an=00h,rx=,wx=,ax=] rp[f=048202h,i=0,an=00h,rx=,wx=,ax=] s0=[7,8h,fd=1,ex=] s1=[7,8h,fd=2,ex=] exp= 0x20e11a0: proto=unix_stream src=unix:1 fe=GLOBAL be=<NONE> srv=<none> ts=09 age=0s calls=2 rq[f=c08200h,i=0,an=00h,rx=30s,wx=,ax=] rp[f=008002h,i=0,an=00h,rx=,wx=,ax=] s0=[7,8h,fd=3,ex=] s1=[7,0h,fd=-1,ex=] exp=30s
Queries are running, data is coming, seems OK.
But again, I'm not able to test BDR at the moment.