A sample setup to test HAProxy configuration with nodejs applications as backends while logging with rsyslog deployed with docker-compose.
First we need to build all docker images and start the containers we are going use for this setup.
# make install
At the end we should see all containers up and running:
Name Command State Ports
--------------------------------------------------------------------------------------------------
haproxy-docker-compose_app1_1 node index.js Up 0.0.0.0:3000->3000/tcp
haproxy-docker-compose_app2_1 node index.js Up 0.0.0.0:3001->3000/tcp
haproxy-docker-compose_haproxy_1 /docker-entrypoint.sh /bin ... Up 0.0.0.0:8080->8080/tcp
haproxy-docker-compose_rsyslog_1 rsyslogd -n -f /etc/rsyslo ... Up 514/tcp
Now we can test if the haproxy container is redirecting our requests to one of our backend services:
# make test
curl -i localhost:8080
HTTP/1.1 200 OK
X-Powered-By: Express
Content-Type: text/html; charset=utf-8
Content-Length: 45
ETag: W/"2d-MkIV9HD2MPle5+by/x6XB59zLEs"
Date: Thu, 13 Dec 2018 15:18:53 GMT
Response from container 8cdc81db5fe1 | app1
By sending a request to /off endpoint, we should force our application to send 500 responses. HAProxy should detect this and subsequently remove that application from the load balancing round-robin mechanism and the only responses should be coming from the other application eg. app1.
# curl localhost:8080/off
Container cde3e75d93b0 | app2 is turned OFF
HAProxy logs all the requests through rsyslog container. We can dive into the logs more:
docker logs haproxy-docker-compose_rsyslog_1 -f
2018-12-14T10:29:50+00:00 haproxy-docker-compose_haproxy_1.haproxy-docker-compose_default haproxy[10]: Proxy http-in started.
2018-12-14T10:29:50+00:00 haproxy-docker-compose_haproxy_1.haproxy-docker-compose_default haproxy[10]: Proxy servers started.
2018-12-14T10:29:50+00:00 haproxy-docker-compose_haproxy_1.haproxy-docker-compose_default haproxy[10]: Proxy server1 started.
2018-12-14T10:29:50+00:00 haproxy-docker-compose_haproxy_1.haproxy-docker-compose_default haproxy[10]: Proxy server2 started.
2018-12-14T10:29:50+00:00 haproxy-docker-compose_haproxy_1.haproxy-docker-compose_default haproxy[11]: Server servers/s1 is DOWN, reason: Layer4 connection problem, info: "Connection refused", check duration: 0ms. 1 active and 0 backup servers left. 0 sessions active, 0 requeued, 0 remaining in queue.
2018-12-14T10:29:54+00:00 haproxy-docker-compose_haproxy_1.haproxy-docker-compose_default haproxy[11]: Server servers/s1 is UP, reason: Layer7 check passed, code: 200, info: "OK", check duration: 2ms. 2 active and 0 backup servers online. 0 sessions requeued, 0 total in queue.
2018-12-14T10:37:18+00:00 haproxy-docker-compose_haproxy_1.haproxy-docker-compose_default haproxy[11]: 192.168.96.1:59914 [14/Dec/2018:10:37:18.186] http-in servers/s2 1/0/0/4/5 200 250 - - --NN 1/1/0/1/0 0/0 "GET / HTTP/1.1"
2018-12-14T10:37:19+00:00 haproxy-docker-compose_haproxy_1.haproxy-docker-compose_default haproxy[11]: 192.168.96.1:59922 [14/Dec/2018:10:37:19.225] http-in servers/s1 1/0/0/3/4 200 250 - - --NN 1/1/0/1/0 0/0 "GET / HTTP/1.1"
2018-12-14T10:37:20+00:00 haproxy-docker-compose_haproxy_1.haproxy-docker-compose_default haproxy[11]: 192.168.96.1:59932 [14/Dec/2018:10:37:20.263] http-in servers/s2 0/0/0/2/2 200 250 - - --NN 1/1/0/1/0 0/0 "GET / HTTP/1.1"
2018-12-14T10:37:33+00:00 haproxy-docker-compose_haproxy_1.haproxy-docker-compose_default haproxy[11]: 192.168.96.1:59986 [14/Dec/2018:10:37:33.400] http-in servers/s1 1/0/0/1/2 200 250 - - --NN 1/1/0/1/0 0/0 "GET / HTTP/1.1"
2018-12-14T10:37:34+00:00 haproxy-docker-compose_haproxy_1.haproxy-docker-compose_default haproxy[11]: 192.168.96.1:59996 [14/Dec/2018:10:37:34.431] http-in servers/s2 0/0/0/1/1 200 250 - - --NN 1/1/0/1/0 0/0 "GET / HTTP/1.1"
2018-12-14T10:37:35+00:00 haproxy-docker-compose_haproxy_1.haproxy-docker-compose_default haproxy[11]: 192.168.96.1:60002 [14/Dec/2018:10:37:35.464] http-in servers/s1 0/0/0/1/1 200 250 - - --NN 1/1/0/1/0 0/0 "GET / HTTP/1.1"
2018-12-14T10:37:36+00:00 haproxy-docker-compose_haproxy_1.haproxy-docker-compose_default haproxy[11]: 192.168.96.1:60012 [14/Dec/2018:10:37:36.501] http-in servers/s2 0/0/0/1/1 200 250 - - --NN 1/1/0/1/0 0/0 "GET / HTTP/1.1"
2018-12-14T10:37:44+00:00 haproxy-docker-compose_haproxy_1.haproxy-docker-compose_default haproxy[11]: 192.168.96.1:60048 [14/Dec/2018:10:37:44.443] http-in servers/s1 0/0/0/1/1 200 250 - - --NN 1/1/0/1/0 0/0 "GET / HTTP/1.1"
As we discussed before, after forcing one of the applications to send 500 responses, HAProxy logs this, saying that s2 (in this case the name of the app2 from HAProxy config perspective) is down, so it is removed from the load balancing.
2018-12-14T10:37:52+00:00 haproxy-docker-compose_haproxy_1.haproxy-docker-compose_default haproxy[11]: Server servers/s2 is DOWN, reason: Layer7 timeout, check duration: 2000ms. 1 active and 0 backup servers left. 1 sessions active, 0 requeued, 0 remaining in queue.
2018-12-14T10:37:57+00:00 haproxy-docker-compose_haproxy_1.haproxy-docker-compose_default haproxy[11]: 192.168.96.1:60054 [14/Dec/2018:10:37:45.476] http-in servers/s2 0/0/0/-1/12003 504 194 - - sHNN 0/0/0/0/0 0/0 "GET / HTTP/1.1"
2018-12-14T10:37:58+00:00 haproxy-docker-compose_haproxy_1.haproxy-docker-compose_default haproxy[11]: 192.168.96.1:60106 [14/Dec/2018:10:37:58.515] http-in servers/s1 0/0/0/4/4 200 250 - - --NN 1/1/0/1/0 0/0 "GET / HTTP/1.1"
2018-12-14T10:37:59+00:00 haproxy-docker-compose_haproxy_1.haproxy-docker-compose_default haproxy[11]: 192.168.96.1:60112 [14/Dec/2018:10:37:59.554] http-in servers/s1 0/0/0/1/1 200 250 - - --NN 1/1/0/1/0 0/0 "GET / HTTP/1.1"