30% overhead using HAProxy?

@acook wrote:

Hello,

I'm using HAProxy to front a simple node application, using the following acl/backend configuration:

acl acl_myapp hdr(host) -i myapp.service.consul

use_backend backend_myapp if acl_myapp

backend backend_myapp
    balance roundrobin
    option  httpchk GET /health
    server  10.134.20.234_31005 10.134.20.234:31005 maxconn 128  weight 100  check

I am running an ApacheBench test against the application to test the max requests/sec I can achieve with my app. I am running ab with 300 concurrent requests, and a total of 6000 requests.

When I run ab against my application directly, on port 31005, for example:

ab -n 6000 -c 300 -k "http://10.134.20.234:31005/"

I see numbers like

Requests per second:    1053.19 [#/sec] (mean)
Requests per second:    1104.31 [#/sec] (mean)
Requests per second:    1069.48 [#/sec] (mean)

However, when I go via HAProxy via setting host header, i.e.

ab -H "Host: myapp.service.consul" -n 6000 -c 300 -k "http://10.134.20.234/"

I see numbers like

Requests per second:    699.89 [#/sec] (mean)
Requests per second:    752.43 [#/sec] (mean)
Requests per second:    747.10 [#/sec] (mean)

Which is around 300 req/sec worse than when going direct to the application.

When I look at the statistics using maxconn of 128, I see:

Queue time:  269 ms
Response time:  198 ms
Total time:  467 ms

If I change it to something really high, like 1000, I see:

Queue time:  0 ms
Response time:  418 ms
Total time:  418 ms

And if change the maxconn to something low like 30, I see:

Queue time:  311 ms
Response time:  41 ms
Total time:  386 ms

Any ideas why I'm seeing such a difference when going through HAProxy?

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