VCL probe in the configuration



This is a “low priority” question. Just a curiosity. :slight_smile: So, I have created a new service and was comparing a diff between our earlier test VCL and the newly configure VCL.
Everything matches except one part which has just appeared in the backend config:

.dynamic = true;
.probe = {
    .request = "HEAD / HTTP/1.1"  "Host:" "Connection: close";
    .window = 5;
    .threshold = 1;
    .timeout = 2s;
    .initial = 5;
    .dummy = true;

Shielding: (none)
Health Check: (none)
Auto Load Balancing: No
Number of origin servers: 1

A probe sort of seems like it would be related to health checks or load balancing. However those are not enabled. Wonder why it appears now, however not in earlier testing. And what effect, if any, will the probe have?



That section of the generated VCL does indeed look like a healthcheck, but the part:

.dummy = true;

is to indicate that this healthcheck is a placeholder and not active.