Gitlab CI - Failed to register runner

Question

I've setup my gitlab installation from source, secured it with letsencrypt and deployed it under https://gitlab.mydomain.com. I can access the website and create repositories, etc. but I can't find a way to register a gitlab ci runner for the installation.

Please enter the gitlab-ci coordinator URL (e.g. https://gitlab.com/ci):
https://gitlab.mydomain.com/ci
Please enter the gitlab-ci token for this runner:
xxxxxxxx-xxxxxxxx
Please enter the gitlab-ci description for this runner:
[server]: test
Please enter the gitlab-ci tags for this runner (comma separated):
test
ERROR: Registering runner... failed     runner=xxxxxxx 
status=couldn't execute POST against https://gitlab.mydomain.com/ci/api/v1/runners/register.json:
Post https://gitlab.mydomain.com/ci/api/v1/runners/register.json: 
read tcp [ipv6address]:33518->[ipv6address]:443: read: connection reset by peer
PANIC: Failed to register this runner. Perhaps you are having network problems

My gitlab system is working fine and I really ran out of explanations why there would be a connection reset by peer. When I try to curl the address from the error message directly, it returns a correct response.

curl -v https://gitlab.mydomain.com/ci/api/v1/runners/register.json
*   Trying ipv6address...
* Connected to gitlab.mydomain.com (ipv6address) port 443 (#0)
* found 174 certificates in /etc/ssl/certs/ca-certificates.crt
* found 700 certificates in /etc/ssl/certs
* ALPN, offering h2
* ALPN, offering http/1.1
* SSL connection using TLS1.2 / ECDHE_RSA_AES_256_GCM_SHA384
*        server certificate verification OK
*        server certificate status verification SKIPPED
*        common name: mydomain.com (matched)
*        server certificate expiration date OK
*        server certificate activation date OK
*        certificate public key: RSA
*        certificate version: #3
*        subject: CN=mydomain.com
*        start date: Wed, 18 May 2016 14:35:00 GMT
*        expire date: Tue, 16 Aug 2016 14:35:00 GMT
*            issuer: C=US,O=Let's Encrypt,CN=Let's Encrypt Authority X3
*        compression: NULL
* ALPN, server did not agree to a protocol
> GET /ci/api/v1/runners/register.json HTTP/1.1
> Host: gitlab.mydomain.com
> User-Agent: curl/7.47.0
> Accept: */*
> 
< HTTP/1.1 405 Method Not Allowed
< Server: nginx
< Date: Sun, 29 May 2016 09:14:09 GMT
< Content-Type: application/json
< Content-Length: 2
< Connection: keep-alive
< Allow: OPTIONS, POST
< Cache-Control: no-cache
< Status: 405 Method Not Allowed

Answer 1

If the runner and gitlab are running on the same host you can get around this problem by entering a the first question the following instead what is given in the docs:

http://gitlab:port

where gitlab is the container name and port the left port number of the container. If you are using gitlab internal ssl certs you specify https instead of http. This always solves this problem when I get it.