harbor leak fd when connect to registry

[feilengcui008]

If you are reporting a problem, please make sure the following information are provided:
1)Version of docker engine and docker-compose
Docker version:
Client:
Version: 1.12.1
API version: 1.24
Go version: go1.7.1
Git commit: 6f9534c
Built: Thu Sep 8 10:31:18 2016
OS/Arch: darwin/amd64
Server:
Version: 1.12.1
API version: 1.24
Go version: go1.6.3
Git commit: 23cf638
Built: Thu Aug 18 17:52:38 2016
OS/Arch: linux/amd64

Compose version:
docker-compose version 1.8.0, build f3628c7

2)Harbor version: master branch

3)reproduce step
3.1 use docker-compose start the harbor in 127.0.0.1
3.2 push an image to library namespace
3.3 docker exec -it deploy_ui /bin/bash and watch fds in /proc/1/fd
3.4 login harbor ui and request project details http://127.0.0.1/repository#/repositories?project_id=1&is_public=1

4)phenomenon
the fds of harbor ui and registry will increase when you request the api related to tags and manifests, when reach the max default number of process 1024, then dns resolve will fail and new request will fail

5)misc
the same to linux x86_64 platform
maybe related to pr547: #547

[reasonerjt]

I can re-produce the issue, reusing the transport in http client and setting Timeout fix this issue, but honestly I only see people suggesting such fix, but don't totally get why resp.Body.Close() is insufficient, as we'll release a new version to include some bug fix this week I'll apply this fix for now.

Will dig more when I have time, this week's schedule is crazy...

[feilengcui008]

@reasonerjt I think the essential reason is that the tarnsport is not reused. Each tarnsport will keep defaul 2 idle conns, if we create trasport every time, it will leak 2 fds for each request

[reasonerjt]

I believe this has been fixed , closing.