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Request based on the SRV record of the service #51

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merged 1 commit into from Jan 17, 2017

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DennyLoko
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I've made this changes to be possible to do a request based on the SRV record of the service. It is useful when you have a service discovery mechanism, like Consul, so you can pass the information and the system will query the SRV record and to the request based on it.

I do not expect this PR to be merged right away, but to start a discussion on the following topic.

Please, review it and suggest the needed changes.

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codecov-io commented Jan 5, 2017

Current coverage is 96.93% (diff: 100%)

No coverage report found for master at 2e0c231.

Powered by Codecov. Last update 2e0c231...5213400

@DennyLoko
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One of the things that I did not implement is the round robin based on the weight of the record.

The net.LookupSRV function already returns the records sorted by priority and randomize the ones with the same weight. So, upon the retry, it will try another service based on this criteria.

@jeevatkm
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jeevatkm commented Jan 6, 2017

@DennyLoko Thanks for the PR, I appreciate it.

I know SRV records lookup is widely used in XMPP/Jabber, SIP, LDAP, etc.; not sure about HTTP(s) world.

Can you please help me to understand, this use case is benefits widely?

@DennyLoko
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DennyLoko commented Jan 6, 2017

Hello @jeevatkm!

We use an extensive number of Docker containers on our microservices infrastructure, and we use Consul as service discovery mechanism to help us reach each container without the need to have a list of IP addresses of each container of each service.

Consul provides a DNS interface for querying the SRV record of the services, so this change could help other users which have the same infrastructure as me.

@jeevatkm
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jeevatkm commented Jan 7, 2017

Thanks for providing real usage scenario. I hope and believe it will be useful for resty users. I will go through PR code changes and share my suggestions.

Thanks again for your time and effort.

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@DennyLoko I have added my recommendations, please have a look and take care.

domain := strings.TrimRight(addrs[idx].Target, ".")
path = strings.TrimLeft(path, "/")

return fmt.Sprintf("%s://%s:%d/%s", DefaultClient.scheme, domain, addrs[idx].Port, path)
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Please use r.client.scheme instead of DefaultClient.scheme.

@@ -465,3 +489,15 @@ func (r *Request) fmtBodyString() (body string) {

return
}

func (r *Request) selectAddr(addrs []*net.SRV, path string, attempt int) string {
if addrs == nil {
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Can you please add test case for when addrs is nil and SRV is record is set. So we can ensure request goes through or gives error info to caller.

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Maybe I didn't understand, but I think this test case already cover this situation.

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@DennyLoko whenever you push your changes, I will merge it. Thanks.

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Sorry for taking so long to reply, it was a rush week.

I've replaced DefaultClient.scheme with r.client.scheme and added some documentation for the SetSRV function.

@@ -465,3 +489,15 @@ func (r *Request) fmtBodyString() (body string) {

return
}

func (r *Request) selectAddr(addrs []*net.SRV, path string, attempt int) string {
if addrs == nil {
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Maybe I didn't understand, but I think this test case already cover this situation.

@jeevatkm jeevatkm self-assigned this Jan 16, 2017
@jeevatkm jeevatkm added this to the v0.11 Milestone milestone Jan 16, 2017
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@DennyLoko no worries, thanks for your response.

Changes looks good, can you please squash these commits?

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Done 👍

@jeevatkm jeevatkm merged commit bbe60b3 into go-resty:master Jan 17, 2017
@DennyLoko DennyLoko deleted the query-srv branch January 17, 2017 17:42
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@DennyLoko Thanks, PR is merged.

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