[go-nuts] [ANN] nats-proxy - http in the front; NATS in the back, microservice library for NATS

[Matt Ho]

https://github.com/savaki/nats-proxy

http in the front; NATS in the back

nats-proxy provides an HTTP gateway that simplifies service discovery by 
using NATS as the transport layer between services.

client --[http]--> gateway --[nats]--> service


*Start the API Gateway*

// Start the Gateway
nc, _ := nats.Connect(nats.DefaultURL)
gw, _ := nats_proxy.Wrap(h, nats_proxy.WithNats(nc))

http.ListenAndServe(":8080", gw) 

 

*Start the Service*

// Start the Service
h := http.HandlerFunc(func(w http.ResponseWriter, req *http.Request) {
  io.WriteString(w, "hello world")
})

nc, _ := nats.Connect(nats.DefaultURL)
r, _ := nats_proxy.Wrap(h,
  nats_proxy.WithNats(nc),
)
r.Subscribe(context.Background())










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[go-nuts] Re: httputil.ReverseProxy + http.DefaultTransport.DialContext results in cancelled DNS requests

[luke . kysow]

Seeing this issue with golang 1.8.3 in Kubernetes but without a reverse 
proxy. Just KubeDNS -> Kubernetes service IP -> other Golang service.

When compiled with go 1.7 we saw "dial tcp: no suitable address found" 
errors and so after looking at this issue 
 upgraded to go 1.8.3 hoping it 
would fix it. Instead it seems to have just been replaced with this error.

dial tcp: lookup other-service.default.svc.cluster.local on 10.244.0.10:53: 
dial udp 10.244.0.10:53: operation was canceled


On Tuesday, December 20, 2016 at 3:55:17 PM UTC-8, Matt Duch wrote:
>
> I'm running into issues when using a ReverseProxy that sits in front of a 
> service that serves static asset files (in this case, 100's in a few 
> seconds). Occasionally (1 out ~500 files) will error out with:
> http: proxy error: dial tcp: lookup myapp.default.svc.cluster.local on 
> 172.18.0.16:53: dial udp 172.18.0.16:53: operation was canceled
> That error occurs within a second of the request being sent, so it 
> shouldn't trigger any timeouts.
>
> When using a default ReverseProxy initialized using:
> proxy := httputil.NewSingleHostReverseProxy(&url.URL{Scheme: scheme,Host: 
> host})
>
> In a configuration like:
> browser -> proxy -> golang http service
>
> Where the proxy and http service (go 1.7.4) are running in docker 
> containers (using kubernetes), and the DNS resolver is kube-dns (kubernetes 
> 1.4). 
> Changing the proxy to use a non-default transport (identical to 
> http.DefaultTransport) but changing DialContext -> Dial:
>
> v.Proxy.Transport = &http.Transport{
>
> Proxy: http.ProxyFromEnvironment,
>
> Dial: (&net.Dialer{
>
> Timeout:   30 * time.Second,
>
> KeepAlive: 30 * time.Second,
>
> }).Dial,
>
> MaxIdleConns:  100,
>
> IdleConnTimeout:   90 * time.Second,
>
> TLSHandshakeTimeout:   10 * time.Second,
>
> ExpectContinueTimeout: 1 * time.Second,
>
> }
>
> solves the problem.
>
> There are no errors in dnsmasq and kube-dns (the containers that provide 
> DNS information). 
> I've stress tested the DNS setup (hundreds of thousands of requests, with 
> one hundred concurrently) without issues (from a go binary). 
> I've hit the backend service directly with 1000 concurrent requests, no 
> issues (from a go binary as well). 
> If I switch from using a hostname in NewSingleHostReverseProxy to the IP 
> address of the backend service, the problem is also solved.
>
> This seems to be a unique to named hosts + DialContext + ReverseProxy. Any 
> ideas as to what might be happening?
>

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