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subscribe.go
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subscribe.go
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package subscribe
import (
"bytes"
"fmt"
"github.com/caddyserver/caddy/v2"
"github.com/caddyserver/caddy/v2/modules/caddyhttp"
"github.com/nats-io/nats.go"
"github.com/sandstorm/caddy-nats-bridge/common"
"go.uber.org/zap"
"io"
"net/http"
"net/http/httptest"
"net/url"
)
type Subscribe struct {
Subject string `json:"subject,omitempty"`
Method string `json:"method,omitempty"`
URL string `json:"path,omitempty"`
QueueGroup string `json:"queue_group,omitempty"`
conn *nats.Conn
sub *nats.Subscription
ctx caddy.Context
logger *zap.Logger
httpApp *caddyhttp.App
}
func (Subscribe) CaddyModule() caddy.ModuleInfo {
return caddy.ModuleInfo{
ID: "nats.handlers.subscribe",
New: func() caddy.Module { return new(Subscribe) },
}
}
func (s *Subscribe) Provision(ctx caddy.Context) error {
s.ctx = ctx
s.logger = ctx.Logger()
return nil
}
func (s *Subscribe) Subscribe(conn *nats.Conn) error {
s.logger.Info(
"subscribing to NATS subject",
zap.String("subject", s.Subject),
zap.String("queue_group", s.QueueGroup),
zap.String("method", s.Method),
zap.String("url", s.URL),
)
httpAppIface, err := s.ctx.App("http")
if err != nil {
return err
}
s.httpApp = httpAppIface.(*caddyhttp.App)
s.conn = conn
if s.QueueGroup != "" {
s.sub, err = conn.QueueSubscribe(s.Subject, s.QueueGroup, s.handler)
} else {
s.sub, err = conn.Subscribe(s.Subject, s.handler)
}
return err
}
func (s *Subscribe) Unsubscribe(conn *nats.Conn) error {
s.logger.Info(
"unsubscribing from NATS subject",
zap.String("subject", s.Subject),
zap.String("queue_group", s.QueueGroup),
zap.String("method", s.Method),
zap.String("url", s.URL),
)
return s.sub.Drain()
}
func (s *Subscribe) handler(msg *nats.Msg) {
repl := caddy.NewReplacer()
common.AddNatsSubscribeVarsToReplacer(repl, msg)
url := repl.ReplaceAll(s.URL, "")
method := repl.ReplaceAll(s.Method, "")
s.logger.Debug(
"handling message NATS on subject",
zap.String("subject", msg.Subject),
zap.String("queue_group", s.QueueGroup),
zap.String("method", method),
zap.String("url", url),
zap.Bool("with_reply", msg.Reply != ""),
)
req, err := s.prepareRequest(method, url, bytes.NewBuffer(msg.Data), msg.Header)
if err != nil {
s.logger.Error("error creating request", zap.Error(err))
return
}
server, err := s.matchServer(s.httpApp.Servers, req)
if err != nil {
s.logger.Error("error matching server", zap.Error(err))
return
}
if msg.Reply != "" {
// the incoming NATS Message has a reply subject set; so it was sent via request() (and not via publish()).
// -> so we can send the response back.
rec := httptest.NewRecorder()
server.ServeHTTP(rec, req)
// rec.Code -> TODO: new status code
//TODO Handle error
msg.RespondMsg(&nats.Msg{
Header: nats.Header(rec.Header()),
Data: rec.Body.Bytes(),
})
return
}
// no reply subject was set -> the original NATS requester is not interested in the response - we can ignore it.
server.ServeHTTP(common.NoopResponseWriter{}, req)
}
func (s *Subscribe) matchServer(servers map[string]*caddyhttp.Server, req *http.Request) (*caddyhttp.Server, error) {
repl := caddy.NewReplacer()
for _, server := range servers {
if !hasListenerAddress(server, req.URL) {
// listener address (host/port) does not match for server, so we can continue with next server.
continue
}
r := caddyhttp.PrepareRequest(req, repl, nil, server)
for _, route := range server.Routes {
if route.MatcherSets.AnyMatch(r) {
return server, nil
}
}
}
return nil, fmt.Errorf("no server matched for the current url: %s", req.URL)
}
// hasListenerAddress is modelled after the same function in caddyhttp/server, but a bit simplified.
func hasListenerAddress(s *caddyhttp.Server, fullAddr *url.URL) bool {
laddrs, err := caddy.ParseNetworkAddress(fullAddr.Host)
if err != nil {
return false
}
if laddrs.PortRangeSize() != 1 {
return false // TODO: support port ranges
}
for _, lnAddr := range s.Listen {
thisAddrs, err := caddy.ParseNetworkAddress(lnAddr)
if err != nil {
continue
}
if thisAddrs.Network != laddrs.Network {
continue
}
if (laddrs.StartPort <= thisAddrs.EndPort) &&
(laddrs.StartPort >= thisAddrs.StartPort) {
return true
}
}
return false
}
func (s *Subscribe) prepareRequest(method string, rawURL string, body io.Reader, header nats.Header) (*http.Request, error) {
u, err := url.Parse(rawURL)
if err != nil {
return nil, fmt.Errorf("invalid url: %s", rawURL)
}
req, err := http.NewRequest(method, rawURL, body)
if header != nil {
req.Header = http.Header(header)
}
req.RequestURI = u.Path
req.RemoteAddr = s.conn.ConnectedAddr()
//TODO: make User-Agent configurable
req.Header.Add("User-Agent", "caddy-nats")
return req, err
}
var (
_ caddy.Provisioner = (*Subscribe)(nil)
_ common.NatsHandler = (*Subscribe)(nil)
)