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Merge pull request #3 from ThreeDotsLabs/sse-handler
Add SSERouter
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,8 +1,9 @@ | ||
| module github.com/ThreeDotsLabs/watermill-http | ||
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| require ( | ||
| github.com/ThreeDotsLabs/watermill v1.0.2 | ||
| github.com/ThreeDotsLabs/watermill v1.1.0 | ||
| github.com/go-chi/chi v4.0.2+incompatible | ||
| github.com/go-chi/render v1.0.1 | ||
| github.com/pkg/errors v0.8.1 | ||
| github.com/stretchr/testify v1.3.0 | ||
| ) |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,194 @@ | ||
| package http | ||
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| import ( | ||
| "context" | ||
| "github.com/go-chi/render" | ||
| "github.com/pkg/errors" | ||
| "net/http" | ||
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| "github.com/ThreeDotsLabs/watermill" | ||
| "github.com/ThreeDotsLabs/watermill/message" | ||
| "github.com/ThreeDotsLabs/watermill/pubsub/gochannel" | ||
| ) | ||
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| type StreamAdapter interface { | ||
| // GetResponse returns the response to be sent back to client. | ||
| // Any errors that occur should be handled and written to `w`, returning false as `ok`. | ||
| GetResponse(w http.ResponseWriter, r *http.Request) (response interface{}, ok bool) | ||
| // Validate validates if the incoming message should be handled by this handler. | ||
| // Typically this involves checking some kind of model ID. | ||
| Validate(r *http.Request, msg *message.Message) (ok bool) | ||
| } | ||
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| type HandleErrorFunc func(w http.ResponseWriter, r *http.Request, err error) | ||
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| type defaultErrorResponse struct { | ||
| Error string `json:"error"` | ||
| } | ||
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| // DefaultErrorHandler writes JSON error response along with Internal Server Error code (500). | ||
| func DefaultErrorHandler(w http.ResponseWriter, r *http.Request, err error) { | ||
| w.WriteHeader(500) | ||
| render.Respond(w, r, defaultErrorResponse{Error: err.Error()}) | ||
| } | ||
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| // SSERouter is a router handling Server-Sent Events. | ||
| type SSERouter struct { | ||
| fanOut *gochannel.FanOut | ||
| config SSERouterConfig | ||
| logger watermill.LoggerAdapter | ||
| } | ||
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| type SSERouterConfig struct { | ||
| UpstreamSubscriber message.Subscriber | ||
| ErrorHandler HandleErrorFunc | ||
| } | ||
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| func (c *SSERouterConfig) setDefaults() { | ||
| if c.ErrorHandler == nil { | ||
| c.ErrorHandler = DefaultErrorHandler | ||
| } | ||
| } | ||
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| func (c SSERouterConfig) validate() error { | ||
| if c.UpstreamSubscriber == nil { | ||
| return errors.New("upstream subscriber is nil") | ||
| } | ||
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| return nil | ||
| } | ||
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| // NewSSERouter creates a new SSERouter. | ||
| func NewSSERouter( | ||
| config SSERouterConfig, | ||
| logger watermill.LoggerAdapter, | ||
| ) (SSERouter, error) { | ||
| config.setDefaults() | ||
| if err := config.validate(); err != nil { | ||
| return SSERouter{}, errors.Wrap(err, "invalid SSERouter config") | ||
| } | ||
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| if logger == nil { | ||
| logger = watermill.NopLogger{} | ||
| } | ||
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| fanOut, err := gochannel.NewFanOut(config.UpstreamSubscriber, logger) | ||
| if err != nil { | ||
| return SSERouter{}, errors.Wrap(err, "could not create a FanOut") | ||
| } | ||
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| return SSERouter{ | ||
| fanOut: fanOut, | ||
| config: config, | ||
| logger: logger, | ||
| }, nil | ||
| } | ||
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| // AddHandler starts a new handler for a given topic. | ||
| func (r SSERouter) AddHandler(topic string, streamAdapter StreamAdapter) http.HandlerFunc { | ||
| r.logger.Trace("Adding handler for topic", watermill.LogFields{ | ||
| "topic": topic, | ||
| }) | ||
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| r.fanOut.AddSubscription(topic) | ||
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| handler := sseHandler{ | ||
| subscriber: r.fanOut, | ||
| topic: topic, | ||
| streamAdapter: streamAdapter, | ||
| config: r.config, | ||
| logger: r.logger, | ||
| } | ||
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| return handler.Handle | ||
| } | ||
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| // Run starts the SSERouter. | ||
| func (r SSERouter) Run(ctx context.Context) error { | ||
| return r.fanOut.Run(ctx) | ||
| } | ||
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| // Running is closed when the SSERouter is running. | ||
| func (r SSERouter) Running() chan struct{} { | ||
| return r.fanOut.Running() | ||
| } | ||
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| type sseHandler struct { | ||
| subscriber message.Subscriber | ||
| topic string | ||
| streamAdapter StreamAdapter | ||
| config SSERouterConfig | ||
| logger watermill.LoggerAdapter | ||
| } | ||
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| func (h sseHandler) Handle(w http.ResponseWriter, r *http.Request) { | ||
| if render.GetAcceptedContentType(r) == render.ContentTypeEventStream { | ||
| h.handleEventStream(w, r) | ||
| return | ||
| } | ||
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| h.handleGenericRequest(w, r) | ||
| } | ||
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| func (h sseHandler) handleGenericRequest(w http.ResponseWriter, r *http.Request) { | ||
| response, ok := h.streamAdapter.GetResponse(w, r) | ||
| if !ok { | ||
| return | ||
| } | ||
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| render.Respond(w, r, response) | ||
| } | ||
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| func (h sseHandler) handleEventStream(w http.ResponseWriter, r *http.Request) { | ||
| messages, err := h.subscriber.Subscribe(r.Context(), h.topic) | ||
| if err != nil { | ||
| h.config.ErrorHandler(w, r, err) | ||
| return | ||
| } | ||
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| responsesChan := make(chan interface{}) | ||
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| go func() { | ||
| defer func() { | ||
| h.logger.Trace("Closing SSE handler", nil) | ||
| close(responsesChan) | ||
| }() | ||
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| response, ok := h.streamAdapter.GetResponse(w, r) | ||
| if !ok { | ||
| return | ||
| } | ||
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| responsesChan <- response | ||
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| h.logger.Trace("Listening for messages", nil) | ||
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| for msg := range messages { | ||
| msg.Ack() | ||
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| response, ok := h.processMessage(w, r, msg) | ||
| if ok { | ||
| responsesChan <- response | ||
| } | ||
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| select { | ||
| case <-r.Context().Done(): | ||
| return | ||
| default: | ||
| } | ||
| } | ||
| }() | ||
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| render.Respond(w, r, responsesChan) | ||
| } | ||
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| func (h sseHandler) processMessage(w http.ResponseWriter, r *http.Request, msg *message.Message) (interface{}, bool) { | ||
| ok := h.streamAdapter.Validate(r, msg) | ||
| if !ok { | ||
| return nil, false | ||
| } | ||
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| h.logger.Trace("Received valid message", watermill.LogFields{"uuid": msg.UUID}) | ||
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| return h.streamAdapter.GetResponse(w, r) | ||
| } |
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