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Track and use in flight HTTP request count in health check #53

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Track and use in flight HTTP request count in health check #53

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29 changes: 29 additions & 0 deletions registry/handlers/app.go
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Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,7 @@ import (
"runtime"
"strconv"
"strings"
"sync/atomic"
"time"

events "github.com/docker/go-events"
Expand Down Expand Up @@ -96,6 +97,9 @@ type App struct {

// readOnly is true if the registry is in a read-only maintenance mode
readOnly bool

// inFlightRequestCount keeps track of current request count handled by the server
inFlightRequestCount atomic.Int64
}

// NewApp takes a configuration and returns a configured app, ready to serve
Expand Down Expand Up @@ -397,6 +401,17 @@ func (app *App) RegisterHealthChecks(healthRegistries ...*health.Registry) {
}
}

// Register in flight request with health checker
inFlightHttpRequestsCheck := func() error {
fmt.Printf("Doing in flight check: %v\n", app.inFlightRequestCount.Load())
if app.inFlightRequestCount.Load() > 1e4 {
return fmt.Errorf("In Flight HTTP Requests count check failed: %v", app.inFlightRequestCount.Load())
}
return nil
}

healthRegistry.RegisterFunc("inflighthttprequests", inFlightHttpRequestsCheck)

for _, fileChecker := range app.Config.Health.FileCheckers {
interval := fileChecker.Interval
if interval == 0 {
Expand Down Expand Up @@ -446,6 +461,17 @@ func (app *App) RegisterHealthChecks(healthRegistries ...*health.Registry) {
}
}

// This updates the inFlightRequestCount atomic counter
// for each handler
func (app *App) inFlightHTTPRequestCountHandler(next http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
app.inFlightRequestCount.Add(1)
defer app.inFlightRequestCount.Add(-1)

next.ServeHTTP(w, r)
})
}

// register a handler with the application, by route name. The handler will be
// passed through the application filters and context will be constructed at
// request time.
Expand All @@ -460,6 +486,9 @@ func (app *App) register(routeName string, dispatch dispatchFunc) {
handler = metrics.InstrumentHandler(httpMetrics, handler)
}

// chain the handler with in flight HTTP requests updater
handler = app.inFlightHTTPRequestCountHandler(handler)

// TODO(stevvooe): This odd dispatcher/route registration is by-product of
// some limitations in the gorilla/mux router. We are using it to keep
// routing consistent between the client and server, but we may want to
Expand Down