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best_eta.go
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best_eta.go
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// Copyright (c) 2017 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
package frontend
import (
"context"
"errors"
"math"
"sync"
"time"
"github.com/opentracing/opentracing-go"
"go.uber.org/zap"
"github.com/uber/jaeger/examples/hotrod/pkg/log"
"github.com/uber/jaeger/examples/hotrod/pkg/pool"
"github.com/uber/jaeger/examples/hotrod/services/config"
"github.com/uber/jaeger/examples/hotrod/services/customer"
"github.com/uber/jaeger/examples/hotrod/services/driver"
"github.com/uber/jaeger/examples/hotrod/services/route"
)
type bestETA struct {
customer customer.Interface
driver driver.Interface
route route.Interface
pool *pool.Pool
logger log.Factory
}
// Response contains ETA for a trip.
type Response struct {
Driver string
ETA time.Duration
}
func newBestETA(tracer opentracing.Tracer, logger log.Factory) *bestETA {
return &bestETA{
customer: customer.NewClient(
tracer,
logger.With(zap.String("component", "customer_client")),
),
driver: driver.NewClient(
tracer,
logger.With(zap.String("component", "driver_client")),
),
route: route.NewClient(
tracer,
logger.With(zap.String("component", "route_client")),
),
pool: pool.New(config.RouteWorkerPoolSize),
logger: logger,
}
}
func (eta *bestETA) Get(ctx context.Context, customerID string) (*Response, error) {
customer, err := eta.customer.Get(ctx, customerID)
if err != nil {
return nil, err
}
eta.logger.For(ctx).Info("Found customer", zap.Any("customer", customer))
if span := opentracing.SpanFromContext(ctx); span != nil {
span.SetBaggageItem("customer", customer.Name)
}
drivers, err := eta.driver.FindNearest(ctx, customer.Location)
if err != nil {
return nil, err
}
eta.logger.For(ctx).Info("Found drivers", zap.Any("drivers", drivers))
results := eta.getRoutes(ctx, customer, drivers)
eta.logger.For(ctx).Info("Found routes", zap.Any("routes", results))
resp := &Response{ETA: math.MaxInt64}
for _, result := range results {
if result.err != nil {
return nil, err
}
if result.route.ETA < resp.ETA {
resp.ETA = result.route.ETA
resp.Driver = result.driver
}
}
if resp.Driver == "" {
return nil, errors.New("No routes found")
}
eta.logger.For(ctx).Info("Dispatch successful", zap.String("driver", resp.Driver), zap.String("eta", resp.ETA.String()))
return resp, nil
}
type routeResult struct {
driver string
route *route.Route
err error
}
// getRoutes calls Route service for each (customer, driver) pair
func (eta *bestETA) getRoutes(ctx context.Context, customer *customer.Customer, drivers []driver.Driver) []routeResult {
results := make([]routeResult, 0, len(drivers))
wg := sync.WaitGroup{}
routesLock := sync.Mutex{}
for _, dd := range drivers {
wg.Add(1)
driver := dd // capture loop var
// Use worker pool to (potentially) execute requests in parallel
eta.pool.Execute(func() {
route, err := eta.route.FindRoute(ctx, driver.Location, customer.Location)
routesLock.Lock()
results = append(results, routeResult{
driver: driver.DriverID,
route: route,
err: err,
})
routesLock.Unlock()
wg.Done()
})
}
wg.Wait()
return results
}