client: Retrieve events sent to server

2013-03-17 23:02:51 -04:00
parent 11bcf164c6
commit a4bce8a07b
3 changed files with 162 additions and 47 deletions
--- a/client/net.go
+++ b/client/net.go
@ -0,0 +1,123 @@
+package main
+
+import (
+	"asink"
+	"bytes"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"strconv"
+	"time"
+)
+
+const MIN_ERROR_WAIT = 100 // 1/10 of a second
+const MAX_ERROR_WAIT = 10000 // 10 seconds
+
+func SendEvent(globals AsinkGlobals, event *asink.Event) error {
+	url := "http://" + globals.server + ":" + strconv.Itoa(int(globals.port)) + "/events/"
+
+	//construct json payload
+	events := asink.EventList{
+		Events: []*asink.Event{event},
+	}
+	b, err := json.Marshal(events)
+	if err != nil {
+		return err
+	}
+	fmt.Println(string(b))
+
+	//actually make the request
+	resp, err := http.Post(url, "application/json", bytes.NewReader(b))
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+
+	//check to make sure request succeeded
+	body, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return err
+	}
+
+	var apistatus asink.APIResponse
+	err = json.Unmarshal(body, &apistatus)
+	if err != nil {
+		return err
+	}
+	if apistatus.Status != asink.SUCCESS {
+		return errors.New("API response was not success: " + apistatus.Explanation)
+	}
+
+	return nil
+}
+
+func GetEvents(globals AsinkGlobals, events chan *asink.Event) {
+	url := "http://" + globals.server + ":" + strconv.Itoa(int(globals.port)) + "/events/"
+	var successiveErrors uint = 0
+
+	errorWait := func(err error) {
+		fmt.Println(err)
+		var waitMilliseconds time.Duration = MIN_ERROR_WAIT << successiveErrors
+		if waitMilliseconds > MAX_ERROR_WAIT {
+			waitMilliseconds = MAX_ERROR_WAIT
+		}
+		time.Sleep(waitMilliseconds * time.Millisecond)
+		successiveErrors++
+	}
+
+	//query DB for latest remote event version number that we've seen locally
+	latestEvent, err := globals.db.DatabaseLatestRemoteEvent() 
+	if err != nil {
+		panic(err)
+	}
+
+	for {
+		//query for events after latest_event
+		var fullUrl string
+		if latestEvent != nil {
+			fullUrl = url + strconv.FormatInt(latestEvent.Id + 1, 10)
+		} else {
+			fullUrl = url + "0"
+		}
+		resp, err := http.Get(fullUrl)
+
+		//if error, perform exponential backoff (with maximum timeout)
+		if err != nil {
+			if resp != nil {
+				resp.Body.Close()
+			}
+			errorWait(err)
+			continue
+		}
+
+		body, err := ioutil.ReadAll(resp.Body)
+		resp.Body.Close() //must be done after the last time resp is used
+		if err != nil {
+			errorWait(err)
+			continue
+		}
+
+		var apistatus asink.APIResponse
+		err = json.Unmarshal(body, &apistatus)
+		if err != nil {
+			errorWait(err)
+			continue
+		}
+		if apistatus.Status != asink.SUCCESS {
+			errorWait(err)
+			continue
+		}
+
+
+		for _, event := range apistatus.Events {
+			if latestEvent != nil && event.Id != latestEvent.Id + 1 {
+				break
+			}
+			events <- event
+			latestEvent = event
+		}
+		successiveErrors = 0
+	}
+}