feat: fan out scrapes over time, support different scrape intervals

This should help avoid rate-limits on upstream, as well as let admins determine
update latency manually.

main/main.go

@@ -9,6 +9,7 @@ import (
 	"os"
 	"strconv"
 	"strings"
+	"time"
 
 	"git.dvdrw.dev/nsmarter/scraper/scraper"
 )
@@ -24,6 +25,7 @@ var chunkSize = 5
 var apiEndpoint string = "https://online.nsmart.rs/publicapi/v1/announcement/announcement.php"
 var apiKey string
 var limitQuerySize = 0
+var timeoutPeriod = 180
 var fillerUrl string = "localhost"
 
 func parseEnvars() {
@@ -41,6 +43,13 @@ func parseEnvars() {
 				Log.Printf("WARN: Invalid value for CHUNK_SIZE. Falling back to default value (%v)\n", defaultChunkSize)
 				chunkSize = defaultChunkSize
 			}
+		case "TIMEOUT_PERIOD":
+			var err error
+			timeoutPeriod, err = strconv.Atoi(pair[1])
+			if err != nil {
+				Log.Printf("WARN: Invalid value for TIMEOUT_PERIOD. Falling back to default value (%v)\n", 180)
+				timeoutPeriod = 180
+			}
 		case "LIMIT_QUERY_SIZE":
 			var err error
 			limitQuerySize, err = strconv.Atoi(pair[1])
@@ -86,16 +95,19 @@ func main() {
 	}
 
 	results := make(chan []scraper.ScrapeResult, 200)
-	for _, chunk := range stationChunks {
-		go scraper.ScheduleScrape(chunk,
-			results,
-			scraper.ApiConfig{Endpoint: apiEndpoint,
-				Key: apiKey})
-	}
+	go func() {
+		for _, chunk := range stationChunks {
+			go scraper.ScheduleScrape(chunk,
+				results,
+				scraper.ApiConfig{Endpoint: apiEndpoint,
+					Key:     apiKey,
+					Timeout: int64(timeoutPeriod)})
+			// Fan out scrapes over time so as to avoid upstream rate limits
+			time.Sleep(time.Millisecond * 100)
+		}
+	}()
 
 	for r := range results {
-		fmt.Printf("Received data: %#v\n", r)
-
 		json, err := json.Marshal(r)
 		if err != nil {
 			fmt.Print("Couldn't serialise struct to JSON: ", err)

scraper/scrape.go

@@ -60,6 +60,7 @@ func scrapeRange(s []Station) string {
 
 type ApiConfig struct {
 	Endpoint, Key string
+	Timeout       int64
 }
 
 func grabData(stations []Station, c ApiConfig) (map[string][]map[string]interface{}, error) {
@@ -296,6 +297,7 @@ func ScheduleScrape(chunk []Station, c chan []ScrapeResult, a ApiConfig) {
 	}
 
 	c <- r
-	time.Sleep(time.Minute * 3)
+	duration := time.Duration(a.Timeout) * time.Second
+	time.Sleep(duration)
 	ScheduleScrape(chunk, c, a)
 }