make num concurrent downloads and download queue size configurable

apidGatewayDeploy_suite_test.go

diff --git a/apidGatewayDeploy_suite_test.go b/apidGatewayDeploy_suite_test.go
index 7411e6f..4604588 100644
--- a/apidGatewayDeploy_suite_test.go
+++ b/apidGatewayDeploy_suite_test.go
@@ -50,6 +50,8 @@
 	bundleCleanupDelay = time.Millisecond
 	bundleRetryDelay = 10 * time.Millisecond
 	bundleDownloadTimeout = 50 * time.Millisecond
+	concurrentDownloads = 1
+	downloadQueueSize = 1
 
 	router := apid.API().Router()
 	// fake an unreliable bundle repo

bundle.go

diff --git a/bundle.go b/bundle.go
index 651576c..6f0c208 100644
--- a/bundle.go
+++ b/bundle.go
@@ -17,11 +17,12 @@
 	"time"
 )
 
-var numConcurrentDownloads = 15
-var bundleRetryDelay time.Duration = time.Second
-var bundleDownloadTimeout time.Duration = 10 * time.Minute
-var downloadQueue = make(chan *DownloadRequest, 200)
-var workerQueue = make(chan chan *DownloadRequest, numConcurrentDownloads)
+var (
+	bundleRetryDelay      time.Duration = time.Second
+	bundleDownloadTimeout time.Duration = 10 * time.Minute
+	downloadQueue                       = make(chan *DownloadRequest, downloadQueueSize)
+	workerQueue                         = make(chan chan *DownloadRequest, concurrentDownloads)
+)
 
 // simple doubling back-off
 func createBackoff(retryIn, maxBackOff time.Duration) func() {
@@ -245,7 +246,7 @@
 func initializeBundleDownloading() {
 
 	// create workers
-	for i := 0; i < numConcurrentDownloads; i++ {
+	for i := 0; i < concurrentDownloads; i++ {
 		worker := BundleDownloader{
 			id:       i + 1,
 			workChan: make(chan *DownloadRequest),

init.go

diff --git a/init.go b/init.go
index 68d75e6..f507357 100644
--- a/init.go
+++ b/init.go
@@ -18,18 +18,22 @@
 	configApiServerBaseURI      = "apigeesync_proxy_server_base"
 	configApidInstanceID        = "apigeesync_apid_instance_id"
 	configApidClusterID         = "apigeesync_cluster_id"
+	configConcurrentDownloads   = "apigeesync_concurrent_downloads"
+	configDownloadQueueSize     = "apigeesync_download_queue_size"
 )
 
 var (
-	services           apid.Services
-	log                apid.LogService
-	data               apid.DataService
-	bundlePath         string
-	debounceDuration   time.Duration
-	bundleCleanupDelay time.Duration
-	apiServerBaseURI   *url.URL
-	apidInstanceID     string
-	apidClusterID      string
+	services            apid.Services
+	log                 apid.LogService
+	data                apid.DataService
+	bundlePath          string
+	debounceDuration    time.Duration
+	bundleCleanupDelay  time.Duration
+	apiServerBaseURI    *url.URL
+	apidInstanceID      string
+	apidClusterID       string
+	downloadQueueSize   int
+	concurrentDownloads int
 )
 
 func init() {
@@ -66,6 +70,8 @@
 	config.SetDefault(configDebounceDuration, time.Second)
 	config.SetDefault(configBundleCleanupDelay, time.Minute)
 	config.SetDefault(configBundleDownloadTimeout, 5*time.Minute)
+	config.SetDefault(configConcurrentDownloads, 15)
+	config.SetDefault(configDownloadQueueSize, 2000)
 
 	debounceDuration = config.GetDuration(configDebounceDuration)
 	if debounceDuration < time.Millisecond {
@@ -84,6 +90,8 @@
 
 	data = services.Data()
 
+	concurrentDownloads = config.GetInt(configConcurrentDownloads)
+	downloadQueueSize = config.GetInt(configDownloadQueueSize)
 	relativeBundlePath := config.GetString(configBundleDirKey)
 	storagePath := config.GetString("local_storage_path")
 	bundlePath = path.Join(storagePath, relativeBundlePath)