[tor-commits] [snowflake-webext/master] Dynamically adjust proxy poll interval

[cohosh at torproject.org]

commit c283c35a7e128d72763b7f4a925103bd0b062227
Author: Cecylia Bocovich <cohosh at torproject.org>
Date:   Thu Apr 2 12:53:10 2020 -0400

    Dynamically adjust proxy poll interval
    
    If the proxy succeeds in opening a datachannel to the client, decrease
    the poll interval. If they fail, increase the poll interval. This will
    cause less reliable/more restrictive proxies to poll less frequently.
---
 config.js    |  4 +++-
 snowflake.js | 22 ++++++++++++++++------
 2 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/config.js b/config.js
index 5b8963a..3f632ca 100644
--- a/config.js
+++ b/config.js
@@ -24,7 +24,9 @@ Config.prototype.minRateLimit = 10 * 1024;
 
 Config.prototype.rateLimitHistory = 5.0;
 
-Config.prototype.defaultBrokerPollInterval = 300.0 * 1000;
+Config.prototype.defaultBrokerPollInterval = 300.0 * 1000; //1 poll every 5 minutes
+Config.prototype.slowestBrokerPollInterval = 6 * 60 * 60.0 * 1000; //1 poll every 6 hours
+Config.prototype.pollAdjustment = 300.0 * 1000;
 
 // Timeout after sending answer before datachannel is opened
 Config.prototype.datachannelTimeout = 20 * 1000;
diff --git a/snowflake.js b/snowflake.js
index 3baddbe..11a7801 100644
--- a/snowflake.js
+++ b/snowflake.js
@@ -22,6 +22,7 @@ class Snowflake {
     this.ui = ui;
     this.broker = broker;
     this.proxyPairs = [];
+    this.pollInterval = this.config.defaultBrokerPollInterval;
     if (void 0 === this.config.rateLimitBytes) {
       this.rateLimit = new DummyRateLimit();
     } else {
@@ -43,9 +44,9 @@ class Snowflake {
   // process. |pollBroker| automatically arranges signalling.
   beginWebRTC() {
     this.pollBroker();
-    return this.pollInterval = setInterval((() => {
-      return this.pollBroker();
-    }), this.config.defaultBrokerPollInterval);
+    return this.pollTimeout = setTimeout((() => {
+      return this.beginWebRTC()
+    }), this.pollInterval);
   }
 
   // Regularly poll Broker for clients to serve until this snowflake is
@@ -74,8 +75,18 @@ class Snowflake {
       return setTimeout((() => {
         if (!pair.webrtcIsReady()) {
           log('proxypair datachannel timed out waiting for open');
-          return pair.close();
+          pair.close();
+          // increase poll interval
+          this.pollInterval =
+                Math.min(this.pollInterval + this.config.pollAdjustment,
+                  this.config.slowestBrokerPollInterval);
+        } else {
+          // decrease poll interval
+          this.pollInterval =
+                Math.max(this.pollInterval - this.config.pollAdjustment,
+                  this.config.defaultBrokerPollInterval);
         }
+        return;
       }), this.config.datachannelTimeout);
     }, function() {
       //on error, close proxy pair
@@ -146,7 +157,7 @@ class Snowflake {
   disable() {
     var results;
     log('Disabling Snowflake.');
-    clearInterval(this.pollInterval);
+    clearTimeout(this.pollTimeout);
     results = [];
     while (this.proxyPairs.length > 0) {
       results.push(this.proxyPairs.pop().close());
@@ -158,7 +169,6 @@ class Snowflake {
 
 Snowflake.prototype.relayAddr = null;
 Snowflake.prototype.rateLimit = null;
-Snowflake.prototype.pollInterval = null;
 
 Snowflake.MESSAGE = {
   CONFIRMATION: 'You\'re currently serving a Tor user via Snowflake.'