From 4b5dc25010c0732a16b42ba0cc6c0326689701e6 Mon Sep 17 00:00:00 2001
From: Zaid Abdulla <zaid@genieacs.com>
Date: Tue, 3 Jan 2017 18:58:57 -0800
Subject: [PATCH] Load distribution in refresh provision

---
 lib/common.coffee         | 9 +++++++++
 lib/default-provisions.js | 3 ++-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/lib/common.coffee b/lib/common.coffee
index 3262db4..1fe2fa0 100644
--- a/lib/common.coffee
+++ b/lib/common.coffee
@@ -301,6 +301,14 @@ escapeRegExp = (str) ->
   return str.replace(/[\-\[\]\/\{\}\(\)\*\+\?\.\\\^\$\|]/g, "\\$&")
 
 
+# djb2 hashing algorithm adapted from http://www.cse.yorku.ca/~oz/hash.html
+djb2 = (str) ->
+  hash = 5381
+  for i in [0...str.length]
+    hash = ((hash << 5) + hash) ^ str.charCodeAt(i)
+  return hash
+
+
 exports.UNDEFINED_TYPE = UNDEFINED_TYPE
 exports.NULL_TYPE = NULL_TYPE
 exports.NUMBER_TYPE = NUMBER_TYPE
@@ -315,3 +323,4 @@ exports.parsePath = parsePath
 exports.addPathMeta = addPathMeta
 exports.hammingWeight = hammingWeight
 exports.escapeRegExp = escapeRegExp
+exports.djb2 = djb2
diff --git a/lib/default-provisions.js b/lib/default-provisions.js
index e2f9ce7..aa1e7a0 100644
--- a/lib/default-provisions.js
+++ b/lib/default-provisions.js
@@ -29,7 +29,8 @@ function refresh(sessionData, provision, declarations, startRevision, endRevisio
   path.length = MAX_DEPTH;
   path.fill("*", l);
   let every = 1000 * (provision[2] || 1);
-  let t = Math.trunc(sessionData.timestamp / every) * every;
+  let offset = Math.abs(common.djb2(sessionData.deviceId)) % 86400000;
+  let t = Math.trunc((sessionData.timestamp + offset) / every) * every - offset;
 
   for (let i = l; i < path.length; ++ i)
     declarations.push([path.slice(0, i), t, {object: 1, writable: 1, value: t}]);