From 279c3a2b3792a514d7e883dc2e6b24e7d78af934 Mon Sep 17 00:00:00 2001
From: David Anderson <davea@ssl.berkeley.edu>
Date: Sat, 8 Oct 2011 05:17:44 +0000
Subject: [PATCH] - scheduler: problem: in the daily quota mechanism,     the
 boundary between days is 00:00 in server local time.     This creates a spike
 of jobs being dispatched     (and files being downloaded) after that time.

    Solution: distribute the boundary uniformly,
    using a random number determined by the host ID.
    (Make sure to save/restore the seed around this,
    so we don't destroy the randomness of other things)


svn path=/trunk/boinc/; revision=24353
---
 checkin_notes            | 14 ++++++++++++++
 sched/handle_request.cpp | 13 +++++++++++--
 2 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/checkin_notes b/checkin_notes
index 7a2069d618..65fd21c591 100644
--- a/checkin_notes
+++ b/checkin_notes
@@ -6969,3 +6969,17 @@ Charlie 7 Oct 2011
         coproc_detect.cpp
     lib/
         coproc.cpp,h
+
+David  7 Oct 2011
+    - scheduler: problem: in the daily quota mechanism,
+        the boundary between days is 00:00 in server local time.
+        This creates a spike of jobs being dispatched
+        (and files being downloaded) after that time.
+
+        Solution: distribute the boundary uniformly,
+        using a random number determined by the host ID.
+        (Make sure to save/restore the seed around this,
+        so we don't destroy the randomness of other things)
+
+    sched/
+        handle_request.cpp
diff --git a/sched/handle_request.cpp b/sched/handle_request.cpp
index 01d7d3012b..e3e826ae82 100644
--- a/sched/handle_request.cpp
+++ b/sched/handle_request.cpp
@@ -1075,7 +1075,7 @@ static inline bool requesting_work() {
 void process_request(char* code_sign_key) {
     PLATFORM* platform;
     int retval;
-    double last_rpc_time;
+    double last_rpc_time, x;
     struct tm *rpc_time_tm;
     bool ok_to_send_work = !config.dont_send_jobs;
     bool have_no_work = false;
@@ -1195,13 +1195,22 @@ void process_request(char* code_sign_key) {
         }
     }
 
+    // in deciding whether it's a new day,
+    // add a random factor (based on host ID)
+    // to smooth out network traffic over the day
+    //
+    retval = rand();
+    srand(g_reply->host.id);
+    x = drand()*86400;
+    srand(retval);
     last_rpc_time = g_reply->host.rpc_time;
-    t = g_reply->host.rpc_time;
+    t = g_reply->host.rpc_time + x;
     rpc_time_tm = localtime(&t);
     g_request->last_rpc_dayofyear = rpc_time_tm->tm_yday;
 
     t = time(0);
     g_reply->host.rpc_time = t;
+    t += x;
     rpc_time_tm = localtime(&t);
     g_request->current_rpc_dayofyear = rpc_time_tm->tm_yday;