From a8f7447cf43184160ade0de01199462c11f3c109 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Tue, 16 May 2023 06:32:16 +0200
Subject: Randomize URL query order within each priority

---
 bbot/agent/agent.cxx | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/bbot/agent/agent.cxx b/bbot/agent/agent.cxx
index ad8cd74..6163c14 100644
--- a/bbot/agent/agent.cxx
+++ b/bbot/agent/agent.cxx
@@ -26,6 +26,7 @@
 #include <thread>       // thread::hardware_concurrency()
 #include <random>
 #include <iomanip>      // setw()
+#include <numeric>      // iota()
 #include <iostream>
 #include <system_error> // generic_category()
 
@@ -53,6 +54,8 @@ using namespace bbot;
 using std::cout;
 using std::endl;
 
+static std::mt19937 rand_gen (std::random_device {} ());
+
 // According to the standard, atomic's use in the signal handler is only safe
 // if it's lock-free.
 //
@@ -1968,9 +1971,9 @@ try
   //
   // NOTE: consider updating agent_checksum if making any logic changes.
   //
-  auto rand_sleep = [g = std::mt19937 (std::random_device {} ())] () mutable
+  auto rand_sleep = [] ()
   {
-    return std::uniform_int_distribution<unsigned int> (50, 60) (g);
+    return std::uniform_int_distribution<unsigned int> (50, 60) (rand_gen);
   };
 
   optional<interactive_mode> imode;
@@ -2190,10 +2193,14 @@ try
       // Note that we have to do it while holding the lock on all the machines
       // since we don't know which machine we will need.
       //
-      // @@ TODO: need to iterate in random order somehow.
-      //
-      for (const string& u: urls)
+      vector<strings::const_iterator> rurls (urls.size ());
+      std::iota (rurls.begin (), rurls.end (), urls.begin ());
+      std::shuffle (rurls.begin (), rurls.end (), rand_gen);
+
+      for (strings::const_iterator i: rurls)
       {
+        const string& u (*i);
+
         if (ops.fake_request_specified ())
         {
           auto t (parse_manifest<task_manifest> (ops.fake_request (), "task"));
-- 
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