From 831450266acd06f50d3d15119aa3991c37efa7af Mon Sep 17 00:00:00 2001
From: Robin Geuze <robing@transip.nl>
Date: Sat, 3 Nov 2018 15:08:13 +0100
Subject: [PATCH] Add a PoolAvailableRule to easily add backup pools

---
 pdns/dnsdist-lua-rules.cc         |  6 ++++++
 pdns/dnsdistdist/dnsdist-rules.hh | 22 ++++++++++++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/pdns/dnsdist-lua-rules.cc b/pdns/dnsdist-lua-rules.cc
index 28630b1fe..8fc84d494 100644
--- a/pdns/dnsdist-lua-rules.cc
+++ b/pdns/dnsdist-lua-rules.cc
@@ -440,6 +440,12 @@ void setupLuaRules()
       return std::shared_ptr<TimedIPSetRule>(new TimedIPSetRule());
     });
 
+  g_lua.writeFunction("PoolAvailableRule", [](std::string poolname) {
+    setLuaSideEffect();
+    auto localPools = g_pools.getCopy();
+    return std::shared_ptr<DNSRule>(new PoolAvailableRule(localPools, poolname));
+  });
+
   g_lua.registerFunction<void(std::shared_ptr<TimedIPSetRule>::*)()>("clear", [](std::shared_ptr<TimedIPSetRule> tisr) {
       tisr->clear();
     });
diff --git a/pdns/dnsdistdist/dnsdist-rules.hh b/pdns/dnsdistdist/dnsdist-rules.hh
index 2321902d9..10a40b601 100644
--- a/pdns/dnsdistdist/dnsdist-rules.hh
+++ b/pdns/dnsdistdist/dnsdist-rules.hh
@@ -991,3 +991,25 @@ private:
   boost::optional<std::string> d_value;
   std::string d_tag;
 };
+
+class PoolAvailableRule : public DNSRule
+{
+public:
+  PoolAvailableRule(pools_t& pools, const std::string& poolname) : d_poolname(poolname)
+  {
+    d_pool = getPool(pools, poolname);
+  }
+
+  bool matches(const DNSQuestion* dq) const override
+  {
+    return (d_pool->countServers(true) > 0);
+  }
+
+  string toString() const override
+  {
+    return "pool '" + d_poolname + "' is available";
+  }
+private:
+  std::string d_poolname;
+  std::shared_ptr<ServerPool> d_pool;
+};
-- 
2.40.0