From 31467a58dd7a711c6341b3f09b45e02c3de7ba21 Mon Sep 17 00:00:00 2001
From: Remi Gacogne <remi.gacogne@powerdns.com>
Date: Fri, 27 Dec 2024 12:59:47 +0100
Subject: [PATCH] dnsdist: Handle the default LB policy in YAML configuration

---
 pdns/dnsdistdist/dnsdist-configuration-yaml.cc    |  7 +++++++
 pdns/dnsdistdist/dnsdist-rust-lib/rust/src/lib.rs | 11 +++++++++++
 pdns/dnsdistdist/dnsdist-settings-definitions.yml |  5 +++++
 pdns/dnsdistdist/docs/reference/yaml-settings.rst |  1 +
 4 files changed, 24 insertions(+)

diff --git a/pdns/dnsdistdist/dnsdist-configuration-yaml.cc b/pdns/dnsdistdist/dnsdist-configuration-yaml.cc
index 1ed9835171..da6dae586b 100644
--- a/pdns/dnsdistdist/dnsdist-configuration-yaml.cc
+++ b/pdns/dnsdistdist/dnsdist-configuration-yaml.cc
@@ -831,6 +831,13 @@ bool loadConfigurationFromFile(const std::string& fileName, bool isClient, bool
       }
     }
 
+    if (!globalConfig.load_balancing_policies.default_policy.empty()) {
+      auto policy = getRegisteredTypeByName<ServerPolicy>(globalConfig.load_balancing_policies.default_policy);
+      dnsdist::configuration::updateRuntimeConfiguration([&policy](dnsdist::configuration::RuntimeConfiguration& config) {
+        config.d_lbPolicy = std::move(policy);
+      });
+    }
+
     for (const auto& pool : globalConfig.pools) {
       std::shared_ptr<ServerPool> poolObj = createPoolIfNotExists(std::string(pool.name));
       if (!pool.packet_cache.empty()) {
diff --git a/pdns/dnsdistdist/dnsdist-rust-lib/rust/src/lib.rs b/pdns/dnsdistdist/dnsdist-rust-lib/rust/src/lib.rs
index ac9a1845e4..81f95759d2 100644
--- a/pdns/dnsdistdist/dnsdist-rust-lib/rust/src/lib.rs
+++ b/pdns/dnsdistdist/dnsdist-rust-lib/rust/src/lib.rs
@@ -2010,6 +2010,8 @@ mod dnsdistsettings {
     #[derive(Deserialize, Serialize, Debug, PartialEq)]
     #[serde(deny_unknown_fields)]
     struct LoadBalancingPoliciesConfiguration {
+        #[serde(rename = "default-policy", default = "crate::default_value_load_balancing_policies_default_policy", skip_serializing_if = "crate::default_value_equal_load_balancing_policies_default_policy")]
+        default_policy: String,
         #[serde(rename = "servfail-on-no-server", default, skip_serializing_if = "crate::is_default")]
         servfail_on_no_server: bool,
         #[serde(rename = "round-robin-servfail-on-no-server", default, skip_serializing_if = "crate::is_default")]
@@ -3058,6 +3060,15 @@ impl Default for dnsdistsettings::CustomLoadBalancingPolicyConfiguration {
 }
 
 
+// DEFAULT HANDLING for load_balancing_policies_default_policy
+fn default_value_load_balancing_policies_default_policy() -> String {
+    String::from("leastOutstanding")
+}
+fn default_value_equal_load_balancing_policies_default_policy(value: &str)-> bool {
+    value == default_value_load_balancing_policies_default_policy()
+}
+
+
 impl Default for dnsdistsettings::LoadBalancingPoliciesConfiguration {
     fn default() -> Self {
         let deserialized: dnsdistsettings::LoadBalancingPoliciesConfiguration = serde_yaml::from_str("").unwrap();
diff --git a/pdns/dnsdistdist/dnsdist-settings-definitions.yml b/pdns/dnsdistdist/dnsdist-settings-definitions.yml
index 1e42374d39..513d1f12ac 100644
--- a/pdns/dnsdistdist/dnsdist-settings-definitions.yml
+++ b/pdns/dnsdistdist/dnsdist-settings-definitions.yml
@@ -1411,6 +1411,11 @@ custom-load-balancing-policy:
 
 load-balancing-policies:
   parameters:
+    - name: "default-policy"
+      type: "String"
+      default: "leastOutstanding"
+      lua-name: "setServerPolicy"
+      runtime-configurable: true
     - name: "servfail-on-no-server"
       type: "bool"
       default: "false"
diff --git a/pdns/dnsdistdist/docs/reference/yaml-settings.rst b/pdns/dnsdistdist/docs/reference/yaml-settings.rst
index b887c5e8a3..ee4c8d37c7 100644
--- a/pdns/dnsdistdist/docs/reference/yaml-settings.rst
+++ b/pdns/dnsdistdist/docs/reference/yaml-settings.rst
@@ -501,6 +501,7 @@ LazyHealthCheckConfiguration
 LoadBalancingPoliciesConfiguration
 ----------------------------------
 
+- **default-policy**: String ``(leastOutstanding)``
 - **servfail-on-no-server**: Boolean ``(false)``
 - **round-robin-servfail-on-no-server**: Boolean ``(false)``
 - **weighted-balancing-factor**: Double ``(0.0)``
-- 
2.47.2