Change PDBs to maxUnavailable: 1

CHANGELOG.md

@@ -8,19 +8,20 @@ All notable changes to this project will be documented in this file.
 
 - Default stackableVersion to operator version ([#711]).
 - Configuration overrides for the JVM security properties, such as DNS caching ([#715]).
-- Support PodDisruptionBudgets ([#730]).
+- Support PodDisruptionBudgets ([#730], [#731]).
 
 ### Changed
 
 - `vector` `0.26.0` -> `0.31.0` ([#709]).
-- `operator-rs` `0.44.0` -> `0.51.1` ([#711], [#730]).
+- `operator-rs` `0.44.0` -> `0.52.1` ([#711], [#730], [#731]).
 - Let secret-operator handle certificate conversion ([#695]).
 
 [#695]: https://github.com/stackabletech/zookeeper-operator/pull/695
 [#709]: https://github.com/stackabletech/zookeeper-operator/pull/709
 [#711]: https://github.com/stackabletech/zookeeper-operator/pull/711
 [#715]: https://github.com/stackabletech/zookeeper-operator/pull/715
 [#730]: https://github.com/stackabletech/zookeeper-operator/pull/730
+[#731]: https://github.com/stackabletech/zookeeper-operator/pull/731
 
 ## [23.7.0] - 2023-07-14
 

Cargo.toml

@@ -24,7 +24,7 @@ serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
 serde_yaml = "0.9"
 snafu = "0.7"
-stackable-operator = { git = "https://github.com/stackabletech/operator-rs.git", tag = "0.51.1" }
+stackable-operator = { git = "https://github.com/stackabletech/operator-rs.git", tag = "0.52.1" }
 strum = { version = "0.25", features = ["derive"] }
 tokio = { version = "1.29", features = ["full"] }
 tokio-zookeeper = "0.2"

deploy/helm/zookeeper-operator/crds/crds.yaml

@@ -3627,11 +3627,13 @@ spec:
                         podDisruptionBudget:
                           enabled: true
                           maxUnavailable: null
+                      description: This is a product-agnostic RoleConfig, which is sufficient for most of the products.
                       properties:
                         podDisruptionBudget:
                           default:
                             enabled: true
                             maxUnavailable: null
+                          description: 'This struct is used to configure: 1.) If PodDisruptionBudgets are created by the operator 2.) The allowed number of Pods to be unavailable (`maxUnavailable`)'
                           properties:
                             enabled:
                               default: true

docs/modules/zookeeper/pages/usage_guide/operations/pod-disruptions.adoc

@@ -1,86 +1,8 @@
 = Allowed Pod disruptions
 
-You can configure the allowed Pod disruptions for Zookeeper nodes as described in xref:concepts:operations/pod_disruptions.adoc[].
+You can configure the permitted Pod disruptions for Zookeeper nodes as described in xref:concepts:operations/pod_disruptions.adoc[].
 
-Unless you configure something else or disable our PodDisruptionBudgets (PDBs), we write the following PDBs:
+Unless you configure something else or disable the provided PodDisruptionBudgets (PDBs), the following PDBs are written:
 
 == Servers
-
-Zookeeper servers need a certain number of nodes to be available to form a quorum to serve client requests.
-
-Taking this into consideration, our operator uses the following algorithm to determine the maximum number of servers allowed to be unavailable at the same time:
-
-`num_servers` is the number of server in the Zookeeper cluster, summed over all `roleGroups`.
-
-[source,rust]
-----
-fn quorum_size(num_servers: u16) -> u16 {
-    // Same as max((num_servers / 2) + 1, 1), but without the need for floating point arithmetics,
-    // which are subject to rounding errors.
-    max((num_servers + 2) / 2, 1)
-}
-
-// Minimum required amount of servers to form quorum.
-let quorum_size = quorum_size(num_servers);
-
-// Subtract one to not cause a single point of failure
-let max_unavailable = num_servers.saturating_sub(quorum_size).saturating_sub(1);
-
-// Clamp to at least a single node allowed to be offline, so we don't block Kubernetes nodes from draining.
-let max_unavailable = max(max_unavailable, 1)
-----
-
-This results e.g. in the following numbers:
-
-TIP: It is strongly recommended to use an odd number of servers (e.g. 3, 5 or 7).
-
-[cols="1,1,1"]
-|===
-|Number of servers
-|Quorum size
-|Maximum unavailable servers
-
-|1
-|1
-|1
-
-|2
-|2
-|1
-
-|3
-|2
-|1
-
-|4
-|3
-|1
-
-|5
-|3
-|1
-
-|6
-|4
-|1
-
-|7
-|4
-|2
-
-|8
-|5
-|2
-
-|9
-|5
-|3
-
-|10
-|6
-|3
-
-|20
-|11
-|8
-|===
+The provided PDBs only allow a single server to be offline at any given time, regardless of the number of replicas or `roleGroups`.

rust/crd/src/lib.rs

@@ -29,7 +29,7 @@ use stackable_operator::{
     memory::{BinaryMultiple, MemoryQuantity},
     product_config_utils::{ConfigError, Configuration},
     product_logging::{self, spec::Logging},
-    role_utils::{Role, RoleConfig, RoleGroup, RoleGroupRef},
+    role_utils::{GenericRoleConfig, Role, RoleGroup, RoleGroupRef},
     schemars::{self, JsonSchema},
     status::condition::{ClusterCondition, HasStatusCondition},
 };
@@ -519,21 +519,12 @@ impl ZookeeperCluster {
         }
     }
 
-    pub fn role_config(&self, role: &ZookeeperRole) -> Option<&RoleConfig> {
+    pub fn role_config(&self, role: &ZookeeperRole) -> Option<&GenericRoleConfig> {
         match role {
             ZookeeperRole::Server => self.spec.servers.as_ref().map(|s| &s.role_config),
         }
     }
 
-    pub fn num_servers(&self) -> u16 {
-        self.spec
-            .servers
-            .iter()
-            .flat_map(|s| s.role_groups.values())
-            .map(|rg| rg.replicas.unwrap_or(1))
-            .sum()
-    }
-
     /// List all pods expected to form the cluster
     ///
     /// We try to predict the pods here rather than looking at the current cluster state in order to

rust/operator-binary/src/operations/pdb.rs

@@ -1,5 +1,3 @@
-use std::cmp::max;
-
 use snafu::{ResultExt, Snafu};
 use stackable_operator::{
     builder::pdb::PodDisruptionBudgetBuilder, client::Client, cluster_resources::ClusterResources,
@@ -34,7 +32,7 @@ pub async fn add_pdbs(
         return Ok(());
     }
     let max_unavailable = pdb.max_unavailable.unwrap_or(match role {
-        ZookeeperRole::Server => max_unavailable_servers(zookeeper.num_servers()),
+        ZookeeperRole::Server => max_unavailable_servers(),
     });
     let pdb = PodDisruptionBudgetBuilder::new_with_role(
         zookeeper,
@@ -57,51 +55,6 @@ pub async fn add_pdbs(
     Ok(())
 }
 
-fn max_unavailable_servers(num_servers: u16) -> u16 {
-    // Minimum required amount of servers to form quorum.
-    let quorum_size = quorum_size(num_servers);
-
-    // Subtract once to not cause a single point of failure
-    let max_unavailable = num_servers.saturating_sub(quorum_size).saturating_sub(1);
-
-    // Clamp to at least a single node allowed to be offline, so we don't block Kubernetes nodes from draining.
-    max(max_unavailable, 1)
-}
-
-fn quorum_size(num_servers: u16) -> u16 {
-    // Same as max((num_servers / 2) + 1, 1), but without the need for floating point arithmetics,
-    // which are subject to rounding errors.
-    max((num_servers + 2) / 2, 1)
-}
-
-#[cfg(test)]
-mod test {
-    use super::*;
-    use rstest::rstest;
-
-    #[rstest]
-    #[case(0, 1, 1)]
-    #[case(1, 1, 1)]
-    #[case(2, 2, 1)]
-    #[case(3, 2, 1)]
-    #[case(4, 3, 1)]
-    #[case(5, 3, 1)]
-    #[case(6, 4, 1)]
-    #[case(7, 4, 2)]
-    #[case(8, 5, 2)]
-    #[case(9, 5, 3)]
-    #[case(10, 6, 3)]
-    #[case(20, 11, 8)]
-    #[case(100, 51, 48)]
-
-    fn test_max_unavailable_servers(
-        #[case] num_servers: u16,
-        #[case] expected_quorum_size: u16,
-        #[case] expected_max_unavailable: u16,
-    ) {
-        let quorum_size = quorum_size(num_servers);
-        let max_unavailable = max_unavailable_servers(num_servers);
-        assert_eq!(quorum_size, expected_quorum_size);
-        assert_eq!(max_unavailable, expected_max_unavailable);
-    }
+fn max_unavailable_servers() -> u16 {
+    1
 }

rust/operator-binary/src/zk_controller.rs

@@ -46,7 +46,7 @@ use stackable_operator::{
             CustomContainerLogConfig,
         },
     },
-    role_utils::{RoleConfig, RoleGroupRef},
+    role_utils::{GenericRoleConfig, RoleGroupRef},
     status::condition::{
         compute_conditions, operations::ClusterOperationsConditionBuilder,
         statefulset::StatefulSetConditionBuilder,
@@ -369,7 +369,7 @@ pub async fn reconcile_zk(zk: Arc<ZookeeperCluster>, ctx: Arc<Ctx>) -> Result<co
     }
 
     let role_config = zk.role_config(&zk_role);
-    if let Some(RoleConfig {
+    if let Some(GenericRoleConfig {
         pod_disruption_budget: pdb,
     }) = role_config
     {