feat: Improve startup times by setting flow.election.max.candidates

Author: sbernauer

CHANGELOG.md

@@ -23,6 +23,8 @@ All notable changes to this project will be documented in this file.
 - test: Bump vector-aggregator to 0.55.0, replace /graphql call with gRPC call ([#940]).
 - BREAKING: Removed product-config machinery. This is a breaking change in terms of configuration.
   Users relying on the product-config `properties.yaml` file have to set these properties via the CRD ([#945]).
+- In case the user specifies a fixed number of NiFi nodes (i.e. no auto-scaling), set `nifi.cluster.flow.election.max.candidates` to that number.
+  This results in much faster NiFi startups, as it doesn't need to wait for the 5 minutes of `nifi.cluster.flow.election.max.wait.time` ([#953]).
 
 ### Fixed
 
@@ -38,6 +40,7 @@ All notable changes to this project will be documented in this file.
 [#936]: https://github.com/stackabletech/nifi-operator/pull/936
 [#940]: https://github.com/stackabletech/nifi-operator/pull/940
 [#945]: https://github.com/stackabletech/nifi-operator/pull/945
+[#953]: https://github.com/stackabletech/nifi-operator/pull/953
 [#959]: https://github.com/stackabletech/nifi-operator/pull/959
 
 ## [26.3.0] - 2026-03-16

Cargo.lock

@@ -33,6 +33,6 @@ tokio = { version = "1.52", features = ["full"] }
 tracing = "0.1"
 url = { version = "2.5.7" }
 
-# [patch."https://github.com/stackabletech/operator-rs.git"]
-# stackable-operator = { git = "https://github.com/stackabletech//operator-rs.git", branch = "main" }
+[patch."https://github.com/stackabletech/operator-rs.git"]
+stackable-operator = { git = "https://github.com/stackabletech//operator-rs.git", branch = "refactor/replica-counting" }
 # stackable-operator = { path = "../operator-rs/crates/stackable-operator" }

Cargo.toml

@@ -204,7 +204,6 @@ spec:
         nifi.security.user.oidc.additional.scopes: "profile"
         nifi.security.user.oidc.claim.identifying.user: "upn"
         nifi.process.group.root.placeholder: "root"
-        nifi.cluster.flow.election.max.wait.time: "10 secs"
     podOverrides:
       spec:
         initContainers:

docs/modules/nifi/assets/attachments/entraid-nifi.yaml

@@ -71,7 +71,6 @@ For example per role group:
 nodes:
   roleGroups:
     default:
-      config: {}
       replicas: 1
       envOverrides:
         MY_ENV_VAR: "MY_VALUE"
@@ -86,7 +85,6 @@ nodes:
     MY_ENV_VAR: "MY_VALUE"
   roleGroups:
     default:
-      config: {}
       replicas: 1
 ----
 

docs/modules/nifi/pages/usage_guide/overrides.adoc

@@ -3,7 +3,10 @@
 use std::collections::BTreeMap;
 
 use snafu::{ResultExt, Snafu, ensure};
-use stackable_operator::memory::MemoryQuantity;
+use stackable_operator::{
+    memory::MemoryQuantity,
+    role_utils::{ZeroReplicasCounting, fixed_replica_count},
+};
 
 use super::{
     ConfigFileName, env_reference, file_reference, format_properties,
@@ -21,7 +24,7 @@ use crate::{
             },
         },
     },
-    crd::{storage::NifiRepository, v1alpha1},
+    crd::{NifiRole, storage::NifiRepository, v1alpha1},
     security::{
         authentication::{
             NifiAuthenticationConfig, STACKABLE_SERVER_TLS_DIR, STACKABLE_TLS_STORE_PASSWORD,
@@ -526,9 +529,26 @@ pub fn build(
         "nifi.cluster.node.protocol.port".to_string(),
         PROTOCOL_PORT.to_string(),
     );
+
+    // In case the number of NiFi nodes is hard-coded to a fixed number (no auto-scaling), we can
+    // tell this NiFi, so that startup is much quicker.
+    let fixed_replica_count = fixed_replica_count(
+        cluster
+            .role_group_configs
+            .get(&NifiRole::Node)
+            .iter()
+            .flat_map(|nodes| nodes.values())
+            .map(|rg| rg.replicas),
+        // We rather treat explicit 0 values as [`None`], so that we don't end up with too few nodes
+        ZeroReplicasCounting::TreatAsZero,
+    );
+    let max_election_candidates = fixed_replica_count
+        .map(|count| count.to_string())
+        // In case we don't know the replica count, we set it to "" as that's what we always did
+        .unwrap_or_default();
     properties.insert(
         "nifi.cluster.flow.election.max.candidates".to_string(),
-        "".to_string(),
+        max_election_candidates,
     );
 
     match cluster.cluster_config.clustering_backend {

rust/operator-binary/src/controller/build/properties/nifi_properties.rs

@@ -186,8 +186,6 @@ spec:
       nifi.properties:
         nifi.web.https.sni.required: "false"
         nifi.web.https.sni.host.check: "false"
-        # Quicker startup, and we only have a single node
-        nifi.cluster.flow.election.max.wait.time: "10 secs"
     podOverrides:
       spec:
         initContainers:

tests/templates/kuttl/cluster-sync-cs-bug/20-install-nifi.yaml.j2

@@ -50,10 +50,6 @@ spec:
       gracefulShutdownTimeout: 1m
       logging:
         enableVectorAgent: {{ lookup('env', 'VECTOR_AGGREGATOR') | length > 0 }}
-    configOverrides:
-      "nifi.properties":
-        # Quicker startup, and we only have a single node
-        "nifi.cluster.flow.election.max.wait.time": "10 secs"
     roleGroups:
       default:
         replicas: 2

tests/templates/kuttl/cluster_operation/20-install-nifi.yaml.j2

@@ -67,10 +67,6 @@ spec:
     config:
       logging:
         enableVectorAgent: {{ lookup('env', 'VECTOR_AGGREGATOR') | length > 0 }}
-    configOverrides:
-      "nifi.properties":
-        # Quicker startup, and we only have a single node
-        "nifi.cluster.flow.election.max.wait.time": "10 secs"
     roleConfig:
       listenerClass: external-unstable
     podOverrides:

tests/templates/kuttl/custom-components-git-sync/30_install-nifi.yaml.j2

@@ -53,10 +53,6 @@ spec:
     config:
       logging:
         enableVectorAgent: {{ lookup('env', 'VECTOR_AGGREGATOR') | length > 0 }}
-    configOverrides:
-      "nifi.properties":
-        # Quicker startup, and we only have a single node
-        "nifi.cluster.flow.election.max.wait.time": "10 secs"
     roleConfig:
       listenerClass: test-external-unstable-$NAMESPACE
     roleGroups: