From 5bfc0c7e13a5eebac06ff43bb78f7d55fadf89c6 Mon Sep 17 00:00:00 2001
From: Joe Gallo <joe.gallo@elastic.co>
Date: Tue, 19 Nov 2024 09:49:15 -0500
Subject: [PATCH]  Optimize IndexLifecycleMetadata#getPolicies (#116988)

---
 .../core/ilm/IndexLifecycleMetadata.java      | 21 ++++++++++++-------
 .../core/template/IndexTemplateRegistry.java  |  6 ++++--
 2 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ilm/IndexLifecycleMetadata.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ilm/IndexLifecycleMetadata.java
index f8cb371687d72..26f4f5c92073c 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ilm/IndexLifecycleMetadata.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ilm/IndexLifecycleMetadata.java
@@ -58,10 +58,22 @@ public class IndexLifecycleMetadata implements Metadata.Custom {
 
     private final Map<String, LifecyclePolicyMetadata> policyMetadatas;
     private final OperationMode operationMode;
+    // a slightly different view of the policyMetadatas -- it's hot in a couple of places so we pre-calculate it
+    private final Map<String, LifecyclePolicy> policies;
+
+    private static Map<String, LifecyclePolicy> policiesMap(final Map<String, LifecyclePolicyMetadata> policyMetadatas) {
+        final Map<String, LifecyclePolicy> policies = new HashMap<>(policyMetadatas.size());
+        for (LifecyclePolicyMetadata policyMetadata : policyMetadatas.values()) {
+            LifecyclePolicy policy = policyMetadata.getPolicy();
+            policies.put(policy.getName(), policy);
+        }
+        return Collections.unmodifiableMap(policies);
+    }
 
     public IndexLifecycleMetadata(Map<String, LifecyclePolicyMetadata> policies, OperationMode operationMode) {
         this.policyMetadatas = Collections.unmodifiableMap(policies);
         this.operationMode = operationMode;
+        this.policies = policiesMap(policyMetadatas);
     }
 
     public IndexLifecycleMetadata(StreamInput in) throws IOException {
@@ -72,6 +84,7 @@ public IndexLifecycleMetadata(StreamInput in) throws IOException {
         }
         this.policyMetadatas = policies;
         this.operationMode = in.readEnum(OperationMode.class);
+        this.policies = policiesMap(policyMetadatas);
     }
 
     @Override
@@ -93,13 +106,7 @@ public OperationMode getOperationMode() {
     }
 
     public Map<String, LifecyclePolicy> getPolicies() {
-        // note: this loop is unrolled rather than streaming-style because it's hot enough to show up in a flamegraph
-        Map<String, LifecyclePolicy> policies = new HashMap<>(policyMetadatas.size());
-        for (LifecyclePolicyMetadata policyMetadata : policyMetadatas.values()) {
-            LifecyclePolicy policy = policyMetadata.getPolicy();
-            policies.put(policy.getName(), policy);
-        }
-        return Collections.unmodifiableMap(policies);
+        return policies;
     }
 
     @Override
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/template/IndexTemplateRegistry.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/template/IndexTemplateRegistry.java
index 05f4e560b73c1..f160b704e9e12 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/template/IndexTemplateRegistry.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/template/IndexTemplateRegistry.java
@@ -580,14 +580,16 @@ private void addIndexLifecyclePoliciesIfMissing(ClusterState state) {
             logger.trace("running in data stream lifecycle only mode. skipping the installation of ILM policies.");
             return;
         }
-        IndexLifecycleMetadata metadata = state.metadata().custom(IndexLifecycleMetadata.TYPE);
+        final IndexLifecycleMetadata metadata = state.metadata().custom(IndexLifecycleMetadata.TYPE);
+        final Map<String, LifecyclePolicy> policies = metadata != null ? metadata.getPolicies() : Map.of();
+
         for (LifecyclePolicy policy : getLifecyclePolicies()) {
             final AtomicBoolean creationCheck = policyCreationsInProgress.computeIfAbsent(
                 policy.getName(),
                 key -> new AtomicBoolean(false)
             );
             if (creationCheck.compareAndSet(false, true)) {
-                final LifecyclePolicy currentPolicy = metadata != null ? metadata.getPolicies().get(policy.getName()) : null;
+                final LifecyclePolicy currentPolicy = policies.get(policy.getName());
                 if (Objects.isNull(currentPolicy)) {
                     logger.debug("adding lifecycle policy [{}] for [{}], because it doesn't exist", policy.getName(), getOrigin());
                     putPolicy(policy, creationCheck);