[Backport 2.19] [Bug fix] Normalize cluster metrics input URI path during validation.

src/main/kotlin/org/opensearch/commons/alerting/model/ClusterMetricsInput.kt

@@ -148,9 +148,10 @@ data class ClusterMetricsInput(
             }
 
             if (apiType.isNotEmpty() && path.isNotEmpty()) {
+                val formattedPath = path.trim('/')
                 val derivedType = ClusterMetricType.values()
                     .filter { it != ClusterMetricType.BLANK }
-                    .find { path.startsWith(it.prependPath) || path.startsWith(it.defaultPath) }
+                    .find { formattedPath.startsWith(it.prependPath.trim('/')) || formattedPath.startsWith(it.defaultPath.trim('/')) }
 
                 require(derivedType != null && derivedType.name == apiType) {
                     "The provided api_type [$apiType] does not match the path [$path]."

src/test/kotlin/org/opensearch/commons/alerting/model/ClusterMetricsInputTests.kt

@@ -630,4 +630,84 @@ class ClusterMetricsInputTests {
         val input = ClusterMetricsInput.parseInner(xcp)
         assertEquals(ClusterMetricsInput.ClusterMetricType.CAT_INDICES, input.clusterMetricType)
     }
+
+    @Test
+    fun `test parseInner accepts matching api_type and path without leading slash`() {
+        val inputJson = """
+            {"uri":{"api_type":"CAT_INDICES","path":"_cat/indices","path_params":"","url":"","clusters":[]}}
+        """.trimIndent()
+        val xcp = org.opensearch.common.xcontent.json.JsonXContent.jsonXContent
+            .createParser(
+                org.opensearch.core.xcontent.NamedXContentRegistry.EMPTY,
+                org.opensearch.core.xcontent.DeprecationHandler.THROW_UNSUPPORTED_OPERATION,
+                inputJson
+            )
+        xcp.nextToken()
+        xcp.nextToken()
+        xcp.nextToken()
+
+        val input = ClusterMetricsInput.parseInner(xcp)
+        assertEquals(ClusterMetricsInput.ClusterMetricType.CAT_INDICES, input.clusterMetricType)
+    }
+
+    @Test
+    fun `test parseInner rejects mismatched api_type and path without leading slash`() {
+        val inputJson = """
+            {"uri":{"api_type":"CLUSTER_STATS","path":"_cat/indices","path_params":"","url":"","clusters":[]}}
+        """.trimIndent()
+        val xcp = org.opensearch.common.xcontent.json.JsonXContent.jsonXContent
+            .createParser(
+                org.opensearch.core.xcontent.NamedXContentRegistry.EMPTY,
+                org.opensearch.core.xcontent.DeprecationHandler.THROW_UNSUPPORTED_OPERATION,
+                inputJson
+            )
+        xcp.nextToken()
+        xcp.nextToken()
+        xcp.nextToken()
+
+        assertFailsWith<IllegalArgumentException>("The provided api_type") {
+            ClusterMetricsInput.parseInner(xcp)
+        }
+    }
+
+    @Test
+    fun `test parseInner accepts matching api_type with path containing trailing slash`() {
+        val inputJson = """
+            {"uri":{"api_type":"CLUSTER_HEALTH","path":"/_cluster/health/","path_params":"","url":"","clusters":[]}}
+        """.trimIndent()
+        val xcp = org.opensearch.common.xcontent.json.JsonXContent.jsonXContent
+            .createParser(
+                org.opensearch.core.xcontent.NamedXContentRegistry.EMPTY,
+                org.opensearch.core.xcontent.DeprecationHandler.THROW_UNSUPPORTED_OPERATION,
+                inputJson
+            )
+        xcp.nextToken()
+        xcp.nextToken()
+        xcp.nextToken()
+
+        val input = ClusterMetricsInput.parseInner(xcp)
+        assertEquals(ClusterMetricsInput.ClusterMetricType.CLUSTER_HEALTH, input.clusterMetricType)
+    }
+
+    @Test
+    fun `test parseInner rejects slash-only path with api_type`() {
+        // path "/" enters validation since path.isNotEmpty(),
+        // but trimmed path doesn't match any ClusterMetricType
+        val inputJson = """
+            {"uri":{"api_type":"CAT_INDICES","path":"/","path_params":"","url":"http://localhost:9200/_cluster/health","clusters":[]}}
+        """.trimIndent()
+        val xcp = org.opensearch.common.xcontent.json.JsonXContent.jsonXContent
+            .createParser(
+                org.opensearch.core.xcontent.NamedXContentRegistry.EMPTY,
+                org.opensearch.core.xcontent.DeprecationHandler.THROW_UNSUPPORTED_OPERATION,
+                inputJson
+            )
+        xcp.nextToken()
+        xcp.nextToken()
+        xcp.nextToken()
+
+        assertFailsWith<IllegalArgumentException>("The provided api_type") {
+            ClusterMetricsInput.parseInner(xcp)
+        }
+    }
 }