19191 FIX mk-sql: skip inaccessible databases in SQL Server Always On Availability Groups

CMK-32435
SUP-27332

Change-Id: I52de1b5e3c79a0fca52cf8fa7becf1d80143c76f

Author: s-kipnis

.werks/19191.md

@@ -0,0 +1,18 @@
+[//]: # (werk v3)
+# mk-sql: skip inaccessible databases in SQL Server Always On Availability Groups
+
+key        | value
+---------- | ---
+date       | 2026-03-20T12:34:51+00:00
+version    | 2.5.0
+class      | fix
+edition    | community
+component  | checks
+level      | 2
+compatible | yes
+
+mk-sql previously queried all SQL Server databases indiscriminately, including secondary replicas in Always On Availability Groups (AG) that were not directly accessible. This caused spurious errors when monitoring SQL Server instances participating in an AG.
+
+Now, mk-sql only queries databases that are actually accessible: standalone databases, primary replicas, and readable secondary replicas. Inaccessible AG secondaries are silently skipped — this is expected behavior, not an error.
+
+This change improves monitoring reliability by eliminating false error messages. No configuration adjustments are necessary, as the update is fully automatic and transparent to users.

packages/mk-sql/src/ms_sql/instance.rs

@@ -427,7 +427,11 @@ impl SqlInstance {
     }
 
     /// Gather databases based on sections content: only if any of sections is database based
-    async fn gather_databases(&self, client: &mut UniClient, sections: &[Section]) -> Vec<String> {
+    async fn gather_active_databases(
+        &self,
+        client: &mut UniClient,
+        sections: &[Section],
+    ) -> Vec<String> {
         let database_based_sections = section::get_per_database_sections();
         let need = database_based_sections.iter().any(|s| {
             sections
@@ -437,7 +441,8 @@ impl SqlInstance {
                 .contains(s)
         });
         if need {
-            self.generate_databases(client).await
+            self.generate_databases(client, sqls::Id::DatabaseNamesActive)
+                .await
         } else {
             Vec::new()
         }
@@ -450,7 +455,7 @@ impl SqlInstance {
         sections: &[Section],
     ) -> String {
         let mut data: Vec<String> = Vec::new();
-        let databases = self.gather_databases(client, sections).await;
+        let databases = self.gather_active_databases(client, sections).await;
         for section in sections.iter() {
             data.push(
                 self.generate_section(client, endpoint, section, &databases)
@@ -767,7 +772,9 @@ impl SqlInstance {
         query: &str,
         sep: char,
     ) -> String {
-        let databases = self.generate_databases(client).await;
+        let databases = self
+            .generate_databases(client, sqls::Id::DatabaseNamesAll)
+            .await;
 
         let result = run_custom_query(client, query)
             .await
@@ -800,6 +807,10 @@ impl SqlInstance {
         query: &str,
         sep: char,
     ) -> String {
+        if databases.is_empty() {
+            log::warn!("No active databases, skip section {}", section.name());
+            return String::new();
+        }
         let chunks = if databases.len() >= 64 {
             let max_chunk = databases.len().div_ceil(4usize);
             let min_chunk = 16usize;
@@ -968,8 +979,8 @@ impl SqlInstance {
     }
 
     /// doesn't return error - the same behavior as plugin
-    pub async fn generate_databases(&self, client: &mut UniClient) -> Vec<String> {
-        let result = run_known_query(client, sqls::Id::DatabaseNames)
+    pub async fn generate_databases(&self, client: &mut UniClient, which: sqls::Id) -> Vec<String> {
+        let result = run_known_query(client, which)
             .await
             .and_then(validate_rows)
             .map(|rows| self.process_databases_rows(&rows));

packages/mk-sql/src/ms_sql/sqls.rs

@@ -21,7 +21,8 @@ pub enum Id {
     ClusterActiveNodes,
     ClusterNodes,
     IsClustered,
-    DatabaseNames,
+    DatabaseNamesAll,
+    DatabaseNamesActive,
     Databases,
     Datafiles,
     Backup,
@@ -168,7 +169,26 @@ WHERE object_name NOT LIKE '%Deprecated%'
             CAST(blocking_session_id AS varchar) AS blocking_session_id
     FROM sys.dm_os_waiting_tasks";
 
-    pub const DATABASE_NAMES: &str = "SELECT name FROM sys.databases";
+    pub const DATABASE_NAMES_ALL: &str = "SELECT name FROM sys.databases";
+
+    /// Skips secondary replica databases participating in availability groups
+    /// sys.fn_hadr_is_primary_replica(d.name) returns
+    /// 1 for primary replica
+    /// 0 for secondary replica
+    /// NULL for databases not participating in availability groups
+    /// ONLY SUPPORTED since version 12 (SQL Server 2014)
+    pub const DATABASE_NAMES_ACTIVE: &str = r#"IF CAST(PARSENAME(CAST(SERVERPROPERTY('ProductVersion') AS varchar(30)), 4) AS int) >= 12
+BEGIN
+    SELECT d.name
+    FROM sys.databases AS d
+    WHERE sys.fn_hadr_is_primary_replica(d.name) IS NULL
+       OR sys.fn_hadr_is_primary_replica(d.name) = 1;
+END
+ELSE
+BEGIN
+    SELECT d.name
+    FROM sys.databases AS d;
+END;"#;
 
     /// Executes `sp_spaceused` for each database parsing output AS resuult set
     /// Requires NVARCHAR support
@@ -446,7 +466,8 @@ lazy_static::lazy_static! {
         (Id::ClusterActiveNodes, QueryMap::new(query::CLUSTER_ACTIVE_NODES, None)),
         (Id::ClusterNodes, QueryMap::new(query::CLUSTER_NODES_NORMAL, Some(query::CLUSTER_NODES_AZURE))),
         (Id::IsClustered, QueryMap::new(query::IS_CLUSTERED, None)),
-        (Id::DatabaseNames, QueryMap::new(query::DATABASE_NAMES, None)),
+        (Id::DatabaseNamesAll, QueryMap::new(query::DATABASE_NAMES_ALL, None)),
+        (Id::DatabaseNamesActive, QueryMap::new(query::DATABASE_NAMES_ACTIVE, None)),
         (Id::Databases, QueryMap::new(query::DATABASES, None)),
         (Id::Datafiles, QueryMap::new(query::DATAFILES, None)),
         (Id::Backup, QueryMap::new(query::BACKUP, None)),

packages/mk-sql/tests/test_ms_sql.rs

@@ -381,7 +381,9 @@ async fn validate_all(i: &SqlInstance, c: &mut UniClient, e: &Endpoint) {
 }
 
 async fn validate_database_names(instance: &SqlInstance, client: &mut UniClient) {
-    let databases = instance.generate_databases(client).await;
+    let databases = instance
+        .generate_databases(client, sqls::Id::DatabaseNamesAll)
+        .await;
     let expected = expected_databases();
     // O^2, but good enough for testing
     assert!(expected.iter().all(|item| databases.contains(item)),);
@@ -449,7 +451,9 @@ async fn validate_table_spaces(
     client: &mut UniClient,
     endpoint: &Endpoint,
 ) {
-    let databases = instance.generate_databases(client).await;
+    let databases = instance
+        .generate_databases(client, sqls::Id::DatabaseNamesAll)
+        .await;
     let expected = expected_databases();
 
     let result = instance
@@ -511,7 +515,9 @@ async fn validate_transaction_logs(
 ) {
     let expected: HashSet<String> = expected_databases();
 
-    let databases = instance.generate_databases(client).await;
+    let databases = instance
+        .generate_databases(client, sqls::Id::DatabaseNamesAll)
+        .await;
     let result = instance
         .generate_transaction_logs_section(
             endpoint,
@@ -544,7 +550,9 @@ async fn validate_transaction_logs(
 
 async fn validate_datafiles(instance: &SqlInstance, client: &mut UniClient, endpoint: &Endpoint) {
     let expected: HashSet<String> = expected_databases();
-    let databases = instance.generate_databases(client).await;
+    let databases = instance
+        .generate_databases(client, sqls::Id::DatabaseNamesAll)
+        .await;
 
     let result = instance
         .generate_datafiles_section(
@@ -583,7 +591,9 @@ async fn validate_datafiles(instance: &SqlInstance, client: &mut UniClient, endp
 async fn validate_databases(instance: &SqlInstance, client: &mut UniClient) {
     let expected: HashSet<String> = expected_databases();
 
-    let databases = instance.generate_databases(client).await;
+    let databases = instance
+        .generate_databases(client, sqls::Id::DatabaseNamesAll)
+        .await;
     let result = instance
         .generate_databases_section(
             client,
@@ -621,7 +631,9 @@ async fn validate_databases(instance: &SqlInstance, client: &mut UniClient) {
 async fn validate_databases_error(instance: &SqlInstance, client: &mut UniClient) {
     let expected: HashSet<String> = expected_databases();
 
-    let databases = instance.generate_databases(client).await;
+    let databases = instance
+        .generate_databases(client, sqls::Id::DatabaseNamesAll)
+        .await;
     let result = instance
         .generate_databases_section(
             client,