StorageSystemReplicas added column replica_is_active

docs/en/operations/system-tables/replicas.md

@@ -82,6 +82,7 @@ The next 4 columns have a non-zero value only where there is an active session w
 -   `absolute_delay` (`UInt64`) - How big lag in seconds the current replica has.
 -   `total_replicas` (`UInt8`) - The total number of known replicas of this table.
 -   `active_replicas` (`UInt8`) - The number of replicas of this table that have a session in ZooKeeper (i.e., the number of functioning replicas).
+-   `replica_is_active` ([Map(String, UInt8)](../../sql-reference/data-types/map.md)) — Map between replica name and is replica active.
 
 If you request all the columns, the table may work a bit slowly, since several reads from ZooKeeper are made for each row.
 If you do not request the last 4 columns (log_max_index, log_pointer, total_replicas, active_replicas), the table works quickly.

src/Storages/StorageReplicatedMergeTree.cpp

@@ -5575,8 +5575,11 @@ void StorageReplicatedMergeTree::getStatus(Status & res, bool with_zk_fields)
             res.total_replicas = all_replicas.size();
 
             for (const String & replica : all_replicas)
-                if (zookeeper->exists(fs::path(zookeeper_path) / "replicas" / replica / "is_active"))
-                    ++res.active_replicas;
+            {
+                bool is_replica_active = zookeeper->exists(fs::path(zookeeper_path) / "replicas" / replica / "is_active");
+                res.active_replicas += static_cast<UInt8>(is_replica_active);
+                res.replica_is_active.emplace(replica, is_replica_active);
+            }
         }
         catch (const Coordination::Exception &)
         {

src/Storages/StorageReplicatedMergeTree.h

@@ -176,6 +176,7 @@ public:
         UInt8 active_replicas;
         /// If the error has happened fetching the info from ZooKeeper, this field will be set.
         String zookeeper_exception;
+        std::unordered_map<std::string, bool> replica_is_active;
     };
 
     /// Get the status of the table. If with_zk_fields = false - do not fill in the fields that require queries to ZK.

src/Storages/System/StorageSystemReplicas.cpp

@@ -2,6 +2,7 @@
 #include <DataTypes/DataTypeString.h>
 #include <DataTypes/DataTypesNumber.h>
 #include <DataTypes/DataTypeDateTime.h>
+#include <DataTypes/DataTypeMap.h>
 #include <Storages/System/StorageSystemReplicas.h>
 #include <Storages/StorageReplicatedMergeTree.h>
 #include <Storages/VirtualColumnUtils.h>
@@ -51,6 +52,7 @@ StorageSystemReplicas::StorageSystemReplicas(const StorageID & table_id_)
         { "total_replicas",                       std::make_shared<DataTypeUInt8>()    },
         { "active_replicas",                      std::make_shared<DataTypeUInt8>()    },
         { "zookeeper_exception",                  std::make_shared<DataTypeString>()   },
+        { "replica_is_active",                    std::make_shared<DataTypeMap>(std::make_shared<DataTypeString>(), std::make_shared<DataTypeUInt8>()) }
     }));
     setInMemoryMetadata(storage_metadata);
 }
@@ -101,7 +103,8 @@ Pipe StorageSystemReplicas::read(
             || column_name == "log_pointer"
             || column_name == "total_replicas"
             || column_name == "active_replicas"
-            || column_name == "zookeeper_exception")
+            || column_name == "zookeeper_exception"
+            || column_name == "replica_is_active")
         {
             with_zk_fields = true;
             break;
@@ -184,6 +187,18 @@ Pipe StorageSystemReplicas::read(
         res_columns[col_num++]->insert(status.total_replicas);
         res_columns[col_num++]->insert(status.active_replicas);
         res_columns[col_num++]->insert(status.zookeeper_exception);
+
+        Map replica_is_active_values;
+        for (const auto & [name, is_active] : status.replica_is_active)
+        {
+            Tuple is_replica_active_value;
+            is_replica_active_value.emplace_back(name);
+            is_replica_active_value.emplace_back(is_active);
+
+            replica_is_active_values.emplace_back(std::move(is_replica_active_value));
+        }
+
+        res_columns[col_num++]->insert(std::move(replica_is_active_values));
     }
 
     Block header = metadata_snapshot->getSampleBlock();

tests/integration/test_replica_is_active/test.py

@@ -0,0 +1,41 @@
+import pytest
+from helpers.client import QueryRuntimeException
+from helpers.cluster import ClickHouseCluster
+
+cluster = ClickHouseCluster(__file__)
+node1 = cluster.add_instance('node1', with_zookeeper=True)
+node2 = cluster.add_instance('node2', with_zookeeper=True)
+node3 = cluster.add_instance('node3', with_zookeeper=True)
+
+@pytest.fixture(scope="module")
+def start_cluster():
+    try:
+        cluster.start()
+
+        for i, node in enumerate((node1, node2, node3)):
+            node_name = 'node' + str(i + 1)
+            node.query(
+                '''
+                CREATE TABLE test_table(date Date, id UInt32, dummy UInt32)
+                ENGINE = ReplicatedMergeTree('/clickhouse/tables/test_table', '{}')
+                PARTITION BY date ORDER BY id
+                '''.format(node_name)
+            )
+
+        yield cluster
+
+    finally:
+        cluster.shutdown()
+
+
+def test_replica_is_active(start_cluster):
+    query_result = node1.query("select replica_is_active from system.replicas where table = 'test_table'")
+    assert query_result == '{\'node1\':1,\'node2\':1,\'node3\':1}\n'
+
+    node3.stop()
+    query_result = node1.query("select replica_is_active from system.replicas where table = 'test_table'")
+    assert query_result == '{\'node1\':1,\'node2\':1,\'node3\':0}\n'
+
+    node2.stop()
+    query_result = node1.query("select replica_is_active from system.replicas where table = 'test_table'")
+    assert query_result == '{\'node1\':1,\'node2\':0,\'node3\':0}\n'