feat: list all groups (#6)

Author: BewareMyPower

README.md

@@ -63,7 +63,9 @@ Updated config file /private/tmp/sncloud.ini
 
 **NOTE**: The commands below assumes `snctl-cpp` is in the `PATH`.
 
-### Create a topic
+### Topics
+
+#### Create a topic
 
 ```bash
 $ snctl-cpp topics create tp0
@@ -72,7 +74,7 @@ $ snctl-cpp topics create tp1 -p 5
 Created topic "tp1" with 5 partitions
 ```
 
-### Delete a topic
+#### Delete a topic
 
 ```bash
 $ snctl-cpp topics delete tp
@@ -81,7 +83,7 @@ $ snctl-cpp topics delete tp0
 Deleted topic "tp0"
 ```
 
-### Describe a topic
+#### Describe a topic
 
 Query the owner brokers for all partitions:
 
@@ -105,7 +107,7 @@ Partition[15] leader: {"id": 644587507, url: "pb2-<xxx>:9093"}
 
 As you can see, when a client specifies `use1-az1` as its zone, only brokers in the same zone (`pb2` and `pb5`) will serve the requests from that client.
 
-### List topics
+#### List topics
 
 List all topics and print the number of partitions for each topic:
 
@@ -116,6 +118,18 @@ topic count: 2
 [1] "my-topic-1" with 10 partitions
 ```
 
+## Consumer Groups
+
+### List all consumer groups
+
+```bash
+$ snctl-cpp groups list
+There are 1 group
+[0] my-group Stable
+```
+
+The format of each line is `[index] <group-id> <state>`.
+
 ## Logging
 
 By default, rdkafka will generate logs to the standard output. `snctl-cpp` can redirect the logs to a file. For example, with the following configs in `sncloud.ini`:

include/snctl-cpp/groups.h

@@ -0,0 +1,43 @@
+/**
+ * Copyright 2025 Yunze Xu
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#pragma once
+
+#include "snctl-cpp/groups/list_groups.h"
+#include "snctl-cpp/subcommand.h"
+
+#include <argparse/argparse.hpp>
+#include <librdkafka/rdkafka.h>
+
+class Groups : public SubCommand {
+public:
+  explicit Groups(argparse::ArgumentParser &parent) : SubCommand("groups") {
+    list_command_.add_description("List all consumer groups");
+
+    add_child(list_command_);
+    attach_parent(parent);
+  }
+
+  void run(rd_kafka_t *rk, rd_kafka_queue_t *rkqu) {
+    if (is_subcommand_used(list_command_)) {
+      list_groups(rk, rkqu);
+    } else {
+      fail();
+    }
+  }
+
+private:
+  argparse::ArgumentParser list_command_{"list"};
+};

include/snctl-cpp/groups/list_groups.h

@@ -0,0 +1,62 @@
+/**
+ * Copyright 2025 Yunze Xu
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#pragma once
+
+#include "snctl-cpp/rk_event_wrapper.h"
+#include <cassert>
+#include <iostream>
+#include <librdkafka/rdkafka.h>
+#include <stdexcept>
+
+inline void list_groups(rd_kafka_t *rk, rd_kafka_queue_t *rkqu) {
+  rd_kafka_ListConsumerGroups(rk, nullptr, rkqu);
+
+  try {
+    auto event = RdKafkaEvent::poll(rkqu);
+    const auto *result =
+        rd_kafka_event_ListConsumerGroups_result(event.handle());
+    assert(result != nullptr);
+
+    size_t count;
+    const auto *errors =
+        rd_kafka_ListConsumerGroups_result_errors(result, &count);
+    if (errors != nullptr) {
+      for (size_t i = 0; i < count; ++i) {
+        const auto *error = errors[i];
+        std::cerr << i << " error: " << rd_kafka_error_string(error)
+                  << std::endl;
+      }
+      return;
+    }
+
+    const auto *groups =
+        rd_kafka_ListConsumerGroups_result_valid(result, &count);
+    assert(groups != nullptr);
+    std::cout << "There are " << count << " group" << (count == 1 ? "" : "s")
+              << std::endl;
+    for (size_t i = 0; i < count; i++) {
+      const auto *group = groups[i];
+      std::cout << "[" << i << "] "
+                << rd_kafka_ConsumerGroupListing_group_id(group) << " "
+                << rd_kafka_consumer_group_state_name(
+                       rd_kafka_ConsumerGroupListing_state(group))
+                << std::endl;
+    }
+
+  } catch (const std::runtime_error &e) {
+    std::cerr << "Failed to list consumer groups: " << e.what() << std::endl;
+  }
+}

src/main.cc

@@ -28,6 +28,7 @@
 #include <vector>
 
 #include "snctl-cpp/configs.h"
+#include "snctl-cpp/groups.h"
 #include "snctl-cpp/raii_helper.h"
 #include "snctl-cpp/topics.h"
 
@@ -55,6 +56,7 @@ int main(int argc, char *argv[]) noexcept(false) {
 
   Topics topics{program};
   Configs configs{program};
+  Groups groups{program};
   try {
     program.parse_args(argc, argv);
   } catch (const std::exception &err) {
@@ -128,6 +130,8 @@ int main(int argc, char *argv[]) noexcept(false) {
       topics.run(rk, rkqu);
     } else if (configs.used_by_parent(program)) {
       configs.run();
+    } else if (groups.used_by_parent(program)) {
+      groups.run(rk, rkqu);
     } else {
       if (program["--get-config"] == true) {
         if (const auto &config_file = configs.config_file();