PIP-121: Implement AutoClusterFailover

include/pulsar/AutoClusterFailover.h

@@ -0,0 +1,105 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.
+ */
+#ifndef PULSAR_AUTO_CLUSTER_FAILOVER_H_
+#define PULSAR_AUTO_CLUSTER_FAILOVER_H_
+
+#include <pulsar/ServiceInfo.h>
+
+#include <chrono>
+
+namespace pulsar {
+
+class Client;
+class AutoClusterFailoverImpl;
+
+class PULSAR_PUBLIC AutoClusterFailover final {
+   public:
+    /**
+     * Leverage `Client`'s internals for service URL probe and cluster switching.
+     */
+    void initialize(Client& client);
+
+    struct Config {
+        ServiceInfo primary;
+        std::vector<ServiceInfo> secondary;
+        std::chrono::milliseconds checkInterval{30000};    // 30 seconds
+        std::chrono::milliseconds failoverDelay{30000};    // 30 seconds
+        std::chrono::milliseconds switchBackDelay{60000};  // 60 seconds
+    };
+
+    /**
+     * Builder helps create an AutoClusterFailover configuration.
+     *
+     * Example:
+     *   ServiceInfo primary{...};
+     *   std::vector<ServiceInfo> secondaries{...};
+     *   AutoClusterFailover provider = AutoClusterFailover::Builder(primary, secondaries)
+     *       .withCheckInterval(std::chrono::seconds(30))
+     *       .withFailoverDelay(std::chrono::seconds(30))
+     *       .withSwitchBackDelay(std::chrono::seconds(60))
+     *       .build();
+     *
+     * Notes:
+     * - primary: the preferred cluster to use when available.
+     * - secondary: ordered list of fallback clusters.
+     * - checkInterval: frequency of health probes.
+     * - failoverDelay: how long the current cluster must be unreachable before switching.
+     * - switchBackDelay: how long the primary must remain healthy before switching back.
+     */
+    class Builder {
+       public:
+        Builder(ServiceInfo primary, std::vector<ServiceInfo> secondary) {
+            config_.primary = std::move(primary);
+            config_.secondary = std::move(secondary);
+        }
+
+        // Set how frequently probes run against the active cluster(s).
+        Builder& withCheckInterval(std::chrono::milliseconds interval) {
+            config_.checkInterval = interval;
+            return *this;
+        }
+
+        // Set how long the current cluster must be unreachable before attempting failover.
+        Builder& withFailoverDelay(std::chrono::milliseconds delay) {
+            config_.failoverDelay = delay;
+            return *this;
+        }
+
+        // Set how long the primary must remain healthy before switching back from a secondary.
+        Builder& withSwitchBackDelay(std::chrono::milliseconds delay) {
+            config_.switchBackDelay = delay;
+            return *this;
+        }
+
+        AutoClusterFailover build() { return AutoClusterFailover(std::move(config_)); }
+
+       private:
+        Config config_;
+    };
+
+    explicit AutoClusterFailover(Config&& config);
+    ~AutoClusterFailover();
+
+   private:
+    std::shared_ptr<AutoClusterFailoverImpl> impl_;
+};
+
+}  // namespace pulsar
+
+#endif

include/pulsar/Client.h

@@ -29,9 +29,11 @@
 #include <pulsar/Reader.h>
 #include <pulsar/Result.h>
 #include <pulsar/Schema.h>
+#include <pulsar/ServiceInfo.h>
 #include <pulsar/TableView.h>
 #include <pulsar/defines.h>
 
+#include <optional>
 #include <string>
 
 namespace pulsar {
@@ -414,11 +416,29 @@ class PULSAR_PUBLIC Client {
     void getSchemaInfoAsync(const std::string& topic, int64_t version,
                             std::function<void(Result, const SchemaInfo&)> callback);
 
+    /**
+     * Update the service information of the client.
+     *
+     * This method is used to switch the connection to a different Pulsar cluster. All connections will be
+     * closed and the internal service info will be updated.
+     *
+     * @param serviceInfo the service URL, authentication and TLS trust certs file path to use
+     */
+    void updateServiceInfo(ServiceInfo serviceInfo);
+
+    /**
+     * Get the current service information of the client.
+     *
+     * @return the current service information
+     */
+    ServiceInfo getServiceInfo() const;
+
    private:
     Client(const std::shared_ptr<ClientImpl>&);
 
     friend class PulsarFriend;
     friend class PulsarWrapper;
+    friend class AutoClusterFailover;
     std::shared_ptr<ClientImpl> impl_;
 };
 }  // namespace pulsar

include/pulsar/ServiceInfo.h

@@ -0,0 +1,42 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.
+ */
+#ifndef PULSAR_SERVICE_INFO_H_
+#define PULSAR_SERVICE_INFO_H_
+
+#include <pulsar/Authentication.h>
+
+#include <optional>
+#include <string>
+
+namespace pulsar {
+
+struct PULSAR_PUBLIC ServiceInfo {
+    std::string serviceUrl;
+    std::optional<AuthenticationPtr> authentication;
+    std::optional<std::string> tlsTrustCertsFilePath;
+
+    bool operator==(const ServiceInfo& other) const {
+        return serviceUrl == other.serviceUrl && authentication == other.authentication &&
+               tlsTrustCertsFilePath == other.tlsTrustCertsFilePath;
+    }
+};
+
+}  // namespace pulsar
+
+#endif