update slot mapping with time interval

README.md

@@ -2299,6 +2299,8 @@ If master is down, the cluster will promote one of its replicas to be the new ma
 - When the master is down, *redis-plus-plus* losts connection to it. In this case, if you try to send commands to this master, *redis-plus-plus* will try to update slot-node mapping from other nodes. If the mapping remains unchanged, i.e. new master hasn't been elected yet, it fails to send command to Redis Cluster and throws exception.
 - When the new master has been elected, the slot-node mapping will be updated by the cluster. In this case, if you send commands to the cluster, *redis-plus-plus* can get an update-to-date mapping, and sends commands to the new master.
 
+Since redis-plus-plus 1.3.13, it also updates the slot-node mapping every `ClusterOptions::slot_map_refresh_interval` time interval (by default, it updates every 10 seconds).
+
 ### Redis Sentinel
 
 [Redis Sentinel provides high availability for Redis](https://redis.io/topics/sentinel). If Redis master is down, Redis Sentinels will elect a new master from slaves, i.e. failover. Besides, Redis Sentinel can also act like a configuration provider for clients, and clients can query master or slave address from Redis Sentinel. So that if a failover occurs, clients can ask the new master address from Redis Sentinel.

src/sw/redis++/async_connection.h

@@ -512,8 +512,6 @@ class ClusterEvent : public CommandEvent<Result, ResultParser> {
         // i.e. ClosedError or IoError, we need to update node-slot mapping.
         try {
             std::rethrow_exception(err);
-        } catch (const SlotUncoveredError &) {
-            detail::update_shards(_key, _pool, AsyncEventUPtr(new UpdateShardsEvent));
         } catch (const IoError &) {
             detail::update_shards(_key, _pool, AsyncEventUPtr(new UpdateShardsEvent));
         } catch (const ClosedError &) {

src/sw/redis++/async_redis_cluster.cpp

@@ -32,14 +32,24 @@ AsyncRedisCluster::AsyncRedisCluster(const ConnectionOptions &opts,
         _loop = std::make_shared<EventLoop>();
     }
 
-    _pool = std::make_shared<AsyncShardsPool>(_loop, pool_opts, opts, role);
+    _pool = std::make_shared<AsyncShardsPool>(_loop, pool_opts, opts, role, ClusterOptions{});
+}
+
+AsyncRedisCluster::AsyncRedisCluster(const ConnectionOptions &opts,
+        const ConnectionPoolOptions &pool_opts,
+        Role role,
+        const ClusterOptions &cluster_opts,
+        const EventLoopSPtr &loop) : _loop(loop) {
+    if (!_loop) {
+        _loop = std::make_shared<EventLoop>();
+    }
+
+    _pool = std::make_shared<AsyncShardsPool>(_loop, pool_opts, opts, role, cluster_opts);
 }
 
 AsyncRedis AsyncRedisCluster::redis(const StringView &hash_tag, bool new_connection) {
     assert(_pool);
 
-    _pool->update();
-
     auto pool = _pool->fetch(hash_tag);
     if (new_connection) {
         // Create a new pool.
@@ -52,8 +62,6 @@ AsyncRedis AsyncRedisCluster::redis(const StringView &hash_tag, bool new_connect
 AsyncSubscriber AsyncRedisCluster::subscriber() {
     assert(_pool);
 
-    _pool->update();
-
     auto opts = _pool->connection_options();
 
     auto connection = std::make_shared<AsyncConnection>(opts, _loop.get());
@@ -65,8 +73,6 @@ AsyncSubscriber AsyncRedisCluster::subscriber() {
 AsyncSubscriber AsyncRedisCluster::subscriber(const StringView &hash_tag) {
     assert(_pool);
 
-    _pool->update();
-
     auto opts = _pool->connection_options(hash_tag);
 
     auto connection = std::make_shared<AsyncConnection>(opts, _loop.get());

src/sw/redis++/async_redis_cluster.h

@@ -39,6 +39,12 @@ class AsyncRedisCluster {
             Role role = Role::MASTER,
             const EventLoopSPtr &loop = nullptr);
 
+    AsyncRedisCluster(const ConnectionOptions &opts,
+            const ConnectionPoolOptions &pool_opts,
+            Role role,
+            const ClusterOptions &cluster_opts,
+            const EventLoopSPtr &loop = nullptr);
+
     explicit AsyncRedisCluster(const std::string &uri) : AsyncRedisCluster(Uri(uri)) {}
 
     AsyncRedisCluster(const AsyncRedisCluster &) = delete;

src/sw/redis++/async_shards_pool.cpp

@@ -29,10 +29,12 @@ const std::size_t AsyncShardsPool::SHARDS;
 AsyncShardsPool::AsyncShardsPool(const EventLoopSPtr &loop,
         const ConnectionPoolOptions &pool_opts,
         const ConnectionOptions &connection_opts,
-        Role role) :
+        Role role,
+        const ClusterOptions &cluster_opts) :
             _pool_opts(pool_opts),
             _connection_opts(connection_opts),
             _role(role),
+            _cluster_opts(cluster_opts),
             _loop(loop) {
     assert(loop);
 
@@ -208,8 +210,12 @@ auto AsyncShardsPool::_fetch_events() -> std::queue<RedeliverEvent> {
     std::queue<RedeliverEvent> events;
 
     std::unique_lock<std::mutex> lock(_mutex);
-    if (_events.empty()) {
-        _cv.wait(lock, [this]() { return !(this->_events).empty(); } );
+
+    if (!_cv.wait_for(lock,
+            _cluster_opts.slot_map_refresh_interval,
+            [this]() { return !(this->_events).empty(); })) {
+        // Reach timeout, but there's still no event, put an update event.
+        _events.push(RedeliverEvent{{}, AsyncEventUPtr(new UpdateShardsEvent)});
     }
 
     events.swap(_events);
@@ -238,7 +244,7 @@ Shards AsyncShardsPool::_get_shards(const std::string &host, int port) {
     auto opts = _connection_opts;
     opts.host = host;
     opts.port = port;
-    ShardsPool pool(_pool_opts, opts, _role);
+    ShardsPool pool(_pool_opts, opts, _role, _cluster_opts);
 
     return pool.shards();
 }

src/sw/redis++/async_shards_pool.h

@@ -43,7 +43,8 @@ class AsyncShardsPool {
     AsyncShardsPool(const EventLoopSPtr &loop,
                 const ConnectionPoolOptions &pool_opts,
                 const ConnectionOptions &connection_opts,
-                Role role);
+                Role role,
+                const ClusterOptions &cluster_opts);
 
     AsyncConnectionPoolSPtr fetch(const StringView &key);
 
@@ -101,6 +102,8 @@ class AsyncShardsPool {
 
     Role _role = Role::MASTER;
 
+    ClusterOptions _cluster_opts;
+
     Shards _shards;
 
     NodeMap _pools;

src/sw/redis++/crc16.cpp

@@ -42,7 +42,7 @@
  * Output for "123456789"     : 31C3
  */
 
-#include "utils.h"
+#include "sw/redis++/utils.h"
 #include <cstdint>
 
 namespace sw {

src/sw/redis++/redis_cluster.cpp

@@ -32,8 +32,6 @@ RedisCluster::RedisCluster(const Uri &uri) :
 Redis RedisCluster::redis(const StringView &hash_tag, bool new_connection) {
     assert(_pool);
 
-    _pool->async_update();
-
     auto pool = _pool->fetch(hash_tag);
     if (new_connection) {
         // Create a new pool
@@ -46,8 +44,6 @@ Redis RedisCluster::redis(const StringView &hash_tag, bool new_connection) {
 Pipeline RedisCluster::pipeline(const StringView &hash_tag, bool new_connection) {
     assert(_pool);
 
-    _pool->async_update();
-
     auto pool = _pool->fetch(hash_tag);
     if (new_connection) {
         // Create a new pool
@@ -60,8 +56,6 @@ Pipeline RedisCluster::pipeline(const StringView &hash_tag, bool new_connection)
 Transaction RedisCluster::transaction(const StringView &hash_tag, bool piped, bool new_connection) {
     assert(_pool);
 
-    _pool->async_update();
-
     auto pool = _pool->fetch(hash_tag);
     if (new_connection) {
         // Create a new pool
@@ -74,17 +68,13 @@ Transaction RedisCluster::transaction(const StringView &hash_tag, bool piped, bo
 Subscriber RedisCluster::subscriber() {
     assert(_pool);
 
-    _pool->async_update();
-
     auto opts = _pool->connection_options();
     return Subscriber(Connection(opts));
 }
 
 Subscriber RedisCluster::subscriber(const StringView &hash_tag) {
     assert(_pool);
 
-    _pool->async_update();
-
     auto opts = _pool->connection_options(hash_tag);
     return Subscriber(Connection(opts));
 }

src/sw/redis++/redis_cluster.h

@@ -47,7 +47,8 @@ class RedisCluster {
 public:
     explicit RedisCluster(const ConnectionOptions &connection_opts,
                     const ConnectionPoolOptions &pool_opts = {},
-                    Role role = Role::MASTER) : _pool(new ShardsPool(pool_opts, connection_opts, role)) {}
+                    Role role = Role::MASTER,
+                    const ClusterOptions &cluster_opts = {}) : _pool(new ShardsPool(pool_opts, connection_opts, role, cluster_opts)) {}
 
     // Construct RedisCluster with URI:
     // "tcp://127.0.0.1" or "tcp://127.0.0.1:6379"

src/sw/redis++/redis_cluster.hpp

@@ -1351,11 +1351,6 @@ ReplyUPtr RedisCluster::_command(Cmd cmd, const StringView &key, Args &&...args)
             SafeConnection safe_connection(*pool);
 
             return _command(cmd, safe_connection.connection(), std::forward<Args>(args)...);
-        } catch (const SlotUncoveredError &) {
-            // Some slot is not covered, update asynchronously to see if new node added.
-            // Check https://github.com/sewenew/redis-plus-plus/issues/255 for detail.
-            // TODO: should we replace other 'update's with 'async_update's?
-            _pool->async_update();
         } catch (const IoError &) {
             // When master is down, one of its replicas will be promoted to be the new master.
             // If we try to send command to the old master, we'll get an *IoError*.

src/sw/redis++/shards_pool.cpp

@@ -26,10 +26,12 @@ const std::size_t ShardsPool::SHARDS;
 
 ShardsPool::ShardsPool(const ConnectionPoolOptions &pool_opts,
                         const ConnectionOptions &connection_opts,
-                        Role role) :
+                        Role role,
+                        const ClusterOptions &cluster_opts) :
                             _pool_opts(pool_opts),
                             _connection_opts(connection_opts),
-                            _role(role) {
+                            _role(role),
+                            _cluster_opts(cluster_opts) {
     if (_connection_opts.type != ConnectionType::TCP) {
         throw Error("Only support TCP connection for Redis Cluster");
     }
@@ -47,7 +49,7 @@ ShardsPool::~ShardsPool() {
     {
         std::lock_guard<std::mutex> lock(_mutex);
 
-        _update_status = UpdateStatus::STOP;
+        _stop = true;
     }
 
     _cv.notify_one();
@@ -172,22 +174,6 @@ std::vector<ConnectionPoolSPtr> ShardsPool::pools() {
     return nodes;
 }
 
-void ShardsPool::async_update() {
-    bool should_update = false;
-    {
-        std::lock_guard<std::mutex> lock(_mutex);
-
-        if (_update_status == UpdateStatus::UPDATED) {
-            should_update = true;
-            _update_status = UpdateStatus::STALE;
-        }
-    }
-
-    if (should_update) {
-        _cv.notify_one();
-    }
-}
-
 void ShardsPool::_init_pool(const Shards &shards) {
     for (const auto &shard : shards) {
         _add_node(shard.second);
@@ -385,34 +371,20 @@ auto ShardsPool::_add_node(const Node &node) -> NodeMap::iterator {
 void ShardsPool::_run() {
     while (true) {
         std::unique_lock<std::mutex> lock(_mutex);
-        if (_update_status == UpdateStatus::UPDATED) {
-            _cv.wait(lock, [this]() { return this->_update_status != UpdateStatus::UPDATED; });
-        }
 
-        if (_update_status == UpdateStatus::STOP) {
+        if (_cv.wait_for(lock,
+                    _cluster_opts.slot_map_refresh_interval,
+                    [this]() { return this->_stop; })) {
             break;
-        } else if (_update_status == UpdateStatus::STALE) {
-            lock.unlock();
-
-            _do_async_update();
-        } else {
-            assert("invalid UpdateStatus");
         }
-    }
-}
-
-void ShardsPool::_do_async_update() {
-    try {
-        update();
 
-        std::lock_guard<std::mutex> lock(_mutex);
+        lock.unlock();
 
-        if (_update_status != UpdateStatus::STOP) {
-            _update_status = UpdateStatus::UPDATED;
+        try {
+            update();
+        } catch (...) {
+            // Ignore exceptions.
         }
-    } catch (...) {
-        // Ignore exceptions.
-        // TODO: should we sleep a while?
     }
 }
 

src/sw/redis++/shards_pool.h

@@ -18,6 +18,7 @@
 #define SEWENEW_REDISPLUSPLUS_SHARDS_POOL_H
 
 #include <cassert>
+#include <chrono>
 #include <condition_variable>
 #include <mutex>
 #include <thread>
@@ -34,10 +35,13 @@ namespace sw {
 
 namespace redis {
 
+struct ClusterOptions {
+    // Automatically update slot map every `slot_map_refresh_interval`.
+    std::chrono::milliseconds slot_map_refresh_interval = std::chrono::seconds(10);
+};
+
 class ShardsPool {
 public:
-    ShardsPool() = default;
-
     ShardsPool(const ShardsPool &that) = delete;
     ShardsPool& operator=(const ShardsPool &that) = delete;
 
@@ -48,7 +52,8 @@ class ShardsPool {
 
     ShardsPool(const ConnectionPoolOptions &pool_opts,
                 const ConnectionOptions &connection_opts,
-                Role role);
+                Role role,
+                const ClusterOptions &cluster_opts);
 
     // Fetch a connection by key.
     ConnectionPoolSPtr fetch(const StringView &key);
@@ -69,8 +74,6 @@ class ShardsPool {
 
     std::vector<ConnectionPoolSPtr> pools();
 
-    void async_update();
-
 private:
     void _init_pool(const Shards &shards);
 
@@ -117,12 +120,7 @@ class ShardsPool {
 
     NodeMap _pools;
 
-    enum class UpdateStatus {
-        STALE = 0,
-        UPDATED,
-        STOP
-    };
-    UpdateStatus _update_status = UpdateStatus::UPDATED;
+    bool _stop = false;
 
     std::thread _worker;
 
@@ -132,6 +130,8 @@ class ShardsPool {
 
     Role _role = Role::MASTER;
 
+    ClusterOptions _cluster_opts;
+
     static const std::size_t SHARDS = 16383;
 };