// 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.


#include <gflags/gflags.h>
#include <map>
#include "bthread/bthread.h"
#include "butil/time.h"
#include "butil/scoped_lock.h"
#include "butil/logging.h"
#include "brpc/log.h"
#include "brpc/protocol.h"
#include "brpc/input_messenger.h"
#include "brpc/reloadable_flags.h"
#include "brpc/socket_map.h"

namespace brpc {

DEFINE_int32(health_check_interval, 3, 
             "seconds between consecutive health-checkings");
// NOTE: Must be limited to positive to guarantee correctness of SocketMapRemove.
BRPC_VALIDATE_GFLAG(health_check_interval, PositiveInteger);

DEFINE_int32(idle_timeout_second, 30, 
             "Pooled connections without data transmission for so many "
             "seconds will be closed. No effect for non-positive values");
BRPC_VALIDATE_GFLAG(idle_timeout_second, PassValidate);

DEFINE_int32(defer_close_second, 0,
             "Defer close of connections for so many seconds even if the"
             " connection is not used by anyone. Close immediately for "
             "non-positive values.");
BRPC_VALIDATE_GFLAG(defer_close_second, PassValidate);

DEFINE_bool(defer_close_respect_idle, false,
            "When defer_close_second > 0, close a connection immediately when "
            "the last reference is removed and the socket has already been "
            "idle for longer than defer_close_second. Disabled by default for "
            "backward compatibility.");
BRPC_VALIDATE_GFLAG(defer_close_respect_idle, PassValidate);

DEFINE_bool(show_socketmap_in_vars, false,
            "[DEBUG] Describe SocketMaps in /vars");
BRPC_VALIDATE_GFLAG(show_socketmap_in_vars, PassValidate);

DEFINE_bool(reserve_one_idle_socket, false,
            "Reserve one idle socket for pooled connections when idle_timeout_second > 0");

static pthread_once_t g_socket_map_init = PTHREAD_ONCE_INIT;
static butil::static_atomic<SocketMap*> g_socket_map = BUTIL_STATIC_ATOMIC_INIT(NULL);

class GlobalSocketCreator : public SocketCreator {
public:
    int CreateSocket(const SocketOptions& opt, SocketId* id) override {
        SocketOptions sock_opt = opt;
        sock_opt.health_check_interval_s = FLAGS_health_check_interval;
        return get_client_side_messenger()->Create(sock_opt, id);
    }
};

static void CreateClientSideSocketMap() {
    SocketMap* socket_map = new SocketMap;
    SocketMapOptions options;
    options.socket_creator = new GlobalSocketCreator;
    options.idle_timeout_second_dynamic = &FLAGS_idle_timeout_second;
    options.defer_close_second_dynamic = &FLAGS_defer_close_second;
    options.defer_close_respect_idle_dynamic = &FLAGS_defer_close_respect_idle;
    if (socket_map->Init(options) != 0) {
        LOG(FATAL) << "Fail to init SocketMap";
        exit(1);
    }
    g_socket_map.store(socket_map, butil::memory_order_release);
}

SocketMap* get_client_side_socket_map() {
    // The consume fence makes sure that we see a NULL or a fully initialized
    // SocketMap.
    return g_socket_map.load(butil::memory_order_consume);
}
SocketMap* get_or_new_client_side_socket_map() {
    get_or_new_client_side_messenger();
    pthread_once(&g_socket_map_init, CreateClientSideSocketMap);
    return g_socket_map.load(butil::memory_order_consume);
}

int SocketMapInsert(const SocketMapKey& key, SocketId* id,
                    SocketOptions& opt) {
    return get_or_new_client_side_socket_map()->Insert(key, id, opt);
}

int SocketMapFind(const SocketMapKey& key, SocketId* id) {
    SocketMap* m = get_client_side_socket_map();
    if (m) {
        return m->Find(key, id);
    }
    return -1;
}

void SocketMapRemove(const SocketMapKey& key) {
    SocketMap* m = get_client_side_socket_map();
    if (m) {
        // TODO: We don't have expected_id to pass right now since the callsite
        // at NamingServiceThread is hard to be fixed right now. As long as
        // FLAGS_health_check_interval is limited to positive, SocketMapInsert
        // never replaces the sockets, skipping comparison is still right.
        m->Remove(key, INVALID_SOCKET_ID);
    }
}

void SocketMapList(std::vector<SocketId>* ids) {
    SocketMap* m = get_client_side_socket_map();
    if (m) {
        m->List(ids);
    } else {
        ids->clear();
    }
}

// ========== SocketMap impl. ============

SocketMapOptions::SocketMapOptions()
    : socket_creator(NULL)
    , suggested_map_size(1024)
    , idle_timeout_second_dynamic(NULL)
    , idle_timeout_second(0)
    , defer_close_second_dynamic(NULL)
    , defer_close_second(0)
    , defer_close_respect_idle_dynamic(NULL) {
}

SocketMap::SocketMap()
    : _exposed_in_bvar(false)
    , _this_map_bvar(NULL)
    , _has_close_idle_thread(false) {
}

SocketMap::~SocketMap() {
    RPC_VLOG << "Destroying SocketMap=" << this;
    if (_has_close_idle_thread) {
        bthread_stop(_close_idle_thread);
        bthread_join(_close_idle_thread, NULL);
    }
    if (!_map.empty()) {
        std::ostringstream err;
        int nleft = 0;
        for (Map::iterator it = _map.begin(); it != _map.end(); ++it) {
            SingleConnection* sc = &it->second;
            if ((!sc->socket->Failed() ||
                 sc->socket->HCEnabled()) &&
                sc->ref_count != 0) {
                ++nleft;
                if (nleft == 0) {
                    err << "Left in SocketMap(" << this << "):";
                }
                err << ' ' << *sc->socket;
            }
        }
        if (nleft) {
            LOG(ERROR) << err.str();
        }
    }

    delete _this_map_bvar;
    _this_map_bvar = NULL;

    delete _options.socket_creator;
    _options.socket_creator = NULL;
}

int SocketMap::Init(const SocketMapOptions& options) {
    if (_options.socket_creator != NULL) {
        LOG(ERROR) << "Already initialized";
        return -1;
    }
    _options = options;
    if (_options.socket_creator == NULL) {
        LOG(ERROR) << "SocketOptions.socket_creator must be set";
        return -1;
    }
    if (_map.init(_options.suggested_map_size, 70) != 0) {
        LOG(ERROR) << "Fail to init _map";
        return -1;
    }
    if (_options.idle_timeout_second_dynamic != NULL ||
        _options.idle_timeout_second > 0) {
        bthread_attr_t attr = BTHREAD_ATTR_NORMAL;
        bthread_attr_set_name(&attr, "RunWatchConnections");
        if (bthread_start_background(&_close_idle_thread, &attr,
                                     RunWatchConnections, this) != 0) {
            LOG(FATAL) << "Fail to start bthread";
            return -1;
        }
        _has_close_idle_thread = true;
    }
    return 0;
}

void SocketMap::Print(std::ostream& os) {
    // TODO: Elaborate.
    size_t count = 0;
    {
        std::unique_lock<butil::Mutex> mu(_mutex);
        count = _map.size();
    }
    os << "count=" << count;
}

void SocketMap::PrintSocketMap(std::ostream& os, void* arg) {
    static_cast<SocketMap*>(arg)->Print(os);
}

void SocketMap::ShowSocketMapInBvarIfNeed() {
    if (FLAGS_show_socketmap_in_vars &&
        !_exposed_in_bvar.exchange(true, butil::memory_order_release)) {
        char namebuf[32];
        int len = snprintf(namebuf, sizeof(namebuf), "rpc_socketmap_%p", this);
        _this_map_bvar = new bvar::PassiveStatus<std::string>(
            butil::StringPiece(namebuf, len), PrintSocketMap, this);
    }
}

int SocketMap::Insert(const SocketMapKey& key, SocketId* id,
                      SocketOptions& opt) {
    ShowSocketMapInBvarIfNeed();

    std::unique_lock<butil::Mutex> mu(_mutex);
    SingleConnection* sc = _map.seek(key);
    if (sc) {
        if (!sc->socket->Failed() || sc->socket->HCEnabled()) {
            ++sc->ref_count;
            *id = sc->socket->id();
            return 0;
        }
        // A socket w/o HC is failed (permanently), replace it.
        ReleaseReference(sc->socket);
        _map.erase(key); // in principle, we can override the entry in map w/o
        // removing and inserting it again. But this would make error branches
        // below have to remove the entry before returning, which is
        // error-prone. We prefer code maintainability here.
        sc = NULL;
    }
    SocketId tmp_id;
    opt.remote_side = key.peer.addr;
    if (_options.socket_creator->CreateSocket(opt, &tmp_id) != 0) {
        PLOG(FATAL) << "Fail to create socket to " << key.peer;
        return -1;
    }
    // Add a reference to make sure that sc->socket is always accessible. Not
    // use SocketUniquePtr which cannot put into containers before c++11.
    // The ref will be removed at entry's removal.
    SocketUniquePtr ptr;
    int rc = Socket::AddressFailedAsWell(tmp_id, &ptr);
    if (rc < 0) {
        LOG(FATAL) << "Fail to address SocketId=" << tmp_id;
        return -1;
    } else if (rc > 0 && !ptr->HCEnabled()) {
        LOG(FATAL) << "Failed socket is not HC-enabled";
        return -1;
    }
    // If health check is enabled, a health-checking-related reference
    // is hold in Socket::Create.
    // If health check is disabled, hold a reference in SocketMap.
    SingleConnection new_sc = { 1, ptr->HCEnabled() ? ptr.get() : ptr.release(), 0 };
    _map[key] = new_sc;
    *id = tmp_id;
    mu.unlock();
    return 0;
}

void SocketMap::Remove(const SocketMapKey& key, SocketId expected_id) {
    return RemoveInternal(key, expected_id, false);
}

void SocketMap::RemoveInternal(const SocketMapKey& key,
                               SocketId expected_id,
                               bool remove_orphan) {
    ShowSocketMapInBvarIfNeed();

    std::unique_lock<butil::Mutex> mu(_mutex);
    SingleConnection* sc = _map.seek(key);
    if (!sc) {
        return;
    }
    if (!remove_orphan &&
        (expected_id == INVALID_SOCKET_ID || expected_id == sc->socket->id())) {
        --sc->ref_count;
    }
    if (sc->ref_count == 0) {
        // NOTE: save the gflag which may be reloaded at any time
        const int defer_close_second = _options.defer_close_second_dynamic ?
            *_options.defer_close_second_dynamic
            : _options.defer_close_second;
        if (!remove_orphan && defer_close_second > 0) {
            const int64_t now_us = butil::cpuwide_time_us();
            // NOTE: save the gflag which may be reloaded at any time
            const bool defer_close_respect_idle = _options.defer_close_respect_idle_dynamic ?
            *_options.defer_close_respect_idle_dynamic : false;
            if (!defer_close_respect_idle) {
                // Start count down on this Socket.
                sc->no_ref_us = now_us;
                return;
            }
            const int64_t defer_us = (int64_t)defer_close_second * 1000000L;
            if (sc->no_ref_us <= sc->socket->last_active_time_us() + defer_us) {
                // When defer_close_respect_idle is enabled, a connection that has
                // already been idle for longer than defer_close_second is closed
                // immediately.
                sc->no_ref_us = now_us;
                return;
            }
        }
        Socket* const s = sc->socket;
        _map.erase(key);
        mu.unlock();
        s->ReleaseAdditionalReference(); // release extra ref
        ReleaseReference(s);
    }
}

void SocketMap::ReleaseReference(Socket* s) {
    if (s->HCEnabled()) {
        s->ReleaseHCRelatedReference();
    } else {
        // Release the extra ref hold in SocketMap::Insert.
        SocketUniquePtr ptr(s);
    }
}

int SocketMap::Find(const SocketMapKey& key, SocketId* id) {
    BAIDU_SCOPED_LOCK(_mutex);
    SingleConnection* sc = _map.seek(key);
    if (sc) {
        *id = sc->socket->id();
        return 0;
    }
    return -1;
}

void SocketMap::List(std::vector<SocketId>* ids) {
    ids->clear();
    BAIDU_SCOPED_LOCK(_mutex);
    for (Map::iterator it = _map.begin(); it != _map.end(); ++it) {
        ids->push_back(it->second.socket->id());
    }
}

void SocketMap::List(std::vector<butil::EndPoint>* pts) {
    pts->clear();
    BAIDU_SCOPED_LOCK(_mutex);
    for (Map::iterator it = _map.begin(); it != _map.end(); ++it) {
        pts->push_back(it->second.socket->remote_side());
    }
}

void SocketMap::ListOrphans(int64_t defer_us, std::vector<SocketMapKey>* out) {
    out->clear();
    const int64_t now = butil::cpuwide_time_us();
    BAIDU_SCOPED_LOCK(_mutex);
    for (Map::iterator it = _map.begin(); it != _map.end(); ++it) {
        SingleConnection& sc = it->second;
        if (sc.ref_count == 0 && now - sc.no_ref_us >= defer_us) {
            out->push_back(it->first);
        }
    }
}

void* SocketMap::RunWatchConnections(void* arg) {
    static_cast<SocketMap*>(arg)->WatchConnections();
    return NULL;
}

void SocketMap::WatchConnections() {
    std::vector<SocketId> main_sockets;
    std::vector<SocketId> pooled_sockets;
    std::vector<SocketMapKey> orphan_sockets;
    const uint64_t CHECK_INTERVAL_US = 1000000UL;
    while (bthread_usleep(CHECK_INTERVAL_US) == 0) {
        // NOTE: save the gflag which may be reloaded at any time.
        const int idle_seconds = _options.idle_timeout_second_dynamic ?
            *_options.idle_timeout_second_dynamic
            : _options.idle_timeout_second;
        if (idle_seconds > 0) {
            // Check idle pooled connections
            List(&main_sockets);
            for (auto main_socket : main_sockets) {
                SocketUniquePtr s;
                if (Socket::Address(main_socket, &s) == 0) {
                    s->ListPooledSockets(&pooled_sockets);
                    for (size_t i = FLAGS_reserve_one_idle_socket ? 1 : 0;
                         i < pooled_sockets.size(); ++i) {
                        SocketUniquePtr s2;
                        if (Socket::Address(pooled_sockets[i], &s2) == 0) {
                            s2->ReleaseReferenceIfIdle(idle_seconds);
                        }
                    }
                }
            }
        }

        // Check connections without Channel. This works when `defer_seconds'
        // <= 0, in which case orphan connections will be closed immediately
        // NOTE: save the gflag which may be reloaded at any time
        const int defer_seconds = _options.defer_close_second_dynamic ?
            *_options.defer_close_second_dynamic :
            _options.defer_close_second;
        ListOrphans(defer_seconds * 1000000L, &orphan_sockets);
        for (size_t i = 0; i < orphan_sockets.size(); ++i) {
            RemoveInternal(orphan_sockets[i], INVALID_SOCKET_ID, true);
        }
    }
}

} // namespace brpc
