// 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 "brpc/reloadable_flags.h"

#include "brpc/load_balancer.h"

namespace brpc {

DEFINE_bool(show_lb_in_vars, false, "Describe LoadBalancers in vars");

DEFINE_int32(default_weight_of_wlb, 0, "Default weight value of Weighted LoadBalancer(wlb). "

             "wlb policy degradation is enabled when default_weight_of_wlb > 0 to avoid some "

             "problems when user is using wlb but forgot to set the weights of some of their "

             "downstream instances. Then these instances will be set default_weight_of_wlb as "

             "their weights. wlb policy degradation is not enabled by default.");

BRPC_VALIDATE_GFLAG(show_lb_in_vars, PassValidate);

// For assigning unique names for lb.

static butil::static_atomic<int> g_lb_counter = BUTIL_STATIC_ATOMIC_INIT(0);

void SharedLoadBalancer::DescribeLB(std::ostream& os, void* arg) {

    (static_cast<SharedLoadBalancer*>(arg))->Describe(os, DescribeOptions());

}

void SharedLoadBalancer::ExposeLB() {

    bool changed = false;

    _st_mutex.lock();

    if (!_exposed) {

        _exposed = true;

        changed = true;

    }

    _st_mutex.unlock();

    if (changed) {

        char name[32];

        snprintf(name, sizeof(name), "_load_balancer_%d", g_lb_counter.fetch_add(

                     1, butil::memory_order_relaxed));

        _st.expose(name);

    }

}

SharedLoadBalancer::SharedLoadBalancer()

    : _lb(NULL)

    , _weight_sum(0)

    , _exposed(false)

    , _st(DescribeLB, this) {

}

SharedLoadBalancer::~SharedLoadBalancer() {

    _st.hide();

    if (_lb) {

        _lb->Destroy();

        _lb = NULL;

    }

}

int SharedLoadBalancer::Init(const char* lb_protocol) {

    std::string lb_name;

    butil::StringPiece lb_params;

    if (!ParseParameters(lb_protocol, &lb_name, &lb_params)) {

        LOG(FATAL) << "Fail to parse this load balancer protocol '" << lb_protocol << '\'';

        return -1;

    }

    const LoadBalancer* lb = LoadBalancerExtension()->Find(lb_name.c_str());

    if (lb == NULL) {

        LOG(FATAL) << "Fail to find LoadBalancer by `" << lb_name << "'";

        return -1;

    }

    _lb = lb->New(lb_params);

    if (_lb == NULL) {

        LOG(FATAL) << "Fail to new LoadBalancer";

        return -1;

    }

    if (FLAGS_show_lb_in_vars && !_exposed) {

        ExposeLB();

    }

    return 0;

}

void SharedLoadBalancer::Describe(std::ostream& os,

                                  const DescribeOptions& options) {

    if (_lb == NULL) {

        os << "lb=NULL";

    } else {

        _lb->Describe(os, options);

    }

}

bool SharedLoadBalancer::ParseParameters(const butil::StringPiece& lb_protocol,

                                         std::string* lb_name,

                                         butil::StringPiece* lb_params) {

    lb_name->clear();

    lb_params->clear();

    if (lb_protocol.empty()) {

        return false;

    }

    const char separator = ':';

    size_t pos = lb_protocol.find(separator);

    if (pos == std::string::npos) {

        lb_name->append(lb_protocol.data(), lb_protocol.size());

    } else {

        lb_name->append(lb_protocol.data(), pos);

        if (pos < lb_protocol.size() - sizeof(separator)) {

            *lb_params = lb_protocol.substr(pos + sizeof(separator));

        }

    }

    return true;

}

} // namespace brpc