content: /*
   * Copyright 1999-2018 Alibaba Group Holding Ltd.
   *
   * 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.
   */
  package com.alibaba.csp.sentinel.cluster.flow;
  
  import com.alibaba.csp.sentinel.cluster.TokenResultStatus;
  import com.alibaba.csp.sentinel.cluster.TokenResult;
  import com.alibaba.csp.sentinel.cluster.flow.rule.ClusterFlowRuleManager;
  import com.alibaba.csp.sentinel.cluster.flow.statistic.ClusterMetricStatistics;
  import com.alibaba.csp.sentinel.cluster.flow.statistic.limit.GlobalRequestLimiter;
  import com.alibaba.csp.sentinel.cluster.server.config.ClusterServerConfigManager;
  import com.alibaba.csp.sentinel.cluster.flow.statistic.data.ClusterFlowEvent;
  import com.alibaba.csp.sentinel.cluster.flow.statistic.metric.ClusterMetric;
  import com.alibaba.csp.sentinel.cluster.server.log.ClusterServerStatLogUtil;
  import com.alibaba.csp.sentinel.slots.block.ClusterRuleConstant;
  import com.alibaba.csp.sentinel.slots.block.flow.FlowRule;
  
  /**
   * Flow checker for cluster flow rules.
   *
   * @author Eric Zhao
   * @since 1.4.0
   */
  final class ClusterFlowChecker {
  
      private static double calcGlobalThreshold(FlowRule rule) {
          double count = rule.getCount();
          switch (rule.getClusterConfig().getThresholdType()) {
              case ClusterRuleConstant.FLOW_THRESHOLD_GLOBAL:
                  return count;
              case ClusterRuleConstant.FLOW_THRESHOLD_AVG_LOCAL:
              default:
                  int connectedCount = ClusterFlowRuleManager.getConnectedCount(rule.getClusterConfig().getFlowId());
                  return count * connectedCount;
          }
      }
  
      static boolean allowProceed(long flowId) {
          String namespace = ClusterFlowRuleManager.getNamespace(flowId);
          return GlobalRequestLimiter.tryPass(namespace);
      }
  
      static TokenResult acquireClusterToken(/*@Valid*/ FlowRule rule, int acquireCount, boolean prioritized) {
          Long id = rule.getClusterConfig().getFlowId();
  
          if (!allowProceed(id)) {
              return new TokenResult(TokenResultStatus.TOO_MANY_REQUEST);
          }
  
          ClusterMetric metric = ClusterMetricStatistics.getMetric(id);
          if (metric == null) {
              return new TokenResult(TokenResultStatus.FAIL);
          }
  
          double latestQps = metric.getAvg(ClusterFlowEvent.PASS);
          double globalThreshold = calcGlobalThreshold(rule) * ClusterServerConfigManager.getExceedCount();
          double nextRemaining = globalThreshold - latestQps - acquireCount;
  
          if (nextRemaining >= 0) {
              // TODO: checking logic and metric operation should be separated.
              metric.add(ClusterFlowEvent.PASS, acquireCount);
              metric.add(ClusterFlowEvent.PASS_REQUEST, 1);
              if (prioritized) {
                  // Add prioritized pass.
                  metric.add(ClusterFlowEvent.OCCUPIED_PASS, acquireCount);
              }
              // Remaining count is cut down to a smaller integer.
              return new TokenResult(TokenResultStatus.OK)
                  .setRemaining((int) nextRemaining)
                  .setWaitInMs(0);
          } else {
              if (prioritized) {
                  // Try to occupy incoming buckets.
                  double occupyAvg = metric.getAvg(ClusterFlowEvent.WAITING);
                  if (occupyAvg <= ClusterServerConfigManager.getMaxOccupyRatio() * globalThreshold) {
                      int waitInMs = metric.tryOccupyNext(ClusterFlowEvent.PASS, acquireCount, globalThreshold);
                      // waitInMs > 0 indicates pre-occupy incoming buckets successfully.
                      if (waitInMs > 0) {
                          ClusterServerStatLogUtil.log("flow|waiting|" + id);
                          return new TokenResult(TokenResultStatus.SHOULD_WAIT)
                              .setRemaining(0)
                              .setWaitInMs(waitInMs);
                      }
                      // Or else occupy failed, should be blocked.
                  }
              }
              // Blocked.
              metric.add(ClusterFlowEvent.BLOCK, acquireCount);
              metric.add(ClusterFlowEvent.BLOCK_REQUEST, 1);
              ClusterServerStatLogUtil.log("flow|block|" + id, acquireCount);
              ClusterServerStatLogUtil.log("flow|block_request|" + id, 1);
              if (prioritized) {
                  // Add prioritized block.
                  metric.add(ClusterFlowEvent.OCCUPIED_BLOCK, acquireCount);
                  ClusterServerStatLogUtil.log("flow|occupied_block|" + id, 1);
              }
  
              return blockedResult();
          }
      }
  
      private static TokenResult blockedResult() {
          return new TokenResult(TokenResultStatus.BLOCKED)
              .setRemaining(0)
              .setWaitInMs(0);
      }
  
      private ClusterFlowChecker() {}
  }
  