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.demo;
  
  import java.util.Arrays;
  import java.util.List;
  import java.util.concurrent.CompletableFuture;
  import java.util.concurrent.TimeUnit;
  import java.util.function.Consumer;
  
  import com.alibaba.csp.sentinel.AsyncEntry;
  import com.alibaba.csp.sentinel.Entry;
  import com.alibaba.csp.sentinel.SphU;
  import com.alibaba.csp.sentinel.context.ContextUtil;
  import com.alibaba.csp.sentinel.slots.block.BlockException;
  import com.alibaba.csp.sentinel.slots.block.RuleConstant;
  import com.alibaba.csp.sentinel.slots.block.flow.FlowRule;
  import com.alibaba.csp.sentinel.slots.block.flow.FlowRuleManager;
  
  /**
   * An example for asynchronous entry in Sentinel.
   *
   * @author Eric Zhao
   * @since 0.2.0
   */
  public class AsyncEntryDemo {
  
      private void invoke(String arg, Consumer<String> handler) {
          CompletableFuture.runAsync(() -> {
              try {
                  TimeUnit.SECONDS.sleep(3);
                  String resp = arg + ": " + System.currentTimeMillis();
                  handler.accept(resp);
              } catch (Exception ex) {
                  ex.printStackTrace();
              }
          });
      }
  
      private void anotherAsync() {
          try {
              final AsyncEntry entry = SphU.asyncEntry("test-another-async");
  
              CompletableFuture.runAsync(() -> {
                  ContextUtil.runOnContext(entry.getAsyncContext(), () -> {
                      try {
                          TimeUnit.SECONDS.sleep(2);
                          // Normal entry nested in asynchronous entry.
                          anotherSyncInAsync();
  
                          System.out.println("Async result: 666");
                      } catch (InterruptedException e) {
                          // Ignore.
                      } finally {
                          entry.exit();
                      }
                  });
              });
          } catch (BlockException ex) {
              ex.printStackTrace();
          }
      }
  
      private void fetchSync() {
          Entry entry = null;
          try {
              entry = SphU.entry("test-sync");
          } catch (BlockException ex) {
              ex.printStackTrace();
          } finally {
              if (entry != null) {
                  entry.exit();
              }
          }
      }
  
      private void fetchSyncInAsync() {
          Entry entry = null;
          try {
              entry = SphU.entry("test-sync-in-async");
          } catch (BlockException ex) {
              ex.printStackTrace();
          } finally {
              if (entry != null) {
                  entry.exit();
              }
          }
      }
  
      private void anotherSyncInAsync() {
          Entry entry = null;
          try {
              entry = SphU.entry("test-another-sync-in-async");
          } catch (BlockException ex) {
              ex.printStackTrace();
          } finally {
              if (entry != null) {
                  entry.exit();
              }
          }
      }
  
      private void directlyAsync() {
          try {
              final AsyncEntry entry = SphU.asyncEntry("test-async-not-nested");
  
              this.invoke("abc", result -> {
                  // If no nested entry later, we don't have to wrap in `ContextUtil.runOnContext()`.
                  try {
                      // Here to handle the async result (without other entry).
                  } finally {
                      // Exit the async entry.
                      entry.exit();
                  }
              });
          } catch (BlockException e) {
              // Request blocked, handle the exception.
              e.printStackTrace();
          }
      }
  
      private void doAsyncThenSync() {
          try {
              // First we call an asynchronous resource.
              final AsyncEntry entry = SphU.asyncEntry("test-async");
              this.invoke("abc", resp -> {
                  // The thread is different from original caller thread for async entry.
                  // So we need to wrap in the async context so that nested invocation entry
                  // can be linked to the parent asynchronous entry.
                  ContextUtil.runOnContext(entry.getAsyncContext(), () -> {
                      try {
                          // In the callback, we do another async invocation several times under the async context.
                          for (int i = 0; i < 7; i++) {
                              anotherAsync();
                          }
  
                          System.out.println(resp);
  
                          // Then we do a sync (normal) entry under current async context.
                          fetchSyncInAsync();
                      } finally {
                          // Exit the async entry.
                          entry.exit();
                      }
                  });
              });
              // Then we call a sync resource.
              fetchSync();
          } catch (BlockException ex) {
              // Request blocked, handle the exception.
              ex.printStackTrace();
          }
      }
  
      public static void main(String[] args) throws Exception {
          initFlowRule();
  
          AsyncEntryDemo service = new AsyncEntryDemo();
  
          // Expected invocation chain:
          //
          // EntranceNode: machine-root
          // -EntranceNode: async-context
          // --test-top
          // ---test-sync
          // ---test-async
          // ----test-another-async
          // -----test-another-sync-in-async
          // ----test-sync-in-async
          ContextUtil.enter("async-context", "originA");
          Entry entry = null;
          try {
              entry = SphU.entry("test-top");
              System.out.println("Do something...");
              service.doAsyncThenSync();
          } catch (BlockException ex) {
              // Request blocked, handle the exception.
              ex.printStackTrace();
          } finally {
              if (entry != null) {
                  entry.exit();
              }
              ContextUtil.exit();
          }
  
          TimeUnit.SECONDS.sleep(20);
      }
  
      private static void initFlowRule() {
          // Rule 1 won't take effect as the limitApp doesn't match.
          FlowRule rule1 = new FlowRule()
              .setResource("test-another-sync-in-async")
              .setLimitApp("originB")
              .as(FlowRule.class)
              .setCount(4)
              .setGrade(RuleConstant.FLOW_GRADE_QPS);
          // Rule 2 will take effect.
          FlowRule rule2 = new FlowRule()
              .setResource("test-another-async")
              .setLimitApp("default")
              .as(FlowRule.class)
              .setCount(5)
              .setGrade(RuleConstant.FLOW_GRADE_QPS);
          List<FlowRule> ruleList = Arrays.asList(rule1, rule2);
          FlowRuleManager.loadRules(ruleList);
      }
  }
  