liubao68 commented on a change in pull request #543: [SCB-324] Fault-Injection 
handler implementation
URL: 
https://github.com/apache/incubator-servicecomb-java-chassis/pull/543#discussion_r165898966
 
 

 ##########
 File path: 
handlers/handler-fault-injection/src/main/java/org/apache/servicecomb/faultinjection/FaultInjectionHandler.java
 ##########
 @@ -0,0 +1,216 @@
+/*
+ * 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.
+ */
+
+package org.apache.servicecomb.faultinjection;
+
+import java.util.Map;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.atomic.AtomicLong;
+
+import org.apache.servicecomb.core.Handler;
+import org.apache.servicecomb.core.Invocation;
+import org.apache.servicecomb.swagger.invocation.AsyncResponse;
+import org.apache.servicecomb.swagger.invocation.context.HttpStatus;
+import org.apache.servicecomb.swagger.invocation.exception.CommonExceptionData;
+import org.apache.servicecomb.swagger.invocation.exception.InvocationException;
+import static org.apache.servicecomb.faultinjection.FaultInjectionConst.*;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Fault injection handler which injects the delay/abort for requests based on
+ * the percentage configured in service file.
+ *
+ */
+public class FaultInjectionHandler implements Handler {
+  private static final Logger LOGGER = 
LoggerFactory.getLogger(FaultInjectionHandler.class);
+
+  @Override
+  public void handle(Invocation invocation, AsyncResponse asyncResp) throws 
Exception {
+    // prepare the key and lookup for request count.
+    String key = invocation.getTransport().getName() + 
invocation.getMicroserviceQualifiedName();
+
+    AtomicLong reqCount = FaultInjectionUtil.getOperMetTotalReq(key);
+    long reqCountCurrent = reqCount.get();
+    // increment the request count here after checking the delay/abort 
condition.
+    reqCount.incrementAndGet();
+
+    // get the config values related to delay percentage.
+    int delayPercent = getFaultInjectionConfig(invocation,
+        "delay.percent",
+        FAULT_INJECTION_DELAY_PERCENTAGE_DEFAULT);
+
+    // check fault delay condition.
+    boolean isDelay = checkFaultInjectionDelayAndAbort(reqCountCurrent, 
delayPercent);
+    if (isDelay) {
+      LOGGER.info("delay is added for the request by fault inject handler");
+      long delay = getFaultInjectionConfig(invocation,
+          "delay.fixedDelay",
+          FAULT_INJECTION_DELAY_DEFAULT);
+
+      Thread.sleep(delay);
+    }
+
+    // get the config values related to delay.
+    int abortPercent = getFaultInjectionConfig(invocation,
+        "abort.percent",
+        FAULT_INJECTION_ABORT_PERCENTAGE_DEFAULT);
+
+    // check fault delay condition.
+    boolean isAbort = checkFaultInjectionDelayAndAbort(reqCountCurrent, 
abortPercent);
+    if (isAbort) {
+      // get the config values related to delay percentage.
+      int errorCode = getFaultInjectionConfig(invocation,
+          "abort.httpStatus",
+          FAULT_INJECTION_ABORT_ERROR_MSG_DEFAULT);
+      // if request need to be abort then return failure with given error code
+      CommonExceptionData errorData = new CommonExceptionData("aborted by 
fault inject");
+      asyncResp.consumerFail(
+          new InvocationException(new HttpStatus(errorCode, "aborted by fault 
inject"), errorData));
+      return;
+    }
+
+    // if no delay and no abort then continue to next handler.
+    invocation.next(asyncResp);
+  }
+
+  /**
+   * It will check the delay/abort condition based on request count and 
percentage
+   * received.
+   * 
+   * @param reqCount
+   * @param percentage
+   * @param key
+   * @return true/false
+   */
+  private boolean checkFaultInjectionDelayAndAbort(long reqCount, int 
percentage) {
+    /*
+     * Example: delay/abort percentage configured is 10% and Get the 
count(suppose
+     * if it is 10th request) from map and calculate resultNew(10th request) 
and
+     * requestOld(9th request). Like this for every request it will calculate
+     * current request count and previous count. if both not matched need to 
add
+     * delay/abort otherwise no need to add.
+     */
+
+    // calculate the value with current request count.
+    long resultNew = (reqCount * percentage) / 100;
+
+    // calculate the value with previous count value.
+    long resultOld = ((reqCount - 1) * percentage) / 100;
+
+    // if both are not matching then delay/abort should be added.
+    if (resultNew != resultOld) {
+      return true;
+    }
+    return false;
+  }
+
+  /**
+   * Handles the reading fault injection configuration.
+   * 
+   * @param invocation
+   *            invocation of request
+   * @param key
+   *            configuration key
+   * @return configuration value
+   */
+  private int getFaultInjectionConfig(Invocation invocation, String key, int 
defaultValue) {
+    int value = 0;
+    String config;
+    FaultInjectionConfig faultCfg = new FaultInjectionConfig();
+
+    //first need to check in config center map which has high priority.
+    Map<String, AtomicInteger> cfgMap = 
FaultInjectionUtil.getConfigCenterMap();
+
+    // get the config base on priority. 
operationName-->schema-->service-->global
+    String operationName = invocation.getOperationName();
+    if (operationName != null) {
+      if 
(invocation.getTransport().getName().equals(FAULTINJECTION_HIGHWAY_TRANSPORT)) {
+        config = CONSUMER_FAULTINJECTION_OPERATION + operationName + "."
+            + CONSUMER_FAULTINJECTION_HIGHWAY + key;
+      } else {
+        config = CONSUMER_FAULTINJECTION_OPERATION + operationName + "."
+            + CONSUMER_FAULTINJECTION_REST + key;
+      }
+
+      if (cfgMap.containsKey(config)) {
+        return cfgMap.get(config).get();
+      }
+
+      value = faultCfg.getConfigVal(config, FAULT_INJECTION_CFG_NULL);
 
 Review comment:
   faultCfg will always read the latest value. So I think it's not necessary to 
use FaultInjectionUtil to cache the values.

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