example: Add separate demo for slot/slot chain SPI (#2085)

sentinel-demo/pom.xml

@@ -22,7 +22,8 @@
         <module>sentinel-demo-apollo-datasource</module>
         <module>sentinel-demo-annotation-spring-aop</module>
         <module>sentinel-demo-parameter-flow-control</module>
-        <module>sentinel-demo-slot-chain-spi</module>
+        <module>sentinel-demo-slot-spi</module>
+        <module>sentinel-demo-slotchain-spi</module>
         <module>sentinel-demo-cluster</module>
         <module>sentinel-demo-command-handler</module>
         <module>sentinel-demo-spring-webflux</module>

sentinel-demo/sentinel-demo-slot-chain-spi/src/main/java/com/alibaba/csp/sentinel/demo/slot/DemoSlotChainBuilder.java

@@ -1,30 +0,0 @@
-/*
- * 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.slot;
-
-import com.alibaba.csp.sentinel.slotchain.ProcessorSlotChain;
-import com.alibaba.csp.sentinel.slotchain.SlotChainBuilder;
-import com.alibaba.csp.sentinel.slots.DefaultSlotChainBuilder;
-
-/**
- * @author Eric Zhao
- *
- * @deprecated since 1.7.2, we can use @SpiOrder(-3500) to adjust the order of {@link DemoSlot},
- * this class is reserved for compatibility with older versions.
- */
-@Deprecated
-public class DemoSlotChainBuilder extends DefaultSlotChainBuilder {
-}

sentinel-demo/sentinel-demo-slot-chain-spi/src/main/resources/META-INF/services/com.alibaba.csp.sentinel.slotchain.ProcessorSlot

@@ -1,2 +0,0 @@
-# Custom slot processor
-com.alibaba.csp.sentinel.demo.slot.DemoSlot

sentinel-demo/sentinel-demo-slot-spi/pom.xml

@@ -9,6 +9,5 @@
     </parent>
     <modelVersion>4.0.0</modelVersion>
 
-    <artifactId>sentinel-demo-slot-chain-spi</artifactId>
+    <artifactId>sentinel-demo-slot-spi</artifactId>
-
 </project>

sentinel-demo/sentinel-demo-slot-spi/src/main/java/com/alibaba/csp/sentinel/demo/slot/DemoApplication.java

@@ -20,13 +20,15 @@ import com.alibaba.csp.sentinel.SphU;
 import com.alibaba.csp.sentinel.slots.block.BlockException;
 
 /**
+ * Demo for adding custom slot.
+ * @see {@link DemoSlot}.
+ *
  * @author Eric Zhao
+ * @author cdfive
  */
-public class SlotChainBuilderSpiDemo {
+public class DemoApplication {
 
     public static void main(String[] args) {
-        // You will see this in record.log, indicating that the custom slot chain builder is activated:
-        // [SlotChainProvider] Global slot chain builder resolved: com.alibaba.csp.sentinel.demo.slot.DemoSlotChainBuilder
         Entry entry = null;
         try {
             entry = SphU.entry("abc");

sentinel-demo/sentinel-demo-slot-spi/src/main/java/com/alibaba/csp/sentinel/demo/slot/DemoSlot.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 1999-2018 Alibaba Group Holding Ltd.
+ * Copyright 1999-2021 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.
@@ -15,23 +15,32 @@
  */
 package com.alibaba.csp.sentinel.demo.slot;
 
+import com.alibaba.csp.sentinel.Constants;
 import com.alibaba.csp.sentinel.context.Context;
 import com.alibaba.csp.sentinel.node.DefaultNode;
 import com.alibaba.csp.sentinel.slotchain.AbstractLinkedProcessorSlot;
 import com.alibaba.csp.sentinel.slotchain.ResourceWrapper;
+import com.alibaba.csp.sentinel.slots.block.degrade.DegradeSlot;
+import com.alibaba.csp.sentinel.slots.block.flow.FlowSlot;
 import com.alibaba.csp.sentinel.spi.Spi;
 
 /**
- * An example slot that records current context and entry resource.
+ * A demo slot that records current context and entry resource.
+ *
+ * Note that the value of order attribute in `@Spi` is -1500, the smaller the value, the higher the order,
+ * so this slot will be executed after {@link FlowSlot}(order=-2000) and before {@link DegradeSlot}(order=-1000),
+ * refer to the constants for slot order definitions in {@link Constants}.
  *
  * @author Eric Zhao
+ * @author cdfive
  */
-@Spi(order = -3500)
+@Spi(order = -1500)
 public class DemoSlot extends AbstractLinkedProcessorSlot<DefaultNode> {
 
     @Override
     public void entry(Context context, ResourceWrapper resourceWrapper, DefaultNode node, int count, boolean prioritized, Object... args)
             throws Throwable {
+        System.out.println("------Entering for entry on DemoSlot------");
         System.out.println("Current context: " + context.getName());
         System.out.println("Current entry resource: " + context.getCurEntry().getResourceWrapper().getName());
 
@@ -40,7 +49,9 @@ public class DemoSlot extends AbstractLinkedProcessorSlot<DefaultNode> {
 
     @Override
     public void exit(Context context, ResourceWrapper resourceWrapper, int count, Object... args) {
-        System.out.println("Exiting for entry on DemoSlot: " + context.getCurEntry().getResourceWrapper().getName());
+        System.out.println("------Exiting for entry on DemoSlot------");
+        System.out.println("Current context: " + context.getName());
+        System.out.println("Current entry resource: " + context.getCurEntry().getResourceWrapper().getName());
 
         fireExit(context, resourceWrapper, count, args);
     }

sentinel-demo/sentinel-demo-slot-spi/src/main/resources/META-INF/services/com.alibaba.csp.sentinel.slotchain.ProcessorSlot

@@ -0,0 +1,2 @@
+# Custom ProcessorSlot
+com.alibaba.csp.sentinel.demo.slot.DemoSlot

sentinel-demo/sentinel-demo-slotchain-spi/pom.xml

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <parent>
+        <artifactId>sentinel-demo</artifactId>
+        <groupId>com.alibaba.csp</groupId>
+        <version>1.8.2-SNAPSHOT</version>
+    </parent>
+    <modelVersion>4.0.0</modelVersion>
+
+    <artifactId>sentinel-demo-slotchain-spi</artifactId>
+</project>

sentinel-demo/sentinel-demo-slotchain-spi/src/main/java/com/alibaba/csp/sentinel/demo/slotchain/DemoDegradeRuleApplication.java

@@ -0,0 +1,78 @@
+/*
+ * Copyright 1999-2021 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.slotchain;
+
+import com.alibaba.csp.sentinel.Entry;
+import com.alibaba.csp.sentinel.SphU;
+import com.alibaba.csp.sentinel.slots.block.BlockException;
+import com.alibaba.csp.sentinel.slots.block.degrade.DegradeRule;
+import com.alibaba.csp.sentinel.slots.block.degrade.DegradeRuleManager;
+import com.alibaba.csp.sentinel.slots.block.degrade.circuitbreaker.CircuitBreakerStrategy;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.ThreadLocalRandom;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * Demo for degrade rule using custom SlotChainBuilder {@link DemoSlotChainBuilder}.
+ *
+ * You will see this in sentinel-record.log, indicating that the custom slot chain builder is activated:
+ * [SlotChainProvider] Global slot chain builder resolved: com.alibaba.csp.sentinel.demo.slotchain.DemoSlotChainBuilder
+ *
+ * @author cdfive
+ */
+public class DemoDegradeRuleApplication {
+
+    private static final String RESOURCE_KEY = "abc";
+
+    public static void main(String[] args) throws Exception {
+        initDegradeRule();
+
+        for (int i = 1; i <= 100; i++) {
+            Entry entry = null;
+            try {
+                entry = SphU.entry(RESOURCE_KEY);
+                TimeUnit.MILLISECONDS.sleep(ThreadLocalRandom.current().nextInt(10, 100));
+                System.out.println(i + "=>" + " passed");
+            } catch (BlockException ex) {
+                System.out.println(i + "=>" + " blocked by " + ex.getClass().getSimpleName());
+            } finally {
+                if (entry != null) {
+                    entry.exit();
+                }
+            }
+        }
+    }
+
+    private static void initDegradeRule() {
+        List<DegradeRule> rules = new ArrayList<>();
+        DegradeRule rule = new DegradeRule(RESOURCE_KEY)
+                .setGrade(CircuitBreakerStrategy.SLOW_REQUEST_RATIO.getType())
+                // Max allowed response time
+                .setCount(20)
+                // Retry timeout (in second)
+                .setTimeWindow(10)
+                // Circuit breaker opens when slow request ratio > 20%
+                .setSlowRatioThreshold(0.2)
+                .setMinRequestAmount(10)
+                .setStatIntervalMs(20000);
+        rules.add(rule);
+
+        DegradeRuleManager.loadRules(rules);
+        System.out.println("Degrade rule loaded: " + rules);
+    }
+}

sentinel-demo/sentinel-demo-slotchain-spi/src/main/java/com/alibaba/csp/sentinel/demo/slotchain/DemoFlowRuleApplication.java

@@ -0,0 +1,76 @@
+/*
+ * Copyright 1999-2021 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.slotchain;
+
+import com.alibaba.csp.sentinel.Entry;
+import com.alibaba.csp.sentinel.SphU;
+import com.alibaba.csp.sentinel.slots.block.BlockException;
+import com.alibaba.csp.sentinel.slots.block.RuleConstant;
+import com.alibaba.csp.sentinel.slots.block.degrade.DegradeRule;
+import com.alibaba.csp.sentinel.slots.block.degrade.DegradeRuleManager;
+import com.alibaba.csp.sentinel.slots.block.degrade.circuitbreaker.CircuitBreakerStrategy;
+import com.alibaba.csp.sentinel.slots.block.flow.FlowRule;
+import com.alibaba.csp.sentinel.slots.block.flow.FlowRuleManager;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.ThreadLocalRandom;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * Demo for flow rule using custom SlotChainBuilder {@link DemoSlotChainBuilder}.
+ *
+ * You will see this in sentinel-record.log, indicating that the custom slot chain builder is activated:
+ * [SlotChainProvider] Global slot chain builder resolved: com.alibaba.csp.sentinel.demo.slotchain.DemoSlotChainBuilder
+ *
+ * @author cdfive
+ */
+public class DemoFlowRuleApplication {
+
+    private static final String RESOURCE_KEY = "abc";
+
+    public static void main(String[] args) throws Exception {
+        initFlowQpsRule();
+
+        for (int i = 1; i <= 100; i++) {
+            Entry entry = null;
+            try {
+                entry = SphU.entry(RESOURCE_KEY);
+                TimeUnit.MILLISECONDS.sleep(ThreadLocalRandom.current().nextInt(10, 100));
+                System.out.println(i + "=>" + " passed");
+            } catch (BlockException ex) {
+                System.out.println(i + "=>" + " blocked by " + ex.getClass().getSimpleName());
+            } finally {
+                if (entry != null) {
+                    entry.exit();
+                }
+            }
+        }
+    }
+
+    private static void initFlowQpsRule() {
+        List<FlowRule> rules = new ArrayList<FlowRule>();
+        FlowRule rule1 = new FlowRule();
+        rule1.setResource(RESOURCE_KEY);
+        // set limit qps to 5
+        rule1.setCount(5);
+        rule1.setGrade(RuleConstant.FLOW_GRADE_QPS);
+        rule1.setLimitApp("default");
+        rules.add(rule1);
+        FlowRuleManager.loadRules(rules);
+        System.out.println("Flow rule loaded: " + rules);
+    }
+}

sentinel-demo/sentinel-demo-slotchain-spi/src/main/java/com/alibaba/csp/sentinel/demo/slotchain/DemoSlotChainBuilder.java

@@ -0,0 +1,99 @@
+/*
+ * Copyright 1999-2021 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.slotchain;
+
+import com.alibaba.csp.sentinel.Constants;
+import com.alibaba.csp.sentinel.log.RecordLog;
+import com.alibaba.csp.sentinel.slotchain.*;
+import com.alibaba.csp.sentinel.slots.DefaultSlotChainBuilder;
+import com.alibaba.csp.sentinel.slots.block.degrade.DegradeSlot;
+import com.alibaba.csp.sentinel.spi.Spi;
+import com.alibaba.csp.sentinel.spi.SpiLoader;
+
+import java.util.List;
+
+/**
+ * A demo {@link SlotChainBuilder} for build custom slot chain.
+ * Two ways to build slot chain are demonstrated.
+ *
+ * Pay attention to that `ProcessorSlotChain` is not a SPI, but the `SlotChainBuilder`.
+ *
+ * Most of the time, we don't need to customize `SlotChainBuilder`,
+ * maybe customize `ProcessorSlot` is enough, refer to `sentinel-demo-slot-spi` module.
+ *
+ * Note that the sentinel's default slots and the order of them are very important, be careful when customizing,
+ * refer to the constants for slot order definitions in {@link Constants}.
+ * You may also refer to {@link DefaultSlotChainBuilder}.
+ *
+ * @author cdfive
+ */
+@Spi
+public class DemoSlotChainBuilder implements SlotChainBuilder {
+
+    @Override
+    public ProcessorSlotChain build() {
+        ProcessorSlotChain chain = new DefaultProcessorSlotChain();
+
+        List<ProcessorSlot> sortedSlotList = SpiLoader.of(ProcessorSlot.class).loadInstanceListSorted();
+        // Filter out `DegradeSlot`
+        // Test for `DemoDegradeRuleApplication`, the demo will not be blocked by `DegradeException`
+        sortedSlotList.removeIf(o -> DegradeSlot.class.equals(o.getClass()));
+        for (ProcessorSlot slot : sortedSlotList) {
+            if (!(slot instanceof AbstractLinkedProcessorSlot)) {
+                RecordLog.warn("The ProcessorSlot(" + slot.getClass().getCanonicalName() + ") is not an instance of AbstractLinkedProcessorSlot, can't be added into ProcessorSlotChain");
+                continue;
+            }
+
+            chain.addLast((AbstractLinkedProcessorSlot<?>) slot);
+        }
+
+        return chain;
+    }
+
+    /**
+     * Another way to build the slot chain, add slot one by one with `SpiLoader#loadInstance`.
+     * Note that the sentinel's default slots and the order of them are very important, be careful when customizing,
+     * refer to the constants for slot order definitions in {@link com.alibaba.csp.sentinel.Constants}.
+     */
+    /*
+    @Override
+    public ProcessorSlotChain build() {
+        ProcessorSlotChain chain = new DefaultProcessorSlotChain();
+
+        // Create a `SpiLoader` instance
+        SpiLoader<ProcessorSlot> spiLoader = SpiLoader.of(ProcessorSlot.class);
+
+        // Add `NodeSelectorSlot`, load by class
+        chain.addLast((AbstractLinkedProcessorSlot<?>) spiLoader.loadInstance(NodeSelectorSlot.class));
+
+        // Add `ClusterBuilderSlot`, load by aliasname(default is classname)
+        chain.addLast((AbstractLinkedProcessorSlot<?>) spiLoader.loadInstance("com.alibaba.csp.sentinel.slots.clusterbuilder.ClusterBuilderSlot"));
+
+        // Add `StatisticSlot`
+        chain.addLast((AbstractLinkedProcessorSlot<?>) spiLoader.loadInstance(StatisticSlot.class));
+
+        // Add `FlowSlot`
+        chain.addLast((AbstractLinkedProcessorSlot<?>) spiLoader.loadInstance(FlowSlot.class));
+
+        // Add `DegradeSlot`
+        // Test for `DemoDegradeRuleApplication`
+        // If we don't add `DegradeSlot`, the demo will not be blocked by `DegradeException`
+        // If it's added, we can see the expected DegradeException
+//        chain.addLast((AbstractLinkedProcessorSlot<?>) spiLoader.loadInstance(DegradeSlot.class));
+        return chain;
+    }
+    */
+}

sentinel-demo/sentinel-demo-slotchain-spi/src/main/resources/META-INF/services/com.alibaba.csp.sentinel.slotchain.SlotChainBuilder

@@ -0,0 +1,2 @@
+# Custom SlotChainBuilder to build slot chain
+com.alibaba.csp.sentinel.demo.slotchain.DemoSlotChainBuilder