Add demo combining StructuredTaskScope and ScopeValue

Author: SvenWoltmann

README.md

@@ -32,6 +32,7 @@ java -cp target/classes --enable-preview eu.happycoders.structuredconcurrency/de
 java -cp target/classes --enable-preview eu.happycoders.structuredconcurrency/demo2_address/AddressVerification2_ShutdownOnSuccess
 java -cp target/classes --enable-preview eu.happycoders.structuredconcurrency/demo3_suppliers/SupplierDeliveryTimeCheck2_StructuredTaskScope
 java -cp target/classes --enable-preview eu.happycoders.structuredconcurrency/demo3_suppliers/SupplierDeliveryTimeCheck3_NestedStructuredTaskScope
+java -cp target/classes --enable-preview eu.happycoders.structuredconcurrency/demo3_suppliers/SupplierDeliveryTimeCheck4_NestedStructuredTaskScopeUsingScopedValue
 ```
 
 ## Java Downloads

src/main/java/eu/happycoders/structuredconcurrency/demo3_suppliers/SupplierDeliveryTimeCheck4_NestedStructuredTaskScopeUsingScopedValue.java

@@ -0,0 +1,71 @@
+package eu.happycoders.structuredconcurrency.demo3_suppliers;
+
+import static eu.happycoders.structuredconcurrency.util.SimpleLogger.log;
+
+import eu.happycoders.structuredconcurrency.demo3_suppliers.model.SupplierDeliveryTime;
+import eu.happycoders.structuredconcurrency.demo3_suppliers.service.SupplierDeliveryTimeServiceUsingScopedValue;
+import java.util.List;
+import java.util.concurrent.StructuredTaskScope;
+import java.util.concurrent.StructuredTaskScope.Subtask;
+import java.util.concurrent.StructuredTaskScope.Subtask.State;
+
+public class SupplierDeliveryTimeCheck4_NestedStructuredTaskScopeUsingScopedValue {
+
+  private static final boolean FAIL_ALL = false;
+
+  public static void main(String[] args) throws Exception {
+    SupplierDeliveryTimeCheck4_NestedStructuredTaskScopeUsingScopedValue supplierDeliveryTimeCheck =
+        new SupplierDeliveryTimeCheck4_NestedStructuredTaskScopeUsingScopedValue(
+            new SupplierDeliveryTimeServiceUsingScopedValue(FAIL_ALL));
+    List<SupplierDeliveryTime> responses =
+        supplierDeliveryTimeCheck.getSupplierDeliveryTimes(
+            List.of("B004V9OA84", "0201310090", "0134685997"),
+            List.of("A", "B", "C", "D", "E"),
+            "t0p-s3cr3t");
+    log("Responses: " + responses);
+  }
+
+  private final SupplierDeliveryTimeServiceUsingScopedValue service;
+
+  public SupplierDeliveryTimeCheck4_NestedStructuredTaskScopeUsingScopedValue(
+      SupplierDeliveryTimeServiceUsingScopedValue service) {
+    this.service = service;
+  }
+
+  public static final ScopedValue<String> API_KEY = ScopedValue.newInstance();
+
+  List<SupplierDeliveryTime> getSupplierDeliveryTimes(
+      List<String> productIds, List<String> supplierIds, String apiKey) throws Exception {
+    return ScopedValue.where(API_KEY, apiKey)
+        .call(() -> getSupplierDeliveryTimes(productIds, supplierIds));
+  }
+
+  List<SupplierDeliveryTime> getSupplierDeliveryTimes(
+      List<String> productIds, List<String> supplierIds) throws InterruptedException {
+    try (StructuredTaskScope<SupplierDeliveryTime> scope = new StructuredTaskScope<>()) {
+      List<Subtask<SupplierDeliveryTime>> subtasks =
+          productIds.stream()
+              .map(productId -> scope.fork(() -> getSupplierDeliveryTime(productId, supplierIds)))
+              .toList();
+
+      scope.join();
+
+      return subtasks.stream()
+          .filter(subtask -> subtask.state() == State.SUCCESS)
+          .map(Subtask::get)
+          .toList();
+    }
+  }
+
+  SupplierDeliveryTime getSupplierDeliveryTime(String productId, List<String> supplierIds)
+      throws SupplierDeliveryTimeCheckException, InterruptedException {
+    try (GetFastestDeliveryTimeScope scope = new GetFastestDeliveryTimeScope()) {
+      for (String supplierId : supplierIds) {
+        scope.fork(() -> service.getDeliveryTime(productId, supplierId));
+      }
+
+      scope.join();
+      return scope.result();
+    }
+  }
+}

src/main/java/eu/happycoders/structuredconcurrency/demo3_suppliers/service/SupplierDeliveryTimeServiceUsingScopedValue.java

@@ -0,0 +1,45 @@
+package eu.happycoders.structuredconcurrency.demo3_suppliers.service;
+
+import static eu.happycoders.structuredconcurrency.demo3_suppliers.SupplierDeliveryTimeCheck4_NestedStructuredTaskScopeUsingScopedValue.API_KEY;
+import static eu.happycoders.structuredconcurrency.util.SimpleLogger.log;
+
+import eu.happycoders.structuredconcurrency.demo3_suppliers.model.SupplierDeliveryTime;
+import java.util.concurrent.ThreadLocalRandom;
+
+public class SupplierDeliveryTimeServiceUsingScopedValue {
+
+  private final boolean failAll;
+
+  public SupplierDeliveryTimeServiceUsingScopedValue(boolean failAll) {
+    this.failAll = failAll;
+  }
+
+  public SupplierDeliveryTime getDeliveryTime(String productId, String supplier)
+      throws InterruptedException {
+    String apiKey = API_KEY.get();
+    log(
+        "Retrieving delivery time from supplier %s (using API key %s)..."
+            .formatted(supplier, apiKey));
+
+    try {
+      Thread.sleep(ThreadLocalRandom.current().nextLong(250, 1000));
+    } catch (InterruptedException e) {
+      log("Retrieving delivery time from supplier " + supplier + " interrupted");
+      throw e;
+    }
+
+    // 40% failure probability --> 2 out of 5 requests should fail
+    if (failAll || ThreadLocalRandom.current().nextDouble() < 0.4) {
+      log("Error retrieving delivery time from supplier " + supplier);
+      throw new RuntimeException("Error retrieving delivery time from supplier " + supplier);
+    }
+
+    int deliveryTimeHours = ThreadLocalRandom.current().nextInt(1, 7 * 24);
+
+    log(
+        "Finished retrieving delivery time from supplier %s: %d hours"
+            .formatted(supplier, deliveryTimeHours));
+
+    return new SupplierDeliveryTime(supplier, deliveryTimeHours);
+  }
+}