Add some default factory methods

Author: bryce-anderson

servicetalk-loadbalancer-experimental/src/main/java/io/servicetalk/loadbalancer/CorePoolConnectionPoolStrategy.java

@@ -44,6 +44,9 @@
 final class CorePoolConnectionPoolStrategy<C extends LoadBalancedConnection>
         implements ConnectionPoolStrategy<C> {
 
+    private static final int DEFAULT_CORE_POOL_SIZE = 2;
+    private static final boolean DEFAULT_FORCE_CORE_POOL = false;
+
     private final int corePoolSize;
     private final boolean forceCorePool;
 
@@ -83,4 +86,18 @@ public C select(List<C> connections, Predicate<C> selector, @Nullable final Cont
         // So sad, we didn't find a healthy connection.
         return null;
     }
+
+    ConnectionPoolStrategyFactory<C> defaultFactory() {
+        return factory(DEFAULT_CORE_POOL_SIZE, DEFAULT_FORCE_CORE_POOL);
+    }
+
+    ConnectionPoolStrategyFactory<C> factory(int corePoolSize, boolean forceCorePool) {
+        ensureNonNegative(corePoolSize, "corePoolSize");
+        return new ConnectionPoolStrategyFactory<C>() {
+            @Override
+            public <T extends C> ConnectionPoolStrategy<T> buildStrategy() {
+                return new CorePoolConnectionPoolStrategy<>(corePoolSize, forceCorePool);
+            }
+        };
+    }
 }

servicetalk-loadbalancer-experimental/src/main/java/io/servicetalk/loadbalancer/P2CConnectionPoolStrategy.java

@@ -27,6 +27,7 @@
 import javax.annotation.Nullable;
 
 import static io.servicetalk.utils.internal.NumberUtils.ensureNonNegative;
+import static io.servicetalk.utils.internal.NumberUtils.ensurePositive;
 import static java.lang.Math.min;
 
 public class P2CConnectionPoolStrategy<C extends LoadBalancedConnection> implements ConnectionPoolStrategy<C> {
@@ -128,4 +129,16 @@ private C p2cPick(ThreadLocalRandom rnd, int randomSearchSpace, List<C> connecti
         // Neither connection was acceptable.
         return null;
     }
+
+    static <C extends LoadBalancedConnection> ConnectionPoolStrategyFactory<C> factory(
+            final int maxEffort, final int corePoolSize, final boolean forceCorePool) {
+        ensurePositive(maxEffort, " maxEffort");
+        ensureNonNegative(corePoolSize, "corePoolSize");
+        return new ConnectionPoolStrategyFactory<C>() {
+            @Override
+            public <T extends C> ConnectionPoolStrategy<T> buildStrategy() {
+                return new P2CConnectionPoolStrategy<T>(maxEffort, corePoolSize, forceCorePool);
+            }
+        };
+    }
 }