add tests

xds/src/main/java/io/grpc/xds/RingHashOptions.java

@@ -50,9 +50,9 @@
 
 /**
  * Utility class that provides a way to configure ring hash size limits. This is applicable
- * for clients that use the ring hash load balancing policy. Note that ring
- * hash size limits involve a tradeoff between client memory consumption and accuracy of
- * backend weights used for load balancing. Also see https://github.com/grpc/proposal/pull/338.
+ * for clients that use the ring hash load balancing policy. Note that size limits involve
+ * a tradeoff between client memory consumption and accuracy of load balancing weight
+ * representations. Also see https://github.com/grpc/proposal/pull/338.
  */
 @ExperimentalApi("https://github.com/grpc/grpc-java/issues/9718")
 public final class RingHashOptions {
@@ -61,11 +61,27 @@ public final class RingHashOptions {
   static final long MAX_RING_SIZE_CAP = 8 * 1024 * 1024L;
 
   // Same as RingHashLoadBalancerProvider.DEFAULT_MAX_RING_SIZE
-  private static volatile long maxRingSizeCap = 4 * 1024L;
+  private static volatile long ringSizeCap = 4 * 1024L;
 
-  public static setMaxRingSizeCap(long maxRingSizeCap) {
-    maxRingSizeCap = Math.max(1, maxRingSizeCap);
-    maxRingSizeCap = Math.min(MAX_RING_SIZE_CAP, maxRingSizeCap);
-    RingHashOptions.maxRingSizeCap = maxRingSizeCap;
+  /**
+   * Set the global limit for min and max ring hash sizes. Note that
+   * this limit is clamped between 1 and 8M, and attempts to set
+   * the limit lower or higher than that range will be silently
+   * moved to the nearest number within that range. Defaults initially
+   * to 4K.
+   */
+  @ExperimentalApi("https://github.com/grpc/grpc-java/issues/9718")
+  public static void setRingSizeCap(long ringSizeCap) {
+    ringSizeCap = Math.max(1, ringSizeCap);
+    ringSizeCap = Math.min(MAX_RING_SIZE_CAP, ringSizeCap);
+    RingHashOptions.ringSizeCap = ringSizeCap;
+  }
+
+  /**
+   * Get the global limit for min and max ring hash sizes.
+   */
+  @ExperimentalApi("https://github.com/grpc/grpc-java/issues/9718")
+  public static long getRingSizeCap() {
+    return RingHashOptions.ringSizeCap;
   }
 }

xds/src/test/java/io/grpc/xds/RingHashLoadBalancerProviderTest.java

@@ -29,6 +29,7 @@
 import io.grpc.SynchronizationContext;
 import io.grpc.internal.JsonParser;
 import io.grpc.xds.RingHashLoadBalancer.RingHashConfig;
+import io.grpc.xds.RingHashOptions;
 import java.io.IOException;
 import java.lang.Thread.UncaughtExceptionHandler;
 import java.util.Locale;
@@ -129,8 +130,28 @@ public void parseLoadBalancingConfig_ringTooLargeUsesCap() throws IOException {
   }
 
   @Test
-  public void parseLoadBalancingConfig_ringMinAndMaxTooLargeUsesCap() throws IOException {
-    long ringSize = RingHashLoadBalancerProvider.MAX_RING_SIZE_CAP + 1;
+  public void parseLoadBalancingConfig_ringCapCanBeRaised() throws IOException {
+    long originalMaxRingSizeCap = RingHashOptions.getRingSizeCap();
+    RingHashOptions.setRingSizeCap(RingHashOptions.MAX_RING_SIZE_CAP);
+    long ringSize = RingHashOptions.MAX_RING_SIZE_CAP;
+    String lbConfig =
+        String.format(
+            Locale.US, "{\"minRingSize\" : %d, \"maxRingSize\" : %d}", ringSize, ringSize);
+    ConfigOrError configOrError =
+        provider.parseLoadBalancingPolicyConfig(parseJsonObject(lbConfig));
+    assertThat(configOrError.getConfig()).isNotNull();
+    RingHashConfig config = (RingHashConfig) configOrError.getConfig();
+    assertThat(config.minRingSize).isEqualTo(RingHashLoadBalancerProvider.MAX_RING_SIZE_CAP);
+    assertThat(config.maxRingSize).isEqualTo(RingHashLoadBalancerProvider.MAX_RING_SIZE_CAP);
+    // Reset to avoid affecting subsequent test cases
+    RingHashOptions.setMaxRingSizeCap(originalMaxRingSizeCap);
+  }
+
+  @Test
+  public void parseLoadBalancingConfig_ringCapIsClampedTo8M() throws IOException {
+    long originalMaxRingSizeCap = RingHashOptions.getRingSizeCap();
+    RingHashOptions.setRingSizeCap(RingHashOptions.MAX_RING_SIZE_CAP + 1);
+    long ringSize = RingHashOptions.MAX_RING_SIZE_CAP + 1;
     String lbConfig =
         String.format(
             Locale.US, "{\"minRingSize\" : %d, \"maxRingSize\" : %d}", ringSize, ringSize);
@@ -140,6 +161,42 @@ public void parseLoadBalancingConfig_ringMinAndMaxTooLargeUsesCap() throws IOExc
     RingHashConfig config = (RingHashConfig) configOrError.getConfig();
     assertThat(config.minRingSize).isEqualTo(RingHashLoadBalancerProvider.MAX_RING_SIZE_CAP);
     assertThat(config.maxRingSize).isEqualTo(RingHashLoadBalancerProvider.MAX_RING_SIZE_CAP);
+    // Reset to avoid affecting subsequent test cases
+    RingHashOptions.setMaxRingSizeCap(originalMaxRingSizeCap);
+  }
+
+  public void parseLoadBalancingConfig_ringCapCanBeLowered() throws IOException {
+    long originalMaxRingSizeCap = RingHashOptions.getRingSizeCap();
+    RingHashOptions.setRingSizeCap(1);
+    long ringSize = RingHashOptions.MAX_RING_SIZE_CAP;
+    String lbConfig =
+        String.format(
+            Locale.US, "{\"minRingSize\" : %d, \"maxRingSize\" : %d}", ringSize, ringSize);
+    ConfigOrError configOrError =
+        provider.parseLoadBalancingPolicyConfig(parseJsonObject(lbConfig));
+    assertThat(configOrError.getConfig()).isNotNull();
+    RingHashConfig config = (RingHashConfig) configOrError.getConfig();
+    assertThat(config.minRingSize).isEqualTo(1);
+    assertThat(config.maxRingSize).isEqualTo(1);
+    // Reset to avoid affecting subsequent test cases
+    RingHashOptions.setMaxRingSizeCap(originalMaxRingSizeCap);
+  }
+
+  public void parseLoadBalancingConfig_ringCapLowerLimitIs1() throws IOException {
+    long originalMaxRingSizeCap = RingHashOptions.getRingSizeCap();
+    RingHashOptions.setRingSizeCap(0);
+    long ringSize = RingHashOptions.MAX_RING_SIZE_CAP;
+    String lbConfig =
+        String.format(
+            Locale.US, "{\"minRingSize\" : %d, \"maxRingSize\" : %d}", ringSize, ringSize);
+    ConfigOrError configOrError =
+        provider.parseLoadBalancingPolicyConfig(parseJsonObject(lbConfig));
+    assertThat(configOrError.getConfig()).isNotNull();
+    RingHashConfig config = (RingHashConfig) configOrError.getConfig();
+    assertThat(config.minRingSize).isEqualTo(1);
+    assertThat(config.maxRingSize).isEqualTo(1);
+    // Reset to avoid affecting subsequent test cases
+    RingHashOptions.setMaxRingSizeCap(originalMaxRingSizeCap);
   }
 
   @Test