xds: Log ORCA UNIMPLEMENTED error to subchannel logger (#10625) (#10631)

Logging to the static instance would result in application logs filling
up if the Orca service is not available.
We'd like to have the logging on the subchannelLogger, so we make it
visible on demand.

Also succeed Orca logging test if log message present. Using
contains over containsExactly seems more reasonable.

Co-authored-by: Yannick Epstein <yannick.epstein@gmail.com>

xds/src/main/java/io/grpc/xds/orca/OrcaOobUtil.java

@@ -58,8 +58,6 @@
 import java.util.Map;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.TimeUnit;
-import java.util.logging.Level;
-import java.util.logging.Logger;
 import javax.annotation.Nullable;
 
 /**
@@ -68,7 +66,6 @@
  */
 @ExperimentalApi("https://github.com/grpc/grpc-java/issues/9129")
 public final class OrcaOobUtil {
-  private static final Logger logger = Logger.getLogger(OrcaPerRequestUtil.class.getName());
 
   private OrcaOobUtil() {}
 
@@ -468,8 +465,8 @@ void handleResponse(OrcaLoadReport response) {
         void handleStreamClosed(Status status) {
           if (Objects.equal(status.getCode(), Code.UNIMPLEMENTED)) {
             disabled = true;
-            logger.log(
-                Level.SEVERE,
+            subchannelLogger.log(
+                ChannelLogLevel.ERROR,
                 "Backend {0} OpenRcaService is disabled. Server returned: {1}",
                 new Object[] {subchannel.getAllAddresses(), status});
             subchannelLogger.log(ChannelLogLevel.ERROR, "OpenRcaService disabled: {0}", status);

xds/src/test/java/io/grpc/xds/orca/OrcaOobUtilTest.java

@@ -153,7 +153,7 @@ private static OrcaLoadReportRequest buildOrcaRequestFromConfig(
   }
 
   private static void assertLog(List<String> logs, String expectedLog) {
-    assertThat(logs).containsExactly(expectedLog);
+    assertThat(logs).contains(expectedLog);
     logs.clear();
   }