add minFailedCalls parameter to createFallbackChannelOptions

Author: kinsaurralde

google-cloud-spanner/src/main/java/com/google/cloud/spanner/spi/v1/GapicSpannerRpc.java

@@ -438,7 +438,7 @@ public <ReqT, RespT> ClientCall<ReqT, RespT> interceptCall(
               return new FallbackChannelBuilder(
                   primaryGcpBuilder,
                   fallbackGcpBuilder,
-                  createFallbackChannelOptions(fallbackTelemetry));
+                  createFallbackChannelOptions(fallbackTelemetry, 1));
             });
       }
 
@@ -613,11 +613,11 @@ public <RequestT, ResponseT> UnaryCallable<RequestT, ResponseT> createUnaryCalla
 
   @VisibleForTesting
   GcpFallbackChannelOptions createFallbackChannelOptions(
-      GcpFallbackOpenTelemetry fallbackTelemetry) {
+      GcpFallbackOpenTelemetry fallbackTelemetry, int minFailedCalls) {
     return GcpFallbackChannelOptions.newBuilder()
         .setPrimaryChannelName("directpath")
         .setFallbackChannelName("cloudpath")
-        .setMinFailedCalls(1)
+        .setMinFailedCalls(minFailedCalls)
         .setGcpFallbackOpenTelemetry(fallbackTelemetry)
         .build();
   }

google-cloud-spanner/src/test/java/com/google/cloud/spanner/spi/v1/GapicSpannerRpcTest.java

@@ -905,11 +905,12 @@ public TestableGapicSpannerRpc(SpannerOptions options) {
 
     @Override
     GcpFallbackChannelOptions createFallbackChannelOptions(
-        GcpFallbackOpenTelemetry fallbackTelemetry) {
+        GcpFallbackOpenTelemetry fallbackTelemetry, int minFailedCalls) {
       // Override default 1-minute period to 10ms for instant testing
       return GcpFallbackChannelOptions.newBuilder()
           .setPrimaryChannelName("directpath")
           .setFallbackChannelName("cloudpath")
+          .setMinFailedCalls(10)
           .setPeriod(Duration.ofMillis(10))
           .setGcpFallbackOpenTelemetry(fallbackTelemetry)
           .build();
@@ -973,7 +974,7 @@ public TestableGapicSpannerRpcWithLowerMinFailedCalls(SpannerOptions options) {
 
     @Override
     GcpFallbackChannelOptions createFallbackChannelOptions(
-        GcpFallbackOpenTelemetry fallbackTelemetry) {
+        GcpFallbackOpenTelemetry fallbackTelemetry, int minFailedCalls) {
       // Override default 1-minute period to 10ms for instant testing
       return GcpFallbackChannelOptions.newBuilder()
           .setPrimaryChannelName("directpath")