sds metrics tag is not correct

[zirain]

@wbpcode per our offline talk, the output of sds metric didn't look correct:

# TYPE envoy_sds_fake_name_if_tls_secret_update_duration histogram
envoy_sds_fake_name_if_tls_secret_update_duration_bucket{le="0.5"} 1
envoy_sds_fake_name_if_tls_secret_update_duration_bucket{le="1"} 1
envoy_sds_fake_name_if_tls_secret_update_duration_bucket{le="5"} 1
envoy_sds_fake_name_if_tls_secret_update_duration_bucket{le="10"} 1
envoy_sds_fake_name_if_tls_secret_update_duration_bucket{le="25"} 1
envoy_sds_fake_name_if_tls_secret_update_duration_bucket{le="50"} 1
envoy_sds_fake_name_if_tls_secret_update_duration_bucket{le="100"} 1
envoy_sds_fake_name_if_tls_secret_update_duration_bucket{le="250"} 1
envoy_sds_fake_name_if_tls_secret_update_duration_bucket{le="500"} 1
envoy_sds_fake_name_if_tls_secret_update_duration_bucket{le="1000"} 1
envoy_sds_fake_name_if_tls_secret_update_duration_bucket{le="2500"} 1
envoy_sds_fake_name_if_tls_secret_update_duration_bucket{le="5000"} 1
envoy_sds_fake_name_if_tls_secret_update_duration_bucket{le="10000"} 1
envoy_sds_fake_name_if_tls_secret_update_duration_bucket{le="30000"} 1
envoy_sds_fake_name_if_tls_secret_update_duration_bucket{le="60000"} 1
envoy_sds_fake_name_if_tls_secret_update_duration_bucket{le="300000"} 1
envoy_sds_fake_name_if_tls_secret_update_duration_bucket{le="600000"} 1
envoy_sds_fake_name_if_tls_secret_update_duration_bucket{le="1800000"} 1
envoy_sds_fake_name_if_tls_secret_update_duration_bucket{le="3600000"} 1
envoy_sds_fake_name_if_tls_secret_update_duration_bucket{le="+Inf"} 1
envoy_sds_fake_name_if_tls_secret_update_duration_sum{} 0
envoy_sds_fake_name_if_tls_secret_update_duration_count{} 1

[adisuissa]

Thanks for reporting this!
Assuming this is coming from the GrpcSubscriptionImpl (

envoy/source/extensions/config_subscription/grpc/grpc_subscription_impl.cc

Line 87 in 7dd8848

stats_.update_duration_.recordValue(update_duration.count());

), this may be something across all xDS types. Do you happen to see the same thing for the other xDS types?