Samrat002 commented on code in PR #28427: URL: https://github.com/apache/flink/pull/28427#discussion_r3610962253
########## flink-core/src/main/java/org/apache/flink/core/plugin/MetricsAware.java: ########## @@ -0,0 +1,57 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance + * with the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +package org.apache.flink.core.plugin; + +import org.apache.flink.annotation.PublicEvolving; +import org.apache.flink.metrics.MetricGroup; + +/** + * Capability marker for {@link Plugin}s that want to register Flink metrics. + * + * <p>This is an opt-in extension to the plugin SPI. A plugin declares {@code implements + * SomePluginSpi, MetricsAware}; plugins that do not implement it are byte-for-byte unchanged and + * emit no metrics. + * + * <p><b>Two-phase init contract.</b> The runtime invokes {@link #setMetricGroup(MetricGroup)} after + * {@link Plugin#configure(org.apache.flink.configuration.Configuration)} and before any operation + * that would emit a metric. The call happens only from runtime entrypoints that own a process-level + * {@link MetricGroup} (TaskManager and JobManager), via {@link + * org.apache.flink.core.fs.FileSystem#attachMetrics(MetricGroup)}. Contexts without such a group + * (CLI, HistoryServer, YARN client, embedded usage) never call it, in which case the plugin must + * continue to operate normally and emit no metrics. + * + * <p><b>Idempotency.</b> {@code setMetricGroup} may be invoked more than once (for example if + * metrics are re-attached). Implementations must treat repeated invocations idempotently: a call + * with the same {@link MetricGroup} must not register duplicate metrics, and a call with a Review Comment: The runtime reuses the same named child group, and plugin-specific metric handles are further scoped by filesystem_type. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
