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/*
* Copyright (C) 2023-2024 Hedera Hashgraph, LLC
*
* Licensed 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 com.swirlds.common.metrics.platform;
import com.swirlds.common.platform.NodeId;
import com.swirlds.metrics.api.Metric;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
/**
* With the help of a {@code MetricsKeyRegistry} we ensure, that there are no two {@link Metric}s with the same
* metric key, but conflicting configurations.
*
* Before a new {@code Metric} is added, we must try to {@link #register(NodeId, String, Class)} its
* metric key. Only if that is successful, can we add the {@code Metric}. When a {@code Metric} is removed,
* it is recommended to {@link #unregister(NodeId, String)} it, to free the key.
*
* Two configurations are conflicting, if the {@code Metric}-class are different or if one of them is global
* and the other one is platform-specific.
*/
public class MetricKeyRegistry {
private record Registration(Set nodeIds, Class clazz) {}
private final Map registrations = new HashMap<>();
/**
* Try to register (and reserve) a metric key. The key of a platform-specific metric can be reused
* on another platform, if the types are the same.
*
* @param nodeId
* the {@link NodeId} for which we want to register the key
* @param key
* the actual metric key
* @param clazz
* the {@link Class} of the metric
* @return {@code true} if the registration was successful, {@code false} otherwise
*/
public synchronized boolean register(final NodeId nodeId, final String key, final Class clazz) {
final Registration registration = registrations.computeIfAbsent(
key, k -> new Registration(nodeId == null ? null : new HashSet<>(), clazz));
if (registration.clazz == clazz) {
if (nodeId == null) {
return registration.nodeIds == null;
} else {
if (registration.nodeIds != null) {
registration.nodeIds.add(nodeId);
return true;
}
}
}
return false;
}
/**
* Unregister a metric key
*
* @param nodeId
* the {@link NodeId} for which the key should be unregistered
* @param key
* the actual metric key
*/
public synchronized void unregister(final NodeId nodeId, final String key) {
if (nodeId == null) {
registrations.computeIfPresent(key, (k, v) -> v.nodeIds == null ? null : v);
} else {
final Registration registration = registrations.get(key);
if (registration != null && (registration.nodeIds != null)) {
registration.nodeIds.remove(nodeId);
if (registration.nodeIds.isEmpty()) {
registrations.remove(key);
}
}
}
}
}