Copyright 2015 Netflix, Inc.
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.
/**
 * Copyright 2015 Netflix, Inc.
 * 
 * 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.netflix.hystrix.metric;

import com.netflix.hystrix.HystrixCollapserKey;
import rx.Observable;
import rx.subjects.PublishSubject;
import rx.subjects.SerializedSubject;
import rx.subjects.Subject;

import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

Per-Collapser stream of HystrixCollapserEvents. This gets written to by HystrixThreadEventStreams. Events are emitted synchronously in the same thread that performs the batch-command execution. /**
 * Per-Collapser stream of {@link HystrixCollapserEvent}s.  This gets written to by {@link HystrixThreadEventStream}s.
 * Events are emitted synchronously in the same thread that performs the batch-command execution.
 */
public class HystrixCollapserEventStream implements HystrixEventStream<HystrixCollapserEvent> {
    private final HystrixCollapserKey collapserKey;

    private final Subject<HystrixCollapserEvent, HystrixCollapserEvent> writeOnlyStream;
    private final Observable<HystrixCollapserEvent> readOnlyStream;

    private static final ConcurrentMap<String, HystrixCollapserEventStream> streams = new ConcurrentHashMap<String, HystrixCollapserEventStream>();

    public static HystrixCollapserEventStream getInstance(HystrixCollapserKey collapserKey) {
        HystrixCollapserEventStream initialStream = streams.get(collapserKey.name());
        if (initialStream != null) {
            return initialStream;
        } else {
            synchronized (HystrixCollapserEventStream.class) {
                HystrixCollapserEventStream existingStream = streams.get(collapserKey.name());
                if (existingStream == null) {
                    HystrixCollapserEventStream newStream = new HystrixCollapserEventStream(collapserKey);
                    streams.putIfAbsent(collapserKey.name(), newStream);
                    return newStream;
                } else {
                    return existingStream;
                }
            }
        }
    }

    HystrixCollapserEventStream(final HystrixCollapserKey collapserKey) {
        this.collapserKey = collapserKey;

        this.writeOnlyStream = new SerializedSubject<HystrixCollapserEvent, HystrixCollapserEvent>(PublishSubject.<HystrixCollapserEvent>create());
        this.readOnlyStream = writeOnlyStream.share();
    }

    public static void reset() {
        streams.clear();
    }

    public void write(HystrixCollapserEvent event) {
        writeOnlyStream.onNext(event);
    }

    public Observable<HystrixCollapserEvent> observe() {
        return readOnlyStream;
    }

    @Override
    public String toString() {
        return "HystrixCollapserEventStream(" + collapserKey.name() + ")";
    }
}