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From ctubbsii <...@git.apache.org>
Subject [GitHub] incubator-fluo pull request #817: fixes #816 introduced better way to setup ...
Date Mon, 20 Mar 2017 20:34:26 GMT
Github user ctubbsii commented on a diff in the pull request:

    https://github.com/apache/incubator-fluo/pull/817#discussion_r107008945
  
    --- Diff: modules/api/src/main/java/org/apache/fluo/api/observer/ObserversFactory.java
---
    @@ -0,0 +1,119 @@
    +/*
    + * 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.fluo.api.observer;
    +
    +import java.util.function.BiConsumer;
    +
    +import org.apache.fluo.api.client.FluoClient;
    +import org.apache.fluo.api.config.FluoConfiguration;
    +import org.apache.fluo.api.config.SimpleConfiguration;
    +import org.apache.fluo.api.data.Bytes;
    +import org.apache.fluo.api.data.Column;
    +import org.apache.fluo.api.metrics.MetricsReporter;
    +import org.apache.fluo.api.observer.Observer.NotificationType;
    +
    +/**
    + * Fluo Workers use this class to create {@link Observer}s to process notifications.
Implementations
    + * of this class should emit zero or more {@link Observer}s.
    + *
    + * <p>
    + * When Fluo is initialized {@link #getObservedColumns(Context, BiConsumer)} is called.
The columns
    + * it emits are stored in Zookeeper. Transactions will use the columns stored in Zookeeper
to
    + * determine when to set notifications. When Workers call
    + * {@link #createObservers(ObserverConsumer, Context)}, the columns emitted must be the
same as
    + * those emitted during initialization. If this is not the case, then the worker will
fail to start.
    + *
    + * @see FluoConfiguration#setObserversFactory(String)
    + * @since 1.1.0
    + */
    +public interface ObserversFactory {
    +
    +  /**
    +   * @since 1.1.0
    +   */
    +  interface Context {
    +    /**
    +     * @return A configuration object with application configuration like that returned
by
    +     *         {@link FluoClient#getAppConfiguration()}
    +     */
    +    SimpleConfiguration getAppConfiguration();
    +
    +    /**
    +     * @return A {@link MetricsReporter} to report application metrics from observers.
    +     */
    +    MetricsReporter getMetricsReporter();
    +  }
    +
    +  /**
    +   * Observers are emitted to the worker using this interface. This interface also allows
    +   * {@link Observer}s to be related to the columns that trigger them.
    +   *
    +   * @since 1.1.0
    +   */
    +  interface ObserverConsumer {
    +    void accept(Column observedColumn, NotificationType ntfyType, Observer observer);
    +
    +    /**
    +     * This method was created to allow Observers written as lambda to be passed {@link
String}
    +     * instead of {@link Bytes}.
    +     * 
    +     * <pre>
    +     * <code>
    +     *   void createObservers(ObserverConsumer obsConsumer, Context ctx) {
    +     *     obsConsumer.accepts(someColumn, WEAK, (tx,row,col) -> {
    +     *      //row is of type String
    +     *     };
    +     *   }
    +     * </code>
    +     * </pre>
    +     */
    +    void accepts(Column observedColumn, NotificationType ntfyType, StringObserver observer);
    +  }
    +
    +  /**
    +   * This is method is called by Fluo Workers to create observers to process notifications.
    +   *
    +   * <p>
    +   * Observers emitted may be called concurrently by multiple threads to process different
    +   * notifications. Observers should be tolerant of this.
    +   *
    +   * @param obsConsumer Emit an applications observers to this consumer.
    +   */
    +  void createObservers(ObserverConsumer obsConsumer, Context ctx);
    --- End diff --
    
    Why not make this interface a `Function<Context,Stream<Observer>>` or maybe
make the factory return a set of observers? That way, the user's code doesn't actually have
to deal with the framework's observer consumer, which I think is an implementation detail
they shouldn't have to interact with.


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