examples/src/main/scala/org/apache/ignite/scalar/examples/ScalarCacheAffinityExample.scala

/*
 * 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.ignite.scalar.examples

import org.apache.ignite.IgniteCache
import org.apache.ignite.scalar.scalar
import org.apache.ignite.scalar.scalar._

import scala.collection.JavaConversions._

/**
 * This example demonstrates the simplest code that populates the distributed cache
 * and co-locates simple closure execution with each key. The goal of this particular
 * example is to provide the simplest code example of this logic.
 * <p/>
 * Remote nodes should always be started with special configuration file which
 * enables P2P class loading: `'ignite.{sh|bat} examples/config/example-ignite.xml'`.
 * <p/>
 * Alternatively you can run `ExampleNodeStartup` in another JVM which will
 * start node with `examples/config/example-ignite.xml` configuration.
 */
object ScalarCacheAffinityExample extends App {
    /** Configuration file name. */
    private val CONFIG = "examples/config/example-ignite.xml"

    /** Name of cache. */
    private val NAME = ScalarCacheAffinityExample.getClass.getSimpleName

    /** Number of keys. */
    private val KEY_CNT = 20

    /** Type alias. */
    type Cache = IgniteCache[Int, String]

    /*
     * Note that in case of `LOCAL` configuration,
     * since there is no distribution, values may come back as `nulls`.
     */
    scalar(CONFIG) {
        val cache = createCache$[Int, String](NAME)

        try {
            populate (cache)

            visitUsingAffinityRun(cache)

            visitUsingMapKeysToNodes(cache)
        }
        finally {
            cache.destroy()
        }
    }

    /**
     * Visits every in-memory data ignite entry on the remote node it resides by co-locating visiting
     * closure with the cache key.
     *
     * @param c Cache to use.
     */
    private def visitUsingAffinityRun(c: IgniteCache[Int, String]) {
        (0 until KEY_CNT).foreach (i =>
            ignite$.compute ().affinityRun (NAME, i,
                () => println ("Co-located using affinityRun [key= " + i + ", value=" + c.localPeek (i) + ']') )
        )
    }

    /**
     * Collocates jobs with keys they need to work.
     *
     * @param c Cache to use.
     */
    private def visitUsingMapKeysToNodes(c: IgniteCache[Int, String]) {
        val keys = (0 until KEY_CNT).toSeq

        // Map all keys to nodes.
        val mappings = ignite$.affinity(NAME).mapKeysToNodes(keys)

        mappings.foreach(mapping => {
            val node = mapping._1
            val mappedKeys = mapping._2

            if (node != null) {
                ignite$.cluster().forNode(node) *< (() => {
                    // Check cache without loading the value.
                    mappedKeys.foreach(key => println("Co-located using mapKeysToNodes [key= " + key +
                        ", value=" + c.localPeek(key) + ']'))
                }, null)
            }
        })
    }

    /**
     * Populates given cache.
     *
     * @param c Cache to populate.
     */
    private def populate(c: Cache) {
        (0 until KEY_CNT).foreach(i => c += (i -> i.toString))
    }
}