org.alfresco.solr.component.AsyncBuildSuggestComponent.java Source code

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package org.alfresco.solr.component;

/*
 * Copyright (C) 2005-2014 Alfresco Software Limited.
 *
 * This file is part of Alfresco
 *
 * Alfresco is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Alfresco is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with Alfresco. If not, see <http://www.gnu.org/licenses/>.
 * 
 * 
 * This file is based upon code copied from the Solr project and modified.
 * The original code is licensed to the Apache Software Foundation. Please see:
 * 
 *   http://lucene.apache.org/solr/
 *   http://www.apache.org/licenses/LICENSE-2.0
 */

import java.io.File;
import java.io.IOException;
import java.lang.invoke.MethodHandles;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.LinkedBlockingQueue;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
import java.util.concurrent.atomic.AtomicInteger;

import org.alfresco.util.cache.AbstractAsynchronouslyRefreshedCache;
import org.alfresco.util.cache.DefaultAsynchronouslyRefreshedCacheRegistry;
import org.apache.lucene.search.suggest.Lookup;
import org.apache.lucene.search.suggest.Lookup.LookupResult;
import org.apache.lucene.util.Accountable;
import org.apache.lucene.util.BytesRef;
import org.apache.lucene.util.CharsRef;
import org.apache.solr.common.params.CommonParams;
import org.apache.solr.common.params.ModifiableSolrParams;
import org.apache.solr.common.params.ShardParams;
import org.apache.solr.common.params.SolrParams;
import org.apache.solr.common.util.NamedList;
import org.apache.solr.common.util.SimpleOrderedMap;
import org.apache.solr.core.CloseHook;
import org.apache.solr.core.SolrCore;
import org.apache.solr.core.SolrEventListener;
import org.apache.solr.handler.component.ResponseBuilder;
import org.apache.solr.handler.component.SearchComponent;
import org.apache.solr.handler.component.ShardRequest;
import org.apache.solr.handler.component.ShardResponse;
import org.apache.solr.handler.component.SuggestComponent;
import org.apache.solr.search.SolrIndexSearcher;
import org.apache.solr.spelling.suggest.SolrSuggester;
import org.apache.solr.spelling.suggest.SuggesterOptions;
import org.apache.solr.spelling.suggest.SuggesterParams;
import org.apache.solr.spelling.suggest.SuggesterResult;
import org.apache.solr.util.RefCounted;
import org.apache.solr.util.plugin.SolrCoreAware;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Originally taken from {@link SuggestComponent} and modified, this
 * class provides a {@link SearchComponent} that builds {@link SolrSuggester}
 * objects asynchronously to avoid blocking search
 * requests or increasing startup time of the servlet container.
 * 
 * @see org.apache.solr.handler.component.SuggestComponent
 */
public class AsyncBuildSuggestComponent extends SearchComponent
        implements SolrCoreAware, SuggesterParams, Accountable {
    private static final Logger LOG = LoggerFactory.getLogger(MethodHandles.lookup().lookupClass());

    /** Name used to identify whether the user query concerns this component */
    public static final String COMPONENT_NAME = "suggest";

    /** Name assigned to an unnamed suggester (at most one suggester) can be unnamed */
    private static final String DEFAULT_DICT_NAME = SolrSuggester.DEFAULT_DICT_NAME;

    /** SolrConfig label to identify  Config time settings */
    private static final String CONFIG_PARAM_LABEL = "suggester";

    /** SolrConfig label to identify boolean value to build suggesters on commit */
    private static final String BUILD_ON_COMMIT_LABEL = "buildOnCommit";

    /** SolrConfig label to identify boolean value to build suggesters on optimize */
    private static final String BUILD_ON_OPTIMIZE_LABEL = "buildOnOptimize";

    /**
     * SolrConfig label to identify boolean value to build suggesters on startup
     */
    private static final String BUILD_ON_STARTUP_LABEL = "buildOnStartup";

    /** SolrConfig label to identify boolean value describing whether suggesters should be built at all. */
    private static final String ENABLED_LABEL = "enabled";

    private static final String ASYNC_CACHE_KEY = "suggester";

    private static final String MIN_SECS_BETWEEN_BUILDS = "solr.suggester.minSecsBetweenBuilds";

    private static File offlineSorterTempDir;

    static {
        try {
            String tempDirPath = System.getProperty("java.io.tmpdir");
            Path tempDirectory = Paths.get(tempDirPath);
            if (!Files.exists(tempDirectory) && (!tempDirectory.toFile().mkdirs())) {
                throw new RuntimeException("No OfflineSorter temp directory");
            }
            if (!Files.isDirectory(tempDirectory) || Files.isHidden(tempDirectory)
                    || !Files.isReadable(tempDirectory)) {
                throw new RuntimeException("No OfflineSorter temp directory");
            }

            //offlineSorterTempDir = OfflineSorter.getDefaultTempDir().toFile();
            offlineSorterTempDir = tempDirectory.toFile();
        } catch (IOException e) {
            throw new RuntimeException("No OfflineSorter temp directory", e);
        }
    }

    protected static TempFileWarningLogger tempFileWarningLogger = new TempFileWarningLogger(LOG,
            "WFSTInputIterator*", new String[] { "input", "sorted" }, offlineSorterTempDir.toPath());

    protected NamedList initParams;

    /**
     * Key is the dictionary name used in SolrConfig, value is the corresponding {@link SolrSuggester}
     */
    protected Map<String, SuggesterCache> suggesters = new ConcurrentHashMap<>();

    /** Container for various labels used in the responses generated by this component */
    private static class SuggesterResultLabels {
        static final String SUGGEST = "suggest";
        static final String SUGGESTIONS = "suggestions";
        static final String SUGGESTION_NUM_FOUND = "numFound";
        static final String SUGGESTION_TERM = "term";
        static final String SUGGESTION_WEIGHT = "weight";
        static final String SUGGESTION_PAYLOAD = "payload";
    }

    @Override
    @SuppressWarnings("unchecked")
    public void init(NamedList args) {
        super.init(args);
        this.initParams = args;
    }

    @Override
    public void inform(SolrCore core) {
        if (initParams != null) {
            LOG.info("Initializing SuggestComponent");
            boolean hasDefault = false;
            for (int i = 0; i < initParams.size(); i++) {
                if (initParams.getName(i).equals(CONFIG_PARAM_LABEL)) {
                    NamedList suggesterParams = (NamedList) initParams.getVal(i);
                    SolrSuggester suggester = new SolrSuggester();
                    boolean buildOnStartup;
                    Object buildOnStartupObj = suggesterParams.get(BUILD_ON_STARTUP_LABEL);
                    if (buildOnStartupObj == null) {
                        File storeFile = suggester.getStoreFile();
                        buildOnStartup = storeFile == null || !storeFile.exists();
                    } else {
                        buildOnStartup = Boolean.parseBoolean((String) buildOnStartupObj);
                    }
                    boolean buildOnCommit = Boolean
                            .parseBoolean((String) suggesterParams.get(BUILD_ON_COMMIT_LABEL));
                    boolean buildOnOptimize = Boolean
                            .parseBoolean((String) suggesterParams.get(BUILD_ON_OPTIMIZE_LABEL));
                    boolean enabled = Boolean.parseBoolean((String) suggesterParams.get(ENABLED_LABEL));
                    long minSecsBetweenBuilds = Long
                            .parseLong(core.getCoreDescriptor().getCoreProperty(MIN_SECS_BETWEEN_BUILDS, "-1"));
                    SuggesterCache suggesterCache = new SuggesterCache(core, suggesterParams, enabled,
                            buildOnCommit, buildOnOptimize, buildOnStartup);

                    String dictionary = suggester.init(suggesterParams, core);
                    if (dictionary != null) {
                        boolean isDefault = dictionary.equals(DEFAULT_DICT_NAME);
                        if (isDefault && !hasDefault) {
                            hasDefault = true;
                        } else if (isDefault) {
                            throw new RuntimeException("More than one dictionary is missing name.");
                        }
                        suggesterCache.setBeanName(dictionary);
                        suggesters.put(dictionary, suggesterCache);
                    } else {
                        if (!hasDefault) {
                            suggesterCache.setBeanName(DEFAULT_DICT_NAME);
                            suggesters.put(DEFAULT_DICT_NAME, suggesterCache);
                            hasDefault = true;
                        } else {
                            throw new RuntimeException("More than one dictionary is missing name.");
                        }
                    }

                    try {
                        suggesterCache.afterPropertiesSet();
                    } catch (Exception e) {
                        LOG.error("Unable to initialise SuggesterCache.", e);
                        throw new RuntimeException("Unable to initialise SuggesterCache.", e);
                    }

                    // Register event listeners for this Suggester
                    core.registerFirstSearcherListener(new SuggesterListener(suggesterCache, minSecsBetweenBuilds));
                    if (buildOnCommit || buildOnOptimize) {
                        LOG.debug("Registering newSearcher listener for suggester: " + suggester.getName());
                        core.registerNewSearcherListener(
                                new SuggesterListener(suggesterCache, minSecsBetweenBuilds));
                    }
                }
            }
        }
    }

    /** Responsible for issuing build and rebload command to the specified {@link SolrSuggester} */
    @Override
    public void prepare(ResponseBuilder rb) throws IOException {
        SolrParams params = rb.req.getParams();
        LOG.debug("SuggestComponent prepare with : " + params);
        if (!params.getBool(COMPONENT_NAME, false)) {
            return;
        }

        boolean buildAll = params.getBool(SUGGEST_BUILD_ALL, false);
        boolean reloadAll = params.getBool(SUGGEST_RELOAD_ALL, false);

        final Collection<SolrSuggester> querysuggesters;
        if (buildAll || reloadAll) {
            Collection<SuggesterCache> suggesterCaches = suggesters.values();
            querysuggesters = new ArrayList<SolrSuggester>(suggesterCaches.size());
            for (SuggesterCache cache : suggesterCaches) {
                querysuggesters.add(cache.get(ASYNC_CACHE_KEY));
            }
        } else {
            querysuggesters = getSuggesters(params);
        }

        if (params.getBool(SUGGEST_BUILD, false) || buildAll) {
            for (SolrSuggester suggester : querysuggesters) {
                suggester.build(rb.req.getCore(), rb.req.getSearcher());
            }
            rb.rsp.add("command", (!buildAll) ? "build" : "buildAll");
        } else if (params.getBool(SUGGEST_RELOAD, false) || reloadAll) {
            for (SolrSuggester suggester : querysuggesters) {
                reloadSuggester(suggester, rb.req.getCore(), rb.req.getSearcher());
            }
            rb.rsp.add("command", (!reloadAll) ? "reload" : "reloadAll");
        }
    }

    private void reloadSuggester(SolrSuggester suggester, SolrCore core, SolrIndexSearcher searcher)
            throws IOException {
        File storeFile = suggester.getStoreFile();
        if (storeFile == null || !storeFile.exists()) {
            suggester.build(core, searcher);
        } else {
            suggester.reload(core, searcher);
        }
    }

    /** Dispatch shard request in <code>STAGE_EXECUTE_QUERY</code> stage */
    @Override
    public int distributedProcess(ResponseBuilder rb) {
        SolrParams params = rb.req.getParams();
        LOG.debug("SuggestComponent distributedProcess with : " + params);
        if (rb.stage < ResponseBuilder.STAGE_EXECUTE_QUERY)
            return ResponseBuilder.STAGE_EXECUTE_QUERY;
        if (rb.stage == ResponseBuilder.STAGE_EXECUTE_QUERY) {
            ShardRequest sreq = new ShardRequest();
            sreq.purpose = ShardRequest.PURPOSE_GET_TOP_IDS;
            sreq.params = new ModifiableSolrParams(rb.req.getParams());
            sreq.params.remove(ShardParams.SHARDS);
            rb.addRequest(this, sreq);
            return ResponseBuilder.STAGE_GET_FIELDS;
        }

        return ResponseBuilder.STAGE_DONE;
    }

    /** 
     * Responsible for using the specified suggester to get the suggestions 
     * for the query and write the results 
     * */
    @Override
    public void process(ResponseBuilder rb) throws IOException {
        SolrParams params = rb.req.getParams();
        LOG.debug("SuggestComponent process with : " + params);
        if (!params.getBool(COMPONENT_NAME, false) || suggesters.isEmpty()) {
            return;
        }

        boolean buildAll = params.getBool(SUGGEST_BUILD_ALL, false);
        boolean reloadAll = params.getBool(SUGGEST_RELOAD_ALL, false);
        Set<SolrSuggester> querySuggesters;
        try {
            querySuggesters = getSuggesters(params);
        } catch (IllegalArgumentException ex) {
            if (!buildAll && !reloadAll) {
                throw ex;
            } else {
                querySuggesters = new HashSet<>();
            }
        }

        String query = params.get(SUGGEST_Q);
        if (query == null) {
            query = rb.getQueryString();
            if (query == null) {
                query = params.get(CommonParams.Q);
            }
        }

        if (query != null) {
            int count = params.getInt(SUGGEST_COUNT, 1);

            boolean highlight = params.getBool(SUGGEST_HIGHLIGHT, false);
            boolean allTermsRequired = params.getBool(SUGGEST_ALL_TERMS_REQUIRED, true);
            String contextFilter = params.get(SUGGEST_CONTEXT_FILTER_QUERY);
            if (contextFilter != null) {
                contextFilter = contextFilter.trim();
                if (contextFilter.length() == 0) {
                    contextFilter = null;
                }
            }

            SuggesterOptions options = new SuggesterOptions(new CharsRef(query), count, contextFilter,
                    allTermsRequired, highlight);
            Map<String, SimpleOrderedMap<NamedList<Object>>> namedListResults = new HashMap<>();
            for (SolrSuggester suggester : querySuggesters) {
                SuggesterResult suggesterResult = suggester.getSuggestions(options);
                toNamedList(suggesterResult, namedListResults);
            }
            rb.rsp.add(SuggesterResultLabels.SUGGEST, namedListResults);
        }
    }

    /** 
     * Used in Distributed Search, merges the suggestion results from every shard
     * */
    @Override
    public void finishStage(ResponseBuilder rb) {
        SolrParams params = rb.req.getParams();
        LOG.debug("SuggestComponent finishStage with : " + params);
        if (!params.getBool(COMPONENT_NAME, false) || rb.stage != ResponseBuilder.STAGE_GET_FIELDS)
            return;
        int count = params.getInt(SUGGEST_COUNT, 1);

        List<SuggesterResult> suggesterResults = new ArrayList<>();

        // Collect Shard responses
        for (ShardRequest sreq : rb.finished) {
            for (ShardResponse srsp : sreq.responses) {
                NamedList<Object> resp;
                if ((resp = srsp.getSolrResponse().getResponse()) != null) {
                    @SuppressWarnings("unchecked")
                    Map<String, SimpleOrderedMap<NamedList<Object>>> namedList = (Map<String, SimpleOrderedMap<NamedList<Object>>>) resp
                            .get(SuggesterResultLabels.SUGGEST);
                    LOG.debug(srsp.getShard() + " : " + namedList);
                    suggesterResults.add(toSuggesterResult(namedList));
                }
            }
        }

        // Merge Shard responses
        SuggesterResult suggesterResult = merge(suggesterResults, count);
        Map<String, SimpleOrderedMap<NamedList<Object>>> namedListResults = new HashMap<>();
        toNamedList(suggesterResult, namedListResults);

        rb.rsp.add(SuggesterResultLabels.SUGGEST, namedListResults);
    }

    /** 
     * Given a list of {@link SuggesterResult} and <code>count</code>
     * returns a {@link SuggesterResult} containing <code>count</code>
     * number of {@link LookupResult}, sorted by their associated 
     * weights
     * */
    private static SuggesterResult merge(List<SuggesterResult> suggesterResults, int count) {
        SuggesterResult result = new SuggesterResult();
        Set<String> allTokens = new HashSet<>();
        Set<String> suggesterNames = new HashSet<>();

        // collect all tokens
        for (SuggesterResult shardResult : suggesterResults) {
            for (String suggesterName : shardResult.getSuggesterNames()) {
                allTokens.addAll(shardResult.getTokens(suggesterName));
                suggesterNames.add(suggesterName);
            }
        }

        // Get Top N for every token in every shard (using weights)
        for (String suggesterName : suggesterNames) {
            for (String token : allTokens) {
                Lookup.LookupPriorityQueue resultQueue = new Lookup.LookupPriorityQueue(count);
                for (SuggesterResult shardResult : suggesterResults) {
                    List<LookupResult> suggests = shardResult.getLookupResult(suggesterName, token);
                    if (suggests == null) {
                        continue;
                    }
                    for (LookupResult res : suggests) {
                        resultQueue.insertWithOverflow(res);
                    }
                }
                List<LookupResult> sortedSuggests = new LinkedList<>();
                Collections.addAll(sortedSuggests, resultQueue.getResults());
                result.add(suggesterName, token, sortedSuggests);
            }
        }
        return result;
    }

    @Override
    public String getDescription() {
        return "Suggester component";
    }

    @Override
    public String getSource() {
        return "$URL: https://svn.apache.org/repos/asf/lucene/dev/branches/lucene_solr_4_9/solr/core/src/java/org/apache/solr/handler/component/SuggestComponent.java $";
    }

    @Override
    public NamedList<String> getStatistics() {
        NamedList<String> stats = new SimpleOrderedMap<>();
        stats.add("totalSizeInBytes", String.valueOf(ramBytesUsed()));
        for (Map.Entry<String, SuggesterCache> entry : suggesters.entrySet()) {
            SolrSuggester suggester = entry.getValue().get(entry.getKey());
            stats.add(entry.getKey(), suggester.toString());
        }
        return stats;
    }

    @Override
    public long ramBytesUsed() {
        return suggesters.values().stream().mapToLong(value -> value.get(ASYNC_CACHE_KEY).ramBytesUsed()).sum();
    }

    private Set<SolrSuggester> getSuggesters(SolrParams params) {
        Set<SolrSuggester> solrSuggesters = new HashSet<>();
        for (String suggesterName : getSuggesterNames(params)) {
            SolrSuggester curSuggester = suggesters.get(suggesterName).get(ASYNC_CACHE_KEY);
            if (curSuggester != null) {
                solrSuggesters.add(curSuggester);
            } else {
                throw new IllegalArgumentException("No suggester named " + suggesterName + " was configured");
            }
        }
        if (solrSuggesters.size() == 0) {
            throw new IllegalArgumentException("No default suggester was configured");
        }
        return solrSuggesters;

    }

    private Set<String> getSuggesterNames(SolrParams params) {
        Set<String> suggesterNames = new HashSet<>();
        String[] suggesterNamesFromParams = params.getParams(SUGGEST_DICT);
        if (suggesterNamesFromParams == null) {
            suggesterNames.add(DEFAULT_DICT_NAME);
        } else {
            for (String name : suggesterNamesFromParams) {
                suggesterNames.add(name);
            }
        }
        return suggesterNames;
    }

    /** Convert {@link SuggesterResult} to NamedList for constructing responses */
    private void toNamedList(SuggesterResult suggesterResult,
            Map<String, SimpleOrderedMap<NamedList<Object>>> resultObj) {
        for (String suggesterName : suggesterResult.getSuggesterNames()) {
            SimpleOrderedMap<NamedList<Object>> results = new SimpleOrderedMap<>();
            for (String token : suggesterResult.getTokens(suggesterName)) {
                SimpleOrderedMap<Object> suggestionBody = new SimpleOrderedMap<>();
                List<LookupResult> lookupResults = suggesterResult.getLookupResult(suggesterName, token);
                suggestionBody.add(SuggesterResultLabels.SUGGESTION_NUM_FOUND, lookupResults.size());
                List<SimpleOrderedMap<Object>> suggestEntriesNamedList = new ArrayList<>();
                for (LookupResult lookupResult : lookupResults) {
                    String suggestionString = lookupResult.key.toString();
                    long weight = lookupResult.value;
                    String payload = (lookupResult.payload != null) ? lookupResult.payload.utf8ToString() : "";

                    SimpleOrderedMap<Object> suggestEntryNamedList = new SimpleOrderedMap<>();
                    suggestEntryNamedList.add(SuggesterResultLabels.SUGGESTION_TERM, suggestionString);
                    suggestEntryNamedList.add(SuggesterResultLabels.SUGGESTION_WEIGHT, weight);
                    suggestEntryNamedList.add(SuggesterResultLabels.SUGGESTION_PAYLOAD, payload);
                    suggestEntriesNamedList.add(suggestEntryNamedList);

                }
                suggestionBody.add(SuggesterResultLabels.SUGGESTIONS, suggestEntriesNamedList);
                results.add(token, suggestionBody);
            }
            resultObj.put(suggesterName, results);
        }
    }

    /** Convert NamedList (suggester response) to {@link SuggesterResult} */
    private SuggesterResult toSuggesterResult(Map<String, SimpleOrderedMap<NamedList<Object>>> suggestionsMap) {
        SuggesterResult result = new SuggesterResult();
        if (suggestionsMap == null) {
            return result;
        }
        // for each token
        for (Map.Entry<String, SimpleOrderedMap<NamedList<Object>>> entry : suggestionsMap.entrySet()) {
            String suggesterName = entry.getKey();
            for (Iterator<Map.Entry<String, NamedList<Object>>> suggestionsIter = entry.getValue()
                    .iterator(); suggestionsIter.hasNext();) {
                Map.Entry<String, NamedList<Object>> suggestions = suggestionsIter.next();
                String tokenString = suggestions.getKey();
                List<LookupResult> lookupResults = new ArrayList<>();
                NamedList<Object> suggestion = suggestions.getValue();
                // for each suggestion
                for (int j = 0; j < suggestion.size(); j++) {
                    String property = suggestion.getName(j);
                    if (property.equals(SuggesterResultLabels.SUGGESTIONS)) {
                        @SuppressWarnings("unchecked")
                        List<NamedList<Object>> suggestionEntries = (List<NamedList<Object>>) suggestion.getVal(j);
                        for (NamedList<Object> suggestionEntry : suggestionEntries) {
                            String term = (String) suggestionEntry.get(SuggesterResultLabels.SUGGESTION_TERM);
                            Long weight = (Long) suggestionEntry.get(SuggesterResultLabels.SUGGESTION_WEIGHT);
                            String payload = (String) suggestionEntry.get(SuggesterResultLabels.SUGGESTION_PAYLOAD);
                            LookupResult res = new LookupResult(new CharsRef(term), weight, new BytesRef(payload));
                            lookupResults.add(res);
                        }
                    }
                    result.add(suggesterName, tokenString, lookupResults);
                }
            }
        }
        return result;
    }

    /** Listener to build or reload the maintained {@link SolrSuggester} by this component */
    private static class SuggesterListener implements SolrEventListener {
        private final SuggesterCache suggesterCache;
        private final long minSecsBetweenBuilds;

        public SuggesterListener(SuggesterCache suggesterCache, long minSecsBetweenBuilds) {
            this.suggesterCache = suggesterCache;
            this.minSecsBetweenBuilds = minSecsBetweenBuilds;
        }

        @Override
        public void init(NamedList args) {
        }

        @Override
        public void newSearcher(SolrIndexSearcher newSearcher, SolrIndexSearcher currentSearcher) {
            if (currentSearcher == null) {
                // firstSearcher event - always queue a suggester build.
                if (LOG.isDebugEnabled()) {
                    LOG.debug("Scheduling first searcher's suggester build, core: "
                            + newSearcher.getCore().getName());
                }
                suggesterCache.refresh(ASYNC_CACHE_KEY);
            } else {
                // only queue a build if the designated time has passed.
                long now = System.currentTimeMillis();
                long lastBuild = suggesterCache.getLastBuild();
                long elapsedTimeMillis = (lastBuild == 0) ? 0 : (now - lastBuild);
                long elapsedTimeSecs = (lastBuild == 0) ? 0 : (elapsedTimeMillis / 1000);
                if (elapsedTimeSecs > minSecsBetweenBuilds) {
                    if (LOG.isDebugEnabled()) {
                        StringBuilder sb = new StringBuilder();
                        sb.append("Scheduling async suggester build");
                        if (lastBuild > 0) {
                            sb.append(", time since last build: ").append(elapsedTimeSecs).append("s (")
                                    .append(elapsedTimeMillis).append("ms)");
                        }
                        sb.append(", core: ").append(newSearcher.getCore().getName());
                        LOG.debug(sb.toString());
                    }
                    suggesterCache.refresh(ASYNC_CACHE_KEY);
                } else {
                    if (LOG.isDebugEnabled()) {
                        StringBuilder sb = new StringBuilder();
                        sb.append("Skipping async suggester build");
                        if (lastBuild > 0) {
                            sb.append(", time since last build: ").append(elapsedTimeSecs).append("s (")
                                    .append(elapsedTimeMillis).append("ms)");
                        }
                        sb.append(", core: ").append(newSearcher.getCore().getName());
                        LOG.debug(sb.toString());
                    }
                }
            }
        }

        @Override
        public void postCommit() {
        }

        @Override
        public void postSoftCommit() {
        }

    }

    static class SuggesterCache extends AbstractAsynchronouslyRefreshedCache<SolrSuggester> {
        private final SolrCore core;
        private final AtomicBoolean isNewSearcher = new AtomicBoolean(false);
        private final NamedList suggesterParams;
        private final boolean buildOnCommit;
        private final boolean buildOnOptimize;
        private final boolean buildOnStartup;
        private final boolean enabled;
        private final SolrSuggester initialSuggester;
        private long lastBuild = 0;

        public SuggesterCache(SolrCore core, NamedList suggesterParams, boolean enabled, boolean buildOnCommit,
                boolean buildOnOptimize, boolean buildOnStartup) {
            this.core = core;
            this.suggesterParams = suggesterParams;
            this.enabled = enabled;
            this.buildOnCommit = buildOnCommit;
            this.buildOnOptimize = buildOnOptimize;
            this.buildOnStartup = buildOnStartup;

            setRegistry(new DefaultAsynchronouslyRefreshedCacheRegistry());
            BlockingQueue<Runnable> threadPool = new LinkedBlockingQueue<Runnable>();
            ThreadPoolExecutor executor = new ThreadPoolExecutor(1, 1, 0L, TimeUnit.MILLISECONDS, threadPool,
                    getThreadFactory(core));
            setThreadPoolExecutor(executor);

            //Shutdown the executor on core close
            core.addCloseHook(new CloseHook() {
                @Override
                public void preClose(SolrCore core) {
                    executor.shutdown();
                }

                @Override
                public void postClose(SolrCore core) {

                }
            });

            // Create and configure the initial empty suggester
            initialSuggester = new SolrSuggester();
            initialSuggester.init(suggesterParams, core);
        }

        /**
         * @return
         */
        private ThreadFactory getThreadFactory(SolrCore core) {
            return new SuggestorThreadFactory("Suggestor-" + core.getName() + "-");
        }

        /**
         * The abstract base class' get() method will block if a value for key has
         * not previously been calculated (e.g. there is no 'live' value).
         * <p>
         * We don't want to block, we just want to return an empty suggester. The
         * newSearcher events will make sure that a suggester is built and put live
         * when possible, so it is fine to do this.
         */
        @Override
        public SolrSuggester get(String key) {
            liveLock.readLock().lock();
            try {
                if (live.get(key) == null) {
                    if (LOG.isDebugEnabled()) {
                        LOG.debug("Cache has no live suggester yet, return empty one while we wait.");
                    }
                    return initialSuggester;
                } else {
                    // Since we have a live suggester, return it.
                    return super.get(key);
                }
            } finally {
                liveLock.readLock().unlock();
            }
        }

        @Override
        protected SolrSuggester buildCache(String key) {
            if (!enabled) {
                // When disabled, provide an empty, yet initialised suggester.
                if (LOG.isDebugEnabled()) {
                    LOG.debug("Disabled suggester builder, returning empty suggester: " + core.getName());
                }
                return initialSuggester;
            }

            if (tempFileWarningLogger.checkFiles()) {
                tempFileWarningLogger.removeFiles();
            }

            RefCounted<SolrIndexSearcher> refCountedSearcher = core.getSearcher();
            try {
                SolrIndexSearcher searcher = refCountedSearcher.get();

                // Create and configure the suggester
                SolrSuggester suggester = new SolrSuggester();
                suggester.init(suggesterParams, core);

                if (!isNewSearcher.getAndSet(true)) {
                    // firstSearcher event
                    try {
                        LOG.info("Loading suggester index for: " + suggester.getName());
                        final long startMillis = System.currentTimeMillis();
                        if (buildOnStartup) {
                            buildSuggesterIndex(suggester, searcher);
                        } else {
                            suggester.reload(core, searcher);
                        }
                        final long timeTakenMillis = System.currentTimeMillis() - startMillis;
                        LOG.info("Loaded suggester " + suggester.getName() + ", took " + timeTakenMillis + " ms");
                    } catch (IOException e) {
                        LOG.error("Exception in reloading suggester index for: " + suggester.getName(), e);
                    }
                } else {
                    // newSearcher event
                    if (buildOnCommit) {
                        buildSuggesterIndex(suggester, searcher);
                    } else if (buildOnOptimize) {
                        if (searcher.getIndexReader().leaves().size() == 1) {
                            buildSuggesterIndex(suggester, searcher);
                        } else {
                            LOG.info("Index is not optimized therefore skipping building suggester index for: "
                                    + suggester.getName());
                        }
                    }
                }
                lastBuild = System.currentTimeMillis();
                return suggester;
            } finally {
                refCountedSearcher.decref();
            }
        }

        /**
         * Returns the time stamp of the last completed suggester build.
         * If no real build has taken place yet, zero is returned.
         *  
         * @return long
         */
        public long getLastBuild() {
            return lastBuild;
        }

        private void buildSuggesterIndex(SolrSuggester suggester, SolrIndexSearcher newSearcher) {
            try {
                LOG.info("Building suggester index for: " + suggester.getName());
                final long startMillis = System.currentTimeMillis();
                suggester.build(core, newSearcher);
                final long timeTakenMillis = System.currentTimeMillis() - startMillis;
                LOG.info("Built suggester " + suggester.getName() + ", took " + timeTakenMillis + " ms");
            } catch (Exception e) {
                LOG.error("Exception in building suggester index for: " + suggester.getName(), e);
            }
        }
    }

    static class SuggestorThreadFactory implements ThreadFactory {
        private final ThreadGroup group;
        private final AtomicInteger threadNumber = new AtomicInteger(1);
        private final String namePrefix;

        SuggestorThreadFactory(String namePrefix) {
            SecurityManager s = System.getSecurityManager();
            group = (s != null) ? s.getThreadGroup() : Thread.currentThread().getThreadGroup();

            this.namePrefix = namePrefix;
        }

        public Thread newThread(Runnable r) {
            Thread t = new Thread(group, r, namePrefix + threadNumber.getAndIncrement(), 0);
            t.setDaemon(true);
            return t;
        }
    }

    @Override
    public Collection<Accountable> getChildResources() {
        return Collections.<Accountable>emptyList();
    }

}