Apache Cassandra Learning Step by Step (5): 实战性的JTwissandra项目

在完成了Apache Cassandra的四个基本学习步骤之后，可以尝试下实战性的编码了。

 

如有必要，建议再简单回顾一下：

 Apache Cassandra Learning Step by Step (1): Setup to play

 Apache Cassandra Learning Step by Step (2): Core Concepts

 Apache Cassandra Learning Step by Step (3): Samples ABC

 Apache Cassandra Learning Step by Step (4): Data Modeling

基于第四点的建模思路，接下来我们要做的，就是搭建一个叫做JTwissandra的实战性项目，就是所谓的Java版本的Twissandra了。

 

其目的是为了以Twitter为假想对象，使用最简约（或者直接说简陋得了）的建模和实现，表达采用Apache Cassandra作为NoSQL平台的基本实现过程。

 

JTwissandra的基本编码环境：

1. Maven来管理

2. JUnit来测试

3. 基于hector client来作为Apache Cassandra的Java 客户端

 

大家可以通过下面的Github链接，直接clone出来最新的代码:

JTwissandra: https://github.com/itstarting/jtwissandra

 

也欢迎大家Fork或在这里直接拍砖——反正咱在NoSQL也是新手，脸皮厚点不要紧啦：）

 

1. 首先需要一个HFactoryHelper来初始化并建立Cassandra的客户端连接池和必要的对象：

package bright.zheng.jtwissandra;import java.io.IOException;import java.util.Properties;import me.prettyprint.cassandra.model.ConfigurableConsistencyLevel;import me.prettyprint.hector.api.Cluster;import me.prettyprint.hector.api.HConsistencyLevel;import me.prettyprint.hector.api.Keyspace;import me.prettyprint.hector.api.factory.HFactory;import org.slf4j.Logger;import org.slf4j.LoggerFactory;/** * Helper for Cassandra initialization *  * @author bright_zheng * */public class HFactoryHelper {private static Logger logger = LoggerFactory.getLogger(HFactoryHelper.class);private static Cluster cluster;private static Keyspace keyspace = initKeyspace();private static Properties properties;        private HFactoryHelper(){}        public static Keyspace getKeyspace(){    return keyspace;    }        private static Keyspace initKeyspace() {        properties = new Properties();        try {            properties.load(HFactoryHelper.class.getResourceAsStream("/config.properties"));        } catch (IOException ioe) {            ioe.printStackTrace();        }                String cluster_name = properties.getProperty("cluster.name", "Test Cluster");        logger.debug("cluster.name={}", cluster_name);        String cluster_hosts = properties.getProperty("cluster.hosts", "127.0.0.1:9160");        logger.debug("cluster.hosts={}", cluster_hosts);        String active_keyspace = properties.getProperty("keyspace", "JTWISSANDRA");        logger.debug("keyspace={}", active_keyspace);                cluster = HFactory.getOrCreateCluster(cluster_name, cluster_hosts);                ConfigurableConsistencyLevel ccl = new ConfigurableConsistencyLevel();        ccl.setDefaultReadConsistencyLevel(HConsistencyLevel.ONE);                return HFactory.createKeyspace(        active_keyspace,        cluster,         ccl);    }}

 

2. 建立各项业务服务的基类BaseService。

package bright.zheng.jtwissandra.service;import java.util.UUID;import me.prettyprint.cassandra.serializers.LongSerializer;import me.prettyprint.cassandra.serializers.StringSerializer;import me.prettyprint.cassandra.service.clock.MicrosecondsClockResolution;import me.prettyprint.cassandra.utils.TimeUUIDUtils;import me.prettyprint.hector.api.ClockResolution;import me.prettyprint.hector.api.Keyspace;import me.prettyprint.hector.api.beans.HColumn;import me.prettyprint.hector.api.factory.HFactory;import org.slf4j.Logger;import org.slf4j.LoggerFactory;import bright.zheng.jtwissandra.HFactoryHelper;/** * Base service which all business services should extend *  * @author bright_zheng * */public class BaseService {protected Logger logger = LoggerFactory.getLogger(getClass());protected static Keyspace KEYSPACE = HFactoryHelper.getKeyspace();protected static final String CF_USER = "USER";protected static final String CF_FRIEND = "FRIEND";protected static final String CF_FOLLOWER = "FOLLOWER";protected static final String CF_TWEET = "TWEET";protected static final String CF_TIMELINE = "TIMELINE";protected static final StringSerializer SERIALIZER_STRING = StringSerializer.get();protected static final LongSerializer SERIALIZER_LONG = LongSerializer.get();protected static final int TWEETS_LIMIT_DEFAULT = 10;protected static final int TWEETS_LIMIT_MAX = 50;protected HColumn<String, String> createColumn(String name, String value) {return HFactory.createColumn(name, value, SERIALIZER_STRING, SERIALIZER_STRING);}protected HColumn<String, Long> createColumn(String name, Long value) {return HFactory.createColumn(name, value, SERIALIZER_STRING, SERIALIZER_LONG);}protected HColumn<Long, String> createColumn(Long name, String value) {return HFactory.createColumn(name, value, SERIALIZER_LONG, SERIALIZER_STRING);}/** * REF: http://wiki.apache.org/cassandra/FAQ#working_with_timeuuid_in_java *  * @return UUID */public UUID getUUID(){//TODO: which UUID should we use to make sure it's unique?ClockResolution clock = new MicrosecondsClockResolution();    return TimeUUIDUtils.getTimeUUID(clock);//return TimeUUIDUtils.getUniqueTimeUUIDinMillis();}protected Long getTimestamp(UUID uuid){//return uuid.timestamp();return TimeUUIDUtils.getTimeFromUUID(uuid);}protected Long generateTimestamp(){return getTimestamp(getUUID());}}

3. 下面是各项业务服务代码：

3.1 UserService

package bright.zheng.jtwissandra.service;import java.util.UUID;import me.prettyprint.hector.api.factory.HFactory;import me.prettyprint.hector.api.mutation.Mutator;import bright.zheng.jtwissandra.bean.User;/** * User service *  * @author bright_zheng * */public class UserService extends BaseService{/** * Sample CLI cmd: * set USER['550e8400-e29b-41d4-a716-446655440000']['user_name'] = 'itstarting'; * set USER['550e8400-e29b-41d4-a716-446655440000']['password'] = '111222'; * set USER['550e8400-e29b-41d4-a716-446655440000']['create_timestamp'] = 1329836819890000; *  * @param user */    public String addUser(User user) {    Mutator<String> mutator = HFactory.createMutator(    KEYSPACE, SERIALIZER_STRING);    UUID uuid = this.getUUID();    String user_uuid = uuid.toString();       Long create_timestamp = this.getTimestamp(uuid);    logger.debug("user_uuid={}", user_uuid);      logger.debug("user_name={}", user.getUser_name());    logger.debug("password={}", user.getUser_password());    logger.debug("create_timestamp={}", create_timestamp);                mutator.addInsertion(user_uuid, CF_USER,         this.createColumn("user_name", user.getUser_name()));        mutator.addInsertion(user_uuid, CF_USER,         this.createColumn("password", user.getUser_password()));        mutator.addInsertion(user_uuid, CF_USER,         this.createColumn("create_timestamp", create_timestamp));                mutator.execute();                //return the generated uuid        return user_uuid;    }       }

3.2 FriendService 

package bright.zheng.jtwissandra.service;import me.prettyprint.hector.api.factory.HFactory;import me.prettyprint.hector.api.mutation.MutationResult;import me.prettyprint.hector.api.mutation.Mutator;/** * Friend service *  * @author bright_zheng * */public class FriendService extends BaseService{/** * Adding a friend has two business logic: * 1. Add the friend's uuid to the Friend CF under my uuid * 2. Add my uuid to the friend's uuid as follower *  * set FRIEND['550e8400-e29b-41d4-a716-446655440000']['1329836819859000'] * = '550e8400-e29b-41d4-a716-446655440001; *  * set FOLLOWER['550e8400-e29b-41d4-a716-446655440001']['1329836819859000''] * = '550e8400-e29b-41d4-a716-446655440000; *  * @param me * @param friend */    public MutationResult followFriend(String me, String friend) {    Mutator<String> mutator = HFactory.createMutator(    KEYSPACE, SERIALIZER_STRING);        Long timestamp = this.generateTimestamp();    logger.debug("timestamp={}", timestamp);                mutator.addInsertion(me, CF_FRIEND,         this.createColumn(timestamp, friend));                mutator.addInsertion(friend, CF_FOLLOWER,         this.createColumn(timestamp, me));                return mutator.execute();    }       }

3.3 TimelineService

package bright.zheng.jtwissandra.service;import java.util.ArrayList;import java.util.Iterator;import java.util.List;import me.prettyprint.hector.api.beans.ColumnSlice;import me.prettyprint.hector.api.beans.HColumn;import me.prettyprint.hector.api.factory.HFactory;import me.prettyprint.hector.api.query.QueryResult;import me.prettyprint.hector.api.query.SliceQuery;import bright.zheng.jtwissandra.bean.Timeline;/** * Timeline service *  * @author bright_zheng * */public class TimelineService extends BaseService{/** * get specified user's first Timeline *  * @param user_uuid * @return */public TimelineWrapper getTimeline(String user_uuid){return getTimeline(user_uuid, 0L, TWEETS_LIMIT_DEFAULT);}/** * get specified user's Timeline with start point *  * @param user_uuid * @param start * @return */public TimelineWrapper getTimeline(String user_uuid, long start){return getTimeline(user_uuid, start, TWEETS_LIMIT_DEFAULT);}/** * get specified user's Timeline with start point and limit *  * @param user_uuid * @param start * @param limit * @return */    public TimelineWrapper getTimeline(String user_uuid, long start, int limit){    if (start<0) start = 0;    if (limit<0) limit = TWEETS_LIMIT_DEFAULT;    if (limit>TWEETS_LIMIT_MAX) limit = TWEETS_LIMIT_MAX;        SliceQuery<String, Long, String> sliceQuery =             HFactory.createSliceQuery(KEYSPACE, SERIALIZER_STRING, SERIALIZER_LONG, SERIALIZER_STRING);                sliceQuery.setColumnFamily(CF_TIMELINE);        sliceQuery.setKey(user_uuid);        sliceQuery.setRange(start, Long.MAX_VALUE, false, limit+1);        QueryResult<ColumnSlice<Long, String>> result = sliceQuery.execute();        List<HColumn<Long, String>> list = result.get().getColumns();                long next = 0L;        if(list==null){        return new TimelineWrapper(null, next);        }else if (list.size()<=limit){                return new TimelineWrapper(convertToTimeline(list), 0L);        }else{        HColumn<Long,String> last = list.get(list.size()-1);        next = last.getName(); //the name is the timestamp as the "next" start        list.remove(list.size()-1);                return new TimelineWrapper(convertToTimeline(list), next);        }    }        private List<Timeline> convertToTimeline(List<HColumn<Long,String>> cols){    Iterator<HColumn<Long,String>> it = cols.iterator();    List<Timeline> result = new ArrayList<Timeline>();    while(it.hasNext()){    HColumn<Long,String> col = it.next();    result.add(new Timeline(col.getValue(), col.getName()));    }    return result;    }        public class TimelineWrapper{    private List<Timeline> timelines;    private long nextTimeline;        public TimelineWrapper(List<Timeline> timelines, long nextTimeline){    this.timelines = timelines;    this.nextTimeline = nextTimeline;    }public long getNextTimeline() {return nextTimeline;}public List<Timeline> getTimelines() {return timelines;}        }}

3.4 TweetService

package bright.zheng.jtwissandra.service;import java.util.ArrayList;import java.util.Iterator;import java.util.List;import java.util.UUID;import me.prettyprint.hector.api.beans.ColumnSlice;import me.prettyprint.hector.api.beans.HColumn;import me.prettyprint.hector.api.beans.Row;import me.prettyprint.hector.api.beans.Rows;import me.prettyprint.hector.api.factory.HFactory;import me.prettyprint.hector.api.mutation.Mutator;import me.prettyprint.hector.api.query.MultigetSliceQuery;import me.prettyprint.hector.api.query.QueryResult;import me.prettyprint.hector.api.query.SliceQuery;import bright.zheng.jtwissandra.bean.Tweet;/** * Tweet service *  * @author bright_zheng * */public class TweetService extends BaseService{/** * Adding a tweet has following logic: * 1. Save the tweet to CF of TWEET * 2. Add the new tweet to my TIMELINE * 3. Add the new tweet to all my followers' TIMELINE *  * @param me * @param friend */    public String addTweet(String user_uuid, String tweet_content) {    Mutator<String> mutator = HFactory.createMutator(    KEYSPACE, SERIALIZER_STRING);    //the tweet uuid    UUID uuid = this.getUUID();    String tweet_uuid = uuid.toString();    logger.debug("tweet_uuid={}", tweet_uuid);        //the timestamp to build the timeline    Long timestamp = this.getTimestamp(uuid);    logger.debug("timestamp={}", timestamp);                mutator.addInsertion(tweet_uuid, CF_TWEET,         this.createColumn("user_uuid", user_uuid));        mutator.addInsertion(tweet_uuid, CF_TWEET,         this.createColumn("tweet_content", tweet_content));                mutator.addInsertion(user_uuid, CF_TIMELINE,         this.createColumn(timestamp, tweet_uuid));                // get back all my follower and insert the tweet to his/her TIMELINE        SliceQuery<String, Long, String> sliceQuery =             HFactory.createSliceQuery(KEYSPACE, SERIALIZER_STRING, SERIALIZER_LONG, SERIALIZER_STRING);                sliceQuery.setColumnFamily(CF_FOLLOWER);        sliceQuery.setKey(user_uuid);        sliceQuery.setRange(Long.MIN_VALUE, Long.MAX_VALUE, false, 500); //TODO: 500 followers hard code here?        QueryResult<ColumnSlice<Long, String>> result = sliceQuery.execute();        Iterator<HColumn<Long, String>> followers = result.get().getColumns().iterator();        while(followers.hasNext()) {        HColumn<Long, String> follower = followers.next();        String follower_uuid = follower.getValue();        logger.debug("follower's uuid={}", follower_uuid);        logger.debug("timestamp={}", follower.getName());                    //insert the tweet to the follower's TIMELINE            mutator.addInsertion(follower_uuid, CF_TIMELINE,             this.createColumn(timestamp, tweet_uuid));        }                mutator.execute();                //return the new generated tweet's uuid        return tweet_uuid;    }        /**     * Should we add this service?     *      * @param tweet_uuid     * @return     */    public Tweet getTweet(String tweet_uuid){    return null;    }        public List<Tweet> getTweets(List<String> tweet_uuids){    MultigetSliceQuery<String, String, String> multigetSlicesQuery =            HFactory.createMultigetSliceQuery(KEYSPACE, SERIALIZER_STRING, SERIALIZER_STRING, SERIALIZER_STRING);        multigetSlicesQuery.setColumnFamily(CF_TWEET);        multigetSlicesQuery.setColumnNames("user_uuid","tweet_content");                multigetSlicesQuery.setKeys(tweet_uuids);        QueryResult<Rows<String, String, String>> results = multigetSlicesQuery.execute();    return convertRowsToTweets(results.get());    }        private List<Tweet> convertRowsToTweets(Rows<String, String, String> rows){    List<Tweet> list = new ArrayList<Tweet>();    Iterator<Row<String, String, String>> iterator = rows.iterator();    while(iterator.hasNext()){    Row<String, String, String> row = iterator.next();    ColumnSlice<String, String> cs = row.getColumnSlice();        list.add(new Tweet(row.getKey(),            cs.getColumnByName("tweet_content").getValue(),           cs.getColumnByName("user_uuid").getValue()));    }    return list;    }    }

4. 当然少不了JUnit测试用例了：

package bright.zheng.jtwissandra;import java.util.ArrayList;import java.util.Arrays;import java.util.Iterator;import java.util.List;import junit.framework.Assert;import org.junit.AfterClass;import org.junit.BeforeClass;import org.junit.Test;import org.slf4j.Logger;import org.slf4j.LoggerFactory;import bright.zheng.jtwissandra.bean.Timeline;import bright.zheng.jtwissandra.bean.Tweet;import bright.zheng.jtwissandra.bean.User;import bright.zheng.jtwissandra.service.FriendService;import bright.zheng.jtwissandra.service.TimelineService;import bright.zheng.jtwissandra.service.TimelineService.TimelineWrapper;import bright.zheng.jtwissandra.service.TweetService;import bright.zheng.jtwissandra.service.UserService;/** * Test cases for all services currently provided. * Please drop and create schema first and then run all cases as one round * The 'me' and 'friend' will be created each round dynamically for easier testing *  * @author bright_zheng * */public class ServiceTest{Logger logger = LoggerFactory.getLogger(ServiceTest.class);private static UserService SERVICE_USER = new UserService();private static FriendService SERVICE_FRIEND = new FriendService();private static TweetService SERVICE_TWEET = new TweetService();private static TimelineService SERVICE_TIMELINE = new TimelineService();private static String me;private static String friend;private static long nextTimeline = 0L;@BeforeClasspublic static void setUp(){//}@Test    public void addUser() {logger.debug("=====================addUser{====================");//add user 1me = SERVICE_USER.addUser(new User("itstarting","1234"));logger.debug("This round of tesing, ME={}", me);Assert.assertNotNull(me);//add user 2friend = SERVICE_USER.addUser(new User("test1","1234"));logger.debug("This round of tesing, FRIEND={}", friend);Assert.assertNotNull(friend);logger.debug("=====================}//addUser====================");    }       /** * I'm following a friend */    @Test    public void followFriend() {logger.debug("=====================followFriend{====================");SERVICE_FRIEND.followFriend(me, friend);logger.debug("=====================}//followFriend====================");    }        /**     * I'm followed by a follower     */    @Test    public void followedByFollower() {logger.debug("=====================followedByFollower{====================");SERVICE_FRIEND.followFriend(friend, me);logger.debug("=====================}//followedByFollower====================");    }        /**     * I'm twittering     */    @Test    public void addTweetByMe() {logger.debug("=====================addTweetByMe{====================");for(int i=0; i<100; i++){String tweet_uuid = SERVICE_TWEET.addTweet(me, "Hellow JTWISSANDRA -- by itstarting:" + i);Assert.assertNotNull(tweet_uuid);}logger.debug("=====================}//addTweetByMe====================");    }        /**     * My friend is twittering     *      */    @Test    public void addTweetByFriend() {logger.debug("=====================addTweetByFriend{====================");for(int i=0; i<100; i++){    String tweet_uuid = SERVICE_TWEET.addTweet(friend, "Hellow JTWISSANDRA -- by test1:" + i);Assert.assertNotNull(tweet_uuid);}logger.debug("=====================}//addTweetByFriend====================");    }        /**     * Get tweets for me     */    @Test    public void getTweetsByMe(){logger.debug("=====================getTweetsByMe{====================");    getTweets(me, 0);logger.debug("=====================}//getTweetsByMe====================");    }        /**     * Get tweets at next Timeline (if any)     */    @Test    public void getTweetsByMeForNextTimeline(){logger.debug("=====================getTweetsByMeForNextTimeline{====================");if(nextTimeline>0L){getTweets(me, nextTimeline);}logger.debug("=====================}//getTweetsByMeForNextTimeline====================");    }        /**     * Get tweets for my friend     */    @Test    public void getTweetsByMyFriend(){logger.debug("=====================getTweetsByMyFriend{====================");    getTweets(friend, 0);logger.debug("=====================}//getTweetsByMyFriend====================");    }        /**     *      */    @Test    public void getTweetsByMyFriendForNextTimeline(){logger.debug("=====================getTweetsByMyFriendForNextTimeline{====================");    getTweets(friend, nextTimeline);logger.debug("=====================}//getTweetsByMyFriendForNextTimeline====================");    }        private void getTweets(String user_uuid, long start){    TimelineWrapper wrapper = SERVICE_TIMELINE.getTimeline(user_uuid, start);    Assert.assertNotNull(wrapper);    List<Timeline> list = wrapper.getTimelines();    List<String> tweet_uuids = new ArrayList<String>();    for(Timeline timeline: list){    String tweet_uuid = timeline.getTweet_uuid();    logger.debug("From Timeline: tweet_uuid={}, tweet_timestamp={}",     tweet_uuid, timeline.getTweet_timestamp());    tweet_uuids.add(tweet_uuid);    }    List<Tweet> tweets = SERVICE_TWEET.getTweets(tweet_uuids);    Iterator<Tweet> it = tweets.iterator();    while(it.hasNext()){    Tweet tweet = it.next();    logger.debug("From Tweet: tweet_uuid={}, tweet_content={}, user_uuid={}",     new Object[]{tweet.getTweet_uuid(),      tweet.getTweet_content(),     tweet.getUser_uuid()    });    }    if(wrapper.getNextTimeline() > 0L){    logger.debug("The start timeline of next page is: {}", wrapper.getNextTimeline());    nextTimeline = wrapper.getNextTimeline();    }else{    logger.debug("No next page available");    nextTimeline = 0L;    }    }        @AfterClass    public static void shutdown(){    //cluster.getConnectionManager().shutdown();    }}

这是个一锅端的测试用例，全部跑一次可以覆盖几乎所有的业务服务逻辑。

  

5. 最后，别忘了在跑之前创建必要的schema：

drop keyspace JTWISSANDRA;create keyspace JTWISSANDRAwith placement_strategy = 'org.apache.cassandra.locator.SimpleStrategy'and strategy_options = [{replication_factor:1}];use JTWISSANDRA;create column family USERwith comparator = UTF8Type   and key_validation_class = UTF8Typeand default_validation_class = UTF8Typeand column_metadata = [{column_name: user_name, validation_class: UTF8Type,    index_name:user_name_idx, index_type:KEYS }{column_name: user_password, validation_class: UTF8Type}{column_name: create_timestamp, validation_class: LongType,   index_name:create_timestamp_idx, index_type:KEYS}];create column family FRIENDwith comparator = LongType   and key_validation_class = UTF8Typeand default_validation_class = UTF8Type;create column family FOLLOWERwith comparator = LongType   and key_validation_class = UTF8Typeand default_validation_class = UTF8Type;create column family TWEETwith comparator = UTF8Type   and key_validation_class = UTF8Typeand default_validation_class = UTF8Typeand column_metadata = [{column_name: user_uuid, validation_class: UTF8Type}{column_name: tweet_content, validation_class: UTF8Type}];create column family TIMELINEwith comparator = LongType   and key_validation_class = UTF8Typeand default_validation_class = UTF8Type;

6. 其他？

 

有些杂项，就不贴了吧，略过……有兴趣的可从Github clone下来跑跑看。

 

 

 

==所发现的问题，接下来再一一列出、分析、讨论，最最希望有丰富经验的高手前来助阵、指点，去我谜团，谢谢！==