Matt Camp's questions

尝试使用官方 docker 映像让 Cassandra 在 docker 中运行。当我执行以下代码行时，它会启动然后停止 docker 而不连接到集群。我检查了该cassandra.yaml文件，它看起来就像我集群上的其他节点一样。文件也一样cassandra-rackdc.properties。docker 可以 ping 所有其他计算机。

我运行以下和一些推导：

docker run --name cassandra -i \
-v /media/mcamp/HDD/Docker/CampgroundContainer1:/var/lib/cassandra \
-e CASSANDRA_SEEDS="192.168.0.114, 192.168.0.101, 192.168.0.106" \
-e CASSANDRA_CLUSTER_NAME=CampCluster \
-e CASSANDRA_DC=campground-wireless \
-e CASSANDRA_RACK=Docker1 \
-e CASSANDRA_ENDPOINT_SNITCH=GossipingPropertyFileSnitch \
-e CASSANDRA_START_RPC=true \
-e CASSANDRA_LISTEN_ADDRESS=172.17.0.2 \
-p 7000:7000 \
 cassandra:latest

我收到以下错误：

INFO  [ScheduledTasks:1] 2017-11-10 03:45:39,428 TokenMetadata.java:498 - Updating topology for all endpoints that have changed
Exception (java.lang.RuntimeException) encountered during startup: Unable to gossip with any seeds
java.lang.RuntimeException: Unable to gossip with any seeds
    at org.apache.cassandra.gms.Gossiper.doShadowRound(Gossiper.java:1415)
    at org.apache.cassandra.service.StorageService.checkForEndpointCollision(StorageService.java:550)
    at org.apache.cassandra.service.StorageService.prepareToJoin(StorageService.java:801)
    at org.apache.cassandra.service.StorageService.initServer(StorageService.java:666)
    at org.apache.cassandra.service.StorageService.initServer(StorageService.java:612)
    at org.apache.cassandra.service.CassandraDaemon.setup(CassandraDaemon.java:393)
    at org.apache.cassandra.service.CassandraDaemon.activate(CassandraDaemon.java:600)
    at org.apache.cassandra.service.CassandraDaemon.main(CassandraDaemon.java:689)
ERROR [main] 2017-11-10 03:46:08,466 CassandraDaemon.java:706 - Exception encountered during startup
java.lang.RuntimeException: Unable to gossip with any seeds
    at org.apache.cassandra.gms.Gossiper.doShadowRound(Gossiper.java:1415) ~[apache-cassandra-3.11.1.jar:3.11.1]
    at org.apache.cassandra.service.StorageService.checkForEndpointCollision(StorageService.java:550) ~[apache-cassandra-3.11.1.jar:3.11.1]
    at org.apache.cassandra.service.StorageService.prepareToJoin(StorageService.java:801) ~[apache-cassandra-3.11.1.jar:3.11.1]
    at org.apache.cassandra.service.StorageService.initServer(StorageService.java:666) ~[apache-cassandra-3.11.1.jar:3.11.1]
    at org.apache.cassandra.service.StorageService.initServer(StorageService.java:612) ~[apache-cassandra-3.11.1.jar:3.11.1]
    at org.apache.cassandra.service.CassandraDaemon.setup(CassandraDaemon.java:393) [apache-cassandra-3.11.1.jar:3.11.1]
    at org.apache.cassandra.service.CassandraDaemon.activate(CassandraDaemon.java:600) [apache-cassandra-3.11.1.jar:3.11.1]
    at org.apache.cassandra.service.CassandraDaemon.main(CassandraDaemon.java:689) [apache-cassandra-3.11.1.jar:3.11.1]
INFO  [StorageServiceShutdownHook] 2017-11-10 03:46:08,469 HintsService.java:220 - Paused hints dispatch
WARN  [StorageServiceShutdownHook] 2017-11-10 03:46:08,469 Gossiper.java:1540 - No local state, state is in silent shutdown, or node hasn't joined, not announcing shutdown
INFO  [StorageServiceShutdownHook] 2017-11-10 03:46:08,469 MessagingService.java:984 - Waiting for messaging service to quiesce
INFO  [ACCEPT-/172.17.0.2] 2017-11-10 03:46:08,470 MessagingService.java:1338 - MessagingService has terminated the accept() thread
INFO  [StorageServiceShutdownHook] 2017-11-10 03:46:09,653 HintsService.java:220 - Paused hints dispatch

我在家里的一些 RaspberryPi 上运行了一个玩具 Cassandra 集群。我目前正在将 CryptoCoin 数据记录到其中，希望能更多地了解 Cassandra 以及沿途的其他一些事情。

我今天的问题是确定我是否在这张表上正确地构建了我的模式。

该表没有很多字段，主键是名称字段和时间戳字段。我想从所有硬币中查询最后 N 小时的数据（每分钟记录一次数据）。如果我使用简单的 WHERE 子句，我会收到“ALLOW FILTERING”警告。我理解它为什么会发生，但我正在努力理解正确的前进道路以确保可扩展的解决方案。现在该表只有大约 320k 条记录，我可以毫无问题地使用 ALLOW FILTERING，但我意识到这可能并非总是如此。

我设置了一个测试来查看运行两种不同的查询方法需要多长时间。ALLOW FILTERING 方法目前是最快的，但它可能会保持这种状态吗？这就是我缺乏知识的地方。

我有一个想法添加另一个字段，即星期几，也可能是一个月字段。想法是这可能允许在查询中进行更多过滤，因此我不必像下面那样遍历所有硬币，但我不知道这是否是个好主意。如果我这样做，我是否将它们设为 PrimaryKey？认为这是我与 Cassandra 最混淆的地方，但并非完全如此；也许只是不够自信。

CQL表说明：

CREATE TABLE cryptocoindb.worldcoinindex (
    name text,
    timestamp int,
    label text,
    price_btc double,
    price_cny double,
    price_eur double,
    price_gbp double,
    price_rur double,
    price_usd double,
    volume_24h double,
    PRIMARY KEY (name, timestamp)
) WITH CLUSTERING ORDER BY (timestamp ASC)
    AND bloom_filter_fp_chance = 0.01
    AND caching = {'keys': 'ALL', 'rows_per_partition': 'NONE'}
    AND comment = ''
    AND compaction = {'class': 'org.apache.cassandra.db.compaction.SizeTieredCompactionStrategy', 'max_threshold': '32', 'min_threshold': '4'}
    AND compression = {'chunk_length_in_kb': '64', 'class': 'org.apache.cassandra.io.compress.LZ4Compressor'}
    AND crc_check_chance = 1.0
    AND dclocal_read_repair_chance = 0.1
    AND default_time_to_live = 0
    AND gc_grace_seconds = 864000
    AND max_index_interval = 2048
    AND memtable_flush_period_in_ms = 0
    AND min_index_interval = 128
    AND read_repair_chance = 0.0
    AND speculative_retry = '99PERCENTILE';

Python中的代码：

# First method using ALLOW FILTERING:
startTime = time.time()
oneDaySec = 60*60*24
prior24hr = int(time.time()-oneDaySec)

query = "SELECT * FROM {}.{} WHERE timestamp > {} ALLOW FILTERING;".format(CASSANDRA_DB, CASSANDRA_TABLE, prior24hr)

rslt = session.execute(query, timeout=None)
worldcoinindex = rslt._current_rows
elapseTime = time.time()-startTime

print("Elapsed Time for this method: {}".format(elapseTime))

此方法经过的时间：0.6223547458648682

# Second method using multiple queries...

startTime = time.time()

# I get the unique coin names here.
qryGetCoinList = "SELECT DISTINCT name FROM {}.{};".format(CASSANDRA_DB, CASSANDRA_TABLE)
rslt = session.execute(qryGetCoinList, timeout=None)
rsltGetCoinList = rslt._current_rows
rsltGetCoinList = rsltGetCoinList.name.tolist()

oneDaySec = 60*60*24
prior24hr = int(time.time()-oneDaySec)

# This iterates over the unique coin names and queries 
# the last 24 hrs worth of data per coin.
# NOTE: There are 518 unique coins.  

rsltTodayPrices = pd.DataFrame()
for coin in rsltGetCoinList:

    qryTodayPrices = """
                    SELECT * FROM {}.{} 
                    WHERE name = '{}' AND timestamp > {};
                    """.format(CASSANDRA_DB, 
                               CASSANDRA_TABLE, 
                               coin, 
                               prior24hr)
    rslt = session.execute(qryTodayPrices, timeout=None)
    TodayPrices = rslt._current_rows
    rsltTodayPrices.append(TodayPrices)

elapseTime = time.time()-startTime
print("Elapsed Time for this method: {}".format(elapseTime))

此方法经过的时间：1.4576539993286133

谢谢！