cassandra - 启用 CQL 二进制协议(protocol)会在 ubuntu 中抛出 YAMLException : Unable to find property - in DataStax 3. 0 安装

Question

我正在尝试从 C# 客户端连接到安装在虚拟机内运行的 Ubuntu 桌面中的 DataStax 3.0 企业版(礼貌 CassandraSharp )。

根据那里的文档，(“默认情况下，Cassandra 不启用 CQL 二进制协议(protocol)(从 1.2-rc2 开始)。您必须在 cassandra.yaml 中启用此功能才能使用 cassandra-sharp”)，我介绍了此条目“start_native_transport: true"到 cassandra.yaml 中，当我从 Ubuntu 终端启动服务时，出现以下错误:

INFO 02:57:53,734 Loading settings from file:/etc/dse/cassandra/cassandra.yaml ERROR 02:57:55,834 Fatal configuration error error Can't construct a java object for tag:yaml.org,2002:org.apache.cassandra.config.Config; exception=Cannot create property=start_native_transport for JavaBean=org.apache.cassandra.config.Config@7f636e4e; Unable to find property 'start_native_transport' on class: org.apache.cassandra.config.Config

知道如何在 DataStax Cassandra 中启用二进制协议(protocol)吗？还是我做错了什么？它是配置文件中特定的位置吗？我是 linux 新手!
此处询问的完整 yaml 文件:

# Cassandra storage config YAML 


# The name of the cluster. This is mainly used to prevent machines in
# one logical cluster from joining another.
cluster_name: 'Test Cluster'

initial_token:

hinted_handoff_enabled: true

max_hint_window_in_ms: 3600000 # one hour

hinted_handoff_throttle_delay_in_ms: 1



# authentication backend, implementing IAuthenticator; used to identify users
authenticator: org.apache.cassandra.auth.AllowAllAuthenticator
#authenticator: com.datastax.bdp.cassandra.auth.PasswordAuthenticator
#authenticator: com.datastax.bdp.cassandra.auth.KerberosAuthenticator

# authorization backend, implementing IAuthorizer; used to limit access/provide permissions
authorizer: org.apache.cassandra.auth.AllowAllAuthorizer
#authorizer: com.datastax.bdp.cassandra.auth.CassandraAuthorizer

permissions_validity_in_ms: 2000

# Replication strategy to use for the auth keyspace.
auth_replication_strategy: org.apache.cassandra.locator.SimpleStrategy

# Replication options to use for the auth keyspace.
auth_replication_options:
    replication_factor: 1

# The partitioner is responsible for distributing rows (by key) across
# nodes in the cluster.  Any IPartitioner may be used, including your
# own as long as it is on the classpath.  Out of the box, Cassandra
# provides org.apache.cassandra.dht.RandomPartitioner
# org.apache.cassandra.dht.ByteOrderedPartitioner,
# org.apache.cassandra.dht.OrderPreservingPartitioner (deprecated),
# and org.apache.cassandra.dht.CollatingOrderPreservingPartitioner
# (deprecated).
# 
# - RandomPartitioner distributes rows across the cluster evenly by md5.
#   When in doubt, this is the best option.
# - ByteOrderedPartitioner orders rows lexically by key bytes.  BOP allows
#   scanning rows in key order, but the ordering can generate hot spots
#   for sequential insertion workloads.
# - OrderPreservingPartitioner is an obsolete form of BOP, that stores
# - keys in a less-efficient format and only works with keys that are
#   UTF8-encoded Strings.
# - CollatingOPP colates according to EN,US rules rather than lexical byte
#   ordering.  Use this as an example if you need custom collation.
#
# See http://wiki.apache.org/cassandra/Operations for more on
# partitioners and token selection.
partitioner: org.apache.cassandra.dht.RandomPartitioner

# directories where Cassandra should store data on disk.
data_file_directories:
    - /var/lib/cassandra/data

# commit log
commitlog_directory: /var/lib/cassandra/commitlog

# Maximum size of the key cache in memory.
#
# Each key cache hit saves 1 seek and each row cache hit saves 2 seeks at the
# minimum, sometimes more. The key cache is fairly tiny for the amount of
# time it saves, so it's worthwhile to use it at large numbers.
# The row cache saves even more time, but must store the whole values of
# its rows, so it is extremely space-intensive. It's best to only use the
# row cache if you have hot rows or static rows.
#
# NOTE: if you reduce the size, you may not get you hottest keys loaded on startup.
#
# Default value is empty to make it "auto" (min(5% of Heap (in MB), 100MB)). Set to 0 to disable key cache.
key_cache_size_in_mb:

# Duration in seconds after which Cassandra should
# safe the keys cache. Caches are saved to saved_caches_directory as
# specified in this configuration file.
#
# Saved caches greatly improve cold-start speeds, and is relatively cheap in
# terms of I/O for the key cache. Row cache saving is much more expensive and
# has limited use.
#
# Default is 14400 or 4 hours.
key_cache_save_period: 14400

# Number of keys from the key cache to save
# Disabled by default, meaning all keys are going to be saved
# key_cache_keys_to_save: 100

# Maximum size of the row cache in memory.
# NOTE: if you reduce the size, you may not get you hottest keys loaded on startup.
#
# Default value is 0, to disable row caching.
row_cache_size_in_mb: 0

# Duration in seconds after which Cassandra should
# safe the row cache. Caches are saved to saved_caches_directory as specified
# in this configuration file.
#
# Saved caches greatly improve cold-start speeds, and is relatively cheap in
# terms of I/O for the key cache. Row cache saving is much more expensive and
# has limited use.
#
# Default is 0 to disable saving the row cache.
row_cache_save_period: 0

# Number of keys from the row cache to save
# Disabled by default, meaning all keys are going to be saved
# row_cache_keys_to_save: 100

# The provider for the row cache to use.
#
# Supported values are: ConcurrentLinkedHashCacheProvider, SerializingCacheProvider
#
# SerializingCacheProvider serialises the contents of the row and stores
# it in native memory, i.e., off the JVM Heap. Serialized rows take
# significantly less memory than "live" rows in the JVM, so you can cache
# more rows in a given memory footprint.  And storing the cache off-heap
# means you can use smaller heap sizes, reducing the impact of GC pauses.
#
# It is also valid to specify the fully-qualified class name to a class
# that implements org.apache.cassandra.cache.IRowCacheProvider.
#
# Defaults to SerializingCacheProvider
row_cache_provider: SerializingCacheProvider

# saved caches
saved_caches_directory: /var/lib/cassandra/saved_caches

# commitlog_sync may be either "periodic" or "batch." 
# When in batch mode, Cassandra won't ack writes until the commit log
# has been fsynced to disk.  It will wait up to
# commitlog_sync_batch_window_in_ms milliseconds for other writes, before
# performing the sync.
#
# commitlog_sync: batch
# commitlog_sync_batch_window_in_ms: 50
#
# the other option is "periodic" where writes may be acked immediately
# and the CommitLog is simply synced every commitlog_sync_period_in_ms
# milliseconds.
commitlog_sync: periodic
commitlog_sync_period_in_ms: 10000

# The size of the individual commitlog file segments.  A commitlog
# segment may be archived, deleted, or recycled once all the data
# in it (potentally from each columnfamily in the system) has been 
# flushed to sstables.  
#
# The default size is 32, which is almost always fine, but if you are
# archiving commitlog segments (see commitlog_archiving.properties),
# then you probably want a finer granularity of archiving; 8 or 16 MB
# is reasonable.
commitlog_segment_size_in_mb: 32

# any class that implements the SeedProvider interface and has a
# constructor that takes a Map<String, String> of parameters will do.
seed_provider:
    # Addresses of hosts that are deemed contact points. 
    # Cassandra nodes use this list of hosts to find each other and learn
    # the topology of the ring.  You must change this if you are running
    # multiple nodes!
    - class_name: org.apache.cassandra.locator.SimpleSeedProvider
      parameters:
          # seeds is actually a comma-delimited list of addresses.
          # Ex: "<ip1>,<ip2>,<ip3>"
          - seeds: "127.0.0.1"

# emergency pressure valve: each time heap usage after a full (CMS)
# garbage collection is above this fraction of the max, Cassandra will
# flush the largest memtables.  
#
# Set to 1.0 to disable.  Setting this lower than
# CMSInitiatingOccupancyFraction is not likely to be useful.
#
# RELYING ON THIS AS YOUR PRIMARY TUNING MECHANISM WILL WORK POORLY:
# it is most effective under light to moderate load, or read-heavy
# workloads; under truly massive write load, it will often be too
# little, too late.
flush_largest_memtables_at: 0.75

# emergency pressure valve #2: the first time heap usage after a full
# (CMS) garbage collection is above this fraction of the max,
# Cassandra will reduce cache maximum _capacity_ to the given fraction
# of the current _size_.  Should usually be set substantially above
# flush_largest_memtables_at, since that will have less long-term
# impact on the system.  
# 
# Set to 1.0 to disable.  Setting this lower than
# CMSInitiatingOccupancyFraction is not likely to be useful.
reduce_cache_sizes_at: 0.85
reduce_cache_capacity_to: 0.6

# For workloads with more data than can fit in memory, Cassandra's
# bottleneck will be reads that need to fetch data from
# disk. "concurrent_reads" should be set to (16 * number_of_drives) in
# order to allow the operations to enqueue low enough in the stack
# that the OS and drives can reorder them.
#
# On the other hand, since writes are almost never IO bound, the ideal
# number of "concurrent_writes" is dependent on the number of cores in
# your system; (8 * number_of_cores) is a good rule of thumb.
concurrent_reads: 32
concurrent_writes: 32

# Total memory to use for memtables.  Cassandra will flush the largest
# memtable when this much memory is used.
# If omitted, Cassandra will set it to 1/3 of the heap.
# memtable_total_space_in_mb: 2048

# Total space to use for commitlogs.  Since commitlog segments are
# mmapped, and hence use up address space, the default size is 32
# on 32-bit JVMs, and 1024 on 64-bit JVMs.
#
# If space gets above this value (it will round up to the next nearest
# segment multiple), Cassandra will flush every dirty CF in the oldest
# segment and remove it.  So a small total commitlog space will tend
# to cause more flush activity on less-active columnfamilies.
# commitlog_total_space_in_mb: 4096

# This sets the amount of memtable flush writer threads.  These will
# be blocked by disk io, and each one will hold a memtable in memory
# while blocked. If you have a large heap and many data directories,
# you can increase this value for better flush performance.
# By default this will be set to the amount of data directories defined.
#memtable_flush_writers: 1

# the number of full memtables to allow pending flush, that is,
# waiting for a writer thread.  At a minimum, this should be set to
# the maximum number of secondary indexes created on a single CF.
memtable_flush_queue_size: 4

# Whether to, when doing sequential writing, fsync() at intervals in
# order to force the operating system to flush the dirty
# buffers. Enable this to avoid sudden dirty buffer flushing from
# impacting read latencies. Almost always a good idea on SSD:s; not
# necessarily on platters.
trickle_fsync: false
trickle_fsync_interval_in_kb: 10240

# TCP port, for commands and data
storage_port: 7000

# SSL port, for encrypted communication.  Unused unless enabled in
# encryption_options
ssl_storage_port: 7001

# Address to bind to and tell other Cassandra nodes to connect to. You
# _must_ change this if you want multiple nodes to be able to
# communicate!
# 
# Leaving it blank leaves it up to InetAddress.getLocalHost(). This
# will always do the Right Thing *if* the node is properly configured
# (hostname, name resolution, etc), and the Right Thing is to use the
# address associated with the hostname (it might not be).
#
# Setting this to 0.0.0.0 is always wrong.
#listen_address: localhost -- commented by nachi 19Mar2013
listen_address: 192.168.42.236

# Address to broadcast to other Cassandra nodes
# Leaving this blank will set it to the same value as listen_address
# broadcast_address: 1.2.3.4

# The address to bind the Thrift RPC service to -- clients connect
# here. Unlike ListenAddress above, you *can* specify 0.0.0.0 here if
# you want Thrift to listen on all interfaces.
# 
# Leaving this blank has the same effect it does for ListenAddress,
# (i.e. it will be based on the configured hostname of the node).
#rpc_address: 0.0.0.0 -- commented by nachi on 19Mar2013
rpc_address: 192.168.42.236
# port for Thrift to listen for clients on
rpc_port: 9160

# enable or disable keepalive on rpc connections
rpc_keepalive: true

# Cassandra provides three options for the RPC Server:
#
# sync  -> One connection per thread in the rpc pool (see below).
#          For a very large number of clients, memory will be your limiting
#          factor; on a 64 bit JVM, 128KB is the minimum stack size per thread.
#          Connection pooling is very, very strongly recommended.
#
# async -> Nonblocking server implementation with one thread to serve 
#          rpc connections.  This is not recommended for high throughput use
#          cases. Async has been tested to be about 50% slower than sync
#          or hsha and is deprecated: it will be removed in the next major release.
#
# hsha  -> Stands for "half synchronous, half asynchronous." The rpc thread pool 
#          (see below) is used to manage requests, but the threads are multiplexed
#          across the different clients.
#
# The default is sync because on Windows hsha is about 30% slower.  On Linux,
# sync/hsha performance is about the same, with hsha of course using less memory.
rpc_server_type: sync

# Uncomment rpc_min|max|thread to set request pool size.
# You would primarily set max for the sync server to safeguard against
# misbehaved clients; if you do hit the max, Cassandra will block until one
# disconnects before accepting more.  The defaults for sync are min of 16 and max
# unlimited.
# 
# For the Hsha server, the min and max both default to quadruple the number of
# CPU cores.
#
# This configuration is ignored by the async server.
#
# rpc_min_threads: 16
# rpc_max_threads: 2048

# uncomment to set socket buffer sizes on rpc connections
# rpc_send_buff_size_in_bytes:
# rpc_recv_buff_size_in_bytes:

# Frame size for thrift (maximum field length).
# 0 disables TFramedTransport in favor of TSocket. This option
# is deprecated; we strongly recommend using Framed mode.
thrift_framed_transport_size_in_mb: 15
start_native_transport: true
# added by nac to enable binary protocol that suppofrts async stuff


# The max length of a thrift message, including all fields and
# internal thrift overhead.
thrift_max_message_length_in_mb: 16

# Set to true to have Cassandra create a hard link to each sstable
# flushed or streamed locally in a backups/ subdirectory of the
# Keyspace data.  Removing these links is the operator's
# responsibility.
incremental_backups: false

# Whether or not to take a snapshot before each compaction.  Be
# careful using this option, since Cassandra won't clean up the
# snapshots for you.  Mostly useful if you're paranoid when there
# is a data format change.
snapshot_before_compaction: false

# Whether or not a snapshot is taken of the data before keyspace truncation
# or dropping of column families. The STRONGLY advised default of true 
# should be used to provide data safety. If you set this flag to false, you will
# lose data on truncation or drop.
auto_snapshot: true

# Add column indexes to a row after its contents reach this size.
# Increase if your column values are large, or if you have a very large
# number of columns.  The competing causes are, Cassandra has to
# deserialize this much of the row to read a single column, so you want
# it to be small - at least if you do many partial-row reads - but all
# the index data is read for each access, so you don't want to generate
# that wastefully either.
column_index_size_in_kb: 64

# Size limit for rows being compacted in memory.  Larger rows will spill
# over to disk and use a slower two-pass compaction process.  A message
# will be logged specifying the row key.
in_memory_compaction_limit_in_mb: 64

# Number of simultaneous compactions to allow, NOT including
# validation "compactions" for anti-entropy repair.  Simultaneous
# compactions can help preserve read performance in a mixed read/write
# workload, by mitigating the tendency of small sstables to accumulate
# during a single long running compactions. The default is usually
# fine and if you experience problems with compaction running too
# slowly or too fast, you should look at
# compaction_throughput_mb_per_sec first.
#
# This setting has no effect on LeveledCompactionStrategy.
#
# concurrent_compactors defaults to the number of cores.
# Uncomment to make compaction mono-threaded, the pre-0.8 default.
#concurrent_compactors: 1

# Multi-threaded compaction. When enabled, each compaction will use
# up to one thread per core, plus one thread per sstable being merged.
# This is usually only useful for SSD-based hardware: otherwise, 
# your concern is usually to get compaction to do LESS i/o (see:
# compaction_throughput_mb_per_sec), not more.
multithreaded_compaction: false

# Throttles compaction to the given total throughput across the entire
# system. The faster you insert data, the faster you need to compact in
# order to keep the sstable count down, but in general, setting this to
# 16 to 32 times the rate you are inserting data is more than sufficient.
# Setting this to 0 disables throttling. Note that this account for all types
# of compaction, including validation compaction.
compaction_throughput_mb_per_sec: 16

# Track cached row keys during compaction, and re-cache their new
# positions in the compacted sstable.  Disable if you use really large
# key caches.
compaction_preheat_key_cache: true

# Throttles all outbound streaming file transfers on this node to the
# given total throughput in Mbps. This is necessary because Cassandra does
# mostly sequential IO when streaming data during bootstrap or repair, which
# can lead to saturating the network connection and degrading rpc performance.
# When unset, the default is 400 Mbps or 50 MB/s.
# stream_throughput_outbound_megabits_per_sec: 400

# Time to wait for a reply from other nodes before failing the command 
rpc_timeout_in_ms: 10000

# Enable socket timeout for streaming operation.
# When a timeout occurs during streaming, streaming is retried from the start
# of the current file. This *can* involve re-streaming an important amount of
# data, so you should avoid setting the value too low.
# Default value is 0, which never timeout streams.
# streaming_socket_timeout_in_ms: 0

# phi value that must be reached for a host to be marked down.
# most users should never need to adjust this.
# phi_convict_threshold: 8

# endpoint_snitch -- Set this to a class that implements
# IEndpointSnitch.  The snitch has two functions:
# - it teaches Cassandra enough about your network topology to route
#   requests efficiently
# - it allows Cassandra to spread replicas around your cluster to avoid
#   correlated failures. It does this by grouping machines into
#   "datacenters" and "racks."  Cassandra will do its best not to have
#   more than one replica on the same "rack" (which may not actually
#   be a physical location)
#
# IF YOU CHANGE THE SNITCH AFTER DATA IS INSERTED INTO THE CLUSTER,
# YOU MUST RUN A FULL REPAIR, SINCE THE SNITCH AFFECTS WHERE REPLICAS
# ARE PLACED.
#
# Out of the box, Cassandra provides
#  - SimpleSnitch:
#    Treats Strategy order as proximity. This improves cache locality
#    when disabling read repair, which can further improve throughput.
#    Only appropriate for single-datacenter deployments.
#  - PropertyFileSnitch:
#    Proximity is determined by rack and data center, which are
#    explicitly configured in cassandra-topology.properties.
#  - GossipingPropertyFileSnitch
#    The rack and datacenter for the local node are defined in
#    cassandra-rackdc.properties and propagated to other nodes via gossip.  If
#    cassandra-topology.properties exists, it is used as a fallback, allowing
#    migration from the PropertyFileSnitch.
#  - RackInferringSnitch:
#    Proximity is determined by rack and data center, which are
#    assumed to correspond to the 3rd and 2nd octet of each node's
#    IP address, respectively.  Unless this happens to match your
#    deployment conventions (as it did Facebook's), this is best used
#    as an example of writing a custom Snitch class.
#  - Ec2Snitch:
#    Appropriate for EC2 deployments in a single Region.  Loads Region
#    and Availability Zone information from the EC2 API. The Region is
#    treated as the Datacenter, and the Availability Zone as the rack.
#    Only private IPs are used, so this will not work across multiple
#    Regions.
#  - Ec2MultiRegionSnitch:
#    Uses public IPs as broadcast_address to allow cross-region
#    connectivity.  (Thus, you should set seed addresses to the public
#    IP as well.) You will need to open the storage_port or
#    ssl_storage_port on the public IP firewall.  (For intra-Region
#    traffic, Cassandra will switch to the private IP after
#    establishing a connection.)
# DataStax Enterprise provides
#  - com.datastax.bdp.snitch.DseDelegateSnitch:
#    Proximity is determined by the settings in dse.yaml:delegated_snitch to
#    allow DSE to add location aware functionality. This is required for DSE.
#
# You can use a custom Snitch by setting this to the full class name
# of the snitch, which will be assumed to be on your classpath.
endpoint_snitch: com.datastax.bdp.snitch.DseDelegateSnitch

# controls how often to perform the more expensive part of host score
# calculation
dynamic_snitch_update_interval_in_ms: 100 
# controls how often to reset all host scores, allowing a bad host to
# possibly recover
dynamic_snitch_reset_interval_in_ms: 600000
# if set greater than zero and read_repair_chance is < 1.0, this will allow
# 'pinning' of replicas to hosts in order to increase cache capacity.
# The badness threshold will control how much worse the pinned host has to be
# before the dynamic snitch will prefer other replicas over it.  This is
# expressed as a double which represents a percentage.  Thus, a value of
# 0.2 means Cassandra would continue to prefer the static snitch values
# until the pinned host was 20% worse than the fastest.
dynamic_snitch_badness_threshold: 0.1

# request_scheduler -- Set this to a class that implements
# RequestScheduler, which will schedule incoming client requests
# according to the specific policy. This is useful for multi-tenancy
# with a single Cassandra cluster.
# NOTE: This is specifically for requests from the client and does
# not affect inter node communication.
# org.apache.cassandra.scheduler.NoScheduler - No scheduling takes place
# org.apache.cassandra.scheduler.RoundRobinScheduler - Round robin of
# client requests to a node with a separate queue for each
# request_scheduler_id. The scheduler is further customized by
# request_scheduler_options as described below.
request_scheduler: org.apache.cassandra.scheduler.NoScheduler

# Scheduler Options vary based on the type of scheduler
# NoScheduler - Has no options
# RoundRobin
#  - throttle_limit -- The throttle_limit is the number of in-flight
#                      requests per client.  Requests beyond 
#                      that limit are queued up until
#                      running requests can complete.
#                      The value of 80 here is twice the number of
#                      concurrent_reads + concurrent_writes.
#  - default_weight -- default_weight is optional and allows for
#                      overriding the default which is 1.
#  - weights -- Weights are optional and will default to 1 or the
#               overridden default_weight. The weight translates into how
#               many requests are handled during each turn of the
#               RoundRobin, based on the scheduler id.
#
# request_scheduler_options:
#    throttle_limit: 80
#    default_weight: 5
#    weights:
#      Keyspace1: 1
#      Keyspace2: 5

# request_scheduler_id -- An identifer based on which to perform
# the request scheduling. Currently the only valid option is keyspace.
# request_scheduler_id: keyspace

# index_interval controls the sampling of entries from the primrary
# row index in terms of space versus time.  The larger the interval,
# the smaller and less effective the sampling will be.  In technicial
# terms, the interval coresponds to the number of index entries that
# are skipped between taking each sample.  All the sampled entries
# must fit in memory.  Generally, a value between 128 and 512 here
# coupled with a large key cache size on CFs results in the best trade
# offs.  This value is not often changed, however if you have many
# very small rows (many to an OS page), then increasing this will
# often lower memory usage without a impact on performance.
index_interval: 128

# Enable or disable inter-node encryption
# Default settings are TLS v1, RSA 1024-bit keys (it is imperative that
# users generate their own keys) TLS_RSA_WITH_AES_128_CBC_SHA as the cipher
# suite for authentication, key exchange and encryption of the actual data transfers.
# NOTE: No custom encryption options are enabled at the moment
# The available internode options are : all, none, dc, rack
#
# If set to dc cassandra will encrypt the traffic between the DCs
# If set to rack cassandra will encrypt the traffic between the racks
#
# The passwords used in these options must match the passwords used when generating
# the keystore and truststore.  For instructions on generating these files, see:
# http://download.oracle.com/javase/6/docs/technotes/guides/security/jsse/JSSERefGuide.html#CreateKeystore
#
encryption_options:
    internode_encryption: none
    keystore: resources/dse/conf/.keystore
    keystore_password: tomcat
    truststore: resources/dse/conf/.truststore
    truststore_password: tomcat
    # More advanced defaults below:
    # protocol: TLS
    # algorithm: SunX509
    # store_type: JKS
    # cipher_suites: [TLS_RSA_WITH_AES_128_CBC_SHA,TLS_RSA_WITH_AES_256_CBC_SHA]
    # require_client_auth: false  [1]: https://github.com/pchalamet/cassandra-sharp/wiki/Having-troubles

Answer 1

Lyuben 是正确的，您在 Cassandra 1.1.9.3 上设置了 Cassandra 1.2+ 属性。

http://www.datastax.com/doc-source/pdf/dse30.pdf - 参见“组件”部分。

您尝试设置“start_native_transport”的属性仅在 Cassandra 1.2+ 中可用。如果有帮助，最新的 Datastax 社区版包括 Cassandra 1.2.3。

我怎么知道？我猜您还尝试使用新的 Datastax CQL3 驱动程序 (https://github.com/datastax/java-driver/tree/master/driver-core)，请参阅先决条件，Cassandra 1.2。