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apache-cassandra-0.6.0-rc1-src
author Shinji KONO <kono@ie.u-ryukyu.ac.jp>
date Fri, 02 Apr 2010 13:36:02 +0900
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1 0.6.0
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2 =====
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3
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4 Features
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5 --------
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6 - row caching: configure with the RowsCached attribute in
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7 ColumnFamily definition
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8 - Hadoop map/reduce support: see contrib/word_count for an example
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9 - experimental authentication support, described under
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10 Authenticator in storage.conf
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11
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12 Configuraton
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13 ------------
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14 - MemtableSizeInMB has been replaced by MemtableThroughputInMB which
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15 triggers a memtable flush when the specified amount of data has
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16 been written, including overwrites.
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17 - MemtableObjectCountInMillions has been replaced by the
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18 MemtableOperationsInMillions directive which causes a memtable flush
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19 to occur after the specified number of operations.
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20 - Like MemtableSizeInMB, BinaryMemtableSizeInMB has been replaced by
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21 BinaryMemtableThroughputInMB.
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22 - Replication factor is now per-keyspace, rather than global.
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23 - KeysCachedFraction is deprecated in favor of KeysCached
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24 - RowWarningThresholdInMB added, to warn before very large rows
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25 get big enough to threaten node stability
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26
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27 Thrift API
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28 ----------
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29 - removed deprecated get_key_range method
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30 - added batch_mutate meethod
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31 - deprecated multiget and batch_insert methods in favor of
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32 multiget_slice and batch_mutate, respectively
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33 - added ConsistencyLevel.ANY, for when you want write
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34 availability even when it may not be readable immediately.
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35 Unlike CL.ZERO, though, it will throw an exception if
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36 it cannot be written *somewhere*.
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37
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38 JMX metrics
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39 -----------
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40 - read and write statistics are reported as lifetime totals,
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41 instead of averages over the last minute. average-since-last
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42 requested are also available for convenience.
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43 - cache hit rate statistics are now available from JMX under
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44 org.apache.cassandra.db.Caches
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45 - compaction JMX metrics are moved to
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46 org.apache.cassandra.db.CompactionManager. PendingTasks is now
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47 a much better estimate of compactions remaining, and the
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48 progress of the current compaction has been added.
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49 - commitlog JMX metrics are moved to org.apache.cassandra.db.Commitlog
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50
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51 Installation/Upgrade
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52 --------------------
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53 - 0.6 network traffic is not compatible with earlier versions. You
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54 will need to shut down all your nodes at once, upgrade, then restart.
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55
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56
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57
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58 0.5.0
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59 =====
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60
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61 0. The commitlog format has changed (but sstable format has not).
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62 When upgrading from 0.4, empty the commitlog either by running
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63 bin/nodeprobe flush on each machine and waiting for the flush to finish,
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64 or simply remove the commitlog directory if you only have test data.
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65 (If more writes come in after the flush command, starting 0.5 will error
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66 out; if that happens, just go back to 0.4 and flush again.)
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67 The format changed twice: from 0.4 to beta1, and from beta2 to RC1.
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68
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69 .5 The gossip protocol has changed, meaning 0.5 nodes cannot coexist
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70 in a cluster of 0.4 nodes or vice versa; you must upgrade your
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71 whole cluster at the same time.
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72
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73 1. Bootstrap, move, load balancing, and active repair have been added.
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74 See http://wiki.apache.org/cassandra/Operations. When upgrading
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75 from 0.4, leave autobootstrap set to false for the first restart
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76 of your old nodes.
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77
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78 2. Performance improvements across the board, especially on the write
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79 path (over 100% improvement in stress.py throughput).
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80
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81 3. Configuration:
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82 - Added "comment" field to ColumnFamily definition.
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83 - Added MemtableFlushAfterMinutes, a global replacement for the
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84 old per-CF FlushPeriodInMinutes setting
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85 - Key cache settings
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86
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87 4. Thrift:
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88 - Added get_range_slice, deprecating get_key_range
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89
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90
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91
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92 0.4.2
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93 =====
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94
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95 1. Improve default garbage collector options significantly --
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96 throughput will be 30% higher or more.
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97
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98
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99
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100 0.4.1
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101 =====
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102
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103 1. SnapshotBeforeCompaction configuration option allows snapshotting
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104 before each compaction, which allows rolling back to any version
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105 of the data.
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106
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107
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108
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109 0.4.0
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110 =====
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111
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112 1. On-disk data format has changed to allow billions of keys/rows per
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113 node instead of only millions. The new format is incompatible with 0.3;
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114 see 0.3 notes below for how to import data from a 0.3 install.
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115
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116 2. Cassandra now supports multiple keyspaces. Typically you will have
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117 one keyspace per application, allowing applications to be able to
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118 create and modify ColumnFamilies at will without worrying about
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119 collisions with others in the same cluster.
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120
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121 3. Many Thrift API changes and documentation. See
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122 http://wiki.apache.org/cassandra/API
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123
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124 4. Removed the web interface in favor of JMX and bin/nodeprobe, which
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125 has significantly enhanced functionality.
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126
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127 5. Renamed configuration "<Table>" to "<Keyspace>".
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128
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129 6. Added commitlog fsync; see "<CommitLogSync>" in configuration.
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130
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131
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132
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133 0.3.0
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134 =====
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135
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136 1. With enough and large enough keys in a ColumnFamily, Cassandra will
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137 run out of memory trying to perform compactions (data file merges).
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138 The size of what is stored in memory is (S + 16) * (N + M) where S
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139 is the size of the key (usually 2 bytes per character), N is the
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140 number of keys and M, is the map overhead (which can be guestimated
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141 at around 32 bytes per key).
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142 So, if you have 10-character keys and 1GB of headroom in your heap
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143 space for compaction, you can expect to store about 17M keys
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144 before running into problems.
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145 See https://issues.apache.org/jira/browse/CASSANDRA-208
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146
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147 2. Because fixing #1 requires a data file format change, 0.4 will not
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148 be binary-compatible with 0.3 data files. A client-side upgrade
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149 can be done relatively easily with the following algorithm:
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150 for key in old_client.get_key_range(everything):
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151 columns = old_client.get_slice or get_slice_super(key, all columns)
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152 new_client.batch_insert or batch_insert_super(key, columns)
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153 The inner loop can be trivially parallelized for speed.
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154
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155 3. Commitlog does not fsync before reporting a write successful.
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156 Using blocking writes mitigates this to some degree, since all
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157 nodes that were part of the write quorum would have to fail
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158 before sync for data to be lost.
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159 See https://issues.apache.org/jira/browse/CASSANDRA-182
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160
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161 Additionally, row size (that is, all the data associated with a single
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162 key in a given ColumnFamily) is limited by available memory, because
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163 compaction deserializes each row before merging.
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164
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165 See https://issues.apache.org/jira/browse/CASSANDRA-16
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166