1. MySQL::Replication

2. what is it?

3. It's a replacement for

4. MySQL Replication

5. why?

6. first...

7. what is replication?

8. synchronising data

9. between multiple databases

10. db1 db2

11. why replicate?

12. examples...

13. redundancy

14. database client client client client client client client client

15. database on client client client client client client client client

16. database on fire client client client client client client client client

17. database on fire client client client client client client client client

18. database on fire client client client client client client client client

19. arhhhh!

20. If we had replicated

21. to a hot standby

22. clients could be moved

25. another example

26. performance

27. database client

28. database client client

29. database client client client

30. database client client client client

31. database client client client client client

32. database client client client client client client

33. database client client client client client client client

34. database client client client client client client client client

35. database client client client client client client client client

36. database client client client client client client client client

37. arhhhh!

38. If we replicated

39. for scale out

40. load would be spread

49. so...

50. why replicate?

51. because it gives you benefits

52. compared to having

53. a single database

54. so...

55. how does it work?

56. in particular...

57. how does MySQL Replication work?

59. master

60. master slave

61. master client slave

62. master client binlog slave

63. master client binlog slave relay

64. master client binlog slave relay

65. the cool thing is

66. each slave

67. can be a master

68. to other slaves

69. master slave slave slave

70. master slave slave master/slave slave

71. master master/slave slave master/slave slave slave

72. this works fine

73. but...

74. slaves can only have a single master

75. master master/slave slave master/slave slave slave

76. so?

77. that means...

78. no multiple masters

79. slave master master master

80. slave master master master

81. why not?

82. don't ask me

83. because I don't know

84. but...

85. we can emulate multiple masters

86. to do this

87. we have to

88. setup a ring topology

89. what?

90. each slave

91. is a master

92. to another slave

93. master slave

94. master slave master/slave

95. master master/slave master/slave slave

96. master/slave master/slave master/slave master/slave

98. so...

99. how does this achieve

100. multiple master replication?

101. by having each master

102. write all queries

103. to it's binlog

104. ...including the queries

105. it replicated

106. from its master

107. huh?

108. queries are passed

109. around the ring

110. kind of like

111. pass the parcel

113. why is this a problem?

114. when the ring breaks

120. arhhhh!

121. so does everything else

122. ...and recovery is hard

123. why?

124. infinite loops!

125. what do you mean?

126. each master

127. is responsible

128. for termination

129. of its own queries

130. around the ring...

131. in other words

132. queries don't replicate infinitely

133. because

134. a master won't relay

135. its own queries twice

137. so...

138. what happens if...

139. a database goes down?

140. we recover by

141. ...reconnecting the links

142. ...and restarting replication

143. ?

146. (OpenOffice doesn't do the arrow I wanted)

147. hang on...

148. who was responsible

149. for terminating

150. the failed database's queries?

151. hrmmm...

152. if there are queries

153. from the failed database

154. still replicating

155. that haven't yet terminated

157. arhhhh

158. Infinite queries, infinitely replicating

159. so...

160. how can I achieve

161. multiple master replication

162. ...that is fault tolerant

163. ...and is easy to recover from?

164. MySQL::Replication

165. It's a replacement

166. for MySQL's built-in replication

167. it's a client/server model

168. each master runs the server

169. slave master master master

170. slave master master server

171. slave server master server

172. slave server server server

173. each slave runs the client

174. ...and the client

175. can run multiple instances

176. (one for each server)

177. (think peer-to-peer)

178. slave server server server

179. client(s) server server server

180. and if something breaks

181. client(s) server server server

182. client(s) server server server

183. client(s) server server server

184. only the peer connection is effected

185. client(s) server server server

186. client(s) server server server

187. and if the failed database recovers

188. we restart from where we left off

189. client(s) server server server

190. client(s) server server server

191. otherwise

192. we just fail it out

193. and can take our time rebuilding

194. it was redundant anyway

195. right?

196. :)

197. ohh

198. ...and no infinite loops

199. why?

200. since we connect

201. directly to the server

202. no intermediary connections

203. can break

204. there's more...

205. relay caching

206. say what?

207. instead of connecting

208. directly to the master

209. the client

210. connects to a local relay

211. if it doesn't have

212. the queries we want

213. it will get them for us

214. example

215. multiple clients

216. in data center A

217. ...each connect

218. to a server

219. in data center B

220. ...each download the same queries

221. what a waste

222. ...in bandwidth

223. ...and server load

224. so...

225. instead

226. ...each connect

227. to a local relay

228. now...

229. only a single client (the relay)

230. connects to the server

231. ...saves bandwidth

232. ...saves server load

233. :)

234. so...

235. CPAN?

236. almost ready

237. client/server working in production

238. I just need to do the documentation

239. then I'll put it on CPAN

240. what about the relay stuff?

241. It's nearly complete...

242. I just need to finish

243. ...a couple more test harnesses

244. ...and write the documentation

245. FAQ

246. what happens with collisions?

247. when two databases

248. update the same record

249. It's a race condition

250. solution?

251. solve it at the application layer

252. use a broker for global IDs

253. or shard writes

254. questions?

255. [email_address]