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ASF GitHub Bot commented on GEARPUMP-32: ---------------------------------------- Github user whjiang commented on a diff in the pull request: https://github.com/apache/incubator-gearpump/pull/67#discussion_r72590179 --- Diff: external/kafka/src/main/scala/org/apache/gearpump/streaming/kafka/lib/source/AbstractKafkaSource.scala --- @@ -74,11 +74,10 @@ abstract class AbstractKafkaSource( private lazy val kafkaClient: KafkaClient = kafkaClientFactory.getKafkaClient(config) private lazy val fetchThread: FetchThread = fetchThreadFactory.getFetchThread(config, kafkaClient) private lazy val messageDecoder = config.getConfiguredInstance( - KafkaConfig.MESSAGE_DECODER_CLASS_CONFIG, classOf[MessageDecoder]) - private lazy val timestampFilter = config.getConfiguredInstance( --- End diff -- why filter is needed previously and now unneeded? > Minimum clock of source Tasks maybe inaccurate > ---------------------------------------------- > > Key: GEARPUMP-32 > URL: https://issues.apache.org/jira/browse/GEARPUMP-32 > Project: Apache Gearpump > Issue Type: Bug > Components: streaming > Affects Versions: 0.8.0 > Reporter: Manu Zhang > Assignee: Manu Zhang > Fix For: 0.8.1 > > > Moved from [https://github.com/gearpump/gearpump/issues/1835] and reported by > [Zhu Yueqian|https://github.com/yueqianzhu] > {quote} > Source tasks have not any upstreamClocks. So, startClock is the minimum of > pending clocks when recover happen. > eg below: > source task1: timeStamp:15,not ACK, minClockValue maybe is 15(<= 15). > source task2: timeStamp:10,ACKed, minClockValue maybe is Long.MaxValue > when recover happen,startClock maybe is 15. where is the data between 10 to > 15 at task2? > {quote} > More context on this issue: > In Gearpump, we maintain a global minimum clock tracked from a message's > timestamp across all tasks. It means messages with timestamp before this > clock have all been processed. An application will restart from this value on > failure, and thus at-least-once message delivery could be guaranteed. > The global minimum clock is the lower bound of all the Tasks' minimum clocks. > For a task, the minimum clock is the lower of > # upstream minimum clock > # a. the minimum timestamp of unacked messages > b. Long.MaxValue if all messages have been acked. > > Note that 2.b allows the global minimum clock to progress and it is almost > safe since the clock is also bounded by the upstream minimum clock. I said > "almost safe" because a source task has no upstream but we assume the > upstream minimum clock is Long.MaxValue. Thus, the scenario described by Zhu > Yueqian could happen and breaks at-least-once guarantee. -- This message was sent by Atlassian JIRA (v6.3.4#6332)