Cool thnx. So if a checkpoint expires the pipeline will block or fail in total or only the specific task related to the operator (running along with the checkpoint task) or nothing happens?
On Tue, May 17, 2016 at 3:49 PM, Robert Metzger <rmetz...@apache.org> wrote: > Hi Stravos, > > I haven't implemented our checkpointing mechanism and I didn't participate > in the design decisions while implementing it, so I can not compare it in > detail to other approaches. > > From a "does it work perspective": Checkpoints are only confirmed if all > parallel subtasks successfully created a valid snapshot of the state. So if > there is a failure in the checkpointing mechanism, no valid checkpoint will > be created. The system will recover from the last valid checkpoint. > There is a timeout for checkpoints. So if a barrier doesn't pass through > the system for a certain period of time, the checkpoint is cancelled. The > default timeout is 10 minutes. > > Regards, > Robert > > > On Mon, May 16, 2016 at 1:22 PM, Stavros Kontopoulos < > st.kontopou...@gmail.com> wrote: > >> Hi, >> >> I was looking into the flink snapshotting algorithm details also >> mentioned here: >> >> http://data-artisans.com/high-throughput-low-latency-and-exactly-once-stream-processing-with-apache-flink/ >> >> https://blog.acolyer.org/2015/08/19/asynchronous-distributed-snapshots-for-distributed-dataflows/ >> >> http://mail-archives.apache.org/mod_mbox/flink-user/201601.mbox/%3CCANC1h_s6MCWSuDf2zSnEeD66LszDoLx0jt64++0kBOKTjkAv7w%40mail.gmail.com%3E >> >> http://apache-flink-user-mailing-list-archive.2336050.n4.nabble.com/About-exactly-once-question-td2545.html >> >> From other sources i understand that it assumes no failures to work for >> message delivery or for example a process hanging for ever: >> https://en.wikipedia.org/wiki/Snapshot_algorithm >> >> https://blog.acolyer.org/2015/04/22/distributed-snapshots-determining-global-states-of-distributed-systems/ >> >> So my understanding (maybe wrong) is that this is a solution which seems >> not to address the fault tolerance issue in a strong manner like for >> example if it was to use a 3pc protocol for local state propagation and >> global agreement. I know the latter is not efficient just mentioning it for >> comparison. >> >> How the algorithm behaves in practical terms under the presence of its >> own failures (this is a background process collecting partial states)? Are >> there timeouts for reaching a barrier? >> >> PS. have not looked deep into the code details yet, planning to. >> >> Best, >> Stavros >> >> >
