Hi Lukasz, Let's explain this problem using a specific example.
Say I have a main input element X, which accesses side input window W. When X arrives at a ParDo operator, W is not ready and not expired either. So, in this case, the ParDo should push back X and wait for W to become ready. Say, after two minutes, W is still unready but is expired due to advanced main input watermark. In this situation, how does Beam expect runners/engines to handle the pushed back value X? Discard X or throw an error? Thanks, Shen On Thu, Mar 8, 2018 at 6:35 PM, Lukasz Cwik <lc...@google.com> wrote: > I believe your missing over this point: "and also to not expire the side > input till the main input watermark advances beyond the garbage collection > hold of the side input." > > On Thu, Mar 8, 2018 at 3:33 PM, Shen Li <cs.she...@gmail.com> wrote: > >> Hi Lukasz, >> >> Thanks again. >> >> > the runner is required to hold back the main input till the side >> input is ready >> >> Yes, I understand these requirements. But what if the side input expires >> before it becomes ready? >> >> Shen >> >> >
