When spilling to disk is enabled, an upstream operator will be blocked
from emitting more tuples to a corresponding output port when the size
of a buffer (in bytes) exceeds a limit (see documentation on how to
configure the limit). This is a back pressure mechanism that Pramod
refers to. There are two ways how data/tuples may be removed from the
buffer to make more space on the buffer available and enable back the
upstream operator. Tuples can be either spooled to a local disk or
completely purged from the buffer. The purge happens only after window
(actually the earliest checkpoint window after the window that the tuple
belongs to) is completely processed by an application/dag. If there is
not enough disk space for spooling, buffer server would fail the
container that it belongs to. There are few JIRAs filed to improve the
current behavior (for example limit amount of disk space that the buffer
server can use for spilling).

Thank you,


On 6/20/18 17:24, Pramod Immaneni wrote: