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I'd like you to reexamine a change.  Please visit


to look at the new patch set (#2).

Change subject: KUDU-2065, KUDU-2011: Release sidecars on cancellation or 

KUDU-2065, KUDU-2011: Release sidecars on cancellation or timeout

Previously, when an outbound call times out after transmission
of the request has begun but not finished, the RPC layer will
continue to send the entire payload (including any sidecars) to
the remote destination until the promised number of bytes specified
in the header are sent. This is problematic for the users of the
RPC layer as there is no well defined point in which the sidecars
are no longer referenced by the RPC layer. The only model in which
this would work is for the caller to either transfer or share ownership
of the sidecars with the RPC layer. This has caused some life cycle
issues with row batches in Impala before (e.g. IMPALA-5093).

This change fixes the problem above by modifying the RPC protocol
to allow a mid-transmission RPC call to be cancelled. Specifically,
a new footer is added to all outbound call requests. It contains
a flag, when true, indicates the outbound call was cancelled after
it has started but before it finished. The server will inspect this
flag and ignore inbound calls with this flag set. This footer enables
the caller to relinquish references to the sidecars early when an
outbound call is cancelled or timed-out. Once the call is cancelled
or timed-out, the RPC layer will send the remainder of the bytes for
the request with some dummy bytes. Since the server always ignores
cancelled call requests, it's okay to send random bytes.

To avoid breaking compatibility, a new RPC feature flag REQUEST_FOOTERS
is introduced in this change. During connection negotiation, the
client will always include this flag in its feature set. A server which
supports parsing footer will include REQUEST_FOOTERS in its feature set
if it sees the client also supports it. A client will only send the
footer if the remote server has the RPC feature flag REQUEST_FOOTERS.

Change-Id: I5c8e294090279649082eebc4f6cfb6fe858bbbfc
M docs/design-docs/rpc.md
M src/kudu/rpc/blocking_ops.cc
M src/kudu/rpc/connection.cc
M src/kudu/rpc/connection.h
M src/kudu/rpc/constants.cc
M src/kudu/rpc/inbound_call.cc
M src/kudu/rpc/inbound_call.h
M src/kudu/rpc/outbound_call.cc
M src/kudu/rpc/outbound_call.h
M src/kudu/rpc/reactor.cc
M src/kudu/rpc/rpc-test-base.h
M src/kudu/rpc/rpc-test.cc
M src/kudu/rpc/rpc_header.proto
M src/kudu/rpc/rtest.proto
M src/kudu/rpc/serialization.cc
M src/kudu/rpc/serialization.h
M src/kudu/rpc/server_negotiation.cc
M src/kudu/rpc/transfer.cc
M src/kudu/rpc/transfer.h
19 files changed, 481 insertions(+), 152 deletions(-)

  git pull ssh://gerrit.cloudera.org:29418/kudu refs/changes/99/7599/2
To view, visit http://gerrit.cloudera.org:8080/7599
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Gerrit-MessageType: newpatchset
Gerrit-Change-Id: I5c8e294090279649082eebc4f6cfb6fe858bbbfc
Gerrit-PatchSet: 2
Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-Owner: Michael Ho <k...@cloudera.com>
Gerrit-Reviewer: Kudu Jenkins
Gerrit-Reviewer: Tidy Bot
Gerrit-Reviewer: Todd Lipcon <t...@apache.org>

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