On Wed, Aug 8, 2012 at 4:14 PM, Ben Pfaff <[email protected]> wrote:
> Until now, the jsonrpc module has used messages received from the
> remote peer as the sole means to determine that the JSON-RPC
> connection is up. This could in theory interact badly with a
> remote peer that stops reading and processing messages from the
> receive queue when there is a backlog in the send queue for a
> given connection (ovsdb-server is an example of a program that
> behaves this way). This commit fixes the problem by expanding
> the definition of "activity" to include successfully sending
> JSON-RPC data that was previously queued.
>
> The above change is exactly analogous to the similar change
> made to the rconn library in commit 133f2dc95454 (rconn: Treat
> draining a message from the send queue as activity.).
>
> Bug #12789.
> Signed-off-by: Ben Pfaff <[email protected]>
> ---
> lib/jsonrpc.c | 13 +++++++++++++
> python/ovs/jsonrpc.py | 11 ++++++++++-
> 2 files changed, 23 insertions(+), 1 deletions(-)
>
> diff --git a/lib/jsonrpc.c b/lib/jsonrpc.c
> index c4d7dd2..9c0aaa9 100644
> --- a/lib/jsonrpc.c
> +++ b/lib/jsonrpc.c
> @@ -880,9 +880,22 @@ jsonrpc_session_run(struct jsonrpc_session *s)
> }
>
> if (s->rpc) {
> + size_t backlog;
> int error;
>
> + backlog = jsonrpc_get_backlog(s->rpc);
> jsonrpc_run(s->rpc);
> + if (jsonrpc_get_backlog(s->rpc) < backlog) {
> + /* Data previously caught in a queue was successfully sent.
Is this comment accurate that "data was sent successfully"? I suppose
that, if jsonrpc_get_backlog(s->rpc) returned 0, then that might mean
an error in jsonrpc_run(s->rpc) too?
> + *
> + * We don't count data that is successfully sent immediately as
> + * activity, because there's a lot of queuing downstream from us,
> + * which means that we can push a lot of data into a connection
> + * that has stalled and won't ever recover.
> + */
> + reconnect_activity(s->reconnect, time_msec());
> + }
> +
> error = jsonrpc_get_status(s->rpc);
> if (error) {
> reconnect_disconnected(s->reconnect, time_msec(), error);
> diff --git a/python/ovs/jsonrpc.py b/python/ovs/jsonrpc.py
> index cb471cb..4496bba 100644
> --- a/python/ovs/jsonrpc.py
> +++ b/python/ovs/jsonrpc.py
> @@ -502,9 +502,18 @@ class Session(object):
>
> def recv(self):
> if self.rpc is not None:
> + backlog = self.rpc.get_backlog()
> error, msg = self.rpc.recv()
> - if not error:
> + if self.rpc.get_backlog() < backlog:
> + # Data previously caught in a queue was successfully sent.
> + #
> + # We don't count data that is successfully sent immediately
> as
> + # activity, because there's a lot of queuing downstream from
> + # us, which means that we can push a lot of data into a
> + # connection that has stalled and won't ever recover.
> self.reconnect.activity(ovs.timeval.msec())
> +
> + if not error:
> if msg.type == Message.T_REQUEST and msg.method == "echo":
> # Echo request. Send reply.
> self.send(Message.create_reply(msg.params, msg.id))
> --
> 1.7.2.5
>
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