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Do send HEARTBEATs if there are new readers

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The emphasis is on "do": with this commit it does it even when there is
no data available in the writer.  These were suppressed previously
because of a quirk in the DDSI specification in versions prior to 2.3,
where it impossible for a writer to send a valid heartbeat if its
history cache was empty.

Not sending them has negative consequences, as establishing a reliable
connection then becomes dependent on the reader sending a pre-emptive
ACKNACK message.  Uusally, this makes no observable difference, but if
the writer temporarily disconnects from the reader (but not vice-versa)
it may require the publishing of a sample to resynchronize the two.

Signed-off-by: Erik Boasson <eb@ilities.com>
This commit is contained in:
Erik Boasson 2020-07-01 12:29:23 +02:00 • committed by eboasson
parent dff08536c4
commit 5a4193ca37
1 changed files with 3 additions and 3 deletions
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6
src/core/ddsi/src/q_entity.c
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@ -3462,15 +3462,15 @@ seqno_t writer_max_drop_seq (const struct writer *wr)
int writer_must_have_hb_scheduled (const struct writer *wr, const struct whc_state *whcst)
{
if (ddsrt_avl_is_empty (&wr->readers) || whcst->max_seq < 0)
if (ddsrt_avl_is_empty (&wr->readers))
{
/* Can't transmit a valid heartbeat if there is no data; and it
wouldn't actually be sent anywhere if there are no readers, so
there is little point in processing the xevent all the time.
Note that add_msg_to_whc and add_proxy_reader_to_writer will
perform a reschedule. 8.4.2.2.3: need not (can't, really!) send
a heartbeat if no data is available. */
perform a reschedule. Since DDSI 2.3, we can send valid
heartbeats in the absence of data. */
return 0;
}
else if (!((const struct wr_prd_match *) ddsrt_avl_root_non_empty (&wr_readers_treedef, &wr->readers))->all_have_replied_to_hb)