Change in osmo-msc[master]: sms queue: avoid repeated Paging for a failed SMS

historical

Hello Vadim Yanitskiy, Keith Whyte, Harald Welte, Jenkins Builder, 

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

    https://gerrit.osmocom.org/13173

to look at the new patch set (#4).

Change subject: sms queue: avoid repeated Paging for a failed SMS
......................................................................

sms queue: avoid repeated Paging for a failed SMS

A Paging might be attempted multiple times by the MSC, but if the MSC's paging
code decides that Paging failed, then that is that and pending requests should
end in failure. Make the SMS code heed that.

So far, sms_pending_failed() starts a new sms_queue_trigger() run. The
intention behind that might have been to fill up the queue when sending SMS has
failed, but the practical effect is actually bad:

As current ttcn3-msc-test runs show, a failed MT SMS gets triggered multiple
times in short succession, i.e. osmo-msc repeatedly sends Paging Requests for
the same subscriber. This is not because Paging decides that it might succeed
if we Page again -- this is a Paging failure being dispatched to the SMS code,
which then in turn re-launches Paging from scratch.

This special case happens actually only when there are few SMS still in the DB
to be delivered. In the TTCN3 test, there is exactly one MT SMS for one
subscriber, and retriggering the queue brings up the same SMS every time.

See f_tc_lu_and_mt_sms_paging_and_nothing() and f_tc_sgsap_mt_sms_and_nothing()
which say:
"/* Expect the MSC to page exactly 10 times before giving up */"

Fix: do not immediately trigger the SMS queue on a failed MT SMS. Instead,
leave it up to the periodical SMS queue trigger to decide.

This patch will cause the MT SMS tests in ttcn3-msc-tests to fail, because the
test expectations are bogus. The patch fixing the test run is listed 'Related'
below.

Related: I7dce12942a65eaaf97f78ca69401c7f93faacb9e (osmo-ttcn3-hacks)
Change-Id: I24bf9f1c1167efe1080ae4cf47ed2ef0bd981e49
---
M src/libmsc/sms_queue.c
1 file changed, 0 insertions(+), 1 deletion(-)

  git pull ssh://gerrit.osmocom.org:29418/osmo-msc refs/changes/73/13173/4
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Gerrit-Project: osmo-msc
Gerrit-Branch: master
Gerrit-MessageType: newpatchset
Gerrit-Change-Id: I24bf9f1c1167efe1080ae4cf47ed2ef0bd981e49
Gerrit-Change-Number: 13173
Gerrit-PatchSet: 4
Gerrit-Owner: Neels Hofmeyr <nhofmeyr at sysmocom.de>
Gerrit-Reviewer: Harald Welte <laforge at gnumonks.org>
Gerrit-Reviewer: Jenkins Builder (1000002)
Gerrit-Reviewer: Keith Whyte <keith at rhizomatica.org>
Gerrit-Reviewer: Neels Hofmeyr <nhofmeyr at sysmocom.de>
Gerrit-Reviewer: Vadim Yanitskiy <axilirator at gmail.com>
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