[Tarantool-patches] [PATCH v2 1/2] applier: fix upstream.lag calculations

[Vitaliia Ioffe]

QA LGTM
 
 
--
Vitaliia Ioffe
 
  
>Понедельник, 16 августа 2021, 18:15 +03:00 от Serge Petrenko <sergepetrenko at tarantool.org>:
> 
>upstream.lag is the delta between the moment when a row was written to
>master's journal and the moment when it was received by the replica.
>It's an important metric to check whether the replica has fallen too far
>behind master.
>
>Not all the rows coming from master have a valid time of creation. For
>example, RAFT system messages don't have one, and we can't assign
>correct time to them: these messages do not originate from the journal,
>and assigning current time to them would lead to jumps in upstream.lag
>results.
>
>Stop updating upstream.lag for rows which don't have creation time
>assigned.
>
>The upstream.lag calculation changes were meant to fix the flaky
>replication/errinj.test:
>
> Test failed! Result content mismatch:
> --- replication/errinj.result Fri Aug 13 15:15:35 2021
> +++ /tmp/tnt/rejects/replication/errinj.reject Fri Aug 13 15:40:39 2021
> @@ -310,7 +310,7 @@
>  ...
>  box.info.replication[1].upstream.lag < 1
>  ---
> -- true
> +- false
>  ...
>
>But the changes were not enough, because now the test
>may see the initial lag value (TIMEOUT_INFINITY).
>So fix the test as well by waiting until upstream.lag becomes < 1.
>---
> src/box/applier.cc | 3 ++-
> test/replication/errinj.result | 5 ++++-
> test/replication/errinj.test.lua | 5 ++++-
> 3 files changed, 10 insertions(+), 3 deletions(-)
>
>diff --git a/src/box/applier.cc b/src/box/applier.cc
>index 902d0bc72..9256078e1 100644
>--- a/src/box/applier.cc
>+++ b/src/box/applier.cc
>@@ -664,7 +664,8 @@ applier_read_tx_row(struct applier *applier, double timeout)
> 
>  coio_read_xrow_timeout_xc(coio, ibuf, row, timeout);
> 
>- applier->lag = ev_now(loop()) - row->tm;
>+ if (row->tm > 0)
>+ applier->lag = ev_now(loop()) - row->tm;
>  applier->last_row_time = ev_monotonic_now(loop());
>  return tx_row;
> }
>diff --git a/test/replication/errinj.result b/test/replication/errinj.result
>index 9d13f6aa7..ec251182f 100644
>--- a/test/replication/errinj.result
>+++ b/test/replication/errinj.result
>@@ -308,7 +308,10 @@ box.info.replication[1].upstream.lag > 0
> ---
> - true
> ...
>-box.info.replication[1].upstream.lag < 1
>+-- Upstream lag is huge until the first row is received.
>+test_run:wait_cond(function()\
>+ return box.info.replication[1].upstream.lag < 1\
>+end)
> ---
> - true
> ...
>diff --git a/test/replication/errinj.test.lua b/test/replication/errinj.test.lua
>index 19234ab35..7f6535ec1 100644
>--- a/test/replication/errinj.test.lua
>+++ b/test/replication/errinj.test.lua
>@@ -130,7 +130,10 @@ test_run:cmd("switch replica")
> while box.info.replication[1].upstream.status ~= 'follow' do fiber.sleep(0.0001) end
> box.info.replication[1].upstream.status
> box.info.replication[1].upstream.lag > 0
>-box.info.replication[1].upstream.lag < 1
>+-- Upstream lag is huge until the first row is received.
>+test_run:wait_cond(function()\
>+ return box.info.replication[1].upstream.lag < 1\
>+end)
> -- wait for ack timeout
> test_run:wait_upstream(1, {status='disconnected', message_re='unexpected EOF'})
> 
>--
>2.30.1 (Apple Git-130)
 
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