Fix modMucMamFlushed metric

[arcusfelis]

This PR addresses "modMucMamFlushed is updated but not created".

Proposed changes include:

• modMucMamFlushed is created now

[mongoose-im]

9070.1 / Erlang 23.0.3 / small_tests / 7e23741
Reports root / small

---

9070.2 / Erlang 23.0.3 / internal_mnesia / 7e23741
Reports root/ big
OK: 1503 / Failed: 0 / User-skipped: 161 / Auto-skipped: 0

---

9070.4 / Erlang 23.0.3 / mysql_redis / 7e23741
Reports root/ big
OK: 2766 / Failed: 0 / User-skipped: 234 / Auto-skipped: 0

---

9070.3 / Erlang 23.0.3 / odbc_mssql_mnesia / 7e23741
Reports root/ big
OK: 2771 / Failed: 0 / User-skipped: 229 / Auto-skipped: 0

---

9070.7 / Erlang 23.0.3 / elasticsearch_and_cassandra_mnesia / 7e23741
Reports root/ big
OK: 331 / Failed: 0 / User-skipped: 38 / Auto-skipped: 0

---

9070.5 / Erlang 23.0.3 / riak_mnesia / 7e23741
Reports root/ big
OK: 1629 / Failed: 0 / User-skipped: 181 / Auto-skipped: 0

---

9070.6 / Erlang 23.0.3 / ldap_mnesia / 7e23741
Reports root/ big
OK: 1405 / Failed: 0 / User-skipped: 259 / Auto-skipped: 0

---

9070.9 / Erlang 22.3 / pgsql_mnesia / 7e23741
Reports root/ big / small
OK: 2784 / Failed: 0 / User-skipped: 216 / Auto-skipped: 0

[codecov]

Codecov Report

Merging #3023 (af7469e) into master (c7935ad) will increase coverage by 0.04%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3023      +/-   ##
==========================================
+ Coverage   78.53%   78.57%   +0.04%     
==========================================
  Files         376      376              
  Lines       31488    31488              
==========================================
+ Hits        24729    24743      +14     
+ Misses       6759     6745      -14     

Impacted Files	Coverage Δ
src/metrics/mongoose_metrics_mam_hooks.erl	86.66% <ø> (+6.66%)	⬆️
src/muc_light/mod_muc_light.erl	82.96% <0.00%> (-0.88%)	⬇️
src/ejabberd_sm.erl	76.07% <0.00%> (-0.31%)	⬇️
src/mod_roster.erl	77.49% <0.00%> (-0.24%)	⬇️
src/mod_muc_room.erl	77.54% <0.00%> (-0.06%)	⬇️
src/mod_muc_log.erl	77.72% <0.00%> (ø)
src/pubsub/mod_pubsub_db_mnesia.erl	92.82% <0.00%> (+0.42%)	⬆️
src/ejabberd_s2s_out.erl	58.35% <0.00%> (+0.45%)	⬆️
src/mam/mod_mam_utils.erl	89.64% <0.00%> (+0.64%)	⬆️
src/metrics/mongoose_metrics.erl	95.36% <0.00%> (+0.66%)	⬆️
... and 5 more

---

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[chrzaszcz]

This cannot work because the hook is not added anywhere in the code, see mongoose_metrics_mam_hooks:get_hooks/1

Could you:

• Make the code actually update the metric :-)
• Make the 1-to-1 and MUC versions consistent. One is using a hook and one is not, I think hooks are just not necessary here. Let the MUC version just update the metric directly like 1-to-1.
• Not needed but nice to have: add a test for the metric - maybe we already have an async writer test and we could just check the metric there?

Finally, please test your changes - at least manually, thanks in advance!

[chrzaszcz]

The comment above explains it.

[mongoose-im]

9074.1 / Erlang 23.0.3 / small_tests / 34eb896
Reports root / small

---

9074.2 / Erlang 23.0.3 / internal_mnesia / 34eb896
Reports root/ big
OK: 1503 / Failed: 0 / User-skipped: 161 / Auto-skipped: 0

---

9074.4 / Erlang 23.0.3 / mysql_redis / 34eb896
Reports root/ big
OK: 2766 / Failed: 0 / User-skipped: 234 / Auto-skipped: 0

---

9074.7 / Erlang 23.0.3 / elasticsearch_and_cassandra_mnesia / 34eb896
Reports root/ big
OK: 331 / Failed: 0 / User-skipped: 38 / Auto-skipped: 0

---

9074.5 / Erlang 23.0.3 / riak_mnesia / 34eb896
Reports root/ big
OK: 1629 / Failed: 0 / User-skipped: 181 / Auto-skipped: 0

---

9074.6 / Erlang 23.0.3 / ldap_mnesia / 34eb896
Reports root/ big
OK: 1405 / Failed: 0 / User-skipped: 259 / Auto-skipped: 0

---

9074.9 / Erlang 22.3 / pgsql_mnesia / 34eb896
Reports root/ big / small
OK: 2784 / Failed: 0 / User-skipped: 216 / Auto-skipped: 0

[chrzaszcz]

It works now, confirmed by a load test, good!