Replace dots in "host" part of metric name with underscores.

[kzemek]

Underscores are not a valid part of a domain name, so they
are safe to replace dots to in the metric name (i.e. this can't lead
to a collision with an existing host name).

Replacing dots with underscores prevents hosts from being treated
as multiple separate metrics nodes e.g. by Graphite and Grafana.

[mongoose-im]

5360.1 / Erlang 19.3 / small_tests / c09f1a8
Reports root / small

---

5360.3 / Erlang 19.3 / mysql_redis / c09f1a8
Reports root/ big
OK: 2821 / Failed: 0 / User-skipped: 222 / Auto-skipped: 0

---

5360.2 / Erlang 19.3 / internal_mnesia / c09f1a8
Reports root/ big
OK: 1067 / Failed: 0 / User-skipped: 45 / Auto-skipped: 0

---

5360.6 / Erlang 19.3 / elasticsearch_and_cassandra_mnesia / c09f1a8
Reports root/ big
OK: 445 / Failed: 0 / User-skipped: 8 / Auto-skipped: 0

---

5360.5 / Erlang 19.3 / ldap_mnesia / c09f1a8
Reports root/ big
OK: 1031 / Failed: 0 / User-skipped: 81 / Auto-skipped: 0

---

5360.4 / Erlang 19.3 / odbc_mssql_mnesia / c09f1a8
Reports root/ big
OK: 2835 / Failed: 0 / User-skipped: 208 / Auto-skipped: 0

---

5360.8 / Erlang 20.0 / pgsql_mnesia / c09f1a8
Reports root/ big / small
OK: 2867 / Failed: 0 / User-skipped: 176 / Auto-skipped: 0

---

5360.9 / Erlang 21.0 / riak_mnesia / c09f1a8
Reports root/ big / small
OK: 1290 / Failed: 0 / User-skipped: 43 / Auto-skipped: 0

[codecov]

Codecov Report

Merging #2025 into master will increase coverage by 0.09%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2025      +/-   ##
==========================================
+ Coverage   74.92%   75.02%   +0.09%     
==========================================
  Files         314      314              
  Lines       28619    28621       +2     
==========================================
+ Hits        21444    21472      +28     
+ Misses       7175     7149      -26     

Impacted Files	Coverage Δ
src/mongoose_metrics.erl	92.59% <100.00%> (+0.11%)	⬆️
..._distrib/mod_global_distrib_outgoing_conns_sup.erl	73.91% <0.00%> (-8.70%)	⬇️
...rc/global_distrib/mod_global_distrib_transport.erl	47.05% <0.00%> (-5.89%)	⬇️
src/mod_muc_log.erl	77.69% <0.00%> (ø)
src/pubsub/mod_pubsub.erl	66.18% <0.00%> (+0.18%)	⬆️
src/ejabberd_c2s.erl	84.88% <0.00%> (+0.36%)	⬆️
src/mod_muc_room.erl	77.24% <0.00%> (+0.76%)	⬆️
src/mod_bosh_socket.erl	81.66% <0.00%> (+1.00%)	⬆️
src/global_distrib/mod_global_distrib_utils.erl	80.80% <0.00%> (+1.01%)	⬆️
src/muc_light/mod_muc_light_utils.erl	85.26% <0.00%> (+1.05%)	⬆️
... and 1 more

---

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[mongoose-im]

5361.1 / Erlang 19.3 / small_tests / da2b9dd
Reports root / small

---

5361.3 / Erlang 19.3 / mysql_redis / da2b9dd
Reports root/ big
OK: 2821 / Failed: 0 / User-skipped: 222 / Auto-skipped: 0

---

5361.2 / Erlang 19.3 / internal_mnesia / da2b9dd
Reports root/ big
OK: 1067 / Failed: 0 / User-skipped: 45 / Auto-skipped: 0

---

5361.4 / Erlang 19.3 / odbc_mssql_mnesia / da2b9dd
Reports root/ big
OK: 2835 / Failed: 0 / User-skipped: 208 / Auto-skipped: 0

---

5361.5 / Erlang 19.3 / ldap_mnesia / da2b9dd
Reports root/ big
OK: 1031 / Failed: 0 / User-skipped: 81 / Auto-skipped: 0

---

5361.6 / Erlang 19.3 / elasticsearch_and_cassandra_mnesia / da2b9dd
Reports root/ big
OK: 445 / Failed: 0 / User-skipped: 8 / Auto-skipped: 0

---

5361.8 / Erlang 20.0 / pgsql_mnesia / da2b9dd
Reports root/ big / small
OK: 2867 / Failed: 0 / User-skipped: 176 / Auto-skipped: 0

---

5361.9 / Erlang 21.0 / riak_mnesia / da2b9dd
Reports root/ big / small
OK: 1290 / Failed: 0 / User-skipped: 43 / Auto-skipped: 0

---

5361.9 / Erlang 21.0 / riak_mnesia / da2b9dd
Reports root/ big / small
OK: 1290 / Failed: 0 / User-skipped: 43 / Auto-skipped: 0

[fenek]

1. It should be configurable for now with a clear deprecation warning (for domains with dots) as it breaks compatibility with existing deployments.
2. Mongoose-metrics.md update is necessary. Possibly there are more sections in documentation that should be changes as well.

[Neustradamus]

@kzemek, @fenek: Have you progressed on this PR?