Do not force internal collectors to call rrdset_next. (#13926)

* Remove calls to rrdset_next().

* Rm checks plugin

* Update documentantion

* Call rrdset_next from within rrdset_done

This wraps up the removal of rrdset_next from internal collectors, which
removes a lot of unecessary code and the need for if/else clauses in
every place.

The pluginsd parser is the only component that calls rrdset_next*()
functions because it's not strictly speaking a collector but more of a
collector manager/proxy.

With the current changes it's possible to simplify the API we expose
from RRD significantly, but this will be follow-up work in the future.

* Remove stale reference to checks.plugin

* Fix RRD unit test

rrdset_next is not meant to be called from these tests.

* Fix db engine unit test.

* Schedule rrdset_next when we have completed at least one collection.

* Mark chart creation clauses as unlikely.

* Add missing brace to fix FreeBSD plugin.

1 files changed, 0 insertions, 5 deletions

diff --git a/collectors/REFERENCE.md b/collectors/REFERENCE.md
index 949858f600..939b189ee7 100644
--- a/collectors/REFERENCE.md
+++ b/collectors/REFERENCE.md
@@ -148,11 +148,6 @@ collect_data() {
         // attach a metric to it
         rd = rrddim_add(st, "id", "name", multiplier, divider, algorithm);
     }
-    else {
-        // this chart is already created
-        // let Netdata know we start a new iteration on it
-        rrdset_next(st);
-    }
 
     // give the collected value(s) to the chart
     rrddim_set_by_pointer(st, rd, collected_value);