Implement the main flow for the Exporting Engine (#7149)

* Add top level tests

* Add a skeleton for preparing buffers

* Initialize graphite instance

* Prepare buffers for all instances

* Add Grafite collected value formatter

* Add support for exporting.conf read and parsing

* - Use new exporting_config instead of netdata_config

* Implement Grafite worker

* Disable exporting engine compilation if libuv is not available

* Add mutex locks

- Configure connectors as connector_<type> in sections of exporting.conf

- Change exporting_select_type to check for connector_ fields

* - Override exporting_config structure if there no exporting.conf so that
  look ups don't fail and we maintain backwards compatibility

* Separate fixtures in unit tests

* Test exporting_discard_responce

* Test response receiving

* Test buffer sending

* Test simple connector worker

- Instance section has the format connector:instance_name
  e.g graphite:my_graphite_instance

- Connectors with : in their name e.g graphite:plaintext are reserved
  So graphite:plaintext is not accepted because it would activate an
  instance with name "plaintext"
  It should be graphite:plaintext:instance_name

* - Enable the add_connector_instance to cleanup the internal structure
  by passing NULL,not NULL arguments

* Implement configurable update interval

- Add additional check to verify instance uniqueness across connectors

* Add host and chart filters

* Add the value calculation over a database series

* Add the calculated over stored data graphite connector

* Add tests for graphite connector

* Add JSON connector

* Add tests for JSON formatting functions

* Add OpenTSDB connector

* Add tests for the OpenTSDB connector

* Add temporaty notes to the documentation

3 files changed, 6 insertions, 0 deletions

diff --git a/database/rrd.h b/database/rrd.h
index 8efe2adb05..c75b0deebe 100644
--- a/database/rrd.h
+++ b/database/rrd.h
@@ -408,6 +408,7 @@ struct rrdset {
                                                     // it goes around in a round-robin fashion
 
     RRDSET_FLAGS flags;                             // configuration flags
+    RRDSET_FLAGS *exporting_flags;                  // array of flags for exporting connector instances
 
     int gap_when_lost_iterations_above;             // after how many lost iterations a gap should be stored
                                                     // netdata will interpolate values for gaps lower than this
@@ -627,6 +628,7 @@ struct rrdhost {
     const char *timezone;                           // the timezone of the host
 
     RRDHOST_FLAGS flags;                            // flags about this RRDHOST
+    RRDHOST_FLAGS *exporting_flags;                 // array of flags for exporting connector instances
 
     int rrd_update_every;                           // the update frequency of the host
     long rrd_history_entries;                       // the number of history entries for the host's charts
diff --git a/database/rrdhost.c b/database/rrdhost.c
index bf540a2097..737e066c9d 100644
--- a/database/rrdhost.c
+++ b/database/rrdhost.c
@@ -597,6 +597,8 @@ void rrdhost_free(RRDHOST *host) {
     while(host->rrdset_root)
         rrdset_free(host->rrdset_root);
 
+    freez(host->exporting_flags);
+
     while(host->alarms)
         rrdcalc_unlink_and_free(host, host->alarms);
 
diff --git a/database/rrdset.c b/database/rrdset.c
index 0f52970304..1939d72a9c 100644
--- a/database/rrdset.c
+++ b/database/rrdset.c
@@ -328,6 +328,8 @@ void rrdset_free(RRDSET *st) {
     // ------------------------------------------------------------------------
     // free its children structures
 
+    freez(st->exporting_flags);
+
     while(st->variables)  rrdsetvar_free(st->variables);
     while(st->alarms)     rrdsetcalc_unlink(st->alarms);
     while(st->dimensions) rrddim_free(st, st->dimensions);