Change ElasticsearchWriter to write perfdata as an array of objects

Prior to this change the ElasticsearchWriter created a new field
for every metric in check command. This leads to a vast number of
fields in the indices, aka a field mapping explosion.

Now, it uses an array of objects. This avoids the explosion,
Makes the index fields more predictable when searching and
Makes the perfdata independently searchable.

Author: martialblog

doc/14-features.md

@@ -370,7 +370,15 @@ See: [ElasticsearchWriter](09-object-types.md#objecttype-elasticsearchwriter)
 Metric values are stored like this:
 
 ```
-check_result.perfdata.<perfdata-label>.value
+check_result.perfdata: [
+ {
+   "crit": 0,
+   "label": "example",
+   "min": 0,
+   "value": 0,
+   "warn": 0
+ }
+]
 ```
 
 The following characters are escaped in perfdata labels:
@@ -388,14 +396,7 @@ add more subsequent levels inside the tree.
 and is therefore replaced by `.`.
 
 Icinga 2 automatically adds the following threshold metrics
-if existing:
-
-```
-check_result.perfdata.<perfdata-label>.min
-check_result.perfdata.<perfdata-label>.max
-check_result.perfdata.<perfdata-label>.warn
-check_result.perfdata.<perfdata-label>.crit
-```
+if existing: min, max, warn, crit
 
 Additionally it is possible to configure custom tags that are applied to the metrics via `host_tags_template` or `service_tags_template`.
 Depending on whether the write event was triggered on a service or host object, additional tags are added to the ElasticSearch entries.

lib/perfdata/elasticsearchwriter.cpp

@@ -189,6 +189,9 @@ void ElasticsearchWriter::AddCheckResult(const Dictionary::Ptr& fields, const Ch
 
 	if (perfdata) {
 		ObjectLock olock(perfdata);
+
+		Array::Ptr perfdatapoints = new Array();
+
 		for (const Value& val : perfdata) {
 			PerfdataValue::Ptr pdv;
 
@@ -212,22 +215,28 @@ void ElasticsearchWriter::AddCheckResult(const Dictionary::Ptr& fields, const Ch
 			boost::replace_all(escapedKey, "\\", "_");
 			boost::algorithm::replace_all(escapedKey, "::", ".");
 
-			String perfdataPrefix = prefix + "perfdata." + escapedKey;
+			Dictionary::Ptr datapoint = new Dictionary();
 
-			fields->Set(perfdataPrefix + ".value", pdv->GetValue());
+			datapoint->Set("label", escapedKey);
+			datapoint->Set("value", pdv->GetValue());
 
 			if (!pdv->GetMin().IsEmpty())
-				fields->Set(perfdataPrefix + ".min", pdv->GetMin());
+				datapoint->Set("min", pdv->GetMin());
 			if (!pdv->GetMax().IsEmpty())
-				fields->Set(perfdataPrefix + ".max", pdv->GetMax());
+				datapoint->Set("max", pdv->GetMax());
 			if (!pdv->GetWarn().IsEmpty())
-				fields->Set(perfdataPrefix + ".warn", pdv->GetWarn());
+				datapoint->Set("warn", pdv->GetWarn());
 			if (!pdv->GetCrit().IsEmpty())
-				fields->Set(perfdataPrefix + ".crit", pdv->GetCrit());
+				datapoint->Set("crit", pdv->GetCrit());
 
 			if (!pdv->GetUnit().IsEmpty())
-				fields->Set(perfdataPrefix + ".unit", pdv->GetUnit());
+				datapoint->Set("unit", pdv->GetUnit());
+
+			perfdatapoints->Add(datapoint);
 		}
+
+		String perfdataPrefix = prefix + "perfdata";
+		fields->Set(perfdataPrefix, std::move(perfdatapoints));
 	}
 }