Add alarm variables to the response of chart and data (#6615)

##### Summary
Implements feature #6054 

Now requests like 

http://localhost:19999/api/v1/chart?chart=example.random
http://localhost:19999/api/v1/data?chart=example.random&options=jsonwrap&options=showcustomvars

- return chart variables in their responses. Chart variables include only those with options set to RRDVAR_OPTION_CUSTOM_CHART_VAR
- for /api/v1/data requests chart variables are returned when parameter options=jsonwrap and options=showcustomvars

##### Component Name
[/database](https://github.com/netdata/netdata/tree/master/database/)
[/web/api/formatters](https://github.com/netdata/netdata/tree/master/web/api/formatters)

8 files changed, 92 insertions, 27 deletions

diff --git a/database/rrdvar.c b/database/rrdvar.c
index 95ab6859ea..0858d0bdcd 100644
--- a/database/rrdvar.c
+++ b/database/rrdvar.c
@@ -248,6 +248,7 @@ int health_variable_lookup(const char *variable, uint32_t hash, RRDCALC *rc, cal
 struct variable2json_helper {
     BUFFER *buf;
     size_t counter;
+    RRDVAR_OPTIONS options;
 };
 
 static int single_variable2json(void *entry, void *data) {
@@ -255,22 +256,37 @@ static int single_variable2json(void *entry, void *data) {
     RRDVAR *rv = (RRDVAR *)entry;
     calculated_number value = rrdvar2number(rv);
 
-    if(unlikely(isnan(value) || isinf(value)))
-        buffer_sprintf(helper->buf, "%s\n\t\t\"%s\": null", helper->counter?",":"", rv->name);
-    else
-        buffer_sprintf(helper->buf, "%s\n\t\t\"%s\": %0.5" LONG_DOUBLE_MODIFIER, helper->counter?",":"", rv->name, (LONG_DOUBLE)value);
+    if (helper->options == RRDVAR_OPTION_DEFAULT || rv->options & helper->options) {
+        if(unlikely(isnan(value) || isinf(value)))
+            buffer_sprintf(helper->buf, "%s\n\t\t\"%s\": null", helper->counter?",":"", rv->name);
+        else
+            buffer_sprintf(helper->buf, "%s\n\t\t\"%s\": %0.5" LONG_DOUBLE_MODIFIER, helper->counter?",":"", rv->name, (LONG_DOUBLE)value);
 
-    helper->counter++;
+        helper->counter++;
+    }
 
     return 0;
 }
 
+void health_api_v1_chart_custom_variables2json(RRDSET *st, BUFFER *buf) {
+    struct variable2json_helper helper = {
+            .buf = buf,
+            .counter = 0,
+            .options = RRDVAR_OPTION_CUSTOM_CHART_VAR
+    };
+
+    buffer_sprintf(buf, "{");
+    avl_traverse_lock(&st->rrdvar_root_index, single_variable2json, (void *)&helper);
+    buffer_strcat(buf, "\n\t\t\t}");
+}
+
 void health_api_v1_chart_variables2json(RRDSET *st, BUFFER *buf) {
     RRDHOST *host = st->rrdhost;
 
     struct variable2json_helper helper = {
             .buf = buf,
-            .counter = 0
+            .counter = 0,
+            .options = RRDVAR_OPTION_DEFAULT
     };
 
     buffer_sprintf(buf, "{\n\t\"chart\": \"%s\",\n\t\"chart_name\": \"%s\",\n\t\"chart_context\": \"%s\",\n\t\"chart_variables\": {", st->id, st->name, st->context);
diff --git a/health/health.h b/health/health.h
index 6920d12de7..0bf3b8ffa8 100644
--- a/health/health.h
+++ b/health/health.h
@@ -62,6 +62,7 @@ extern void health_alarms2json(RRDHOST *host, BUFFER *wb, int all);
 extern void health_alarm_log2json(RRDHOST *host, BUFFER *wb, uint32_t after);
 
 void health_api_v1_chart_variables2json(RRDSET *st, BUFFER *buf);
+void health_api_v1_chart_custom_variables2json(RRDSET *st, BUFFER *buf);
 
 extern int health_alarm_log_open(RRDHOST *host);
 extern void health_alarm_log_close(RRDHOST *host);
diff --git a/web/api/formatters/json_wrapper.c b/web/api/formatters/json_wrapper.c
index 4911d2f0ea..5ef2caf101 100644
--- a/web/api/formatters/json_wrapper.c
+++ b/web/api/formatters/json_wrapper.c
@@ -182,11 +182,14 @@ void rrdr_json_wrapper_begin(RRDR *r, BUFFER *wb, uint32_t format, RRDR_OPTIONS
 
     rrdr_buffer_print_format(wb, format);
 
-    buffer_sprintf(wb, "%s,\n"
-                       "   %sresult%s: "
-                   , sq
-                   , kq, kq
-    );
+    if((options & RRDR_OPTION_CUSTOM_VARS) && (options & RRDR_OPTION_JSON_WRAP)) {
+        buffer_sprintf(wb, "%s,\n   %schart_variables%s: ", sq, kq, kq);
+        health_api_v1_chart_custom_variables2json(r->st, wb);
+    }
+    else
+        buffer_sprintf(wb, "%s", sq);
+
+    buffer_sprintf(wb, ",\n   %sresult%s: ", kq, kq);
 
     if(string_value) buffer_strcat(wb, sq);
     //info("JSONWRAPPER(): %s: END", r->st->id);
diff --git a/web/api/formatters/rrdset2json.c b/web/api/formatters/rrdset2json.c
index 2bbd2a70f3..4d91399270 100644
--- a/web/api/formatters/rrdset2json.c
+++ b/web/api/formatters/rrdset2json.c
@@ -73,7 +73,10 @@ void rrdset2json(RRDSET *st, BUFFER *wb, size_t *dimensions_count, size_t *memor
     if(dimensions_count) *dimensions_count += dimensions;
     if(memory_used) *memory_used += memory;
 
-    buffer_strcat(wb, "\n\t\t\t},\n\t\t\t\"green\": ");
+    buffer_sprintf(wb, "\n\t\t\t},\n\t\t\t\"chart_variables\": ");
+    health_api_v1_chart_custom_variables2json(st, wb);
+
+    buffer_strcat(wb, ",\n\t\t\t\"green\": ");
     buffer_rrd_value(wb, st->green);
     buffer_strcat(wb, ",\n\t\t\t\"red\": ");
     buffer_rrd_value(wb, st->red);
diff --git a/web/api/netdata-swagger.json b/web/api/netdata-swagger.json
index 63bc5638de..44e862d174 100644
--- a/web/api/netdata-swagger.json
+++ b/web/api/netdata-swagger.json
@@ -243,7 +243,8 @@
                 "percentage",
                 "unaligned",
                 "match-ids",
-                "match-names"
+                "match-names",
+                "showcustomvars"
               ],
               "collectionFormat": "pipes"
             },
@@ -975,6 +976,14 @@
             }
           }
         },
+        "chart_variables": {
+          "type": "object",
+          "properties": {
+            "key": {
+              "$ref": "#/definitions/chart_variables"
+            }
+          }
+        },
         "green": {
           "type": "number",
           "description": "Chart health green threshold"
@@ -1011,13 +1020,8 @@
         "chart_variables": {
           "type": "object",
           "properties": {
-            "varname1": {
-              "type": "number",
-              "format": "float"
-            },
-            "varname2": {
-              "type": "number",
-              "format": "float"
+            "key": {
+              "$ref": "#/definitions/chart_variables"
             }
           }
         },
@@ -1049,6 +1053,19 @@
         }
       }
     },
+    "chart_variables": {
+      "type": "object",
+      "properties": {
+        "varname1": {
+          "type": "number",
+          "format": "float"
+        },
+        "varname2": {
+          "type": "number",
+          "format": "float"
+        }
+      }
+    },
     "dimension": {
       "type": "object",
       "properties": {
@@ -1145,6 +1162,14 @@
           "type": "string",
           "description": "The format of the result returned."
         },
+        "chart_variables": {
+          "type": "object",
+          "properties": {
+            "key": {
+              "$ref": "#/definitions/chart_variables"
+            }
+          }
+        },
         "result": {
           "description": "The result requested, in the format requested."
         }
diff --git a/web/api/netdata-swagger.yaml b/web/api/netdata-swagger.yaml
index 3386e01a7e..0052e646c2 100644
--- a/web/api/netdata-swagger.yaml
+++ b/web/api/netdata-swagger.yaml
@@ -163,7 +163,7 @@ paths:
           type: array
           items:
             type: string
-            enum: [ 'nonzero', 'flip', 'jsonwrap', 'min2max', 'seconds', 'milliseconds', 'abs', 'absolute', 'absolute-sum', 'null2zero', 'objectrows', 'google_json', 'percentage', 'unaligned', 'match-ids', 'match-names' ]
+            enum: [ 'nonzero', 'flip', 'jsonwrap', 'min2max', 'seconds', 'milliseconds', 'abs', 'absolute', 'absolute-sum', 'null2zero', 'objectrows', 'google_json', 'percentage', 'unaligned', 'match-ids', 'match-names', 'showcustomvars' ]
             collectionFormat: pipes
           default: [seconds, jsonwrap]
           allowEmptyValue: false
@@ -654,6 +654,11 @@ definitions:
         properties:
           key:
             $ref: '#/definitions/dimension'
+      chart_variables:
+        type: object
+        properties:
+          key:
+            $ref: '#/definitions/chart_variables'
       green:
         type: number
         description: 'Chart health green threshold'
@@ -681,12 +686,8 @@ definitions:
       chart_variables:
         type: object
         properties:
-          varname1:
-            type: number
-            format: float
-          varname2:
-            type: number
-            format: float
+          key:
+            $ref: '#/definitions/chart_variables'
       family_variables:
         type: object
         properties:
@@ -705,6 +706,15 @@ definitions:
           varname2:
             type: number
             format: float
+  chart_variables:
+    type: object
+    properties:
+      varname1:
+        type: number
+        format: float
+      varname2:
+        type: number
+        format: float
   dimension:
     type: object
     properties:
@@ -776,6 +786,11 @@ definitions:
       format:
         type: string
         description: 'The format of the result returned.'
+      chart_variables:
+        type: object
+        properties:
+          key:
+            $ref: '#/definitions/chart_variables'
       result:
         description: 'The result requested, in the format requested.'
   alarms:
diff --git a/web/api/queries/rrdr.h b/web/api/queries/rrdr.h
index 4f6350389b..6473ae7457 100644
--- a/web/api/queries/rrdr.h
+++ b/web/api/queries/rrdr.h
@@ -22,6 +22,7 @@ typedef enum rrdr_options {
     RRDR_OPTION_DISPLAY_ABS  = 0x00002000, // for badges, display the absolute value, but calculate colors with sign
     RRDR_OPTION_MATCH_IDS    = 0x00004000, // when filtering dimensions, match only IDs
     RRDR_OPTION_MATCH_NAMES  = 0x00008000, // when filtering dimensions, match only names
+    RRDR_OPTION_CUSTOM_VARS  = 0x00010000, // when wraping response in a JSON, return custom variables in response
 } RRDR_OPTIONS;
 
 typedef enum rrdr_value_flag {
diff --git a/web/api/web_api_v1.c b/web/api/web_api_v1.c
index 2273224bb1..2d12049632 100644
--- a/web/api/web_api_v1.c
+++ b/web/api/web_api_v1.c
@@ -32,6 +32,7 @@ static struct {
         , {"match-ids"       , 0    , RRDR_OPTION_MATCH_IDS}
         , {"match_names"     , 0    , RRDR_OPTION_MATCH_NAMES}
         , {"match-names"     , 0    , RRDR_OPTION_MATCH_NAMES}
+        , {"showcustomvars"  , 0    , RRDR_OPTION_CUSTOM_VARS}
         , {                  NULL, 0, 0}
 };