Modify Collector structure

collector/generic_collector.go

@@ -16,7 +16,9 @@ package collector
 
 import (
 	"encoding/json"
+	"fmt"
 	"io/ioutil"
+	"regexp"
 	"time"
 
 	"github.com/google/cadvisor/info/v2"
@@ -28,6 +30,17 @@ type GenericCollector struct {
 
 	//holds information extracted from the config file for a collector
 	configFile Config
+
+	//holds information necessary to extract metrics
+	info *collectorInfo
+}
+
+type collectorInfo struct {
+	//minimum polling frequency among all metrics
+	minPollingFrequency time.Duration
+
+	//regular expresssions for all metrics
+	regexps []*regexp.Regexp
 }
 
 //Returns a new collector using the information extracted from the configfile
@@ -45,8 +58,30 @@ func NewCollector(collectorName string, configfile string) (*GenericCollector, e
 
 	//TODO : Add checks for validity of config file (eg : Accurate JSON fields)
 
+	if len(configInJSON.MetricsConfig) == 0 {
+		return nil, fmt.Errorf("No metrics provided in config")
+	}
+
+	minPollFrequency := configInJSON.MetricsConfig[0].PollingFrequency
+	regexprs := make([]*regexp.Regexp, len(configInJSON.MetricsConfig))
+
+	for ind, metricConfig := range configInJSON.MetricsConfig {
+		if metricConfig.PollingFrequency < minPollFrequency {
+			minPollFrequency = metricConfig.PollingFrequency
+		}
+
+		regexprs[ind], err = regexp.Compile(metricConfig.Regex)
+		if err != nil {
+			return nil, fmt.Errorf("Invalid regexp %v for metric %v", metricConfig.Regex, metricConfig.Name)
+		}
+	}
+
 	return &GenericCollector{
-		name: collectorName, configFile: configInJSON,
+		name:       collectorName,
+		configFile: configInJSON,
+		info: &collectorInfo{
+			minPollingFrequency: minPollFrequency,
+			regexps:             regexprs},
 	}, nil
 }
 

collector/generic_collector_test.go

@@ -22,19 +22,39 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
+func TestEmptyConfig(t *testing.T) {
+	assert := assert.New(t)
+
+	emptyConfig := `
+        {
+                "endpoint" : "http://localhost:8000/nginx_status",
+                "metrics_config"  : [
+                ]
+        }
+        `
+
+	//Create a temporary config file 'temp.json' with invalid json format
+	assert.NoError(ioutil.WriteFile("temp.json", []byte(emptyConfig), 0777))
+
+	_, err := NewCollector("tempCollector", "temp.json")
+	assert.Error(err)
+
+	assert.NoError(os.Remove("temp.json"))
+}
+
 func TestConfigWithErrors(t *testing.T) {
 	assert := assert.New(t)
 
-	//Syntax error: Missed '"' after active connections
+	//Syntax error: Missed '"' after activeConnections
 	invalid := `
 	{
-		"endpoint" : "host:port/nginx_status",
-		"metricsConfig"  : [
+		"endpoint" : "http://localhost:8000/nginx_status",
+		"metrics_config"  : [
 			{
 				 "name" : "activeConnections,  
-		  		 "metricType" : "gauge",
+		  		 "metric_type" : "gauge",
 		 	 	 "units" : "integer",
-		  		 "pollingFrequency" : "10s",
+		  		 "polling_frequency" : 10,
 		    		 "regex" : "Active connections: ([0-9]+)"			
 			}
 		]
@@ -50,6 +70,41 @@ func TestConfigWithErrors(t *testing.T) {
 	assert.NoError(os.Remove("temp.json"))
 }
 
+func TestConfigWithRegexErrors(t *testing.T) {
+	assert := assert.New(t)
+
+	//Error: Missed operand for '+' in activeConnections regex
+	invalid := `
+        {
+                "endpoint" : "host:port/nginx_status",
+                "metrics_config"  : [
+                        {
+                                 "name" : "activeConnections",
+                                 "metric_type" : "gauge",
+                                 "units" : "integer",
+                                 "polling_frequency" : 10,
+                                 "regex" : "Active connections: (+)"
+                        },
+                        {
+                                 "name" : "reading",
+                                 "metric_type" : "gauge",
+                                 "units" : "integer",
+                                 "polling_frequency" : 10,
+                                 "regex" : "Reading: ([0-9]+) .*"
+                        }
+                ]
+        }
+        `
+
+	//Create a temporary config file 'temp.json'
+	assert.NoError(ioutil.WriteFile("temp.json", []byte(invalid), 0777))
+
+	_, err := NewCollector("tempCollector", "temp.json")
+	assert.Error(err)
+
+	assert.NoError(os.Remove("temp.json"))
+}
+
 func TestConfig(t *testing.T) {
 	assert := assert.New(t)