feat: Add config option to set additional attributes on all events (#259

)

## Which problem is this PR solving?
When deploying the agent in multiple clusters, telemetry from each
cluster get mixed together and there is no easy way to separate it.
There are other use cases of setting per-cluster values too, eg SHA,
cloud provider, etc.

This PR adds a configuration option to set a collection of key-value
pairs that will be set on all events. For example; cluster-name=dev
would add the field cluster-name with a value of dev.

- Closes #54 

## Short description of the changes
- Add new look up env func that returns a map[string]string created from
a env var that holds a string of comma separated key value pairs
- Adds AgentAttributes to config and populate from
`ADDITIONAL_ATTRIBUTES` env var using new env look up func
- Add the map of attributes to libhoney fields during libhoney init
- Update config tests to verify expected behaviour

## How to verify that this has the expected result
When additional attributes are provided, they are added to all events.

config/config.go

@@ -101,6 +101,9 @@ type Config struct {
 
 	// The name of the pod the agent is running on.
 	AgentPodName string
+
+	// Additional attributes to add to all events.
+	AdditionalAttributes map[string]string
 }
 
 // NewConfig returns a new Config struct.
@@ -135,6 +138,7 @@ func NewConfig() Config {
 		AgentServiceAccount:           utils.LookupEnvOrString("AGENT_SERVICE_ACCOUNT_NAME", ""),
 		AgentPodIP:                    utils.LookupEnvOrString("AGENT_POD_IP", ""),
 		AgentPodName:                  utils.LookupEnvOrString("AGENT_POD_NAME", ""),
+		AdditionalAttributes:          utils.LookupEnvAsStringMap("ADDITIONAL_ATTRIBUTES"),
 	}
 }
 

config/config_test.go

@@ -60,6 +60,7 @@ func TestEnvVars(t *testing.T) {
 	t.Setenv("AGENT_SERVICE_ACCOUNT_NAME", "service_account_name")
 	t.Setenv("AGENT_POD_IP", "pod_ip")
 	t.Setenv("AGENT_POD_NAME", "pod_name")
+	t.Setenv("ADDITIONAL_ATTRIBUTES", "key1=value1,key2=value2")
 
 	config := config.NewConfig()
 	assert.Equal(t, "1234567890123456789012", config.APIKey)
@@ -74,4 +75,5 @@ func TestEnvVars(t *testing.T) {
 	assert.Equal(t, "service_account_name", config.AgentServiceAccount)
 	assert.Equal(t, "pod_ip", config.AgentPodIP)
 	assert.Equal(t, "pod_name", config.AgentPodName)
+	assert.Equal(t, map[string]string{"key1": "value1", "key2": "value2"}, config.AdditionalAttributes)
 }

handlers/libhoney_event_handler.go

@@ -84,6 +84,9 @@ func initLibhoney(config config.Config, version string) func() {
 	if config.AgentPodName != "" {
 		libhoney.AddField("meta.agent.pod.name", config.AgentPodName)
 	}
+	for k, v := range config.AdditionalAttributes {
+		libhoney.AddField(k, v)
+	}
 
 	return libhoney.Close
 }

smoke-tests/deployment.yaml

@@ -124,6 +124,9 @@ spec:
             ## uncomment this to enable profiling
             # - name: DEBUG
             #   value: "$DEBUG"
+            ## uncomment this to add extra attributes to all events
+            # - name: ADDITIONAL_ATTRIBUTES
+            #   value: "key1=value1,key2=value2"
           securityContext:
             capabilities:
               add:

utils/env.go

@@ -3,6 +3,7 @@ package utils
 import (
 	"os"
 	"strconv"
+	"strings"
 )
 
 // LookupEnvOrBool returns a bool parsed from the environment variable with the given key
@@ -24,3 +25,19 @@ func LookupEnvOrString(key string, def string) string {
 	}
 	return def
 }
+
+// LookupEnvAsStringMap returns a map of strings from the environment variable with the given key
+// attributes are comma separated, key/value pairs are separated by an equals sign
+// Example: key1=value1,key2=value2
+func LookupEnvAsStringMap(key string) map[string]string {
+	values := make(map[string]string)
+	if env := os.Getenv(key); env != "" {
+		for _, value := range strings.Split(env, ",") {
+			parts := strings.Split(value, "=")
+			if len(parts) == 2 {
+				values[parts[0]] = parts[1]
+			}
+		}
+	}
+	return values
+}