Additional code cleanup

Godeps

@@ -1,6 +1,7 @@
 code.cloudfoundry.org/clock e9dc86bbf0e5bbe6bf7ff5a6f71e048959b61f71
 collectd.org 2ce144541b8903101fb8f1483cc0497a68798122
 github.com/aerospike/aerospike-client-go 9701404f4c60a6ea256595d24bf318f721a7e8b8
+github.com/Azure/go-autorest 9ad9326b278af8fa5cc67c30c0ce9a58cc0862b2
 github.com/amir/raidman c74861fe6a7bb8ede0a010ce4485bdbb4fc4c985
 github.com/apache/thrift 4aaa92ece8503a6da9bc6701604f69acf2b99d07
 github.com/aws/aws-sdk-go c861d27d0304a79f727e9a8a4e2ac1e74602fdc0

internal/models/running_output.go

@@ -113,6 +113,11 @@ func (ro *RunningOutput) AddMetric(m telegraf.Metric) {
 		m, _ = metric.New(name, tags, fields, t)
 	}
 
+	if output, ok := ro.Output.(telegraf.AggregatingOutput); ok {
+		output.Add(m)
+		return
+	}
+
 	ro.metrics.Add(m)
 	if ro.metrics.Len() == ro.MetricBatchSize {
 		batch := ro.metrics.Batch(ro.MetricBatchSize)
@@ -125,6 +130,12 @@ func (ro *RunningOutput) AddMetric(m telegraf.Metric) {
 
 // Write writes all cached points to this output.
 func (ro *RunningOutput) Write() error {
+	if output, ok := ro.Output.(telegraf.AggregatingOutput); ok {
+		metrics := output.Push()
+		ro.metrics.Add(metrics...)
+		output.Reset()
+	}
+
 	nFails, nMetrics := ro.failMetrics.Len(), ro.metrics.Len()
 	ro.BufferSize.Set(int64(nFails + nMetrics))
 	log.Printf("D! Output [%s] buffer fullness: %d / %d metrics. ",

output.go

@@ -13,6 +13,12 @@ type Output interface {
 	Write(metrics []Metric) error
 }
 
+type AggregatingOutput interface {
+	Add(in Metric)
+	Push() []Metric
+	Reset()
+}
+
 type ServiceOutput interface {
 	// Connect to the Output
 	Connect() error

plugins/outputs/all/all.go

@@ -4,6 +4,7 @@ import (
 	_ "github.com/influxdata/telegraf/plugins/outputs/amon"
 	_ "github.com/influxdata/telegraf/plugins/outputs/amqp"
 	_ "github.com/influxdata/telegraf/plugins/outputs/application_insights"
+	_ "github.com/influxdata/telegraf/plugins/outputs/azuremonitor"
 	_ "github.com/influxdata/telegraf/plugins/outputs/cloudwatch"
 	_ "github.com/influxdata/telegraf/plugins/outputs/cratedb"
 	_ "github.com/influxdata/telegraf/plugins/outputs/datadog"

plugins/outputs/azuremonitor/README.md

@@ -0,0 +1,74 @@
+## Azure Monitor Custom Metrics Output for Telegraf
+
+This plugin will send custom metrics to Azure Monitor.
+
+All metrics are written as summarized values: min, max, sum, count. The Telegraf field name is appended to the metric name. All Telegraf tags are set as the metric dimensions.
+
+## Azure Authentication
+
+This plugin can use one of several different types of credentials to authenticate
+with the Azure Monitor Custom Metrics ingestion API endpoint. In the following
+order the plugin will attempt to authenticate.
+1. Managed Service Identity (MSI) token
+    - This is the prefered authentication method.
+    - Note: MSI is only available to ARM-based resources.
+2. AAD Application Tokens (Service Principals)
+    - Primarily useful if Telegraf is writing metrics for other resources. [More information](https://docs.microsoft.com/en-us/azure/active-directory/develop/active-directory-application-objects).
+    - A Service Principal or User Principal needs to be assigned the `Monitoring Contributor` roles.
+3. AAD User Tokens (User Principals)
+    - Allows Telegraf to authenticate like a user. It is best to use this method for development.
+
+## Config
+
+For this output plugin to function correctly the following variables
+must be configured.
+
+* resourceId
+* region
+
+### region
+
+The region is the Azure region that you wish to connect to.
+Examples include but are not limited to:
+* useast
+* centralus
+* westcentralus
+* westeurope
+* southeastasia
+
+### resourceId
+
+The resourceId used for Azure Monitor metrics.
+
+### Configuration:
+
+```
+# Configuration for sending aggregate metrics to Azure Monitor
+[[outputs.azuremonitor]]
+## The resource ID against which metric will be logged.  If not
+## specified, the plugin will attempt to retrieve the resource ID
+## of the VM via the instance metadata service (optional if running 
+## on an Azure VM with MSI)
+#resource_id = "/subscriptions/<subscription_id>/resourceGroups/<resource_group>/providers/Microsoft.Compute/virtualMachines/<vm_name>"
+## Azure region to publish metrics against.  Defaults to eastus.
+## Leave blank to automatically query the region via MSI.
+#region = "useast"
+
+## Write HTTP timeout, formatted as a string.  If not provided, will default
+## to 5s. 0s means no timeout (not recommended).
+# timeout = "5s"
+
+## Whether or not to use managed service identity.
+#useManagedServiceIdentity = true
+
+## Fill in the following values if using Active Directory Service
+## Principal or User Principal for authentication.
+## Subscription ID
+#azureSubscription = ""
+## Tenant ID
+#azureTenant = ""
+## Client ID
+#azureClientId = ""
+## Client secrete
+#azureClientSecret = ""
+```

plugins/outputs/azuremonitor/azuremetadata.go

@@ -0,0 +1,186 @@
+package azuremonitor
+
+import (
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"net/url"
+	"strconv"
+	"time"
+)
+
+// VirtualMachineMetadata contains information about a VM from the metadata service
+type VirtualMachineMetadata struct {
+	Raw             string
+	AzureResourceID string
+	Compute         struct {
+		Location             string `json:"location"`
+		Name                 string `json:"name"`
+		Offer                string `json:"offer"`
+		OsType               string `json:"osType"`
+		PlacementGroupID     string `json:"placementGroupId"`
+		PlatformFaultDomain  string `json:"platformFaultDomain"`
+		PlatformUpdateDomain string `json:"platformUpdateDomain"`
+		Publisher            string `json:"publisher"`
+		ResourceGroupName    string `json:"resourceGroupName"`
+		Sku                  string `json:"sku"`
+		SubscriptionID       string `json:"subscriptionId"`
+		Tags                 string `json:"tags"`
+		Version              string `json:"version"`
+		VMID                 string `json:"vmId"`
+		VMScaleSetName       string `json:"vmScaleSetName"`
+		VMSize               string `json:"vmSize"`
+		Zone                 string `json:"zone"`
+	} `json:"compute"`
+	Network struct {
+		Interface []struct {
+			Ipv4 struct {
+				IPAddress []struct {
+					PrivateIPAddress string `json:"privateIpAddress"`
+					PublicIPAddress  string `json:"publicIpAddress"`
+				} `json:"ipAddress"`
+				Subnet []struct {
+					Address string `json:"address"`
+					Prefix  string `json:"prefix"`
+				} `json:"subnet"`
+			} `json:"ipv4"`
+			Ipv6 struct {
+				IPAddress []interface{} `json:"ipAddress"`
+			} `json:"ipv6"`
+			MacAddress string `json:"macAddress"`
+		} `json:"interface"`
+	} `json:"network"`
+}
+
+// msiToken is the managed service identity token
+type msiToken struct {
+	AccessToken  string `json:"access_token"`
+	RefreshToken string `json:"refresh_token"`
+	ExpiresIn    string `json:"expires_in"`
+	ExpiresOn    string `json:"expires_on"`
+	NotBefore    string `json:"not_before"`
+	Resource     string `json:"resource"`
+	TokenType    string `json:"token_type"`
+
+	expiresAt time.Time
+	notBefore time.Time
+	raw       string
+}
+
+func (m *msiToken) parseTimes() {
+	val, err := strconv.ParseInt(m.ExpiresOn, 10, 64)
+	if err == nil {
+		m.expiresAt = time.Unix(val, 0)
+	}
+
+	val, err = strconv.ParseInt(m.NotBefore, 10, 64)
+	if err == nil {
+		m.notBefore = time.Unix(val, 0)
+	}
+}
+
+// ExpiresInDuration returns the duration until the token expires
+func (m *msiToken) expiresInDuration() time.Duration {
+	expiresDuration := m.expiresAt.Sub(time.Now().UTC())
+	return expiresDuration
+}
+
+// GetMsiToken retrieves a managed service identity token from the specified port on the local VM
+func (a *AzureMonitor) getMsiToken(clientID string) (*msiToken, error) {
+	// Acquire an MSI token.  Documented at:
+	// https://docs.microsoft.com/en-us/azure/active-directory/managed-service-identity/how-to-use-vm-token
+	//
+	//GET http://169.254.169.254/metadata/identity/oauth2/token?api-version=2018-02-01&resource=https%3A%2F%2Fmanagement.azure.com%2F&client_id=712eac09-e943-418c-9be6-9fd5c91078bl HTTP/1.1 Metadata: true
+
+	// Create HTTP request for MSI token to access Azure Resource Manager
+	var msiEndpoint *url.URL
+	msiEndpoint, err := url.Parse(msiInstanceMetadataURL)
+	if err != nil {
+		return nil, err
+	}
+
+	msiParameters := url.Values{}
+	// Resource ID defaults to https://management.azure.com
+	msiParameters.Add("resource", defaultMSIResource)
+	msiParameters.Add("api-version", "2018-02-01")
+
+	// Client id is optional
+	if clientID != "" {
+		msiParameters.Add("client_id", clientID)
+	}
+
+	msiEndpoint.RawQuery = msiParameters.Encode()
+	req, err := http.NewRequest("GET", msiEndpoint.String(), nil)
+	if err != nil {
+		return nil, err
+	}
+	req.Header.Add("Metadata", "true")
+
+	resp, err := a.client.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	reply, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return nil, err
+	}
+
+	if resp.StatusCode >= 300 || resp.StatusCode < 200 {
+		return nil, fmt.Errorf("E! Get Error. %d HTTP response: %s response body: %s",
+			resp.StatusCode, resp.Status, reply)
+	}
+
+	var token msiToken
+	if err := json.Unmarshal(reply, &token); err != nil {
+		return nil, err
+	}
+	token.parseTimes()
+	token.raw = string(reply)
+	return &token, nil
+}
+
+// GetInstanceMetadata retrieves metadata about the current Azure VM
+func (a *AzureMonitor) GetInstanceMetadata() error {
+	req, err := http.NewRequest("GET", vmInstanceMetadataURL, nil)
+	if err != nil {
+		return fmt.Errorf("Error creating HTTP request")
+	}
+	req.Header.Set("Metadata", "true")
+
+	resp, err := a.client.Do(req)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+
+	reply, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return err
+	}
+
+	if resp.StatusCode >= 300 || resp.StatusCode < 200 {
+		return fmt.Errorf("Post Error. HTTP response code:%d message:%s reply:\n%s",
+			resp.StatusCode, resp.Status, reply)
+	}
+
+	var metadata VirtualMachineMetadata
+	if err := json.Unmarshal(reply, &metadata); err != nil {
+		return err
+	}
+
+	if a.ResourceID == "" {
+		a.ResourceID = fmt.Sprintf(resourceIDTemplate,
+			metadata.Compute.SubscriptionID, metadata.Compute.ResourceGroupName, metadata.Compute.Name)
+	}
+
+	if a.Region == "" {
+		a.Region = metadata.Compute.Location
+	}
+
+	a.url = fmt.Sprintf(urlTemplate, a.Region, a.ResourceID)
+
+	return nil
+}

plugins/outputs/azuremonitor/azuremonitor.go

@@ -0,0 +1,445 @@
+package azuremonitor
+
+import (
+	"bytes"
+	"encoding/binary"
+	"encoding/json"
+	"fmt"
+	"hash/fnv"
+	"io/ioutil"
+	"log"
+	"net/http"
+	"regexp"
+	"time"
+
+	"github.com/Azure/go-autorest/autorest/adal"
+	"github.com/Azure/go-autorest/autorest/azure"
+	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/internal"
+	"github.com/influxdata/telegraf/metric"
+	"github.com/influxdata/telegraf/plugins/outputs"
+)
+
+var _ telegraf.AggregatingOutput = (*AzureMonitor)(nil)
+var _ telegraf.Output = (*AzureMonitor)(nil)
+
+// AzureMonitor allows publishing of metrics to the Azure Monitor custom metrics service
+type AzureMonitor struct {
+	useMsi              bool              `toml:"use_managed_service_identity"`
+	ResourceID          string            `toml:"resource_id"`
+	Region              string            `toml:"region"`
+	Timeout             internal.Duration `toml:"Timeout"`
+	AzureSubscriptionID string            `toml:"azure_subscription"`
+	AzureTenantID       string            `toml:"azure_tenant"`
+	AzureClientID       string            `toml:"azure_client_id"`
+	AzureClientSecret   string            `toml:"azure_client_secret"`
+	StringAsDimension   bool              `toml:"string_as_dimension"`
+
+	url         string
+	msiToken    *msiToken
+	oauthConfig *adal.OAuthConfig
+	adalToken   adal.OAuthTokenProvider
+
+	client *http.Client
+
+	cache map[time.Time]map[uint64]*aggregate
+}
+
+type aggregate struct {
+	telegraf.Metric
+	updated bool
+}
+
+const (
+	defaultRegion          string = "eastus"
+	defaultMSIResource     string = "https://monitoring.azure.com/"
+	urlTemplate            string = "https://%s.monitoring.azure.com%s/metrics"
+	resourceIDTemplate     string = "/subscriptions/%s/resourceGroups/%s/providers/Microsoft.Compute/virtualMachines/%s"
+	vmInstanceMetadataURL  string = "http://169.254.169.254/metadata/instance?api-version=2017-12-01"
+	msiInstanceMetadataURL string = "http://169.254.169.254/metadata/identity/oauth2/token"
+)
+
+var sampleConfig = `
+  ## The resource ID against which metric will be logged.  If not
+  ## specified, the plugin will attempt to retrieve the resource ID
+  ## of the VM via the instance metadata service (optional if running 
+  ## on an Azure VM with MSI)
+  #resource_id = "/subscriptions/<subscription_id>/resourceGroups/<resource_group>/providers/Microsoft.Compute/virtualMachines/<vm_name>"
+  ## Azure region to publish metrics against.  Defaults to eastus.
+  ## Leave blank to automatically query the region via MSI.
+  #region = "useast"
+
+  ## Write HTTP timeout, formatted as a string.  If not provided, will default
+  ## to 5s. 0s means no timeout (not recommended).
+  # timeout = "5s"
+
+  ## Whether or not to use managed service identity.
+  #use_managed_service_identity = true
+
+  ## Fill in the following values if using Active Directory Service
+  ## Principal or User Principal for authentication.
+  ## Subscription ID
+  #azure_subscription = ""
+  ## Tenant ID
+  #azure_tenant = ""
+  ## Client ID
+  #azure_client_id = ""
+  ## Client secrete
+  #azure_client_secret = ""
+`
+
+// Description provides a description of the plugin
+func (a *AzureMonitor) Description() string {
+	return "Configuration for sending aggregate metrics to Azure Monitor"
+}
+
+// SampleConfig provides a sample configuration for the plugin
+func (a *AzureMonitor) SampleConfig() string {
+	return sampleConfig
+}
+
+// Connect initializes the plugin and validates connectivity
+func (a *AzureMonitor) Connect() error {
+	a.client = &http.Client{
+		Transport: &http.Transport{
+			Proxy: http.ProxyFromEnvironment,
+		},
+		Timeout: a.Timeout.Duration,
+	}
+
+	// If no direct AD values provided, fall back to MSI
+	if a.AzureSubscriptionID == "" && a.AzureTenantID == "" && a.AzureClientID == "" && a.AzureClientSecret == "" {
+		a.useMsi = true
+	} else if a.AzureSubscriptionID == "" || a.AzureTenantID == "" || a.AzureClientID == "" || a.AzureClientSecret == "" {
+		return fmt.Errorf("E! Must provide values for azure_subscription, azure_tenant, azure_client and azure_client_secret, or leave all blank to default to MSI")
+	}
+
+	if !a.useMsi {
+		// If using direct AD authentication create the AD access client
+		oauthConfig, err := adal.NewOAuthConfig(azure.PublicCloud.ActiveDirectoryEndpoint, a.AzureTenantID)
+		if err != nil {
+			return fmt.Errorf("E! Could not initialize AD client: %s", err)
+		}
+		a.oauthConfig = oauthConfig
+	}
+
+	// Pull region and resource identifier
+	err := a.GetInstanceMetadata()
+	if err != nil && a.ResourceID == "" && a.Region == "" {
+		return fmt.Errorf("E! No resource id specified, and Azure Instance metadata service not available.  If not running on an Azure VM, provide a value for resource_id")
+	}
+
+	err = a.validateCredentials()
+	if err != nil {
+		return fmt.Errorf("E! Unable to fetch authentication credentials: %v", err)
+	}
+
+	a.Reset()
+
+	return nil
+}
+
+func (a *AzureMonitor) validateCredentials() error {
+	if a.useMsi {
+		// Check expiry on the token
+		if a.msiToken == nil || a.msiToken.expiresInDuration() < time.Minute {
+			msiToken, err := a.getMsiToken(a.AzureClientID)
+			if err != nil {
+				return err
+			}
+			a.msiToken = msiToken
+		}
+		return nil
+	}
+
+	adToken, err := adal.NewServicePrincipalToken(
+		*(a.oauthConfig), a.AzureClientID, a.AzureClientSecret,
+		azure.PublicCloud.ActiveDirectoryEndpoint)
+	if err != nil {
+		return fmt.Errorf("Could not acquire ADAL token: %s", err)
+	}
+	a.adalToken = adToken
+	return nil
+}
+
+// Close shuts down an any active connections
+func (a *AzureMonitor) Close() error {
+	a.client = nil
+	return nil
+}
+
+type azureMonitorMetric struct {
+	Time time.Time         `json:"time"`
+	Data *azureMonitorData `json:"data"`
+}
+
+type azureMonitorData struct {
+	BaseData *azureMonitorBaseData `json:"baseData"`
+}
+
+type azureMonitorBaseData struct {
+	Metric         string                `json:"metric"`
+	Namespace      string                `json:"namespace"`
+	DimensionNames []string              `json:"dimNames"`
+	Series         []*azureMonitorSeries `json:"series"`
+}
+
+type azureMonitorSeries struct {
+	DimensionValues []string `json:"dimValues"`
+	Min             float64  `json:"min"`
+	Max             float64  `json:"max"`
+	Sum             float64  `json:"sum"`
+	Count           int64    `json:"count"`
+}
+
+// Write writes metrics to the remote endpoint
+func (a *AzureMonitor) Write(metrics []telegraf.Metric) error {
+	azmetrics := make(map[uint64]*azureMonitorMetric, len(metrics))
+	for _, m := range metrics {
+		id := hashIDWithTagKeysOnly(m)
+		if azm, ok := azmetrics[id]; !ok {
+			azmetrics[id] = translate(m)
+		} else {
+			azmetrics[id].Data.BaseData.Series = append(
+				azm.Data.BaseData.Series,
+				translate(m).Data.BaseData.Series...,
+			)
+		}
+	}
+
+	var body []byte
+	for _, m := range azmetrics {
+		// Azure Monitor accepts new batches of points in new-line delimited
+		// JSON, following RFC 4288 (see https://github.com/ndjson/ndjson-spec).
+		jsonBytes, err := json.Marshal(&m)
+		if err != nil {
+			return err
+		}
+		body = append(body, jsonBytes...)
+		body = append(body, '\n')
+	}
+
+	if err := a.validateCredentials(); err != nil {
+		return fmt.Errorf("E! Unable to fetch authentication credentials: %v", err)
+	}
+
+	req, err := http.NewRequest("POST", a.url, bytes.NewBuffer(body))
+	if err != nil {
+		return err
+	}
+
+	req.Header.Set("Authorization", "Bearer "+a.msiToken.AccessToken)
+	req.Header.Set("Content-Type", "application/x-ndjson")
+
+	resp, err := a.client.Do(req)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode >= 300 || resp.StatusCode < 200 {
+		reply, err := ioutil.ReadAll(resp.Body)
+		if err != nil {
+			reply = nil
+		}
+		return fmt.Errorf("E! Get Error. %d HTTP response: %s response body: %s",
+			resp.StatusCode, resp.Status, reply)
+	}
+
+	return nil
+}
+
+func hashIDWithTagKeysOnly(m telegraf.Metric) uint64 {
+	h := fnv.New64a()
+	h.Write([]byte(m.Name()))
+	h.Write([]byte("\n"))
+	for _, tag := range m.TagList() {
+		h.Write([]byte(tag.Key))
+		h.Write([]byte("\n"))
+	}
+	b := make([]byte, binary.MaxVarintLen64)
+	n := binary.PutUvarint(b, uint64(m.Time().UnixNano()))
+	h.Write(b[:n])
+	h.Write([]byte("\n"))
+	return h.Sum64()
+}
+
+func translate(m telegraf.Metric) *azureMonitorMetric {
+	var dimensionNames []string
+	var dimensionValues []string
+	for i, tag := range m.TagList() {
+		// Azure custom metrics service supports up to 10 dimensions
+		if i > 10 {
+			log.Printf("W! [outputs.azuremonitor] metric [%s] exceeds 10 dimensions", m.Name())
+			continue
+		}
+		dimensionNames = append(dimensionNames, tag.Key)
+		dimensionValues = append(dimensionValues, tag.Value)
+	}
+
+	min, _ := m.GetField("min")
+	max, _ := m.GetField("max")
+	sum, _ := m.GetField("sum")
+	count, _ := m.GetField("count")
+	return &azureMonitorMetric{
+		Time: m.Time(),
+		Data: &azureMonitorData{
+			BaseData: &azureMonitorBaseData{
+				Metric:         m.Name(),
+				Namespace:      "default",
+				DimensionNames: dimensionNames,
+				Series: []*azureMonitorSeries{
+					&azureMonitorSeries{
+						DimensionValues: dimensionValues,
+						Min:             min.(float64),
+						Max:             max.(float64),
+						Sum:             sum.(float64),
+						Count:           count.(int64),
+					},
+				},
+			},
+		},
+	}
+}
+
+// Add will append a metric to the output aggregate
+func (a *AzureMonitor) Add(m telegraf.Metric) {
+	// Azure Monitor only supports aggregates 30 minutes into the past
+	// and 4 minutes into the future. Future metrics are dropped when pushed.
+	t := m.Time()
+	tbucket := time.Date(t.Year(), t.Month(), t.Day(), t.Hour(), t.Minute(), 0, 0, t.Location())
+	if tbucket.Before(time.Now().Add(-time.Minute * 30)) {
+		log.Printf("W! attempted to aggregate metric over 30 minutes old: %v, %v", t, tbucket)
+		return
+	}
+
+	// Azure Monitor doesn't have a string value type, so convert string
+	// fields to dimensions (a.k.a. tags) if enabled.
+	if a.StringAsDimension {
+		for fk, fv := range m.Fields() {
+			if v, ok := fv.(string); ok {
+				m.AddTag(fk, v)
+			}
+		}
+	}
+
+	for _, f := range m.FieldList() {
+		fv, ok := convert(f.Value)
+		if !ok {
+			continue
+		}
+
+		// Azure Monitor does not support fields so the field
+		// name is appended to the metric name.
+		name := m.Name() + "_" + sanitize(f.Key)
+		id := hashIDWithField(m.HashID(), f.Key)
+
+		_, ok = a.cache[tbucket]
+		if !ok {
+			// Time bucket does not exist and needs to be created.
+			a.cache[tbucket] = make(map[uint64]*aggregate)
+		}
+
+		nf := make(map[string]interface{}, 4)
+		nf["min"] = fv
+		nf["max"] = fv
+		nf["sum"] = fv
+		nf["count"] = 1
+		// Fetch existing aggregate
+		agg, ok := a.cache[tbucket][id]
+		if ok {
+			aggfields := agg.Fields()
+			if fv > aggfields["min"].(float64) {
+				nf["min"] = aggfields["min"]
+			}
+			if fv < aggfields["max"].(float64) {
+				nf["max"] = aggfields["max"]
+			}
+			nf["sum"] = fv + aggfields["sum"].(float64)
+			nf["count"] = aggfields["count"].(int64) + 1
+		}
+
+		na, _ := metric.New(name, m.Tags(), nf, tbucket)
+		a.cache[tbucket][id] = &aggregate{na, true}
+	}
+}
+
+func convert(in interface{}) (float64, bool) {
+	switch v := in.(type) {
+	case int64:
+		return float64(v), true
+	case uint64:
+		return float64(v), true
+	case float64:
+		return v, true
+	case bool:
+		if v {
+			return 1, true
+		}
+		return 0, true
+	default:
+		return 0, false
+	}
+}
+
+var invalidNameCharRE = regexp.MustCompile(`[^a-zA-Z0-9_]`)
+
+func sanitize(value string) string {
+	return invalidNameCharRE.ReplaceAllString(value, "_")
+}
+
+func hashIDWithField(id uint64, fk string) uint64 {
+	h := fnv.New64a()
+	b := make([]byte, binary.MaxVarintLen64)
+	n := binary.PutUvarint(b, id)
+	h.Write(b[:n])
+	h.Write([]byte("\n"))
+	h.Write([]byte(fk))
+	h.Write([]byte("\n"))
+	return h.Sum64()
+}
+
+// Push sends metrics to the output metric buffer
+func (a *AzureMonitor) Push() []telegraf.Metric {
+	var metrics []telegraf.Metric
+	for tbucket, aggs := range a.cache {
+		// Do not send metrics early
+		if tbucket.After(time.Now().Add(-time.Minute)) {
+			continue
+		}
+		for _, agg := range aggs {
+			// Only send aggregates that have had an update since
+			// the last push.
+			if !agg.updated {
+				continue
+			}
+			metrics = append(metrics, agg.Metric)
+		}
+	}
+	return metrics
+}
+
+// Reset clears the cache of aggregate metrics
+func (a *AzureMonitor) Reset() {
+	for tbucket := range a.cache {
+		// Remove aggregates older than 30 minutes
+		if tbucket.Before(time.Now().Add(-time.Minute * 30)) {
+			delete(a.cache, tbucket)
+			continue
+		}
+		for id := range a.cache[tbucket] {
+			a.cache[tbucket][id].updated = false
+		}
+	}
+}
+
+func init() {
+	outputs.Add("azuremonitor", func() telegraf.Output {
+		return &AzureMonitor{
+			StringAsDimension: false,
+			Timeout:           internal.Duration{Duration: time.Second * 5},
+			Region:            defaultRegion,
+			cache:             make(map[time.Time]map[uint64]*aggregate, 36),
+		}
+	})
+}

plugins/outputs/azuremonitor/azuremonitor_test.go

@@ -0,0 +1,40 @@
+package azuremonitor
+
+import (
+	"time"
+
+	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/metric"
+)
+
+// MockMetrics returns a mock []telegraf.Metric object for using in unit tests
+// of telegraf output sinks.
+func getMockMetrics() []telegraf.Metric {
+	metrics := make([]telegraf.Metric, 0)
+	// Create a new point batch
+	metrics = append(metrics, getTestMetric(1.0))
+	return metrics
+}
+
+// TestMetric Returns a simple test point:
+//     measurement -> "test1" or name
+//     tags -> "tag1":"value1"
+//     value -> value
+//     time -> time.Date(2009, time.November, 10, 23, 0, 0, 0, time.UTC)
+func getTestMetric(value interface{}, name ...string) telegraf.Metric {
+	if value == nil {
+		panic("Cannot use a nil value")
+	}
+	measurement := "test1"
+	if len(name) > 0 {
+		measurement = name[0]
+	}
+	tags := map[string]string{"tag1": "value1"}
+	pt, _ := metric.New(
+		measurement,
+		tags,
+		map[string]interface{}{"value": value},
+		time.Now().UTC(),
+	)
+	return pt
+}