telegraf/plugins/httpjson/httpjson.go

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package httpjson
import (
"encoding/json"
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"errors"
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"fmt"
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"io/ioutil"
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"net/http"
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"net/url"
"strings"
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"sync"
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"github.com/influxdb/telegraf/plugins"
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)
type HttpJson struct {
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Services []Service
client HTTPClient
}
type Service struct {
Name string
Servers []string
Method string
Parameters map[string]string
}
type HTTPClient interface {
// Returns the result of an http request
//
// Parameters:
// req: HTTP request object
//
// Returns:
// http.Response: HTTP respons object
// error : Any error that may have occurred
MakeRequest(req *http.Request) (*http.Response, error)
}
type RealHTTPClient struct {
client *http.Client
}
func (c RealHTTPClient) MakeRequest(req *http.Request) (*http.Response, error) {
return c.client.Do(req)
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}
var sampleConfig = `
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# Specify services via an array of tables
[[httpjson.services]]
# a name for the service being polled
name = "webserver_stats"
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# URL of each server in the service's cluster
servers = [
"http://localhost:9999/stats/",
"http://localhost:9998/stats/",
]
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# HTTP method to use (case-sensitive)
method = "GET"
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# HTTP parameters (all values must be strings)
[httpjson.services.parameters]
event_type = "cpu_spike"
threshold = "0.75"
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`
func (h *HttpJson) SampleConfig() string {
return sampleConfig
}
func (h *HttpJson) Description() string {
return "Read flattened metrics from one or more JSON HTTP endpoints"
}
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// Gathers data for all servers.
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func (h *HttpJson) Gather(acc plugins.Accumulator) error {
var wg sync.WaitGroup
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totalServers := 0
for _, service := range h.Services {
totalServers += len(service.Servers)
}
errorChannel := make(chan error, totalServers)
for _, service := range h.Services {
for _, server := range service.Servers {
wg.Add(1)
go func(service Service, server string) {
defer wg.Done()
if err := h.gatherServer(acc, service, server); err != nil {
errorChannel <- err
}
}(service, server)
}
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}
wg.Wait()
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close(errorChannel)
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// Get all errors and return them as one giant error
errorStrings := []string{}
for err := range errorChannel {
errorStrings = append(errorStrings, err.Error())
}
if len(errorStrings) == 0 {
return nil
}
return errors.New(strings.Join(errorStrings, "\n"))
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}
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// Gathers data from a particular server
// Parameters:
// acc : The telegraf Accumulator to use
// serverURL: endpoint to send request to
// service : the service being queried
//
// Returns:
// error: Any error that may have occurred
func (h *HttpJson) gatherServer(acc plugins.Accumulator, service Service, serverURL string) error {
resp, err := h.sendRequest(service, serverURL)
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if err != nil {
return err
}
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var jsonOut interface{}
if err = json.Unmarshal([]byte(resp), &jsonOut); err != nil {
return errors.New("Error decoding JSON response")
}
tags := map[string]string{
"server": serverURL,
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}
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processResponse(acc, service.Name, tags, jsonOut)
return nil
}
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// Sends an HTTP request to the server using the HttpJson object's HTTPClient
// Parameters:
// serverURL: endpoint to send request to
//
// Returns:
// string: body of the response
// error : Any error that may have occurred
func (h *HttpJson) sendRequest(service Service, serverURL string) (string, error) {
// Prepare URL
requestURL, err := url.Parse(serverURL)
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if err != nil {
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return "", fmt.Errorf("Invalid server URL \"%s\"", serverURL)
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}
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params := url.Values{}
for k, v := range service.Parameters {
params.Add(k, v)
}
requestURL.RawQuery = params.Encode()
// Create + send request
req, err := http.NewRequest(service.Method, requestURL.String(), nil)
if err != nil {
return "", err
}
resp, err := h.client.MakeRequest(req)
if err != nil {
return "", err
}
defer resp.Body.Close()
body, err := ioutil.ReadAll(resp.Body)
if err != nil {
return string(body), err
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}
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// Process response
if resp.StatusCode != http.StatusOK {
err = fmt.Errorf("Response from url \"%s\" has status code %d (%s), expected %d (%s)",
requestURL.String(),
resp.StatusCode,
http.StatusText(resp.StatusCode),
http.StatusOK,
http.StatusText(http.StatusOK))
return string(body), err
}
return string(body), err
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}
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// Flattens the map generated from the JSON object and stores its float values using a
// plugins.Accumulator. It ignores any non-float values.
// Parameters:
// acc: the Accumulator to use
// prefix: What the name of the measurement name should be prefixed by.
// tags: telegraf tags to
func processResponse(acc plugins.Accumulator, prefix string, tags map[string]string, v interface{}) {
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switch t := v.(type) {
case map[string]interface{}:
for k, v := range t {
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processResponse(acc, prefix+"_"+k, tags, v)
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}
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case float64:
acc.Add(prefix, v, tags)
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}
}
func init() {
plugins.Add("httpjson", func() plugins.Plugin {
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return &HttpJson{client: RealHTTPClient{client: &http.Client{}}}
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})
}