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client.go
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client.go
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package zincmetric
import (
"bytes"
"errors"
"fmt"
"net/http"
"net/url"
"time"
)
// Client provides io.Writer interface implementation
// to allow writing metring to ZincSearch service.
type Client struct {
user, pass string
index string
// Option configurable
client *http.Client
flushInterval time.Duration
dataCh chan []byte
closeCh chan struct{}
// ZincSearch endpoints (should be pre-built using buildEndpoints())
healthURL string // /healthx
singleDocumentURL string // /api/{index}/_doc
bulkDocumentsURL string // /api/_bulkv2
}
// New creates a new client to export metrics to ZincSearch service.
func New(
host string,
user string,
pass string,
index string,
ops ...OptionFunc,
) (*Client, error) {
exporter := &Client{
user: user,
pass: pass,
index: index,
client: &http.Client{},
flushInterval: time.Second,
dataCh: make(chan []byte),
closeCh: make(chan struct{}),
}
for _, op := range ops {
op(exporter)
}
if err := exporter.buildEndpoints(host, index); err != nil {
return nil, err
}
if err := exporter.ping(); err != nil {
return nil, err
}
go exporter.run()
return exporter, nil
}
// Write writes data to ZincSearch service.
// Data is expected to be in JSON format.
func (c *Client) Write(data []byte) (int, error) {
select {
case <-c.closeCh:
return 0, errors.New("client closed")
case c.dataCh <- bytes.Clone(data):
return len(data), nil
}
}
// Close closes the metrics client and flushes all
// remaining metrics to ZincSearch service.
func (c *Client) Close() error {
close(c.closeCh)
return nil
}
// buildEndpoints pre-builds endpoints to be used for communicating
// with ZincSearch service.
func (c *Client) buildEndpoints(host, index string) error {
var err error
c.singleDocumentURL, err = url.JoinPath(host, "api", index, "_doc")
if err != nil {
return err
}
c.bulkDocumentsURL, err = url.JoinPath(host, "api", "_bulkv2")
if err != nil {
return err
}
c.healthURL, err = url.JoinPath(host, "/healthz")
if err != nil {
return err
}
return nil
}
// createDocument posts a new document to ZincSearch service.
func (c *Client) createDocument(data []byte) error {
req, err := http.NewRequest(http.MethodPost, c.singleDocumentURL, bytes.NewReader(data))
if err != nil {
return err
}
req.SetBasicAuth(c.user, c.pass)
req.Header.Set("Content-Type", "application/json")
resp, err := c.client.Do(req)
if err != nil {
return err
}
defer resp.Body.Close()
if resp.StatusCode != http.StatusOK {
return fmt.Errorf("not 200 response code: %d", resp.StatusCode)
}
return nil
}
// createBulkDocuments posts a bulk of new documents to ZincSearch service.
func (c *Client) createBulkDocuments(data [][]byte) error {
// Construct request body, this should be faster and simpler than unmarshaling each data peace individually.
// Format:
// {
// "index": "string",
// "records": [
// {
// "additionalProp1": {}
// }
// ]
// }
buff := new(bytes.Buffer)
_, err := buff.WriteString(fmt.Sprintf(`{"index":"%s","records":[`, c.index))
if err != nil {
return err
}
_, err = buff.Write(append(bytes.Join(data, []byte(`,`)), []byte(`]}`)...))
if err != nil {
return err
}
req, err := http.NewRequest(http.MethodPost, c.bulkDocumentsURL, buff)
if err != nil {
return err
}
req.SetBasicAuth(c.user, c.pass)
req.Header.Set("Content-Type", "application/json")
resp, err := c.client.Do(req)
if err != nil {
return err
}
defer resp.Body.Close()
if resp.StatusCode != http.StatusOK {
return fmt.Errorf("not 200 response code: %d", resp.StatusCode)
}
return nil
}
// ping does a health check ping to the ZincSearch /healthz endpoint.
// Non 200 status code is treated as error.
func (c *Client) ping() error {
req, err := http.NewRequest(http.MethodGet, c.healthURL, nil)
if err != nil {
return err
}
resp, err := c.client.Do(req)
if err != nil {
return err
}
defer resp.Body.Close()
if resp.StatusCode != http.StatusOK {
return fmt.Errorf("not 200 response code: %d", resp.StatusCode)
}
return nil
}
// run runs pusher tread, that gathers and pushes data to ZincSearch service.
func (c *Client) run() {
buff := make([][]byte, 0)
tick := time.NewTicker(c.flushInterval)
defer tick.Stop()
defer func() {
// Flush remaining buffer.
c.createBulkDocuments(buff)
}()
for {
select {
case <-c.closeCh:
return
case b := <-c.dataCh:
buff = append(buff, b)
case <-tick.C:
if err := c.flushBuffer(buff); err != nil {
// TODO: would be nice to log this, should potentially introduce Logger interface.
break // Don't clear the buffer in case of error.
}
buff = nil
}
}
}
// flushBuffer pushes data in buffer to ZincSearch service.
func (c *Client) flushBuffer(buff [][]byte) error {
if len(buff) == 0 {
return nil
}
if len(buff) == 1 {
return c.createDocument(buff[0])
}
return c.createBulkDocuments(buff)
}