Felipe M.
8a4b11281d
Expose /metrics with counters for routed requests, routing errors, upstream outcomes, and upstream latency histograms. Instrument the router and proxy forwarding path and document the new metrics.
97 lines
2.2 KiB
Go
97 lines
2.2 KiB
Go
package main
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import (
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"bytes"
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"encoding/json"
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"fmt"
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"io"
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"net/http"
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"time"
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)
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type Proxy struct {
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client *http.Client
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cfg Config
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metrics *Metrics
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}
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func NewProxy(cfg Config, metrics *Metrics) *Proxy {
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return &Proxy{
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client: &http.Client{Timeout: cfg.RequestTimeout},
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cfg: cfg,
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metrics: metrics,
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}
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}
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type pushResponse struct {
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Status string `json:"status"`
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}
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func (p *Proxy) Forward(w http.ResponseWriter, r *http.Request, backendURL, path string, body []byte, platform string) {
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start := time.Now()
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target := backendURL + path
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req, err := http.NewRequestWithContext(r.Context(), http.MethodPost, target, bytes.NewReader(body))
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if err != nil {
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p.metrics.observeUpstream(platform, "error", time.Since(start))
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writePushError(w, fmt.Sprintf("failed to create upstream request: %v", err))
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return
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}
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req.Header.Set("Content-Type", "application/json")
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resp, err := p.client.Do(req)
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if err != nil {
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p.metrics.observeUpstream(platform, "error", time.Since(start))
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writePushError(w, fmt.Sprintf("upstream request failed: %v", err))
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return
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}
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defer func() { _ = resp.Body.Close() }()
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respBody, err := io.ReadAll(resp.Body)
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if err != nil {
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p.metrics.observeUpstream(platform, "error", time.Since(start))
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writePushError(w, fmt.Sprintf("failed to read upstream response: %v", err))
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return
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}
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p.metrics.observeUpstream(platform, upstreamOutcome(resp.StatusCode, respBody), time.Since(start))
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for k, vals := range resp.Header {
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for _, v := range vals {
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w.Header().Add(k, v)
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}
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}
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if w.Header().Get("Content-Type") == "" {
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w.Header().Set("Content-Type", "application/json")
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}
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w.WriteHeader(resp.StatusCode)
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_, _ = w.Write(respBody)
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}
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func upstreamOutcome(statusCode int, body []byte) string {
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var resp pushResponse
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if err := json.Unmarshal(body, &resp); err == nil {
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switch resp.Status {
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case "OK":
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return "success"
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case "FAIL":
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return "fail"
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}
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}
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if statusCode >= 400 {
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return "fail"
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}
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return "success"
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}
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func writePushError(w http.ResponseWriter, message string) {
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w.Header().Set("Content-Type", "application/json")
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w.WriteHeader(http.StatusOK)
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payload, _ := json.Marshal(map[string]string{
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"status": "FAIL",
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"error": message,
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})
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_, _ = w.Write(payload)
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}
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