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arm_error_collector.go
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arm_error_collector.go
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package middleware
import (
"context"
"crypto/tls"
"errors"
"fmt"
"net/http"
"net/http/httptrace"
"time"
"github.com/Azure/azure-sdk-for-go/sdk/azcore"
"github.com/Azure/azure-sdk-for-go/sdk/azcore/arm"
"github.com/Azure/azure-sdk-for-go/sdk/azcore/policy"
"github.com/Azure/azure-sdk-for-go/sdk/azcore/runtime"
"github.com/Azure/azure-sdk-for-go/sdk/azcore/to"
)
const (
headerKeyRequestID = "X-Ms-Client-Request-Id"
headerKeyCorrelationID = "X-Ms-Correlation-Request-id"
ArmErrorCodeCastToArmResponseErrorFailed ArmErrorCode = "CastToArmResponseErrorFailed"
ArmErrorCodeTransportError ArmErrorCode = "TransportError"
ArmErrorCodeUnexpectedTransportError ArmErrorCode = "UnexpectedTransportError"
ArmErrorCodeContextCanceled ArmErrorCode = "ContextCanceled"
ArmErrorCodeContextDeadlineExceeded ArmErrorCode = "ContextDeadlineExceeded"
)
// ArmError is unified Error Experience across AzureResourceManager, it contains Code Message.
type ArmError struct {
Code ArmErrorCode `json:"code"`
Message string `json:"message"`
}
type ArmErrorCode string
type RequestInfo struct {
Request *http.Request
ArmResId *arm.ResourceID
}
func newRequestInfo(req *http.Request, resId *arm.ResourceID) *RequestInfo {
return &RequestInfo{Request: req, ArmResId: resId}
}
type ResponseInfo struct {
Response *http.Response
Error *ArmError
Latency time.Duration
RequestId string
CorrelationId string
ConnTracking *HttpConnTracking
}
type HttpConnTracking struct {
TotalLatency string
DnsLatency string
ConnLatency string
TlsLatency string
Protocol string
ReqConnInfo *httptrace.GotConnInfo
}
// ArmRequestMetricCollector is a interface that collectors need to implement.
// TODO: use *policy.Request or *http.Request?
type ArmRequestMetricCollector interface {
// RequestStarted is called when a request is about to be sent.
// context is not provided, get it from RequestInfo.Request.Context()
RequestStarted(*RequestInfo)
// RequestCompleted is called when a request is finished
// context is not provided, get it from RequestInfo.Request.Context()
// if an error occurred, ResponseInfo.Error will be populated
RequestCompleted(*RequestInfo, *ResponseInfo)
}
// ArmRequestMetricPolicy is a policy that collects metrics/telemetry for ARM requests.
type ArmRequestMetricPolicy struct {
Collector ArmRequestMetricCollector
}
// Do implements the azcore/policy.Policy interface.
func (p *ArmRequestMetricPolicy) Do(req *policy.Request) (*http.Response, error) {
httpReq := req.Raw()
if httpReq == nil || httpReq.URL == nil {
// not able to collect telemetry, just pass through
return req.Next()
}
armResId, err := arm.ParseResourceID(httpReq.URL.Path)
if err != nil {
// TODO: error handling without break the request.
}
connTracking := &HttpConnTracking{}
// have to add to the context at first - then clone the policy.Request struct
// this allows the connection tracing to happen
// otherwise we can't change the underlying http request of req, we have to use
// newARMReq
newCtx := addConnectionTracingToRequestContext(httpReq.Context(), connTracking)
newARMReq := req.Clone(newCtx)
requestInfo := newRequestInfo(httpReq, armResId)
started := time.Now()
p.requestStarted(requestInfo)
var resp *http.Response
var reqErr error
// defer this function in case there's a panic somewhere down the pipeline.
// It's the calling user's responsibility to handle panics, not this policy
defer func() {
latency := time.Since(started)
respInfo := &ResponseInfo{
Response: resp,
Latency: latency,
ConnTracking: connTracking,
}
if reqErr != nil {
// either it's a transport error
// or it is already handled by previous policy
respInfo.Error = parseTransportError(reqErr)
} else {
respInfo.Error = parseArmErrorFromResponse(resp)
}
// need to get the request id and correlation id from the response.request header
// because the headers were added by policy and might be called after this policy
if resp != nil && resp.Request != nil {
respInfo.RequestId = resp.Request.Header.Get(headerKeyRequestID)
respInfo.CorrelationId = resp.Request.Header.Get(headerKeyCorrelationID)
}
p.requestCompleted(requestInfo, respInfo)
}()
resp, reqErr = newARMReq.Next()
return resp, reqErr
}
// shortcut function to handle nil collector
func (p *ArmRequestMetricPolicy) requestStarted(iReq *RequestInfo) {
if p.Collector != nil {
p.Collector.RequestStarted(iReq)
}
}
// shortcut function to handle nil collector
func (p *ArmRequestMetricPolicy) requestCompleted(iReq *RequestInfo, iResp *ResponseInfo) {
if p.Collector != nil {
p.Collector.RequestCompleted(iReq, iResp)
}
}
func parseArmErrorFromResponse(resp *http.Response) *ArmError {
if resp == nil {
return &ArmError{Code: ArmErrorCodeUnexpectedTransportError, Message: "nil response"}
}
if resp.StatusCode > 399 {
// for 4xx, 5xx response, ARM should include {error:{code, message}} in the body
err := runtime.NewResponseError(resp)
respErr := &azcore.ResponseError{}
if errors.As(err, &respErr) {
return &ArmError{Code: ArmErrorCode(respErr.ErrorCode), Message: respErr.Error()}
}
return &ArmError{Code: ArmErrorCodeCastToArmResponseErrorFailed, Message: fmt.Sprintf("Response body is not in ARM error form: {error:{code, message}}: %s", err.Error())}
}
return nil
}
// distinguash
// - Context Cancelled (request configured context to have timeout)
// - ClientTimeout (context still valid, http client have timeout configured)
// - Transport Error (DNS/Dial/TLS/ServerTimeout)
func parseTransportError(err error) *ArmError {
if err == nil {
return nil
}
if errors.Is(err, context.Canceled) {
return &ArmError{Code: ArmErrorCodeContextCanceled, Message: err.Error()}
}
if errors.Is(err, context.DeadlineExceeded) {
return &ArmError{Code: ArmErrorCodeContextDeadlineExceeded, Message: err.Error()}
}
return &ArmError{Code: ArmErrorCodeTransportError, Message: err.Error()}
}
func addConnectionTracingToRequestContext(ctx context.Context, connTracking *HttpConnTracking) context.Context {
var getConn, dnsStart, connStart, tlsStart *time.Time
trace := &httptrace.ClientTrace{
GetConn: func(hostPort string) {
getConn = to.Ptr(time.Now())
},
GotConn: func(connInfo httptrace.GotConnInfo) {
if getConn != nil {
connTracking.TotalLatency = fmt.Sprintf("%dms", time.Now().Sub(*getConn).Milliseconds())
}
connTracking.ReqConnInfo = &connInfo
},
DNSStart: func(_ httptrace.DNSStartInfo) {
dnsStart = to.Ptr(time.Now())
},
DNSDone: func(dnsInfo httptrace.DNSDoneInfo) {
if dnsInfo.Err == nil {
if dnsStart != nil {
connTracking.DnsLatency = fmt.Sprintf("%dms", time.Now().Sub(*dnsStart).Milliseconds())
}
} else {
connTracking.DnsLatency = dnsInfo.Err.Error()
}
},
ConnectStart: func(_, _ string) {
connStart = to.Ptr(time.Now())
},
ConnectDone: func(_, _ string, err error) {
if err == nil {
if connStart != nil {
connTracking.ConnLatency = fmt.Sprintf("%dms", time.Now().Sub(*connStart).Milliseconds())
}
} else {
connTracking.ConnLatency = err.Error()
}
},
TLSHandshakeStart: func() {
tlsStart = to.Ptr(time.Now())
},
TLSHandshakeDone: func(t tls.ConnectionState, err error) {
if err == nil {
if tlsStart != nil {
connTracking.TlsLatency = fmt.Sprintf("%dms", time.Now().Sub(*tlsStart).Milliseconds())
}
connTracking.Protocol = t.NegotiatedProtocol
} else {
connTracking.TlsLatency = err.Error()
}
},
}
ctx = httptrace.WithClientTrace(ctx, trace)
return ctx
}