1 files changed, 228 insertions, 0 deletions

diff --git a/vendor/go.opencensus.io/plugin/ochttp/trace.go b/vendor/go.opencensus.io/plugin/ochttp/trace.go
new file mode 100644
index 0000000..819a2d5
--- /dev/null
+++ b/vendor/go.opencensus.io/plugin/ochttp/trace.go
@@ -0,0 +1,228 @@
+// Copyright 2018, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package ochttp
+
+import (
+        "io"
+        "net/http"
+        "net/http/httptrace"
+
+        "go.opencensus.io/plugin/ochttp/propagation/b3"
+        "go.opencensus.io/trace"
+        "go.opencensus.io/trace/propagation"
+)
+
+// TODO(jbd): Add godoc examples.
+
+var defaultFormat propagation.HTTPFormat = &b3.HTTPFormat{}
+
+// Attributes recorded on the span for the requests.
+// Only trace exporters will need them.
+const (
+        HostAttribute       = "http.host"
+        MethodAttribute     = "http.method"
+        PathAttribute       = "http.path"
+        UserAgentAttribute  = "http.user_agent"
+        StatusCodeAttribute = "http.status_code"
+)
+
+type traceTransport struct {
+        base           http.RoundTripper
+        startOptions   trace.StartOptions
+        format         propagation.HTTPFormat
+        formatSpanName func(*http.Request) string
+        newClientTrace func(*http.Request, *trace.Span) *httptrace.ClientTrace
+}
+
+// TODO(jbd): Add message events for request and response size.
+
+// RoundTrip creates a trace.Span and inserts it into the outgoing request's headers.
+// The created span can follow a parent span, if a parent is presented in
+// the request's context.
+func (t *traceTransport) RoundTrip(req *http.Request) (*http.Response, error) {
+        name := t.formatSpanName(req)
+        // TODO(jbd): Discuss whether we want to prefix
+        // outgoing requests with Sent.
+        ctx, span := trace.StartSpan(req.Context(), name,
+                trace.WithSampler(t.startOptions.Sampler),
+                trace.WithSpanKind(trace.SpanKindClient))
+
+        if t.newClientTrace != nil {
+                req = req.WithContext(httptrace.WithClientTrace(ctx, t.newClientTrace(req, span)))
+        } else {
+                req = req.WithContext(ctx)
+        }
+
+        if t.format != nil {
+                // SpanContextToRequest will modify its Request argument, which is
+                // contrary to the contract for http.RoundTripper, so we need to
+                // pass it a copy of the Request.
+                // However, the Request struct itself was already copied by
+                // the WithContext calls above and so we just need to copy the header.
+                header := make(http.Header)
+                for k, v := range req.Header {
+                        header[k] = v
+                }
+                req.Header = header
+                t.format.SpanContextToRequest(span.SpanContext(), req)
+        }
+
+        span.AddAttributes(requestAttrs(req)...)
+        resp, err := t.base.RoundTrip(req)
+        if err != nil {
+                span.SetStatus(trace.Status{Code: trace.StatusCodeUnknown, Message: err.Error()})
+                span.End()
+                return resp, err
+        }
+
+        span.AddAttributes(responseAttrs(resp)...)
+        span.SetStatus(TraceStatus(resp.StatusCode, resp.Status))
+
+        // span.End() will be invoked after
+        // a read from resp.Body returns io.EOF or when
+        // resp.Body.Close() is invoked.
+        resp.Body = &bodyTracker{rc: resp.Body, span: span}
+        return resp, err
+}
+
+// bodyTracker wraps a response.Body and invokes
+// trace.EndSpan on encountering io.EOF on reading
+// the body of the original response.
+type bodyTracker struct {
+        rc   io.ReadCloser
+        span *trace.Span
+}
+
+var _ io.ReadCloser = (*bodyTracker)(nil)
+
+func (bt *bodyTracker) Read(b []byte) (int, error) {
+        n, err := bt.rc.Read(b)
+
+        switch err {
+        case nil:
+                return n, nil
+        case io.EOF:
+                bt.span.End()
+        default:
+                // For all other errors, set the span status
+                bt.span.SetStatus(trace.Status{
+                        // Code 2 is the error code for Internal server error.
+                        Code:    2,
+                        Message: err.Error(),
+                })
+        }
+        return n, err
+}
+
+func (bt *bodyTracker) Close() error {
+        // Invoking endSpan on Close will help catch the cases
+        // in which a read returned a non-nil error, we set the
+        // span status but didn't end the span.
+        bt.span.End()
+        return bt.rc.Close()
+}
+
+// CancelRequest cancels an in-flight request by closing its connection.
+func (t *traceTransport) CancelRequest(req *http.Request) {
+        type canceler interface {
+                CancelRequest(*http.Request)
+        }
+        if cr, ok := t.base.(canceler); ok {
+                cr.CancelRequest(req)
+        }
+}
+
+func spanNameFromURL(req *http.Request) string {
+        return req.URL.Path
+}
+
+func requestAttrs(r *http.Request) []trace.Attribute {
+        return []trace.Attribute{
+                trace.StringAttribute(PathAttribute, r.URL.Path),
+                trace.StringAttribute(HostAttribute, r.URL.Host),
+                trace.StringAttribute(MethodAttribute, r.Method),
+                trace.StringAttribute(UserAgentAttribute, r.UserAgent()),
+        }
+}
+
+func responseAttrs(resp *http.Response) []trace.Attribute {
+        return []trace.Attribute{
+                trace.Int64Attribute(StatusCodeAttribute, int64(resp.StatusCode)),
+        }
+}
+
+// TraceStatus is a utility to convert the HTTP status code to a trace.Status that
+// represents the outcome as closely as possible.
+func TraceStatus(httpStatusCode int, statusLine string) trace.Status {
+        var code int32
+        if httpStatusCode < 200 || httpStatusCode >= 400 {
+                code = trace.StatusCodeUnknown
+        }
+        switch httpStatusCode {
+        case 499:
+                code = trace.StatusCodeCancelled
+        case http.StatusBadRequest:
+                code = trace.StatusCodeInvalidArgument
+        case http.StatusGatewayTimeout:
+                code = trace.StatusCodeDeadlineExceeded
+        case http.StatusNotFound:
+                code = trace.StatusCodeNotFound
+        case http.StatusForbidden:
+                code = trace.StatusCodePermissionDenied
+        case http.StatusUnauthorized: // 401 is actually unauthenticated.
+                code = trace.StatusCodeUnauthenticated
+        case http.StatusTooManyRequests:
+                code = trace.StatusCodeResourceExhausted
+        case http.StatusNotImplemented:
+                code = trace.StatusCodeUnimplemented
+        case http.StatusServiceUnavailable:
+                code = trace.StatusCodeUnavailable
+        case http.StatusOK:
+                code = trace.StatusCodeOK
+        }
+        return trace.Status{Code: code, Message: codeToStr[code]}
+}
+
+var codeToStr = map[int32]string{
+        trace.StatusCodeOK:                 `OK`,
+        trace.StatusCodeCancelled:          `CANCELLED`,
+        trace.StatusCodeUnknown:            `UNKNOWN`,
+        trace.StatusCodeInvalidArgument:    `INVALID_ARGUMENT`,
+        trace.StatusCodeDeadlineExceeded:   `DEADLINE_EXCEEDED`,
+        trace.StatusCodeNotFound:           `NOT_FOUND`,
+        trace.StatusCodeAlreadyExists:      `ALREADY_EXISTS`,
+        trace.StatusCodePermissionDenied:   `PERMISSION_DENIED`,
+        trace.StatusCodeResourceExhausted:  `RESOURCE_EXHAUSTED`,
+        trace.StatusCodeFailedPrecondition: `FAILED_PRECONDITION`,
+        trace.StatusCodeAborted:            `ABORTED`,
+        trace.StatusCodeOutOfRange:         `OUT_OF_RANGE`,
+        trace.StatusCodeUnimplemented:      `UNIMPLEMENTED`,
+        trace.StatusCodeInternal:           `INTERNAL`,
+        trace.StatusCodeUnavailable:        `UNAVAILABLE`,
+        trace.StatusCodeDataLoss:           `DATA_LOSS`,
+        trace.StatusCodeUnauthenticated:    `UNAUTHENTICATED`,
+}
+
+func isHealthEndpoint(path string) bool {
+        // Health checking is pretty frequent and
+        // traces collected for health endpoints
+        // can be extremely noisy and expensive.
+        // Disable canonical health checking endpoints
+        // like /healthz and /_ah/health for now.
+        if path == "/healthz" || path == "/_ah/health" {
+                return true
+        }
+        return false
+}