File context.obscpio of Package distribution-container
07070100000000000081a40000000000000000000000016328304800000733000000000000000000000000000000000000001300000000context/context.gopackage context
import (
"context"
"sync"
"github.com/distribution/distribution/v3/uuid"
)
// instanceContext is a context that provides only an instance id. It is
// provided as the main background context.
type instanceContext struct {
context.Context
id string // id of context, logged as "instance.id"
once sync.Once // once protect generation of the id
}
func (ic *instanceContext) Value(key interface{}) interface{} {
if key == "instance.id" {
ic.once.Do(func() {
// We want to lazy initialize the UUID such that we don't
// call a random generator from the package initialization
// code. For various reasons random could not be available
// https://github.com/distribution/distribution/issues/782
ic.id = uuid.Generate().String()
})
return ic.id
}
return ic.Context.Value(key)
}
var background = &instanceContext{
Context: context.Background(),
}
// Background returns a non-nil, empty Context. The background context
// provides a single key, "instance.id" that is globally unique to the
// process.
func Background() context.Context {
return background
}
// stringMapContext is a simple context implementation that checks a map for a
// key, falling back to a parent if not present.
type stringMapContext struct {
context.Context
m map[string]interface{}
}
// WithValues returns a context that proxies lookups through a map. Only
// supports string keys.
func WithValues(ctx context.Context, m map[string]interface{}) context.Context {
mo := make(map[string]interface{}, len(m)) // make our own copy.
for k, v := range m {
mo[k] = v
}
return stringMapContext{
Context: ctx,
m: mo,
}
}
func (smc stringMapContext) Value(key interface{}) interface{} {
if ks, ok := key.(string); ok {
if v, ok := smc.m[ks]; ok {
return v
}
}
return smc.Context.Value(key)
}
07070100000001000081a40000000000000000000000016328304800000f62000000000000000000000000000000000000000f00000000context/doc.go// Package context provides several utilities for working with
// Go's context in http requests. Primarily, the focus is on logging relevant
// request information but this package is not limited to that purpose.
//
// The easiest way to get started is to get the background context:
//
// ctx := context.Background()
//
// The returned context should be passed around your application and be the
// root of all other context instances. If the application has a version, this
// line should be called before anything else:
//
// ctx := context.WithVersion(context.Background(), version)
//
// The above will store the version in the context and will be available to
// the logger.
//
// Logging
//
// The most useful aspect of this package is GetLogger. This function takes
// any context.Context interface and returns the current logger from the
// context. Canonical usage looks like this:
//
// GetLogger(ctx).Infof("something interesting happened")
//
// GetLogger also takes optional key arguments. The keys will be looked up in
// the context and reported with the logger. The following example would
// return a logger that prints the version with each log message:
//
// ctx := context.Context(context.Background(), "version", version)
// GetLogger(ctx, "version").Infof("this log message has a version field")
//
// The above would print out a log message like this:
//
// INFO[0000] this log message has a version field version=v2.0.0-alpha.2.m
//
// When used with WithLogger, we gain the ability to decorate the context with
// loggers that have information from disparate parts of the call stack.
// Following from the version example, we can build a new context with the
// configured logger such that we always print the version field:
//
// ctx = WithLogger(ctx, GetLogger(ctx, "version"))
//
// Since the logger has been pushed to the context, we can now get the version
// field for free with our log messages. Future calls to GetLogger on the new
// context will have the version field:
//
// GetLogger(ctx).Infof("this log message has a version field")
//
// This becomes more powerful when we start stacking loggers. Let's say we
// have the version logger from above but also want a request id. Using the
// context above, in our request scoped function, we place another logger in
// the context:
//
// ctx = context.WithValue(ctx, "http.request.id", "unique id") // called when building request context
// ctx = WithLogger(ctx, GetLogger(ctx, "http.request.id"))
//
// When GetLogger is called on the new context, "http.request.id" will be
// included as a logger field, along with the original "version" field:
//
// INFO[0000] this log message has a version field http.request.id=unique id version=v2.0.0-alpha.2.m
//
// Note that this only affects the new context, the previous context, with the
// version field, can be used independently. Put another way, the new logger,
// added to the request context, is unique to that context and can have
// request scoped variables.
//
// HTTP Requests
//
// This package also contains several methods for working with http requests.
// The concepts are very similar to those described above. We simply place the
// request in the context using WithRequest. This makes the request variables
// available. GetRequestLogger can then be called to get request specific
// variables in a log line:
//
// ctx = WithRequest(ctx, req)
// GetRequestLogger(ctx).Infof("request variables")
//
// Like above, if we want to include the request data in all log messages in
// the context, we push the logger to a new context and use that one:
//
// ctx = WithLogger(ctx, GetRequestLogger(ctx))
//
// The concept is fairly powerful and ensures that calls throughout the stack
// can be traced in log messages. Using the fields like "http.request.id", one
// can analyze call flow for a particular request with a simple grep of the
// logs.
package context
07070100000002000081a40000000000000000000000016328304800002155000000000000000000000000000000000000001000000000context/http.gopackage context
import (
"context"
"errors"
"net"
"net/http"
"strings"
"sync"
"time"
"github.com/distribution/distribution/v3/uuid"
"github.com/gorilla/mux"
log "github.com/sirupsen/logrus"
)
// Common errors used with this package.
var (
ErrNoRequestContext = errors.New("no http request in context")
ErrNoResponseWriterContext = errors.New("no http response in context")
)
func parseIP(ipStr string) net.IP {
ip := net.ParseIP(ipStr)
if ip == nil {
log.Warnf("invalid remote IP address: %q", ipStr)
}
return ip
}
// RemoteAddr extracts the remote address of the request, taking into
// account proxy headers.
func RemoteAddr(r *http.Request) string {
if prior := r.Header.Get("X-Forwarded-For"); prior != "" {
proxies := strings.Split(prior, ",")
if len(proxies) > 0 {
remoteAddr := strings.Trim(proxies[0], " ")
if parseIP(remoteAddr) != nil {
return remoteAddr
}
}
}
// X-Real-Ip is less supported, but worth checking in the
// absence of X-Forwarded-For
if realIP := r.Header.Get("X-Real-Ip"); realIP != "" {
if parseIP(realIP) != nil {
return realIP
}
}
return r.RemoteAddr
}
// RemoteIP extracts the remote IP of the request, taking into
// account proxy headers.
func RemoteIP(r *http.Request) string {
addr := RemoteAddr(r)
// Try parsing it as "IP:port"
if ip, _, err := net.SplitHostPort(addr); err == nil {
return ip
}
return addr
}
// WithRequest places the request on the context. The context of the request
// is assigned a unique id, available at "http.request.id". The request itself
// is available at "http.request". Other common attributes are available under
// the prefix "http.request.". If a request is already present on the context,
// this method will panic.
func WithRequest(ctx context.Context, r *http.Request) context.Context {
if ctx.Value("http.request") != nil {
// NOTE(stevvooe): This needs to be considered a programming error. It
// is unlikely that we'd want to have more than one request in
// context.
panic("only one request per context")
}
return &httpRequestContext{
Context: ctx,
startedAt: time.Now(),
id: uuid.Generate().String(),
r: r,
}
}
// GetRequest returns the http request in the given context. Returns
// ErrNoRequestContext if the context does not have an http request associated
// with it.
func GetRequest(ctx context.Context) (*http.Request, error) {
if r, ok := ctx.Value("http.request").(*http.Request); r != nil && ok {
return r, nil
}
return nil, ErrNoRequestContext
}
// GetRequestID attempts to resolve the current request id, if possible. An
// error is return if it is not available on the context.
func GetRequestID(ctx context.Context) string {
return GetStringValue(ctx, "http.request.id")
}
// WithResponseWriter returns a new context and response writer that makes
// interesting response statistics available within the context.
func WithResponseWriter(ctx context.Context, w http.ResponseWriter) (context.Context, http.ResponseWriter) {
irw := instrumentedResponseWriter{
ResponseWriter: w,
Context: ctx,
}
return &irw, &irw
}
// GetResponseWriter returns the http.ResponseWriter from the provided
// context. If not present, ErrNoResponseWriterContext is returned. The
// returned instance provides instrumentation in the context.
func GetResponseWriter(ctx context.Context) (http.ResponseWriter, error) {
v := ctx.Value("http.response")
rw, ok := v.(http.ResponseWriter)
if !ok || rw == nil {
return nil, ErrNoResponseWriterContext
}
return rw, nil
}
// getVarsFromRequest let's us change request vars implementation for testing
// and maybe future changes.
var getVarsFromRequest = mux.Vars
// WithVars extracts gorilla/mux vars and makes them available on the returned
// context. Variables are available at keys with the prefix "vars.". For
// example, if looking for the variable "name", it can be accessed as
// "vars.name". Implementations that are accessing values need not know that
// the underlying context is implemented with gorilla/mux vars.
func WithVars(ctx context.Context, r *http.Request) context.Context {
return &muxVarsContext{
Context: ctx,
vars: getVarsFromRequest(r),
}
}
// GetRequestLogger returns a logger that contains fields from the request in
// the current context. If the request is not available in the context, no
// fields will display. Request loggers can safely be pushed onto the context.
func GetRequestLogger(ctx context.Context) Logger {
return GetLogger(ctx,
"http.request.id",
"http.request.method",
"http.request.host",
"http.request.uri",
"http.request.referer",
"http.request.useragent",
"http.request.remoteaddr",
"http.request.contenttype")
}
// GetResponseLogger reads the current response stats and builds a logger.
// Because the values are read at call time, pushing a logger returned from
// this function on the context will lead to missing or invalid data. Only
// call this at the end of a request, after the response has been written.
func GetResponseLogger(ctx context.Context) Logger {
l := getLogrusLogger(ctx,
"http.response.written",
"http.response.status",
"http.response.contenttype")
duration := Since(ctx, "http.request.startedat")
if duration > 0 {
l = l.WithField("http.response.duration", duration.String())
}
return l
}
// httpRequestContext makes information about a request available to context.
type httpRequestContext struct {
context.Context
startedAt time.Time
id string
r *http.Request
}
// Value returns a keyed element of the request for use in the context. To get
// the request itself, query "request". For other components, access them as
// "request.<component>". For example, r.RequestURI
func (ctx *httpRequestContext) Value(key interface{}) interface{} {
if keyStr, ok := key.(string); ok {
if keyStr == "http.request" {
return ctx.r
}
if !strings.HasPrefix(keyStr, "http.request.") {
goto fallback
}
parts := strings.Split(keyStr, ".")
if len(parts) != 3 {
goto fallback
}
switch parts[2] {
case "uri":
return ctx.r.RequestURI
case "remoteaddr":
return RemoteAddr(ctx.r)
case "method":
return ctx.r.Method
case "host":
return ctx.r.Host
case "referer":
referer := ctx.r.Referer()
if referer != "" {
return referer
}
case "useragent":
return ctx.r.UserAgent()
case "id":
return ctx.id
case "startedat":
return ctx.startedAt
case "contenttype":
ct := ctx.r.Header.Get("Content-Type")
if ct != "" {
return ct
}
}
}
fallback:
return ctx.Context.Value(key)
}
type muxVarsContext struct {
context.Context
vars map[string]string
}
func (ctx *muxVarsContext) Value(key interface{}) interface{} {
if keyStr, ok := key.(string); ok {
if keyStr == "vars" {
return ctx.vars
}
keyStr = strings.TrimPrefix(keyStr, "vars.")
if v, ok := ctx.vars[keyStr]; ok {
return v
}
}
return ctx.Context.Value(key)
}
// instrumentedResponseWriter provides response writer information in a
// context. This variant is only used in the case where CloseNotifier is not
// implemented by the parent ResponseWriter.
type instrumentedResponseWriter struct {
http.ResponseWriter
context.Context
mu sync.Mutex
status int
written int64
}
func (irw *instrumentedResponseWriter) Write(p []byte) (n int, err error) {
n, err = irw.ResponseWriter.Write(p)
irw.mu.Lock()
irw.written += int64(n)
// Guess the likely status if not set.
if irw.status == 0 {
irw.status = http.StatusOK
}
irw.mu.Unlock()
return
}
func (irw *instrumentedResponseWriter) WriteHeader(status int) {
irw.ResponseWriter.WriteHeader(status)
irw.mu.Lock()
irw.status = status
irw.mu.Unlock()
}
func (irw *instrumentedResponseWriter) Flush() {
if flusher, ok := irw.ResponseWriter.(http.Flusher); ok {
flusher.Flush()
}
}
func (irw *instrumentedResponseWriter) Value(key interface{}) interface{} {
if keyStr, ok := key.(string); ok {
if keyStr == "http.response" {
return irw
}
if !strings.HasPrefix(keyStr, "http.response.") {
goto fallback
}
parts := strings.Split(keyStr, ".")
if len(parts) != 3 {
goto fallback
}
irw.mu.Lock()
defer irw.mu.Unlock()
switch parts[2] {
case "written":
return irw.written
case "status":
return irw.status
case "contenttype":
contentType := irw.Header().Get("Content-Type")
if contentType != "" {
return contentType
}
}
}
fallback:
return irw.Context.Value(key)
}
07070100000003000081a4000000000000000000000001632830480000193c000000000000000000000000000000000000001500000000context/http_test.gopackage context
import (
"net/http"
"net/http/httptest"
"net/http/httputil"
"net/url"
"reflect"
"testing"
"time"
)
func TestWithRequest(t *testing.T) {
var req http.Request
start := time.Now()
req.Method = "GET"
req.Host = "example.com"
req.RequestURI = "/test-test"
req.Header = make(http.Header)
req.Header.Set("Referer", "foo.com/referer")
req.Header.Set("User-Agent", "test/0.1")
ctx := WithRequest(Background(), &req)
for _, testcase := range []struct {
key string
expected interface{}
}{
{
key: "http.request",
expected: &req,
},
{
key: "http.request.id",
},
{
key: "http.request.method",
expected: req.Method,
},
{
key: "http.request.host",
expected: req.Host,
},
{
key: "http.request.uri",
expected: req.RequestURI,
},
{
key: "http.request.referer",
expected: req.Referer(),
},
{
key: "http.request.useragent",
expected: req.UserAgent(),
},
{
key: "http.request.remoteaddr",
expected: req.RemoteAddr,
},
{
key: "http.request.startedat",
},
} {
v := ctx.Value(testcase.key)
if v == nil {
t.Fatalf("value not found for %q", testcase.key)
}
if testcase.expected != nil && v != testcase.expected {
t.Fatalf("%s: %v != %v", testcase.key, v, testcase.expected)
}
// Key specific checks!
switch testcase.key {
case "http.request.id":
if _, ok := v.(string); !ok {
t.Fatalf("request id not a string: %v", v)
}
case "http.request.startedat":
vt, ok := v.(time.Time)
if !ok {
t.Fatalf("value not a time: %v", v)
}
now := time.Now()
if vt.After(now) {
t.Fatalf("time generated too late: %v > %v", vt, now)
}
if vt.Before(start) {
t.Fatalf("time generated too early: %v < %v", vt, start)
}
}
}
}
type testResponseWriter struct {
flushed bool
status int
written int64
header http.Header
}
func (trw *testResponseWriter) Header() http.Header {
if trw.header == nil {
trw.header = make(http.Header)
}
return trw.header
}
func (trw *testResponseWriter) Write(p []byte) (n int, err error) {
if trw.status == 0 {
trw.status = http.StatusOK
}
n = len(p)
trw.written += int64(n)
return
}
func (trw *testResponseWriter) WriteHeader(status int) {
trw.status = status
}
func (trw *testResponseWriter) Flush() {
trw.flushed = true
}
func TestWithResponseWriter(t *testing.T) {
trw := testResponseWriter{}
ctx, rw := WithResponseWriter(Background(), &trw)
if ctx.Value("http.response") != rw {
t.Fatalf("response not available in context: %v != %v", ctx.Value("http.response"), rw)
}
grw, err := GetResponseWriter(ctx)
if err != nil {
t.Fatalf("error getting response writer: %v", err)
}
if grw != rw {
t.Fatalf("unexpected response writer returned: %#v != %#v", grw, rw)
}
if ctx.Value("http.response.status") != 0 {
t.Fatalf("response status should always be a number and should be zero here: %v != 0", ctx.Value("http.response.status"))
}
if n, err := rw.Write(make([]byte, 1024)); err != nil {
t.Fatalf("unexpected error writing: %v", err)
} else if n != 1024 {
t.Fatalf("unexpected number of bytes written: %v != %v", n, 1024)
}
if ctx.Value("http.response.status") != http.StatusOK {
t.Fatalf("unexpected response status in context: %v != %v", ctx.Value("http.response.status"), http.StatusOK)
}
if ctx.Value("http.response.written") != int64(1024) {
t.Fatalf("unexpected number reported bytes written: %v != %v", ctx.Value("http.response.written"), 1024)
}
// Make sure flush propagates
rw.(http.Flusher).Flush()
if !trw.flushed {
t.Fatalf("response writer not flushed")
}
// Write another status and make sure context is correct. This normally
// wouldn't work except for in this contrived testcase.
rw.WriteHeader(http.StatusBadRequest)
if ctx.Value("http.response.status") != http.StatusBadRequest {
t.Fatalf("unexpected response status in context: %v != %v", ctx.Value("http.response.status"), http.StatusBadRequest)
}
}
func TestWithVars(t *testing.T) {
var req http.Request
vars := map[string]string{
"foo": "asdf",
"bar": "qwer",
}
getVarsFromRequest = func(r *http.Request) map[string]string {
if r != &req {
t.Fatalf("unexpected request: %v != %v", r, req)
}
return vars
}
ctx := WithVars(Background(), &req)
for _, testcase := range []struct {
key string
expected interface{}
}{
{
key: "vars",
expected: vars,
},
{
key: "vars.foo",
expected: "asdf",
},
{
key: "vars.bar",
expected: "qwer",
},
} {
v := ctx.Value(testcase.key)
if !reflect.DeepEqual(v, testcase.expected) {
t.Fatalf("%q: %v != %v", testcase.key, v, testcase.expected)
}
}
}
// SingleHostReverseProxy will insert an X-Forwarded-For header, and can be used to test
// RemoteAddr(). A fake RemoteAddr cannot be set on the HTTP request - it is overwritten
// at the transport layer to 127.0.0.1:<port> . However, as the X-Forwarded-For header
// just contains the IP address, it is different enough for testing.
func TestRemoteAddr(t *testing.T) {
var expectedRemote string
backend := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
defer r.Body.Close()
if r.RemoteAddr == expectedRemote {
t.Errorf("Unexpected matching remote addresses")
}
actualRemote := RemoteAddr(r)
if expectedRemote != actualRemote {
t.Errorf("Mismatching remote hosts: %v != %v", expectedRemote, actualRemote)
}
w.WriteHeader(200)
}))
defer backend.Close()
backendURL, err := url.Parse(backend.URL)
if err != nil {
t.Fatal(err)
}
proxy := httputil.NewSingleHostReverseProxy(backendURL)
frontend := httptest.NewServer(proxy)
defer frontend.Close()
// X-Forwarded-For set by proxy
expectedRemote = "127.0.0.1"
proxyReq, err := http.NewRequest("GET", frontend.URL, nil)
if err != nil {
t.Fatal(err)
}
_, err = http.DefaultClient.Do(proxyReq)
if err != nil {
t.Fatal(err)
}
// RemoteAddr in X-Real-Ip
getReq, err := http.NewRequest("GET", backend.URL, nil)
if err != nil {
t.Fatal(err)
}
expectedRemote = "1.2.3.4"
getReq.Header["X-Real-ip"] = []string{expectedRemote}
_, err = http.DefaultClient.Do(getReq)
if err != nil {
t.Fatal(err)
}
// Valid X-Real-Ip and invalid X-Forwarded-For
getReq.Header["X-forwarded-for"] = []string{"1.2.3"}
_, err = http.DefaultClient.Do(getReq)
if err != nil {
t.Fatal(err)
}
}
07070100000004000081a40000000000000000000000016328304800000fb6000000000000000000000000000000000000001200000000context/logger.gopackage context
import (
"context"
"fmt"
"runtime"
"sync"
"github.com/sirupsen/logrus"
)
var (
defaultLogger *logrus.Entry = logrus.StandardLogger().WithField("go.version", runtime.Version())
defaultLoggerMu sync.RWMutex
)
// Logger provides a leveled-logging interface.
type Logger interface {
// standard logger methods
Print(args ...interface{})
Printf(format string, args ...interface{})
Println(args ...interface{})
Fatal(args ...interface{})
Fatalf(format string, args ...interface{})
Fatalln(args ...interface{})
Panic(args ...interface{})
Panicf(format string, args ...interface{})
Panicln(args ...interface{})
// Leveled methods, from logrus
Debug(args ...interface{})
Debugf(format string, args ...interface{})
Debugln(args ...interface{})
Error(args ...interface{})
Errorf(format string, args ...interface{})
Errorln(args ...interface{})
Info(args ...interface{})
Infof(format string, args ...interface{})
Infoln(args ...interface{})
Warn(args ...interface{})
Warnf(format string, args ...interface{})
Warnln(args ...interface{})
WithError(err error) *logrus.Entry
}
type loggerKey struct{}
// WithLogger creates a new context with provided logger.
func WithLogger(ctx context.Context, logger Logger) context.Context {
return context.WithValue(ctx, loggerKey{}, logger)
}
// GetLoggerWithField returns a logger instance with the specified field key
// and value without affecting the context. Extra specified keys will be
// resolved from the context.
func GetLoggerWithField(ctx context.Context, key, value interface{}, keys ...interface{}) Logger {
return getLogrusLogger(ctx, keys...).WithField(fmt.Sprint(key), value)
}
// GetLoggerWithFields returns a logger instance with the specified fields
// without affecting the context. Extra specified keys will be resolved from
// the context.
func GetLoggerWithFields(ctx context.Context, fields map[interface{}]interface{}, keys ...interface{}) Logger {
// must convert from interface{} -> interface{} to string -> interface{} for logrus.
lfields := make(logrus.Fields, len(fields))
for key, value := range fields {
lfields[fmt.Sprint(key)] = value
}
return getLogrusLogger(ctx, keys...).WithFields(lfields)
}
// GetLogger returns the logger from the current context, if present. If one
// or more keys are provided, they will be resolved on the context and
// included in the logger. While context.Value takes an interface, any key
// argument passed to GetLogger will be passed to fmt.Sprint when expanded as
// a logging key field. If context keys are integer constants, for example,
// its recommended that a String method is implemented.
func GetLogger(ctx context.Context, keys ...interface{}) Logger {
return getLogrusLogger(ctx, keys...)
}
// SetDefaultLogger sets the default logger upon which to base new loggers.
func SetDefaultLogger(logger Logger) {
entry, ok := logger.(*logrus.Entry)
if !ok {
return
}
defaultLoggerMu.Lock()
defaultLogger = entry
defaultLoggerMu.Unlock()
}
// GetLogrusLogger returns the logrus logger for the context. If one more keys
// are provided, they will be resolved on the context and included in the
// logger. Only use this function if specific logrus functionality is
// required.
func getLogrusLogger(ctx context.Context, keys ...interface{}) *logrus.Entry {
var logger *logrus.Entry
// Get a logger, if it is present.
loggerInterface := ctx.Value(loggerKey{})
if loggerInterface != nil {
if lgr, ok := loggerInterface.(*logrus.Entry); ok {
logger = lgr
}
}
if logger == nil {
fields := logrus.Fields{}
// Fill in the instance id, if we have it.
instanceID := ctx.Value("instance.id")
if instanceID != nil {
fields["instance.id"] = instanceID
}
defaultLoggerMu.RLock()
logger = defaultLogger.WithFields(fields)
defaultLoggerMu.RUnlock()
}
fields := logrus.Fields{}
for _, key := range keys {
v := ctx.Value(key)
if v != nil {
fields[fmt.Sprint(key)] = v
}
}
return logger.WithFields(fields)
}
07070100000005000081a40000000000000000000000016328304800000b5b000000000000000000000000000000000000001100000000context/trace.gopackage context
import (
"context"
"runtime"
"time"
"github.com/distribution/distribution/v3/uuid"
)
// WithTrace allocates a traced timing span in a new context. This allows a
// caller to track the time between calling WithTrace and the returned done
// function. When the done function is called, a log message is emitted with a
// "trace.duration" field, corresponding to the elapsed time and a
// "trace.func" field, corresponding to the function that called WithTrace.
//
// The logging keys "trace.id" and "trace.parent.id" are provided to implement
// dapper-like tracing. This function should be complemented with a WithSpan
// method that could be used for tracing distributed RPC calls.
//
// The main benefit of this function is to post-process log messages or
// intercept them in a hook to provide timing data. Trace ids and parent ids
// can also be linked to provide call tracing, if so required.
//
// Here is an example of the usage:
//
// func timedOperation(ctx Context) {
// ctx, done := WithTrace(ctx)
// defer done("this will be the log message")
// // ... function body ...
// }
//
// If the function ran for roughly 1s, such a usage would emit a log message
// as follows:
//
// INFO[0001] this will be the log message trace.duration=1.004575763s trace.func=github.com/distribution/distribution/context.traceOperation trace.id=<id> ...
//
// Notice that the function name is automatically resolved, along with the
// package and a trace id is emitted that can be linked with parent ids.
func WithTrace(ctx context.Context) (context.Context, func(format string, a ...interface{})) {
if ctx == nil {
ctx = Background()
}
pc, file, line, _ := runtime.Caller(1)
f := runtime.FuncForPC(pc)
ctx = &traced{
Context: ctx,
id: uuid.Generate().String(),
start: time.Now(),
parent: GetStringValue(ctx, "trace.id"),
fnname: f.Name(),
file: file,
line: line,
}
return ctx, func(format string, a ...interface{}) {
GetLogger(ctx,
"trace.duration",
"trace.id",
"trace.parent.id",
"trace.func",
"trace.file",
"trace.line").
Debugf(format, a...)
}
}
// traced represents a context that is traced for function call timing. It
// also provides fast lookup for the various attributes that are available on
// the trace.
type traced struct {
context.Context
id string
parent string
start time.Time
fnname string
file string
line int
}
func (ts *traced) Value(key interface{}) interface{} {
switch key {
case "trace.start":
return ts.start
case "trace.duration":
return time.Since(ts.start)
case "trace.id":
return ts.id
case "trace.parent.id":
if ts.parent == "" {
return nil // must return nil to signal no parent.
}
return ts.parent
case "trace.func":
return ts.fnname
case "trace.file":
return ts.file
case "trace.line":
return ts.line
}
return ts.Context.Value(key)
}
07070100000006000081a40000000000000000000000016328304800000760000000000000000000000000000000000000001600000000context/trace_test.gopackage context
import (
"context"
"runtime"
"testing"
"time"
)
// TestWithTrace ensures that tracing has the expected values in the context.
func TestWithTrace(t *testing.T) {
pc, file, _, _ := runtime.Caller(0) // get current caller.
f := runtime.FuncForPC(pc)
base := []valueTestCase{
{
key: "trace.id",
notnilorempty: true,
},
{
key: "trace.file",
expected: file,
notnilorempty: true,
},
{
key: "trace.line",
notnilorempty: true,
},
{
key: "trace.start",
notnilorempty: true,
},
}
ctx, done := WithTrace(Background())
defer done("this will be emitted at end of test")
checkContextForValues(ctx, t, append(base, valueTestCase{
key: "trace.func",
expected: f.Name(),
}))
traced := func() {
parentID := ctx.Value("trace.id") // ensure the parent trace id is correct.
pc, _, _, _ := runtime.Caller(0) // get current caller.
f := runtime.FuncForPC(pc)
ctx, done := WithTrace(ctx)
defer done("this should be subordinate to the other trace")
time.Sleep(time.Second)
checkContextForValues(ctx, t, append(base, valueTestCase{
key: "trace.func",
expected: f.Name(),
}, valueTestCase{
key: "trace.parent.id",
expected: parentID,
}))
}
traced()
time.Sleep(time.Second)
}
type valueTestCase struct {
key string
expected interface{}
notnilorempty bool // just check not empty/not nil
}
func checkContextForValues(ctx context.Context, t *testing.T, values []valueTestCase) {
for _, testcase := range values {
v := ctx.Value(testcase.key)
if testcase.notnilorempty {
if v == nil || v == "" {
t.Fatalf("value was nil or empty for %q: %#v", testcase.key, v)
}
continue
}
if v != testcase.expected {
t.Fatalf("unexpected value for key %q: %v != %v", testcase.key, v, testcase.expected)
}
}
}
07070100000007000081a400000000000000000000000163283048000002cc000000000000000000000000000000000000001000000000context/util.gopackage context
import (
"context"
"time"
)
// Since looks up key, which should be a time.Time, and returns the duration
// since that time. If the key is not found, the value returned will be zero.
// This is helpful when inferring metrics related to context execution times.
func Since(ctx context.Context, key interface{}) time.Duration {
if startedAt, ok := ctx.Value(key).(time.Time); ok {
return time.Since(startedAt)
}
return 0
}
// GetStringValue returns a string value from the context. The empty string
// will be returned if not found.
func GetStringValue(ctx context.Context, key interface{}) (value string) {
if valuev, ok := ctx.Value(key).(string); ok {
value = valuev
}
return value
}
07070100000008000081a400000000000000000000000163283048000002d7000000000000000000000000000000000000001300000000context/version.gopackage context
import "context"
type versionKey struct{}
func (versionKey) String() string { return "version" }
// WithVersion stores the application version in the context. The new context
// gets a logger to ensure log messages are marked with the application
// version.
func WithVersion(ctx context.Context, version string) context.Context {
ctx = context.WithValue(ctx, versionKey{}, version)
// push a new logger onto the stack
return WithLogger(ctx, GetLogger(ctx, versionKey{}))
}
// GetVersion returns the application version from the context. An empty
// string may returned if the version was not set on the context.
func GetVersion(ctx context.Context) string {
return GetStringValue(ctx, versionKey{})
}
07070100000009000081a4000000000000000000000001632830480000016e000000000000000000000000000000000000001800000000context/version_test.gopackage context
import "testing"
func TestVersionContext(t *testing.T) {
ctx := Background()
if GetVersion(ctx) != "" {
t.Fatalf("context should not yet have a version")
}
expected := "2.1-whatever"
ctx = WithVersion(ctx, expected)
version := GetVersion(ctx)
if version != expected {
t.Fatalf("version was not set: %q != %q", version, expected)
}
}
0707010000000a000041ed0000000000000000000000016328304800000000000000000000000000000000000000000000000800000000context07070100000000000000000000000000000000000000010000000000000000000000000000000000000000000000000000000b00000000TRAILER!!!
