4d91e791c0
This moves the instance id out of the app so that it is associated with an instantiation of the runtime. The instance id is stored on the background context. This allows allow contexts using the main background context to include an instance id for log messages. It also simplifies the application slightly. Signed-off-by: Stephen J Day <stephen.day@docker.com>
76 lines
1.9 KiB
Go
76 lines
1.9 KiB
Go
package context
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import (
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"code.google.com/p/go-uuid/uuid"
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"golang.org/x/net/context"
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)
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// Context is a copy of Context from the golang.org/x/net/context package.
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type Context interface {
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context.Context
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}
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// instanceContext is a context that provides only an instance id. It is
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// provided as the main background context.
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type instanceContext struct {
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Context
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id string // id of context, logged as "instance.id"
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}
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func (ic *instanceContext) Value(key interface{}) interface{} {
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if key == "instance.id" {
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return ic.id
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}
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return ic.Context.Value(key)
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}
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var background = &instanceContext{
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Context: context.Background(),
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id: uuid.New(),
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}
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// Background returns a non-nil, empty Context. The background context
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// provides a single key, "instance.id" that is globally unique to the
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// process.
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func Background() Context {
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return background
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}
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// WithValue returns a copy of parent in which the value associated with key is
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// val. Use context Values only for request-scoped data that transits processes
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// and APIs, not for passing optional parameters to functions.
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func WithValue(parent Context, key, val interface{}) Context {
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return context.WithValue(parent, key, val)
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}
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// stringMapContext is a simple context implementation that checks a map for a
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// key, falling back to a parent if not present.
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type stringMapContext struct {
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context.Context
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m map[string]interface{}
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}
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// WithValues returns a context that proxies lookups through a map. Only
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// supports string keys.
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func WithValues(ctx context.Context, m map[string]interface{}) context.Context {
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mo := make(map[string]interface{}, len(m)) // make our own copy.
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for k, v := range m {
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mo[k] = v
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}
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return stringMapContext{
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Context: ctx,
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m: mo,
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}
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}
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func (smc stringMapContext) Value(key interface{}) interface{} {
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if ks, ok := key.(string); ok {
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if v, ok := smc.m[ks]; ok {
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return v
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}
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}
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return smc.Context.Value(key)
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}
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