package context import ( "code.google.com/p/go-uuid/uuid" "golang.org/x/net/context" ) // Context is a copy of Context from the golang.org/x/net/context package. type Context interface { context.Context } // instanceContext is a context that provides only an instance id. It is // provided as the main background context. type instanceContext struct { Context id string // id of context, logged as "instance.id" } func (ic *instanceContext) Value(key interface{}) interface{} { if key == "instance.id" { return ic.id } return ic.Context.Value(key) } var background = &instanceContext{ Context: context.Background(), id: uuid.New(), } // 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 { return background } // WithValue returns a copy of parent in which the value associated with key is // val. Use context Values only for request-scoped data that transits processes // and APIs, not for passing optional parameters to functions. func WithValue(parent Context, key, val interface{}) Context { return context.WithValue(parent, key, val) } // 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) }