github.com/timstclair/heapster@v0.20.0-alpha1/Godeps/_workspace/src/google.golang.org/appengine/internal/api_common.go (about)

     1  // Copyright 2015 Google Inc. All rights reserved.
     2  // Use of this source code is governed by the Apache 2.0
     3  // license that can be found in the LICENSE file.
     4  
     5  package internal
     6  
     7  import (
     8  	"github.com/golang/protobuf/proto"
     9  	netcontext "golang.org/x/net/context"
    10  )
    11  
    12  type CallOverrideFunc func(ctx netcontext.Context, service, method string, in, out proto.Message) error
    13  
    14  var callOverrideKey = "holds []CallOverrideFunc"
    15  
    16  func WithCallOverride(ctx netcontext.Context, f CallOverrideFunc) netcontext.Context {
    17  	// We avoid appending to any existing call override
    18  	// so we don't risk overwriting a popped stack below.
    19  	var cofs []CallOverrideFunc
    20  	if uf, ok := ctx.Value(&callOverrideKey).([]CallOverrideFunc); ok {
    21  		cofs = append(cofs, uf...)
    22  	}
    23  	cofs = append(cofs, f)
    24  	return netcontext.WithValue(ctx, &callOverrideKey, cofs)
    25  }
    26  
    27  func callOverrideFromContext(ctx netcontext.Context) (CallOverrideFunc, netcontext.Context, bool) {
    28  	cofs, _ := ctx.Value(&callOverrideKey).([]CallOverrideFunc)
    29  	if len(cofs) == 0 {
    30  		return nil, nil, false
    31  	}
    32  	// We found a list of overrides; grab the last, and reconstitute a
    33  	// context that will hide it.
    34  	f := cofs[len(cofs)-1]
    35  	ctx = netcontext.WithValue(ctx, &callOverrideKey, cofs[:len(cofs)-1])
    36  	return f, ctx, true
    37  }
    38  
    39  type logOverrideFunc func(level int64, format string, args ...interface{})
    40  
    41  var logOverrideKey = "holds a logOverrideFunc"
    42  
    43  func WithLogOverride(ctx netcontext.Context, f logOverrideFunc) netcontext.Context {
    44  	return netcontext.WithValue(ctx, &logOverrideKey, f)
    45  }
    46  
    47  var appIDOverrideKey = "holds a string, being the full app ID"
    48  
    49  func WithAppIDOverride(ctx netcontext.Context, appID string) netcontext.Context {
    50  	return netcontext.WithValue(ctx, &appIDOverrideKey, appID)
    51  }
    52  
    53  var namespaceKey = "holds the namespace string"
    54  
    55  func withNamespace(ctx netcontext.Context, ns string) netcontext.Context {
    56  	return netcontext.WithValue(ctx, &namespaceKey, ns)
    57  }
    58  
    59  func NamespaceFromContext(ctx netcontext.Context) string {
    60  	// If there's no namespace, return the empty string.
    61  	ns, _ := ctx.Value(&namespaceKey).(string)
    62  	return ns
    63  }
    64  
    65  // FullyQualifiedAppID returns the fully-qualified application ID.
    66  // This may contain a partition prefix (e.g. "s~" for High Replication apps),
    67  // or a domain prefix (e.g. "example.com:").
    68  func FullyQualifiedAppID(ctx netcontext.Context) string {
    69  	if id, ok := ctx.Value(&appIDOverrideKey).(string); ok {
    70  		return id
    71  	}
    72  	return fullyQualifiedAppID(ctx)
    73  }
    74  
    75  func Logf(ctx netcontext.Context, level int64, format string, args ...interface{}) {
    76  	if f, ok := ctx.Value(&logOverrideKey).(logOverrideFunc); ok {
    77  		f(level, format, args...)
    78  		return
    79  	}
    80  	logf(fromContext(ctx), level, format, args...)
    81  }
    82  
    83  // NamespacedContext wraps a Context to support namespaces.
    84  func NamespacedContext(ctx netcontext.Context, namespace string) netcontext.Context {
    85  	n := &namespacedContext{
    86  		namespace: namespace,
    87  	}
    88  	return withNamespace(WithCallOverride(ctx, n.call), namespace)
    89  }
    90  
    91  type namespacedContext struct {
    92  	namespace string
    93  }
    94  
    95  func (n *namespacedContext) call(ctx netcontext.Context, service, method string, in, out proto.Message) error {
    96  	// Apply any namespace mods.
    97  	if mod, ok := NamespaceMods[service]; ok {
    98  		mod(in, n.namespace)
    99  	}
   100  	return Call(ctx, service, method, in, out)
   101  }