README
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teivah/onecontext
teivah/onecontext is a set of context utilities.
One Context
Have you ever faced the situation where you have to merge multiple existing contexts? If not, then you might, eventually.
For example, we can face the situation where we are building an application using a library that gives us a global context (for example, urfave/cli).
This context expires once the application is stopped.
Meanwhile, we are exposing a gRPC service like this:
func (f *Foo) Get(ctx context.Context, bar *Bar) (*Baz, error) {
}
Here, we receive another context provided by gRPC.
Then, in the Get implementation, we want to query a database and provide a context for that.
Ideally, we would like to provide a merged context that would expire either:
- When the application is stopped
- Or when the received gRPC context expires
It's is precisely the purpose of this library.
In our case, we can now merge the two contexts in a single one like this:
ctx, cancel := onecontext.Merge(ctx1, ctx2)
It returns a merged context that we can now propagate.
Detach
onecontext.Detach returns a context detached from the original cancellation signal. It can be helpful, for example, if we implement an HTTP handler and that we have to pass a context to another goroutine that may expire after we send back a response.
Reset Values
onecontext.ResetValues reset the values of an existing context.
Documentation
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Overview ¶
Package onecontext provides a mechanism to merge multiple existing contexts.
Index ¶
Constants ¶
This section is empty.
Variables ¶
var ErrCanceled = errors.New("context canceled")
ErrCanceled is the returned when the CancelFunc returned by Merge is called.
Functions ¶
Types ¶
type DetachedContext ¶
type DetachedContext struct {
// contains filtered or unexported fields
}
DetachedContext holds the logic to detach a cancellation signal from a context.
func Detach ¶
func Detach(ctx context.Context) (*DetachedContext, func())
Detach detaches the cancellation signal from a context.
func (*DetachedContext) Deadline ¶
func (c *DetachedContext) Deadline() (time.Time, bool)
Deadline returns a nil deadline.
func (*DetachedContext) Done ¶
func (c *DetachedContext) Done() <-chan struct{}
Done returns a cancellation signal that expires only when the context is canceled from the cancel function returned in Detach.
func (*DetachedContext) Err ¶
func (c *DetachedContext) Err() error
Err returns an error if the context is canceled from the cancel function returned in Detach.
func (*DetachedContext) Value ¶
func (c *DetachedContext) Value(key interface{}) interface{}
Value returns the value associated with the key from the original context.
type OneContext ¶
type OneContext struct {
// contains filtered or unexported fields
}
OneContext is the struct holding the context grouping logic.
func (*OneContext) Deadline ¶
func (o *OneContext) Deadline() (time.Time, bool)
Deadline returns the minimum deadline among all the contexts.
func (*OneContext) Done ¶
func (o *OneContext) Done() <-chan struct{}
Done returns a channel for cancellation.
func (*OneContext) Err ¶
func (o *OneContext) Err() error
Err returns the first error raised by the contexts, otherwise a nil error.
func (*OneContext) Value ¶
func (o *OneContext) Value(key interface{}) interface{}
Value returns the value associated with the key from one of the contexts.
type ResetValuesContext ¶
type ResetValuesContext struct {
// contains filtered or unexported fields
}
ResetValuesContext holds the logic reset the values of a context.
func ResetValues ¶
func ResetValues(ctx context.Context) *ResetValuesContext
ResetValues reset the values of a context.
func (*ResetValuesContext) Deadline ¶
func (c *ResetValuesContext) Deadline() (time.Time, bool)
Deadline returns the original context deadline.
func (*ResetValuesContext) Done ¶
func (c *ResetValuesContext) Done() <-chan struct{}
Done returns the original done channel.
func (*ResetValuesContext) Err ¶
func (c *ResetValuesContext) Err() error
Err returns the original context error.
func (*ResetValuesContext) Value ¶
func (c *ResetValuesContext) Value(_ interface{}) interface{}
Value returns nil regardless of the key.
Source Files