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Implement notification endpoint webhook dispatch

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This changeset implements webhook notification endpoints for dispatching
registry events. Repository instances can be decorated by a listener that
converts calls into context-aware events, using a bridge. Events generated in
the bridge are written to a sink. Implementations of sink include a broadcast
and endpoint sink which can be used to configure event dispatch. Endpoints
represent a webhook notification target, with queueing and retries built in.
They can be added to a Broadcaster, which is a simple sink that writes a block
of events to several sinks, to provide a complete dispatch mechanism.

The main caveat to the current approach is that all unsent notifications are
inmemory. Best effort is made to ensure that notifications are not dropped, to
the point where queues may back up on faulty endpoints. If the endpoint is
fixed, the events will be retried and all messages will go through.

Internally, this functionality is all made up of Sink objects. The queuing
functionality is implemented with an eventQueue sink and retries are
implemented with retryingSink. Replacing the inmemory queuing with something
persistent should be as simple as replacing broadcaster with a remote queue and
that sets up the sinks to be local workers listening to that remote queue.

Metrics are kept for each endpoint and exported via expvar. This may not be a
permanent appraoch but should provide enough information for troubleshooting
notification problems.

Signed-off-by: Stephen J Day <stephen.day@docker.com>
This commit is contained in:
Stephen J Day 2015-01-27 23:27:46 -08:00
parent 14fb80d6c3
commit 9f0c8d6616
11 changed files with 1569 additions and 26 deletions
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29
storage/notifications/event.go
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@ -36,7 +36,7 @@ type Envelope struct {
// Event provides the fields required to describe a registry event.
type Event struct {
// ID provides a unique identifier for the event.
ID string `json:"uuid,omitempty"`
ID string `json:"id,omitempty"`
// Timestamp is the time at which the event occurred.
Timestamp time.Time `json:"timestamp,omitempty"`
@ -74,6 +74,8 @@ type Event struct {
// ActorRecord specifies the agent that initiated the event. For most
// situations, this could be from the authorizaton context of the request.
// Data in this record can refer to both the initiating client and the
// generating request.
type ActorRecord struct {
// Name corresponds to the subject or username associated with the
// request context that generated the event.
@ -82,6 +84,22 @@ type ActorRecord struct {
// Addr contains the ip or hostname and possibly port of the client
// connection that initiated the event.
Addr string `json:"addr,omitempty"`
// Host is the externally accessible host name of the registry instance,
// as specified by the http host header on incoming requests.
Host string `json:"host,omitempty"`
// RequestID uniquely identifies the registry request that generated the
// event.
RequestID string `json:"requestID,omitempty"`
// TODO(stevvooe): Look into setting a session cookie to get this
// without docker daemon.
// SessionID
// TODO(stevvooe): Push the "Docker-Command" header to replace cookie and
// get the actual command.
// Command
}
// SourceRecord identifies the registry node that generated the event. Put
@ -93,12 +111,9 @@ type SourceRecord struct {
// os.Hostname() along with the running port.
Addr string `json:"addr,omitempty"`
// Host is the dns name of the registry cluster, as configured.
Host string `json:"host,omitempty"`
// RequestID uniquely identifies the registry request that generated the
// event.
RequestID string `json:"request_id,omitempty"`
// InstanceID identifies a running instance of an application. Changes
// after each restart.
InstanceID string `json:"instanceID,omitempty"`
}
var (