To ensure consistent fieldpath matching for events, we generate the
fieldpath matching using protobuf definitions. This is done through a
plugin called "fieldpath" that defines a `Field` method for each type
with the plugin enabled. Generated code handles top-level envelope
fields, as well as deferred serialization for matching any types.
In practice, this means that we can cheaply match events on `topic` and
`namespace`. If we want to match on attributes within the event, we can
use the `event` prefix to address these fields. For example, the
following will match all envelopes that have a field named
`container_id` that has the value `testing`:
```
ctr events "event.container_id==testing"
```
The above will decode the underlying event and check that particular
field. Accordingly, if only `topic` or `namespace` is used, the event
will not be decoded and only match on the envelope.
Signed-off-by: Stephen J Day <stephen.day@docker.com>
This change further plumbs the components required for implementing
event filters. Specifically, we now have the ability to filter on the
`topic` and `namespace`.
In the course of implementing this functionality, it was found that
there were mismatches in the events API that created extra serialization
round trips. A modification to `typeurl.MarshalAny` and a clear
separation between publishing and forwarding allow us to avoid these
serialization issues.
Unfortunately, this has required a few tweaks to the GRPC API, so this
is a breaking change. `Publish` and `Forward` have been clearly separated in
the GRPC API. `Publish` honors the contextual namespace and performs
timestamping while `Forward` simply validates and forwards. The behavior
of `Subscribe` is to propagate events for all namespaces unless
specifically filtered (and hence the relation to this particular change.
The following is an example of using filters to monitor the task events
generated while running the [bucketbench tool](https://github.com/estesp/bucketbench):
```
$ ctr events 'topic~=/tasks/.+,namespace==bb'
...
2017-07-28 22:19:51.78944874 +0000 UTC bb /tasks/start {"container_id":"bb-ctr-6-8","pid":25889}
2017-07-28 22:19:51.791893688 +0000 UTC bb /tasks/start {"container_id":"bb-ctr-4-8","pid":25882}
2017-07-28 22:19:51.792608389 +0000 UTC bb /tasks/start {"container_id":"bb-ctr-2-9","pid":25860}
2017-07-28 22:19:51.793035217 +0000 UTC bb /tasks/start {"container_id":"bb-ctr-5-6","pid":25869}
2017-07-28 22:19:51.802659622 +0000 UTC bb /tasks/start {"container_id":"bb-ctr-0-7","pid":25877}
2017-07-28 22:19:51.805192898 +0000 UTC bb /tasks/start {"container_id":"bb-ctr-3-6","pid":25856}
2017-07-28 22:19:51.832374931 +0000 UTC bb /tasks/exit {"container_id":"bb-ctr-8-6","id":"bb-ctr-8-6","pid":25864,"exited_at":"2017-07-28T22:19:51.832013043Z"}
2017-07-28 22:19:51.84001249 +0000 UTC bb /tasks/exit {"container_id":"bb-ctr-2-9","id":"bb-ctr-2-9","pid":25860,"exited_at":"2017-07-28T22:19:51.839717714Z"}
2017-07-28 22:19:51.840272635 +0000 UTC bb /tasks/exit {"container_id":"bb-ctr-7-6","id":"bb-ctr-7-6","pid":25855,"exited_at":"2017-07-28T22:19:51.839796335Z"}
...
```
In addition to the events changes, we now display the namespace origin
of the event in the cli tool.
This will be followed by a PR to add individual field filtering for the
events API for each event type.
Signed-off-by: Stephen J Day <stephen.day@docker.com>
In the course of setting out to add filters and address some cleanup, it
was found that we had a few problems in the events subsystem that needed
addressing before moving forward.
The biggest change was to move to the more standard terminology of
publish and subscribe. We make this terminology change across the Go
interface and the GRPC API, making the behavior more familier. The
previous system was very context-oriented, which is no longer required.
With this, we've removed a large amount of dead and unneeded code. Event
transactions, context storage and the concept of `Poster` is gone. This
has been replaced in most places with a `Publisher`, which matches the
actual usage throughout the codebase, removing the need for helpers.
There are still some questions around the way events are handled in the
shim. Right now, we've preserved some of the existing bugs which may
require more extensive changes to resolve correctly.
Signed-off-by: Stephen J Day <stephen.day@docker.com>
