1. EventSources now pass themselves thorugh to the run function as a
second argument. This enables the use of arrow functions along with the
EventSources API
`(configuration, source) => source.close()`. Order of arguments could
potentially be switched at a later date.
2. BlockingEventSources now let you pass an 'event' through at
instantation time. If you do this, the event will immediately be dispatched
once the EventSource is opened. The usecase for this is for 'unfreezing' cached
BlockingEvents. This makes it easier to provide a cache for
BlockingEventSources by caching its data rather than the entire
BlockingEventSource itself.
```
new BlockingEventSource(
(config, source) => { /* something */ },
{
cursor: 1024, // this would also come from a cache
currentEvent: getFromSomeSortOfCache(eventSourceId) //this is the new bit
}
);
// more realistically
new BlockingEventSource(
(config, source) => { return data.findSomething(slug, config) },
getFromSomeSortOfCache(eventSourceId)
);
```
...also:
Temporarily overwrites native setTimeout and setInterval for e2e/acceptance
testing similar to how XHR is overwritten for e2e/acceptance testing.
This makes the blocking query acceptance tests run faster until we add a
better burstable rate limiter for blocking queries.
More recommendations for blocking queries clients was added here:
https://github.com/hashicorp/consul/pull/5358
This commit mainly adds cursor/index validation/correction based on
these recommendations (plus tests)
The recommendations also suggest that clients should include rate
limiting. Because of this, we've moved the throttling out of Consul UI
specific code and into Blocking Query specific code. Currently the 'rate
limiting' in this commit only adds a sleep to every iteration of the
loop, which is not the recommended approach, but the code here organizes
the throttling functionality into something we can work with later to
provide something more apt.
- Maintain http headers as JSON-API meta for all API requests (#4946)
- Add EventSource ready for implementing blocking queries
- EventSource project implementation to enable blocking queries for service and node listings (#5267)
- Add setting to enable/disable blocking queries (#5352)
John Cowen