Polling

[jbaxleyiii]

Added ability to poll endpoint on a per query basis

Per #145

Docs:

One way to create a reactive-esque query is to use polling. Apollo accepts a pollInterval on the WatchQueryOptions which is the interval that a forced refetch will be called.

const handle = client.watchQuery({
  query: `
    query getCategory($categoryId: Int!) {
      category(id: $categoryId) {
        name
        color
      }
    }
  `,
  variables: {
    categoryId: 5,
  },
  forceFetch: false,
  returnPartialData: true,
  pollInterval: 1000, // ms to poll
});

Some cases may call for the ability to dynamically stop or start a polling interval on an existing query. The subscription handle returned by handle.subscribe() includes stopPolling and startPolling methods. These can be used like so:

const handle = client.watchQuery({
  query: `
    query getCategory($categoryId: Int!) {
      category(id: $categoryId) {
        name
        color
      }
    }
  `,
  variables: {
    categoryId: 5,
  },
  forceFetch: false,
  returnPartialData: true,
});

const subscription = handle.subscribe();

subscription.startPolling(50) // 50 ms poll starting
subscription.stopPolling() // stop polling

Docs PR: https://github.com/apollostack/docs/pull/53

[jbaxleyiii]

@stubailo I think this should be good to. I'll open a PR on the docs as well

[stubailo]

@martijnwalraven @Urigo one thing I'm not sure about - should these helper functions be on the subscription handle, or the observable itself? It's a bit odd that refetch or startPolling will actually affect all subscribers, but the function is on the handle.. although it would be inconvenient to have to pass around two objects everywhere.

[stubailo]

Filed a followup issue, this looks amazing though!

[stubailo]

#164