Session should be fully stored before response is returned

[purplefox]

In SessionHandlerImpl, the session is stored in the headers end handler, but the store is async, so may not happen until after the next request for that session hits the server.

This could mean the session is not found.

We need to somehow store the session and not send the response back to the client until the session is fully stored.

[maumock]

Hammer option

    try {
        //Future used to block this thread until all work is complete.
        final CompletableFuture<Void> future = new CompletableFuture<>();
        //Run method async
        CompletableFuture.runAsync(()->{
            this.sessionStore.put(context.session(), res -> {
                if (res.succeeded()) {
                  future.complete(null);
                } else {
                  // Failed to store session
                  context.fail(res.cause());
                  future.completeExceptionally(res.cause());
                }
              });
        }).join();

        //Wait until future is notified to proceed.
        future.get();
        System.out.println("future done");
    } catch (Exception e) {
        context.fail(e);
    }

[leolux]

Maybe it could be implemented with the BlockingHandlerDecorator from this commit 4ffa350

[purplefox]

Now fixed by making headers end handlers take a future (required change in core too)

[apatrida]

@purplefox is there a chance that storing objects in sessions (clustered w/hazelcast) could have this same issue? we are currently debugging a case where something stored into a session (future URL to redirect towards), is not in the session on the next page which comes quickly. Debugging it is always there (we slow things down when debugging), but randomly fails to be there at other times. Or is it our imagination?