The problem has been exaggerated for the sake of justifying http2/3 but in practical terms it barely affects the average user experience. 80% optimal was good enough. On the other hand it reduces cost by a few percentage points for the vanishingly few web hosts large enough such that that would have a meaningful financial impact.
The only people saving here are the people running servers that serve world-scale numbers of requests. The average user notices nearly no difference.
I think you need to reread my initial post in this thread. The importance of minimizing rtt blocking is acknowledged in my questioning of chrome’s decision to not implement http push.
> I'm not sure I fully follow here, but I would like to be able to
What I'm calling out is that you may have fallen into the trap (as I did years back) that you need to be an asshole to drive towards solving hard problems. You don't, and it actually blocked me from creating the psychological safety necessary to get good ideas out of people who otherwise wouldn't feel comfortable speaking up. Genuinely good/supporting vibes from my direction to you - do with it what you will, but I do believe your ego is showing here more than mine. We can agree to disagree since I believe each of us will over-index on our past life experiences vs. those of some random person on Hacker News.
> I think you need to reread my initial post in this thread. The importance of minimizing rtt blocking is acknowledged in my questioning of chrome’s decision to not implement http push.
I think I get what you're saying, but honestly the way you're wording your points is a bit confusing. I am going to chalk this up to "I'm just too dumb" for sake of laziness at this point.
Something like gRPC could be implemented as a websocket protocol but you lose all the http semantics for each internal request. You can't expect a load balancer to handle your custom socket protocol but with a standard like http/2 nginx is able to do it.
Though http keepalive seems to already solve your use-case, without TLS 1.3’s connection rtt optimizations, if you indeed aren’t running requests in parallel.
Sorry but no. Not solved.
They also have a newer post about 0-RTT and how QUIC makes it even faster.
https://blog.cloudflare.com/even-faster-connection-establish...
That only applies to cloudflare’s implementation of 0-rtt. That isn’t a general restriction.
Additionally 0-rtt isn’t the only rtt optimization in tls 1.3.
Either way your original point was moot since http keepalive is sufficient to avoid tls connection costs for serial requests.
And because they're unaware of each other it's likely they'll eventually start competing with each other and cause packet loss
To keep a TCP efficient, the sending process needs to fill up the send buffer to a reasonable amount, generally by writing data to the kernel with write()/send(). If the sending process doesn't do this, the sending TCP will not send full frames as fast as the network or receiver allows, and do so at a steady cadence.
But to prioritise the data flow of multiple responses across multiple connections, the sender needs to pause existing TCP flows in progress as soon as it has higher priority response data ready to send if the higher priority TCP will send at full rate. Yet if the higher priority TCP is sending slower than full rate temporarily due to slow start, congestion control or receive window full, etc., the lower priority TCP needs to be resumed just enough to fill the gaps.
It's not even possible to do this with the ordinary sockets API, so it's certainly not trivial.
With HTTP/2 and TCP in kernel, it's still not optimal because prioritised response data will be queued behind data already in the TCP send buffer, but at least there's only one send buffer's worth to compete with rather than lots.
With HTTP/3 and QUIC in userspace, adaptive prioritisation can be optimised further because the decision is made on every packet just before it leaves the machine.
Per-packet prioritisation would be possible in theory with HTTP/1 and HTTP/2 by implementing TCP in userspace, or by implementing HTTP in kernelspace, in either case tightly coupling TCP and HTTP. I don't know of anyone doing it, because it would be a lot of work for a marginal gain.
> "part of the idea with HTTP2 that the server can see everything you're asking for and more intelligently prioritize"
HTTP/2 prioritisation does in fact optimize continuously by starting lower priority streams when higher priority data isn't yet available, then pausing streams in mid-send as other higher priority streams' data becomes available.
The size of the send buffer makes a difference to how fast this can react, as I described. Details at Cloudflare: https://blog.cloudflare.com/http-2-prioritization-with-nginx...
> "if the most important response takes longer to generate than lower priority responses, the server may end up starting to send data for a lower priority response and then interrupt its stream when the higher priority response becomes available"
> "the problem with large send buffers is that it limits the nimbleness of the server to adjust the data it is sending on a connection as high priority responses become available. Once the response data has been written into the TCP send buffer it is beyond the server’s control and has been committed to be delivered in the order it is written"
You proposed to replace this with HTTP/1.1 and multiple TCPs, which does not provide an equivalent optimization.
Browsers do in fact optimize HTTP/1.1 per asset by keeping a list of requests in priority order and running a limited number of TCP connections in parallel, but if they can use HTTP/2 that usually works out faster. On the internet for reasons described in the Cloudflare article, and also because giving as many requests to the server as possible up front allows the HTTP server to start fetching or generating lower priority assets sooner, hiding some backend latency - especially significant with load balancers, other reverse proxies, or HDD cold storage.
By that logic, electricity wasted on inefficient power adapters and devices in standby mode is irrelevant: The marginal savings per household are cents per year.
If it doesn't hurt me as an end user (and I don't see how HTTP/2 does), what's the objection here? Nor is any smaller service provider forced to adopt it server-side.
You’re right no one is forced to adopt this new web stack and for that I am grateful. Given recent events I will likely not adopt google’s web stack.
I agree that the benefits only fit certain use cases, but it is still nice to have it and it is already widely adapted.