On 28.01.2019, at 01:39, Chris Muller ma.chris.m@gmail.com wrote:
Hi,
Yes, the SqueakMap server image is one part of the dynamic, but I think another is a bug in the trunk image. I think the reason Tim is not seeing 45 seconds before error is because the timeout setting of the high-up client is not being passed all the way down to the lowest-level layers -- e.g., from HTTPSocket --> WebClient --> SocketStream --> Socket. By the time it gets down to Socket which does the actual work, it's operating on its own 30 second timeout.
I would expect subsecond reponse times. 30 seconds is just unacceptably long.
Well, it depends on if, for example, you're in the middle of Antarctica with a slow internet connection in an office with a fast connection. A 30 second timeout is just the maximum amount of time the client will wait for the entire process before presenting a debugger, that's all it can do.
We can be sure that Tim should get subsecond response times instead of timeouts after 30 seconds.
Right, but timeout settings are a necessary tool sometimes, my point was that we should fix client code in trunk to make timeouts work properly.
Incidentally, 99% of SqueakMap requests ARE subsecond -- just go to map.squeak.org and click around and see. For the remaining 1% that aren't, the issue is known and we're working on a new server to fix that.
It is a fixed amount of time, I *think* still between 30 and 45 seconds, that it takes the SqueakMap server to save its model after an
and so if in the meantime it can simply be made to wait 45s instead of 30s, then current SqueakMap will only be that occasional delay at worst, instead of the annoying debugger we currently get.
You would save seconds, not milliseconds by not downloading files again.
IIUC, you're saying we would save one hope in the "download" -- instead of client <--> alan <--> andreas, it would just be client <--> alan. Is that right?
No. If the client doesn't have the mcz in the package cache but nginx has it in its cache, then we save the transfer of data between alan and andreas.
Are alan and andreas co-located?
They're VMs on rackspace. The slowest bandwidth Rackspace has is 200 MBit/s, the fastest 2 GBit/s, i forgot which we have. The network is not the limiting factor here, Squeak is.
The file doesn't have to be read from the disk either.
I assume you mean "read from disk" on alan? What about after it's cached so many mcz's in RAM that its paging out to swap file? To me, wasing precious RAM (of any server) to cache old MCZ file contents that no one will ever download (because they become old very quickly) feels wasteful. Dragster cars are wasteful too, but yes, they are "faster"... on a dragstrip. :) I guess there'd have to be some kind of application-specific smart management of the cache...
Levente, what about the trunk directory listing, can it cache that? That is the _#1 thing_ source.squeak.org is accessing and sending back over, and over, and over again -- every time that MC progress box that says, "Updating [repository name]".
If the client does have the mcz, then we save the complete file transfer.
I don't know what the speed between alan <---> andreas is, but I doubt it's much slower than client <---> alan in most cases, so the savings would seem to be minimal..?
The image wouldn't have to open a file, read its content from the disk and send that through a socket.
By "the image" I assume you mean the SqueakSource server image. But opening the file takes very little time. Original web-sites were .html files, remember how fast those were? Plus, filesystems "cache" file contents into their own internal caches anyway...
Yes, it still has to return back through alan but I assume alan does not wait for a "full download" received from andreas before its already pipeing back to the Squeak client. If true, then it seems like it only amounts to saving one hop, which would hardly be noticeable over what we have now.
Nginx does that thing magnitudes faster than Squeak.
The UX would not be magnitudes faster though, right?
That would also let us save bandwidth by not downloading files already sitting in the client's package cache.
How so? Isn't the package-cache checked before hitting the server at all? It certainly should be.
No, it's not. Currently that's not possible, because different files can have the same name. And currently we have no way to tell them apart.
No. No two MCZ's may have the same name, certainly not withiin the same repository, because MCRepository cannot support that. So maybe
Not at the same time, but it's possible, and it just happened recently with Chronology-ul.21. It is perfectly possible that a client has a version in its package cache with the same name as a different version on the server.
But we don't want to restrict what's possible in our software design because of that. That situation is already a headache anyway. Same name theoretically can come only from the same person (if we ensure unique initials) and so this is avoidable / fixable by resaving one of them as a different name...
we need project subdirectories under package-cache to properly simulate each cached Repository. I had no idea we were neutering 90% of the benefits of our package-cache because of this too, and just sitting here, I can't help wonder whether this is why MCProxy doesn't work properly either!
The primary purpose of a cache is to *check it first* to speed up access to something, right? What you say about package-cache sounds
I don't know. It wasn't me who designed it. :)
I meant ANY "cache".
https://en.wikipedia.org/wiki/Cache_(computing)
For Monticello, package-cache's other use-case is when an authentication issue occurs when trying to save to a HTTP repository. At that point the Version object with the new ancestry was already constructed in memory, so rather than worry about trying to "undo" all that, it was simpler and better to save it to a package-cache, persist it safely so the client can simply move forward from there (get access to the HTTP and copy it or whatever).
- Chris
really bad we should fix that, not surrender to it.
Yes, that should be fixed, but it needs changes on the server side. What I always had in mind was to extend the repository listing with hashes/uuids so that the client could figure out if it needs to download a specific version. But care must be taken not to break the code for non-ss repositories (e.g. simple directory listings).
Levente
- Chris