Cache DBFile::exists() and reduce calls to file_exists() #388

emteknetnz · 2020-04-12T11:37:32Z

Performance improvements, primarily to the the file manager section in the CMS

Profiled using xhprof when viewing the gallery view in the file manager. There is an excessively large number of calls to file_exists() due to excessive rechecking during graphql requests

This pull request contains:

add some caching to DBFile::exists()
prevent a possible duplicate check to FlysystemAssetStore::applyToFileOnFilesystem()
prevent a double check in Sha1FileHashingService::getTimestamp()

Note: the branch name includes 1.5 though it was later rebased off 1 since this requires a minor release as it adds new API

Related PRs

Related PR asset-admin: silverstripe/silverstripe-asset-admin#1078

Travis cwp-recipie-kitchen-sink integration testing

https://travis-ci.org/github/creative-commoners/cwp-recipe-kitchen-sink/builds/675232333

Profiling results

FileManager gallery view - 50 files - 49 draft and 1 published

The way the asset abstraction works, the public store gets checked first and if that's not found the protected store gets the gets checked. Because most of the files are in the protected store, this is pretty much a worst case scenario.

The same file is checked for existence many times repeatedly, it's not very optimised. Variants are such as thumbnails are checked for existence separately from the main file.

This was done on a vagrant setup so it'll be much slower than a proper server

Times are measure in xhprof using Incl. Wall Time (microsec) - which is the total time spent in the function and all child functions. 100,000 microsec = 100 milliseconds

DBFile::exists() - 306 Calls

baseline
331,094
322,158
413,078

pull request
146,256
104,318
103,692

Calls to League\Flysystem\Adapter\Local::has - this is the main function that calls file_exists()

baseline - 4,019 calls
66,568
69,775
76,692

pull request - 1,634 calls
35,296
32,674
35,566

src/Storage/DBFile.php

src/Storage/Sha1FileHashingService.php

…ts(). Other small optimisation tweaks.

maxime-rainville · 2020-04-22T00:00:24Z

Is this only a problem when profiling or is this a real world problem? My expectation was that an existence check would be a relatively inexpensive operation ... which is why I do it everywhere.

If this is only a problem when profiling then adding ReadOnlyCacheService sounds like a potentially risky change if you don't make sure to invalidate that cache.

emteknetnz · 2020-04-22T05:07:02Z

@maxime-rainville I do have an very slow local setup, so going from ~325 to ~125 milliseconds would be an uncommonly large gain on a proper server. However this is still large boost percentage wise, and I do think that a 50-100 millisecond improvement on a proper server is not out of the question.

Is it a real world problem? Well the file manager is tolerable as is now, so it's not like we have to do iterative performance improvements. At the same time, I would say the file manager is pretty slow right now so it is something where we could make UX gains by simply making it faster

The cache is effectively invalidated at the end of every request i.e. it's not-persisted anywhere other than in code

The cache is also opt-in of sorts where you must specifically enable it, rather than it being on by default. See the related PR silverstripe/silverstripe-asset-admin#1078 for how this is done.

I've also tried to make it very clear that this cache should only ever be used in read-only operations - hence the name of the class.

maxime-rainville · 2020-04-24T04:46:53Z

So you're seeing this as something that is only enabled on requests where we are 100% sure that we're only reading files and never updating them?

That makes some sense. I'll have a closer look.

maxime-rainville · 2020-04-28T02:50:22Z

src/Services/ReadOnlyCacheService.php

+ * Used to cache results for the duration of a request during read-only file operations
+ * Do not use this during any create, update or delete operations
+ */
+class ReadOnlyCacheService


Maybe this should implement the Flushable interface?

I don't think we should officially support this API. Mark it as @internal.

It's not flushable, there's nothing to flush. The cache is only used for a single request and then it's gone

Resettable is the appropriate interface for classes which have in-memory caches.

maxime-rainville

Still not super sure about this one. Feels a bit hackish.

If this had massive performance impact, I'd say it's worth doing, but from what I can tell, it's leading to a small performance gain and it introduces more complexity.

If we're looking at squeezing more performance out of assets, I think we'd be better off trying to wrap FlysystemAssetStore or the underlying Filesystem object with their own caching layer. It would be a little less straight forward, but it would lead to more comprehensive results.

maxime-rainville · 2020-04-28T03:10:12Z

src/Flysystem/FlysystemAssetStore.php

@@ -321,7 +321,7 @@ private function applyToFileOnFilesystem(callable $callable, ParsedFileID $parse
                if ($parsedFileID->getHash()) {
                    $mainFileID = $strategy->buildFileID($strategy->stripVariant($parsedFileID));

-                    if (!$fs->has($mainFileID)) {
+                    if ($mainFileID !== $fileID && !$fs->has($mainFileID)) {


That part is low-impact, I'm happy to merge it as an incremental improvement.

maxime-rainville · 2020-04-28T03:10:34Z

src/Storage/Sha1FileHashingService.php

@@ -189,10 +190,20 @@ private function buildCacheKey($fileID, $fs)
     */
    private function getTimestamp($fileID, $fs)
    {
+        $timestamp = '';


That part is low-impact, I'm happy to merge it as an incremental improvement.

emteknetnz · 2020-04-28T03:51:50Z

@maxime-rainville

wrap FlysystemAssetStore or the underlying Filesystem object with their own caching layer

What would implementation on this potentially look like? How would you wrap FlysystemAssetStore while still retaining backwards compatibility?

maxime-rainville · 2020-04-28T05:35:07Z

A good example of that is the FileHashingService. We store the hash of files in cache so we don't have to recalculate it all the time. Whenever, we move/delete a file we invalidate its hash in the cache. This is built on the assumption that files are not affected by any outside process ... which is not ideal, but we've already crossed that bride, so I think it would be safe to extend that assumption.

Maybe we update the asset store to do something similar for file existence:

whenever a call to exist is made, we cache the returned value
whenever a call is made to a function that move/delete files, we invalidate the existence cache for that file.

Alternatively we could do something similar directly on PublicAssetAdapter/ProtectedAssetAdapter. This would be more complex, but would also have a bigger payoff because it would also be used by all the FileIDHelperParsers.

Either way, I think it makes more sense to put that caching logic in the AssetStore than DBFile. DBFile is mostly concerned with DB stuff. AssetStore is the thing that interacts with the physical files.

maxime-rainville · 2020-04-28T05:37:59Z

On a side note, Flysystem has some caching solution https://flysystem.thephpleague.com/v1/docs/advanced/caching/

Maybe we could look at using that instead.

emteknetnz · 2020-04-28T05:55:35Z

That Memory caching on Flysystem looks pretty tasty, and being non-persistant there's less ways for things to go wrong.

Of course we'd need a pretty solid test plan to find edge cases. Presumably if anything happens to the physical file system that doesn't go via Flysystem, and therefore the cache won't get invalidated, then we're going to have problems

maxime-rainville · 2020-04-28T06:17:04Z

If you decide to bypass our file abstraction and access the files directly, I think you assume some degree of risk. Still, in memory per-request caching sounds like it would be pretty safe and we could leave it on all the time.

FYI If your file gets updated outside of the CMS, you'll get problems with the File Hash caching. That bit us in the ass with AWS EFS because a file system change in one server would be propagated to another server without the hashing cache being invalidated.

christopherdarling · 2022-09-22T03:22:14Z

Re @maxime-rainville's suggestion of the Flysystem Cached Adapter - I've been looking at implementing it but noted that this doesn't appear to be supported in Flysystem v2 so maybe it's worthwhile being built in to core?

emteknetnz force-pushed the pulls/1.5/less-file-exists branch from f4fe11d to 24cc6d6 Compare April 12, 2020 11:38

emteknetnz changed the title ~~Cache DBFile->exists() and reduce calls to file_exists()~~ Cache DBFile::exists() and reduce calls to file_exists() Apr 12, 2020

emteknetnz force-pushed the pulls/1.5/less-file-exists branch from 24cc6d6 to 2d74eee Compare April 12, 2020 11:38

emteknetnz requested a review from maxime-rainville April 12, 2020 11:52

emteknetnz commented Apr 12, 2020

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emteknetnz mentioned this pull request Apr 12, 2020

Enable ReadOnlyCacheService silverstripe/silverstripe-asset-admin#1070

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emteknetnz changed the title ~~Cache DBFile::exists() and reduce calls to file_exists()~~ WIP: Cache DBFile::exists() and reduce calls to file_exists() Apr 12, 2020

emteknetnz force-pushed the pulls/1.5/less-file-exists branch from 810f4a6 to dccbc90 Compare April 13, 2020 04:01

emteknetnz changed the base branch from 1.5 to 1 April 15, 2020 05:53

emteknetnz changed the title ~~WIP: Cache DBFile::exists() and reduce calls to file_exists()~~ Cache DBFile::exists() and reduce calls to file_exists() Apr 15, 2020

emteknetnz added affects/v4 change/minor type/enhancement labels Apr 15, 2020

emteknetnz force-pushed the pulls/1.5/less-file-exists branch from dccbc90 to 2b88c7c Compare April 15, 2020 06:05

NEW Add ReadOnlyCacheService to cache read-only calls to DBFile::exis…

e202f65

…ts(). Other small optimisation tweaks.

emteknetnz force-pushed the pulls/1.5/less-file-exists branch from 2b88c7c to e202f65 Compare April 15, 2020 10:05

emteknetnz added the complexity/low label Apr 15, 2020

emteknetnz removed the request for review from maxime-rainville April 20, 2020 10:39

emteknetnz mentioned this pull request Apr 20, 2020

Enable ReadOnlyCacheService silverstripe/silverstripe-asset-admin#1078

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maxime-rainville self-requested a review April 24, 2020 04:47

maxime-rainville self-assigned this Apr 24, 2020

maxime-rainville reviewed Apr 28, 2020

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Cache DBFile::exists() and reduce calls to file_exists() #388

Cache DBFile::exists() and reduce calls to file_exists() #388

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christopherdarling commented Sep 22, 2022

Cache DBFile::exists() and reduce calls to file_exists() #388

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Cache DBFile::exists() and reduce calls to file_exists() #388

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Related PRs

Travis cwp-recipie-kitchen-sink integration testing

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