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Improve check on loading cached file if the file not found #19773

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Improve check on loading cached file if the file not found #19773

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2 changes: 1 addition & 1 deletion framework/caching/FileCache.php
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Original file line number Diff line number Diff line change
Expand Up @@ -110,7 +110,7 @@ protected function getValue($key)
{
$cacheFile = $this->getCacheFile($key);

if (@filemtime($cacheFile) > time()) {
if (file_exists($cacheFile) && @filemtime($cacheFile) > time()) {
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  1. It may result in additional stat call.
  2. It becomes non-atomic operation.

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Yes, why do we want to avoid it at all costs?

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@filemtime assumes that file already exists - which is already wrong assumption. Then it solves situation with non-existing file by suppressing error - which is also wrong approach. PHP has dedicated function(s) to check whether the file exists - so why not to use it properly? It is not adding extra stat call since stat data are memory cached on first attempt. The currently implemented mechanism is also not 100% atomic anyway since there is microtime between @filemtime and @fopen and @flock in the block (BTW would not file_get_contents() be better?). Should you wish I can add extra suppress operator @file_exists($path) even though I don't think it'd be necessary.

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@lubosdz because there's a time gap between file_exists and filemtime. file_get_contents() with locking flags might be, indeed, better in terms of atomicity.

$fp = @fopen($cacheFile, 'r');
if ($fp !== false) {
@flock($fp, LOCK_SH);
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