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Removed complex replag handling, now just query master when record isn't present on slave.

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followup to r92009
This commit is contained in:
Ian Baker 2011-08-15 23:40:57 +00:00
parent 56cc7371dd
commit 36babe9a7d
1 changed files with 11 additions and 23 deletions
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34
includes/upload/UploadStash.php
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@ -22,10 +22,6 @@ class UploadStash {
// Format of the key for files -- has to be suitable as a filename itself (e.g. ab12cd34ef.jpg)
const KEY_FORMAT_REGEX = '/^[\w-\.]+\.\w*$/';
// When a given stashed file can't be loaded, wait for the slaves to catch up. If they're more than MAX_LAG
// behind, throw an exception instead. (at what point is broken better than slow?)
const MAX_LAG = 30;
/**
* repository that this uses to store temp files
* public because we sometimes need to get a LocalFile within the same repo.
@ -98,23 +94,9 @@ class UploadStash {
$dbr = $this->repo->getSlaveDb();
if ( !isset( $this->fileMetadata[$key] ) ) {
// try this first. if it fails to find the row, check for lag, wait, try again. if its still missing, throw an exception.
// this more complex solution keeps things moving for page loads with many requests
// (ie. validating image ownership) when replag is high
if ( !$this->fetchFileMetadata( $key ) ) {
$lag = $dbr->getLag();
if ( $lag > 0 && $lag <= self::MAX_LAG ) {
// if there's not too much replication lag, just wait for the slave to catch up to our last insert.
sleep( ceil( $lag ) );
} elseif ( $lag > self::MAX_LAG ) {
// that's a lot of lag to introduce into the middle of the UI.
throw new UploadStashMaxLagExceededException(
'Couldn\'t load stashed file metadata, and replication lag is above threshold: (MAX_LAG=' . self::MAX_LAG . ')'
);
}
// now that the waiting has happened, try again
$this->fetchFileMetadata( $key );
// If nothing was received, it's likely due to replication lag. Check the master to see if the record is there.
$this->fetchFileMetadata( $key, true );
}
if ( !isset( $this->fileMetadata[$key] ) ) {
@ -470,9 +452,16 @@ class UploadStash {
* @param $key String: key
* @return boolean
*/
protected function fetchFileMetadata( $key ) {
protected function fetchFileMetadata( $key, $readFromMaster = false ) {
// populate $fileMetadata[$key]
$dbr = $this->repo->getSlaveDb();
$dbr = null;
if( $readFromMaster ) {
// sometimes reading from the master is necessary, if there's replication lag.
$dbr = $this->repo->getMasterDb();
} else {
$dbr = $this->repo->getSlaveDb();
}
$row = $dbr->selectRow(
'uploadstash',
'*',
@ -685,5 +674,4 @@ class UploadStashFileException extends MWException {};
class UploadStashZeroLengthFileException extends MWException {};
class UploadStashNotLoggedInException extends MWException {};
class UploadStashWrongOwnerException extends MWException {};
class UploadStashMaxLagExceededException extends MWException {};
class UploadStashNoSuchKeyException extends MWException {};