I'm developing one of my first applications with the Laravel 4 framework (which, by the way, is a joy to design with). For one component, there is an AJAX request to query an external server. The issue is, I want to cache these responses for a certain period of time only if they are successful.
Laravel has the Cache::remember() function, but the issue is there seems to be no "failed" mode (at least, none described in their documentation) where a cache would not be stored.
For example, take this simplified function:
try {
$server->query();
} catch (Exception $e) {
return Response::json('error', 400);
}
I would like to use Cache::remember on the output of this, but only if no Exception was thrown. I can think of some less-than-elegant ways to do this, but I would think that Laravel, being such an... eloquent... framework, would have a better way. Any help? Thanks!
This is what worked for me:
if (Cache::has($key)) {
$data = Cache::get($key);
} else {
try {
$data = longQueryOrProcess($key);
Cache::forever($key, $data); // only stored when no error
} catch (Exception $e) {
// deal with error, nothing cached
}
}
And of course you could use Cache::put($key, $data, $minutes); instead of forever
I found this question, because I was looking for an answer about this topic.
In the meanwhile I found a solution and like to share it here:
(also check out example 2 further on in the code)
<?php
/**
* Caching the query - Example 1
*/
function cacheQuery_v1($server)
{
// Set the time in minutes for the cache
$minutes = 10;
// Check if the query is cached
if (Cache::has('db_query'))
{
return Cache::get('db_query');
}
// Else run the query and cache the data or return the
// error response if an exception was catched
try
{
$query = $server->query(...);
}
catch (Exception $e)
{
return Response::json('error', 400);
}
// Cache the query output
Cache::put('db_query', $query, $minutes);
return $query;
}
/**
* Caching the query - Example 2
*/
function cacheQuery_v2($server)
{
// Set the time in minutes for the cache
$minutes = 10;
// Try to get the cached data. Else run the query and cache the output.
$query = Cache::remember('db_query', $minutes, function() use ($server) {
return $server->query(...);
});
// Check if the $query is NULL or returned output
if (empty($query))
{
return Response::json('error', 400);
}
return $query;
}
I recommend you to use Laravel's Eloquent ORM and/or the Query Builder to operate with the Database.
Happy coding!
We're working around this by storing the last good value in Cache::forever(). If there's an error in the cache update callback, we just pull the last value out of the forever key. If it's successful, we update the forever key.
Related
I have a controller with a download action in typo3. For some time I have implemented it like this and it is working:
function downloadAction() {
// ...
// send headers ...
// ...
if ($fh = fopen($this->file, 'r')) {
while (!feof($fh)) {
echo fread($fh, $chunkSize); // send file in little chunks to output buffer
flush();
}
fclose($fh);
}
exit; // Stopp middlewares and so on.
}
I am wondering if I should/could return an object of type ResponseInterface in typo3 11. So it is obviously that exit stopps the middleware pipeline and other things and I don't really know if there are any side effects.
I tried the following to return a ResponseInterface :
function downloadAction(): ResponseInterface {
// ...
return $this->responseFactory->createResponse();
->withAddedHeader(...)
// ...
->withBody($this->streamFactory->createStreamFromFile($this->file))
->withStatus(200, 'OK');
}
The problem is that the solution with the ResponseInterface works only with small files. The problem seems to be in Bootstrap::handleFrontendRequest().
protected function handleFrontendRequest(ServerRequestInterface $request): string
{
// ...
if (headers_sent() === false) {
// send headers
}
$body = $response->getBody(); // get the stream
$body->rewind();
$content = $body->getContents(); // Problem: Read the hole stream into RAM instead of
// sending it in chunks to the output buffer
// ...
return $content;
}
typo3 tries to read the whole stream/file into RAM. That crashes the application.
So how should I trigger a file download these days with typo3?
I need to use transactions on mongodb in laravel-5.8. I am using jenssegers-laravel-mongodb and use like below snippet in my code but it does not rollback when one of queries failed.
$session = MongoDB::startSession();
$session->startTransaction();
try {
Player::document()->update($updates, ['session' => $session]);
$session->commitTransaction();
return true;
} catch (\Exception $e) {
$session->abortTransaction();
return false;
}
As I found out, this package does not support transactions. I desperately need to support transactions in my code. Could you advise me what to do?
Instead of using MongoDb class try using the Laravel's DB class, manually change the database driver your are connecting to and run the DB transactional commands as show below
\DB::connection(config('database.connections.mongodb'));
\DB::beginTransaction();
try {
Player::document()->update($updates, ['session' => $session]);
\DB::commit();
return true;
} catch (\Exception $e) {
\DB::rollback();
return false;
}
So, I want to update two different user accounts with the same value.
Scenario: User 1 transfers money to User 2:
$transfer_from = $account->decrement('balance', $amount);
$transfer_to = Account::where('user_wallet_address', $receiver_wallet_address)->increment('balance', $amount);
But, what I want, is something like this:
$account->decrement('balance', $amount)->$transfer_to;
As in if the decrement succeeds, then update the other user's balance, otherwise, both should fail
Thoughts?
Please use database transaction feature
See below code example:
public function readRecord() {
DB::beginTransaction();
try {
// put your code here in try block
$transfer_from = $account->decrement('balance', $amount);
$transfer_to = Account::where('user_wallet_address', $receiver_wallet_address)->increment('balance', $amount);
DB::commit();
} catch (Exception $ex) {
// If any failure case generate, it will rollback the DB operations automatically.
DB::rollBack();
echo $ex->getMessage() . $ex->getLine();
}
I hope this will help you. In this case if any failure case generate it will automatic revert the DB translocation and you don't need to do anything.
Reference URL: https://laravel.com/docs/5.7/database
Currently I am trying to upload some images parallel with dropzone.js.
This is part of the code, that handles the upload.
\DB::beginTransaction();
$maxPos = GalleryImage::lockForUpdate()->max('pos');
try {
// some other code
// ....
$galleryImage->pos = $maxPos + 1;
$galleryImage->save();
} catch (\Exception $e) {
\DB::rollBack();
\Log::error($e->getMessage());
return response('An error occured', 500);
}
\DB::commit();
If I do not use the lockForUpdate() I end up with duplicate positions in database.
The problem with above solution ist, that if the table is empty I get the error:
Serialization failure: 1213 Deadlock found when trying to get lock; try restarting transaction
But only for the second image I am uploading.
Additionally the autoincrement id skips the value 2 and goes like 1,3,4,5,6,7, ...
The Positions in the table are shown correctly 1,2,3,4....
I think the problem has to do with the table beeing empty initially, as I did not notice this problem, when there are already some entries in the table.
Any suggestions what I am doing wrong? Or Maybe using lockForUpdate() in combination with an aggregate function is wrong at all...
I recommend a different approach to transactions.
try {
app('db')->transaction(function ()) {
$maxPos = GalleryImage::lockForUpdate()->max('pos');
// other code (...)
$galleryImage->pos = $maxPos + 1;
$galleryImage->save();
}
} catch (\Exception $e) {
// display an error to user
}
Should any exception occurs inside the callback, the transaction will rollback and free any locks.
For some reason I have to initialize session with default save handler.
Previous code explicitly sets custom handler with session_set_save_handler().
Changing previous code is not a realistic option in my situation, so does anyone know how to restore handler to default eg is there session_restore_save_handler or session_unset_save_handler functions or equivalents?
As of PHP 5.4 you can revert to the default session handler by instantiating the SessionHandler class directly:
session_set_save_handler(new SessionHandler(), true);
Here I have to answer on my own question since no one said anything:
First, there is no session_restore_save_handler or session_unset_save_handler given from PHP and (by so far) no native way to get things back as they were before. For some reason, PHP team didn't give us option to juggle with session handlers in this way.
Second, native session mechanism can be emulated with following code
class FileSessionHandler
{
private $savePath;
function open($savePath, $sessionName)
{
$this->savePath = $savePath;
if (!is_dir($this->savePath)) {
mkdir($this->savePath, 0777);
}
return true;
}
function close()
{
return true;
}
function read($id)
{
return (string)#file_get_contents("$this->savePath/sess_$id");
}
function write($id, $data)
{
return file_put_contents("$this->savePath/sess_$id", $data) === false ? false : true;
}
function destroy($id)
{
$file = "$this->savePath/sess_$id";
if (file_exists($file)) {
unlink($file);
}
return true;
}
function gc($maxlifetime)
{
foreach (glob("$this->savePath/sess_*") as $file) {
if (filemtime($file) + $maxlifetime < time() && file_exists($file)) {
unlink($file);
}
}
return true;
}
}
$handler = new FileSessionHandler();
session_set_save_handler(
array($handler, 'open'),
array($handler, 'close'),
array($handler, 'read'),
array($handler, 'write'),
array($handler, 'destroy'),
array($handler, 'gc')
);
register_shutdown_function('session_write_close');
This logic is closest to PHP's native session dealing one, but with , of course, unpredictable behavior in different circumstances. All I can right now conclude is that basic session operations is full covered with it.