Google-cloud-php: [Spanner] Unreleased session cache can be deleted.

[yuichiro12]

Clearing sessionPool before closing db connection generates broken cache file.

Here is the php code for reproduction.

<?php
require_once __DIR__.'/../../vendor/autoload.php';

use Symfony\Component\Cache\Adapter\FilesystemAdapter;
use Google\Cloud\Spanner\Session\CacheSessionPool;
use Google\Cloud\Spanner\SpannerClient;

$projectId = '...';
$instanceId = '...';
$databaseId = '...';
$cacheDir = sys_get_temp_dir() . '/spanner-cache';
echo 'cacheDir: ' . $cacheDir . PHP_EOL;
$cacheItemPool = new FilesystemAdapter('', 0, $cacheDir);
$sessionPool = new CacheSessionPool($cacheItemPool);

$spanner = new SpannerClient(['projectId' => $projectId]);
$db = $spanner->connect($instanceId, $databaseId, ['sessionPool' => $sessionPool]);

$sessionPool->warmup();

for($i = 0; $i < 5; $i++) {
    $result = $db->execute('SELECT ' . random_int(0, 10000))->rows()->current();
    printf('result %d: %s'.PHP_EOL, $i, array_values($result)[0]);
}

$sessionPool->clear();
// Cache file broken
$db->close();

Executing this php script causes following warnings (and create broken cache file).

cacheDir: /.../spanner-cache
result 0: 1013
result 1: 2345
result 2: 764
result 3: 3854
result 4: 3992
PHP Warning:  array_push() expects parameter 1 to be array, null given in /.../vendor/google/cloud-spanner/src/Session/CacheSessionPool.php on line 306
PHP Stack trace:
PHP   1. {main}() /.../public/spanner-test/session-not-found.php:0
PHP   2. Google\Cloud\Spanner\Database->close() /.../session-not-found.php:36
PHP   3. Google\Cloud\Spanner\Session\CacheSessionPool->release() /.../vendor/google/cloud-spanner/src/Database.php:1380
PHP   4. Google\Cloud\Core\Lock\SemaphoreLock->synchronize() /.../vendor/google/cloud-spanner/src/Session/CacheSessionPool.php:309
PHP   5. Google\Cloud\Spanner\Session\CacheSessionPool->Google\Cloud\Spanner\Session\{closure}() /.../vendor/google/cloud-core/src/Lock/LockTrait.php:67
PHP   6. array_push() /.../vendor/google/cloud-spanner/src/Session/CacheSessionPool.php:306

Warning: array_push() expects parameter 1 to be array, null given in /.../vendor/google/cloud-spanner/src/Session/CacheSessionPool.php on line 306

Call Stack:
    0.0004     369744   1. {main}() /.../public/spanner-test/session-not-found.php:0
    1.2530    6222616   2. Google\Cloud\Spanner\Database->close() /.../public/spanner-test/session-not-found.php:36
    1.2530    6222616   3. Google\Cloud\Spanner\Session\CacheSessionPool->release() /.../vendor/google/cloud-spanner/src/Database.php:1380
    1.2530    6223312   4. Google\Cloud\Core\Lock\SemaphoreLock->synchronize() /.../vendor/google/cloud-spanner/src/Session/CacheSessionPool.php:309
    1.2530    6223360   5. Google\Cloud\Spanner\Session\CacheSessionPool->Google\Cloud\Spanner\Session\{closure}() /.../vendor/google/cloud-core/src/Lock/LockTrait.php:67
    1.2579    6413192   6. array_push() /.../vendor/google/cloud-spanner/src/Session/CacheSessionPool.php:306

Then again, executing the same script causes fatal error because of broken cache file.

cacheDir: /.../spanner-cache
PHP Notice:  Undefined index: inUse in /.../vendor/google/cloud-spanner/src/Session/CacheSessionPool.php on line 588
PHP Stack trace:
PHP   1. {main}() /.../public/spanner-test/session-not-found.php:0
PHP   2. Google\Cloud\Spanner\Session\CacheSessionPool->warmup() /.../public/spanner-test/session-not-found.php:20
PHP   3. Google\Cloud\Core\Lock\SemaphoreLock->synchronize() /.../vendor/google/cloud-spanner/src/Session/CacheSessionPool.php:407
PHP   4. Google\Cloud\Spanner\Session\CacheSessionPool->Google\Cloud\Spanner\Session\{closure}() /.../vendor/google/cloud-core/src/Lock/LockTrait.php:67
PHP   5. Google\Cloud\Spanner\Session\CacheSessionPool->getSessionCount() /.../vendor/google/cloud-spanner/src/Session/CacheSessionPool.php:397

Notice: Undefined index: inUse in /.../vendor/google/cloud-spanner/src/Session/CacheSessionPool.php on line 588

Call Stack:
    0.0003     369744   1. {main}() /.../public/spanner-test/session-not-found.php:0
    0.0770    4491728   2. Google\Cloud\Spanner\Session\CacheSessionPool->warmup() /.../public/spanner-test/session-not-found.php:20
    0.0770    4492048   3. Google\Cloud\Core\Lock\SemaphoreLock->synchronize() /.../vendor/google/cloud-spanner/src/Session/CacheSessionPool.php:407
    0.0771    4492096   4. Google\Cloud\Spanner\Session\CacheSessionPool->Google\Cloud\Spanner\Session\{closure}() /.../vendor/google/cloud-core/src/Lock/LockTrait.php:67
    0.0821    4493104   5. Google\Cloud\Spanner\Session\CacheSessionPool->getSessionCount() /.../vendor/google/cloud-spanner/src/Session/CacheSessionPool.php:397

PHP Notice:  Undefined index: toCreate in /.../vendor/google/cloud-spanner/src/Session/CacheSessionPool.php on line 589
PHP Stack trace:
PHP   1. {main}() /.../public/spanner-test/session-not-found.php:0
PHP   2. Google\Cloud\Spanner\Session\CacheSessionPool->warmup() /.../public/spanner-test/session-not-found.php:20
PHP   3. Google\Cloud\Core\Lock\SemaphoreLock->synchronize() /.../vendor/google/cloud-spanner/src/Session/CacheSessionPool.php:407
PHP   4. Google\Cloud\Spanner\Session\CacheSessionPool->Google\Cloud\Spanner\Session\{closure}() /.../vendor/google/cloud-core/src/Lock/LockTrait.php:67
PHP   5. Google\Cloud\Spanner\Session\CacheSessionPool->getSessionCount() /.../vendor/google/cloud-spanner/src/Session/CacheSessionPool.php:397

Notice: Undefined index: toCreate in /.../vendor/google/cloud-spanner/src/Session/CacheSessionPool.php on line 589

Call Stack:
    0.0003     369744   1. {main}() /.../public/spanner-test/session-not-found.php:0
    0.0770    4491728   2. Google\Cloud\Spanner\Session\CacheSessionPool->warmup() /.../public/spanner-test/session-not-found.php:20
    0.0770    4492048   3. Google\Cloud\Core\Lock\SemaphoreLock->synchronize() /.../vendor/google/cloud-spanner/src/Session/CacheSessionPool.php:407
    0.0771    4492096   4. Google\Cloud\Spanner\Session\CacheSessionPool->Google\Cloud\Spanner\Session\{closure}() /.../vendor/google/cloud-core/src/Lock/LockTrait.php:67
    0.0821    4493104   5. Google\Cloud\Spanner\Session\CacheSessionPool->getSessionCount() /.../vendor/google/cloud-spanner/src/Session/CacheSessionPool.php:397

PHP Notice:  Undefined index: toCreate in /.../vendor/google/cloud-spanner/src/Session/CacheSessionPool.php on line 402
PHP Stack trace:
PHP   1. {main}() /.../public/spanner-test/session-not-found.php:0
PHP   2. Google\Cloud\Spanner\Session\CacheSessionPool->warmup() /.../public/spanner-test/session-not-found.php:20
PHP   3. Google\Cloud\Core\Lock\SemaphoreLock->synchronize() /.../vendor/google/cloud-spanner/src/Session/CacheSessionPool.php:407
PHP   4. Google\Cloud\Spanner\Session\CacheSessionPool->Google\Cloud\Spanner\Session\{closure}() /.../vendor/google/cloud-core/src/Lock/LockTrait.php:67

Notice: Undefined index: toCreate in /.../vendor/google/cloud-spanner/src/Session/CacheSessionPool.php on line 402

Call Stack:
    0.0003     369744   1. {main}() /.../public/spanner-test/session-not-found.php:0
    0.0770    4491728   2. Google\Cloud\Spanner\Session\CacheSessionPool->warmup() /.../public/spanner-test/session-not-found.php:20
    0.0770    4492048   3. Google\Cloud\Core\Lock\SemaphoreLock->synchronize() /.../vendor/google/cloud-spanner/src/Session/CacheSessionPool.php:407
    0.0771    4492096   4. Google\Cloud\Spanner\Session\CacheSessionPool->Google\Cloud\Spanner\Session\{closure}() /.../vendor/google/cloud-core/src/Lock/LockTrait.php:67

PHP Fatal error:  Uncaught Error: Unsupported operand types in /.../vendor/google/cloud-spanner/src/Session/CacheSessionPool.php:402
Stack trace:
#0 /.../vendor/google/cloud-core/src/Lock/LockTrait.php(67): Google\Cloud\Spanner\Session\CacheSessionPool->Google\Cloud\Spanner\Session\{closure}()
#1 /.../vendor/google/cloud-spanner/src/Session/CacheSessionPool.php(407): Google\Cloud\Core\Lock\SemaphoreLock->synchronize(Object(Closure))
#2 /.../public/spanner-test/session-not-found.php(20): Google\Cloud\Spanner\Session\CacheSessionPool->warmup()
#3 {main}
  thrown in /.../vendor/google/cloud-spanner/src/Session/CacheSessionPool.php on line 402

Fatal error: Uncaught Error: Unsupported operand types in /.../vendor/google/cloud-spanner/src/Session/CacheSessionPool.php on line 402

Error: Unsupported operand types in /.../vendor/google/cloud-spanner/src/Session/CacheSessionPool.php on line 402

Call Stack:
    0.0003     369744   1. {main}() /.../public/spanner-test/session-not-found.php:0
    0.0770    4491728   2. Google\Cloud\Spanner\Session\CacheSessionPool->warmup() /.../public/spanner-test/session-not-found.php:20
    0.0770    4492048   3. Google\Cloud\Core\Lock\SemaphoreLock->synchronize() /.../vendor/google/cloud-spanner/src/Session/CacheSessionPool.php:407
    0.0771    4492096   4. Google\Cloud\Spanner\Session\CacheSessionPool->Google\Cloud\Spanner\Session\{closure}() #####################yyyworkspace/laravel-extension-template/vendor/google/cloud-core/src/Lock/LockTrait.php:67

Cache should be able to be cleared whenever needed. However, this session pool creates broken cache and prevent us from making the next connection.

[dwsupplee]

Thank you very much for the bug report @yuichiro12! I opened #1071 which should resolve this issue. Would you be able to check out the change and confirms it works, please?

[dwsupplee]

@yuichiro12 We've verified the patch and will get this out in a bugfix release today. thanks again!