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Improve sync lock setting/reading to avoid race conditions (#4316)

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This commit is contained in:
Thomas Bruederli 2015-01-22 20:09:22 +01:00
parent 62b69dd961
commit af216b50e3
1 changed files with 11 additions and 7 deletions
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18
plugins/libkolab/lib/kolab_storage_cache.php
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@ -935,7 +935,6 @@ class kolab_storage_cache
return;
$this->_read_folder_data();
$sql_query = "SELECT `synclock`, `ctag` FROM `{$this->folders_table}` WHERE `folder_id` = ?";
// abort if database is not set-up
if ($this->db->is_error()) {
@ -943,16 +942,21 @@ class kolab_storage_cache
return;
}
$this->synclock = true;
$read_query = "SELECT `synclock`, `ctag` FROM `{$this->folders_table}` WHERE `folder_id` = ?";
$write_query = "UPDATE `{$this->folders_table}` SET `synclock` = ? WHERE `folder_id` = ? AND `synclock` = ?";
// wait if locked (expire locks after 10 minutes)
while ($this->metadata && intval($this->metadata['synclock']) > 0 && $this->metadata['synclock'] + $this->max_sync_lock_time > time()) {
// wait if locked (expire locks after 10 minutes) ...
// ... or if setting lock fails (another process meanwhile set it)
while (
(intval($this->metadata['synclock']) + $this->max_sync_lock_time > time()) ||
(($res = $this->db->query($write_query, time(), $this->folder_id, intval($this->metadata['synclock']))) &&
!($affected = $this->db->affected_rows($res)))
) {
usleep(500000);
$this->metadata = $this->db->fetch_assoc($this->db->query($sql_query, $this->folder_id));
$this->metadata = $this->db->fetch_assoc($this->db->query($read_query, $this->folder_id));
}
// set lock
$this->db->query("UPDATE `{$this->folders_table}` SET `synclock` = ? WHERE `folder_id` = ?", time(), $this->folder_id);
$this->synclock = $affected > 0;
}
/**