Commit f8e2383b authored by Marcus Boon's avatar Marcus Boon
Browse files

MDL-59866 session: Add retry for redis sessions

There is an edge case whereby redis will fail
to accept connections on the first try but
retrying the connection seems to make it work

Included in this commit:
* Retry functionality in the session init
parent 109aa076
......@@ -157,9 +157,18 @@ class redis extends handler {
throw new exception('redissessionhandlerproblem', 'error');
// MDL-59866: Add retries for connections (up to 5 times) to make sure it goes through.
$counter = 1;
$maxnumberofretries = 5;
while ($counter <= $maxnumberofretries) {
try {
$delay = rand(100000, 500000);
// One second timeout was chosen as it is long for connection, but short enough for a user to be patient.
if (!$this->connection->connect($this->host, $this->port, 1)) {
if (!$this->connection->connect($this->host, $this->port, 1, null, $delay)) {
throw new RedisException('Unable to connect to host.');
......@@ -187,9 +196,22 @@ class redis extends handler {
return true;
} catch (RedisException $e) {
error_log('Failed to connect to redis at '.$this->host.':'.$this->port.', error returned was: '.$e->getMessage());
return false;
$logstring = "Failed to connect (try {$counter} out of {$maxnumberofretries}) to redis ";
$logstring .= "at {$this->host}:{$this->port}, error returned was: {$e->getMessage()}";
// @codingStandardsIgnoreStart
// @codingStandardsIgnoreEnd
// Introduce a random sleep between 100ms and 500ms.
usleep(rand(100000, 500000));
// We have exhausted our retries, time to give up.
return false;
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