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MDL-59866 session: Add retry for redis sessions

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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
This commit is contained in:
Marcus Boon
2017-12-12 14:48:26 +10:00
parent 5fdb912a82
commit 7da0e04ca3
1 changed files with 51 additions and 29 deletions
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lib/classes/session/redis.php
+51 -29
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@@ -157,39 +157,61 @@ class redis extends handler {
throw new exception('redissessionhandlerproblem', 'error');
}
try {
// 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)) {
throw new RedisException('Unable to connect to host.');
// 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, null, $delay)) {
throw new RedisException('Unable to connect to host.');
}
if ($this->auth !== '') {
if (!$this->connection->auth($this->auth)) {
throw new RedisException('Unable to authenticate.');
}
}
if (!$this->connection->setOption(\Redis::OPT_SERIALIZER, $this->serializer)) {
throw new RedisException('Unable to set Redis PHP Serializer option.');
}
if ($this->prefix !== '') {
// Use custom prefix on sessions.
if (!$this->connection->setOption(\Redis::OPT_PREFIX, $this->prefix)) {
throw new RedisException('Unable to set Redis Prefix option.');
}
}
if ($this->database !== 0) {
if (!$this->connection->select($this->database)) {
throw new RedisException('Unable to select Redis database '.$this->database.'.');
}
}
$this->connection->ping();
return true;
} catch (RedisException $e) {
$logstring = "Failed to connect (try {$counter} out of {$maxnumberofretries}) to redis ";
$logstring .= "at {$this->host}:{$this->port}, error returned was: {$e->getMessage()}";
// @codingStandardsIgnoreStart
error_log($logstring);
// @codingStandardsIgnoreEnd
}
if ($this->auth !== '') {
if (!$this->connection->auth($this->auth)) {
throw new RedisException('Unable to authenticate.');
}
}
$counter++;
if (!$this->connection->setOption(\Redis::OPT_SERIALIZER, $this->serializer)) {
throw new RedisException('Unable to set Redis PHP Serializer option.');
}
if ($this->prefix !== '') {
// Use custom prefix on sessions.
if (!$this->connection->setOption(\Redis::OPT_PREFIX, $this->prefix)) {
throw new RedisException('Unable to set Redis Prefix option.');
}
}
if ($this->database !== 0) {
if (!$this->connection->select($this->database)) {
throw new RedisException('Unable to select Redis database '.$this->database.'.');
}
}
$this->connection->ping();
return true;
} catch (RedisException $e) {
error_log('Failed to connect to redis at '.$this->host.':'.$this->port.', error returned was: '.$e->getMessage());
return false;
// Introduce a random sleep between 100ms and 500ms.
usleep(rand(100000, 500000));
}
// We have exhausted our retries, time to give up.
return false;
}
/**