/**
* Calculate the node priority from its job count, stick to the current node
*
* As the priority is based on the number of jobs, higher is better.
*
* @param Node $node
* @param string $currentNodeId
*
* @return float Node priority
*/
private function calculateNodePriority(Node $node, $currentNodeId)
{
$priority = $node->getJobCount();
if ($node->getId() === $currentNodeId) {
$margin = 1 + $this->marginToSwitch;
$priority = $priority * $margin;
}
// Apply a weight determined by the node priority as assigned by Disque.
// Priority 1 means the node is healthy.
// Priority 10 to 100 means the node is probably failing, or has failed
$disquePriority = $node->getPriority();
// Disque node priority should never be lower than 1, but let's be sure
if ($disquePriority < Node::PRIORITY_OK) {
$disquePriorityWeight = 1;
} elseif (Node::PRIORITY_OK <= $disquePriority && $disquePriority < Node::PRIORITY_POSSIBLE_FAILURE) {
// Node is OK, but Disque may have assigned a lower priority to it
// We use the base-10 logarithm in the formula, so priorities
// 1 to 10 transform into a weight of 1 to 0.5. When Disque starts
// using more priority steps, priority 9 will discount about a half
// of the job count.
$disquePriorityWeight = 1 / (1 + log10($disquePriority));
} else {
// Node is failing, or it has failed
$disquePriorityWeight = 0;
}
$priority = $priority * $disquePriorityWeight;
return (double) $priority;
}
/**
* Copy node stats from the old to the new node
*
* @param Node $oldNode
* @param Node $newNode
*/
private function copyNodeStats(Node $oldNode, Node $newNode)
{
$oldNodeJobCount = $oldNode->getTotalJobCount();
$newNode->addJobCount($oldNodeJobCount);
}
/**
* Reveal the whole Disque cluster from a node HELLO response
*
* The HELLO response from a Disque node contains addresses of all other
* nodes in the cluster. We want to learn about them and save them, so that
* we can switch to them later, if needed.
*
* @param Node $node The current node
*/
private function revealClusterFromHello(Node $node)
{
$hello = $node->getHello();
$revealedNodes = [];
foreach ($hello[HelloResponse::NODES] as $node) {
$id = $node[HelloResponse::NODE_ID];
$revealedNode = $this->revealNodeFromHello($id, $node);
// Update or set the node's priority as determined by Disque
$priority = $node[HelloResponse::NODE_PRIORITY];
$revealedNode->setPriority($priority);
$revealedNodes[$id] = $revealedNode;
}
$this->nodes = $revealedNodes;
}