DominionEnterprises\Mongo\Queue::ensureIndex PHP Method

    private function ensureIndex(array $index)
    {
        //if $index is a prefix of any existing index we are good
        foreach ($this->collection->listIndexes() as $existingIndex) {
            $slice = array_slice($existingIndex['key'], 0, count($index), true);
            if ($slice === $index) {
                return;
            }
        }
        for ($i = 0; $i < 5; ++$i) {
            for ($name = uniqid(); strlen($name) > 0; $name = substr($name, 0, -1)) {
                //creating an index with same name and different spec does nothing.
                //creating an index with same spec and different name does nothing.
                //so we use any generated name, and then find the right spec after we have called,
                //and just go with that name.
                try {
                    $this->collection->createIndex($index, ['name' => $name, 'background' => true]);
                } catch (\MongoDB\Exception\Exception $e) {
                    //this happens when the name was too long, let continue
                }
                foreach ($this->collection->listIndexes() as $existingIndex) {
                    if ($existingIndex['key'] === $index) {
                        return;
                    }
                }
            }
        }
        throw new \Exception('couldnt create index after 5 attempts');
        //@codeCoverageIgnoreEnd
    }