The Oracle Always Free plan is an excellent option, but I found myself struggling with their firewall settings while attempting to run an Nginx web server. Despite enabling port 80 in both the network security groups and security lists, it was still being blocked for unknown reasons.
Firstly I checked the ufw settings and it was disabled definitely. However, when I looked at the iptable rules by executing
sudo iptables -L, I was surprised by lots of existing rules there.
Sometimes we have to run background tasks with a quite long duration time. However, the RabbitMQ has a default time limitation for waiting the ack. If the execution time is exceed, you will got an error message like “Delivery acknowledgement timeouts” and your channel will be broken.
Suppose you have two processes executing the following PHP code at the same time, what results will be printed?
Surprisingly, one process prints the query results, while another process prints an empty collection (array). The code that returned an empty collection did not trigger a deadlock exception as expected.