Docker compose

With Docker Compose you can use built-in YAML features to make your Compose file neater and more efficient. Anchors and aliases let you create re-usable blocks. This is useful if you start to find common configurations that span multiple services. Having re-usable blocks minimizes potential mistakes.

Anchors are created using the & sign. The sign is followed by an alias name. You can use this alias with the * sign later to reference the value following the anchor. Make sure there is no space between the & and the * characters and the following alias name.

Docker usually tries to interpret any node at the root of a Compose file. The parser will ignore extension fields prefixed with x-. You can use these fields to encapsulate shared configuration for later reference

    ulimits:
      nofile:
        soft: 262144
        hard: 262144

The ulimits configuration in a Docker Compose file is used to set ulimits for the container. Ulimits are a mechanism for limiting the resources that can be used by a process and its children.

In your case, nofile is the ulimit being set. nofile stands for the number of open file descriptors. A file descriptor is a handle that a process uses to read from or write to an open file, or to access a network socket.

The soft and hard limits are two types of limits that can be set:

• soft: This is the limit that the kernel enforces for the corresponding resource. The process can consume resources up to this limit without any intervention from the kernel.
• hard: This is the maximum limit for the resource. It acts as a ceiling for the soft limit. Only a process with the CAP_SYS_RESOURCE capability can increase the hard limit.

In your Docker Compose file, both the soft and hard limits for the number of open file descriptors (nofile) are set to 262144. This means that the process running in the container can open up to 262144 files, sockets, or any other items that consume a file descripto