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051-environment.md

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title Container Runtime Environment Variables
expires_at never
tags
diego-release
bbs

Container Runtime Environment

Diego provides several collections of environment variables to processes running in containers. These include the following layers, in order:

  • Environment variables baked into the Docker image (for Docker-image-based containers only)
  • Container-level environment variables (defined on the Task and DesiredLRP objects)
  • Configuration environment variables (LRPs only, described below)
  • Process-level environment variables (defined on the RunAction object)

Configuration-level Environment Variables

LRPs have additional runtime properties that are exposed to processes in the container via environment variables. These are as follows:

Instance Identifiers

  • INSTANCE_INDEX is an integer denoting the index of the ActualLRP. This will be in the range 0, 1, 2, ...N-1 where N is the number of instances on the DesiredLRP.
  • INSTANCE_GUID is a unique identifier associated with an ActualLRP. This will change every time a container is created.
  • CF_INSTANCE_INDEX and CF_INSTANCE_GUID are aliases of these environment variables.

Networking Information

These environment variables are provided only if the operator deploying Diego has enabled -exportNetworkEnvVars on the Cell rep.

  • CF_INSTANCE_IP provides the IP of the host running the container. This is the IP used to address the container from the outside.
  • CF_INSTANCE_PORT contains the host-side port corresponding to the first port in the DesiredLRP ports array.
  • CF_INSTANCE_ADDR is identical to $CF_INSTANCE_IP:$CF_INSTANCE_PORT.
  • CF_INSTANCE_PORTS contains a list of JSON objects of the form [{"external":60413,"internal":8080},{"external":60414,"internal":2222}]. The internal ports are the container-side ports specified in the DesiredLRP ports array, and the external ports are the corresponding host-side ports.