I am running server apps inside Docker on Mesos, some apps are scaled to multiple instances. When I am collecting data inside the app, I want the app to be able to store some type of identifiers so later on when I read data, I know which app it is collected from. For example, I scaled an app to 3 instances on mesos, and from the data, I want to read that the data is from either app_1, app_2 or app_3. I thought of using host IP, but those scaled apps are sometimes spawned inside the same node. I cannot use something like pid because it will change when the app restarts.
Thus I tried to read if there are environment variables that can help me distinguish between them, but they are all the same across the platform except HOSTNAME, so I wonder if anyone has other ideas. Thank you very much.
You can use the MESOS_TASK_ID task-level environment variable for this, see the Marathon docs for more details. Also, note that a Marathon application instance corresponds to a Mesos task.