Using curl and grep to select currently active endpoint

This is a pattern I use in deployment scripts when there’s a high-availability pair of servers and I need to find which one is currently active before doing anything else. The && and || operators turn the grep match into an if-else, setting a variable that the rest of the script can use.

Let’s say there are two servers, and we need to select the currently active one.

• Server IP are

  10.0.105.114

  10.0.105.115

• API to get active endpoint is /api/HA
• API base path is /api/open/v1

  if the server is active, then the response will contain json key as ‘Role’ and value as ‘Active’

• We use the linux CURL to get response and filter output using grep command

$ curl -s https://10.0.105.114/api/HA | grep -iq "Role.:.Active" &&
ACTIVE_ENDPOINT=https://10.0.105.114/api/open/v1 ||
ACTIVE_ENDPOINT=https://10.0.105.115/api/open/v1

$ echo $ACTIVE_ENDPOINT
https://10.0.105.114/api/open/v1

• The above command uses curl then pipes/passes the output to grep
• grep uses i for ignore case when searching for text “Role.:.Active”
• grep uses q for quiet, meaning do not write anything on standard-output/terminal

• && basically does the if true then use the current server,

  meaning else use the other server

• print the selected endpoint saved in the ACTIVE_ENDPOINT variable by using echo $ACTIVE_ENDPOINT