If you have installed the SAP Cloud Connector, you will know that out-of-the-box it is capable of providing a High Availability feature at the application layer.
Essentially, you can install 2x SAP Cloud Connectors on 2x VMs and then they can be paired so that one acts as Master and one as “Shadow” (secondary).
The Shadow instance connects to the Master to replicate the required configuration.
If you decide to patch the Cloud Connector (everything needs patching right?!), then you can simply patch the Shadow instance, trigger a failover then patch the old Master.
There is only one complication in this, and that is that it’s not “easy” to see which is acting in which role unless you log into the web administration console.
You can go through the log files to see which has taken over the role of Master at some point, but this is a not easy and doesn’t lend itself to being scripted for automated detection of the current role.
Here’s a nice easy way to detect the current role, and could be used (for example) as part of a Custom Instance monitor script for SAP LaMa automation of the Cloud Connector:
awk '/<haRole>/ { match($1,/<haRole>(.*)<\/haRole>/,role); if (role[1] != "" ) { print role[1]; exit } }' /opt/sap/scc/scc_config/scc_config.iniOut will be either “shadow”, or “master”.
I use awk a lot of the time for pattern group matching because I like the simplicity, it’s a powerful tool and deserves the very long O’Reilly book.
Here’s what that single code line is doing:
| awk | The call to the program binary. |
| ‘ | Start the contents of the inline AWK script (prevents interpretation by the shell). |
| /<haRole>/ | Match every line that contains the <haRole> tag. |
| { | On each line match, execute this block of code (we close with “}”). |
| $1 | Match against the 1st space delimited parameter on the line. |
| /<haRole>(.*)<\/haRole>/, | Obtain any text “.*” between <haRole> tag. |
| role | Store the match in a new array called “role”. |
| if (role[1] != “” ) | Check that after the matching, the role array has 2 entries (zero initialised array). |
| { print role[1]; exit } | If we do have 2 entries, print the second one (1st is the complete matched text string) from the array and exit. |
| }’ | Close off the command and AWK script. |
/opt/sap/scc/
scc_config/
scc_config.ini | The name of the input file for AWK to scan. |
It’s a nice simple way of checking the current role, and can be embedded into a shell script for easy execution.
