Is a flexible and small daemon (~40kb) that checks and manages back-end nodes declared in a HAProxy and interacts with it for automatic up/down The idea behind psentinel is pretty simple: runs between haproxy and a back-end application to decouple it from the haproxy direct check. Psentinel can execute a shell script/executable to check the back-end application and reply to haproxy about the running state. It can be also manually disabled, very usefull for manual or automatic deploy and continuous integration

From root user:

to compile/install : make && make install

to execute as daemon : psentinel -d

Probably is better to create and execute from an unprivileged user (please read the psentinel.pdf for more info)

psentinel sends 200 OK to haprxy if monitored application is up and running 503 Disabled if manually paused by user 500 Error if the check script fails

Psentinel executable can act as client or daemon. as client (talking with daemon via AF_UNIX socket) is possible to know the status of monitored services

psentinel -c status

or disable one specific service

psentinel -c disable

or pause all the pausable services

psentinel -c pause

Please read the psentinel.pdf for more..