cic-internal-integration/apps/util/liveness/README.md

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---
description: liveness (Untitled Document)
distribution: global
Generator: makeinfo
keywords: liveness (Untitled Document)
lang: en
resource-type: document
title: liveness (Untitled Document)
---
[]{#liveness}[]{#liveness-1}
## 1 liveness {#liveness .chapter}
[]{#ilveness_005foverview}[]{#Overview}
### 1.1 Overview {#overview .section}
This is a cluster-specific convenience setup for enabling a
Kubernetes-style liveness/readiness test as outlined in
<https://kubernetes.io/docs/tasks/configure-pod-container/configure-liveness-readiness-startup-probes/>.
Conceptually, it provides an application with means to:
- Run a collection of functions to validate sanity of the environment
- Set a no-error state before execution of the main routine
- Modify the error state during execution
- Invalidating all state when execution ends
[]{#Python-module}
### 1.2 Python module {#python-module .section}
Three python methods are provided.
[]{#load}
#### 1.2.1 load {#load .subsection}
This is meant to be called after configurations and environment has been
set up, but before the execution logic has commenced.
It receives a list of externally defined fully-qualified python modules.
Each of these modules must implement the method `health(*args,**kwargs)`
in its global namespace.
Any module returning `False` will cause a `RuntimeException`.
The component will not trap any other exception from the modules.
If successful, it will write the `pid` of the application to the
specified run data folder. By default this is `/run/<HOSTNAME>`, but the
path can be modified if desired.
[]{#set}
#### 1.2.2 set {#set .subsection}
This is meant to be called during the execution of the main program
routine begins.
[]{#at-startup}
#### 1.2.2.1 at startup {#at-startup .subsubsection}
It should be called once at the *start* of execution of the main program
routine.
For one-shot routines, this would mean the start of any code only run
when the module name is `__main__`.
For daemons, it would be just before handing over execution to the main
loop.
[]{#during-execution}
#### 1.2.2.2 during execution {#during-execution .subsubsection}
Call `set(error_code=<error>, ...` any time the health state temporarily
changes. Any `error` value other than `0` is considered an unhealthy
state.
[]{#at-shutdown}
#### 1.2.2.3 at shutdown {#at-shutdown .subsubsection}
Call `reset(...)`, which will indicate that the state is to be
considered the same as at startup.
[]{#shell}
### 1.3 shell {#shell .section}
A bash script is provided for *Kubernetes* to perform the health check.
It performs the following checks:
1. A numeric value exists in `<rundir>/<unitname>/pid`{.sample}.
2. The numeric value is a directory in `/proc`{.sample} (a valid pid)
3. The file `<rundir>/<unitname>/error`{.sample} contains \"0\"
If any of these checks fail should inditcate that the container is
unhealthy.
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