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