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47 lines
1.5 KiB
Markdown
47 lines
1.5 KiB
Markdown
---
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description: Don’t worry, creating a new check is quite easy.
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---
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# Implementing a new check
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## Creating a new check class
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If you want to implement a new check, you need to create a new class that inherits from `argos.checks.BaseCheck`.
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You need to implement two methods, and specify the type of the data you want to check.
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Let's create a new check that ensures that the specified header is present.
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```python
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class HeaderExists(BaseCheck):
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"""Checks that the response contains the specified header."""
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config = "header-exists"
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expected_cls = ExpectedStringValue
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async def run(self):
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response = await self.http_client.head(self.task.url)
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result = (self.expected.value in response.headers)
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return self.response(status=result)
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```
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## Using configuration values to determine the severity
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The agents don't have access to the configuration values, so they can't determine the severity of the check, albeit in some case that could be useful.
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If that's your case, you can implement the `finalize` method, and return some extra values in the `run` method, like this:
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```python
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async def run(self):
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# ... see earlier example
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return self.response(status=result, extra_arg="extra_value")
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@classmethod
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async def finalize(cls, config, result, extra_arg):
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# You can use the extra_arg here to determine the severity
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return Status.SUCCESS, Severity.OK
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```
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## Document the new check
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Please, document the use of the new check in `docs/checks.md` and `argos/config-example.yaml`.
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