check_http

README

HTTP Check

Performs an HTTP GET request and returns a result based on the HTTP response code and if requested, an expected value or expression.

• OK: HTTP response code was not >= 300 and if requested, there was a match on the expected value or expression
• WARNING: HTTP response code was >= 300 and < 400
• CRITICAL: Connection failed or HTTP response code was >= 400 or on a failed match if an expected value or expression was supplied

Options

• --url (-u): The URL to check. Required.
• --insecure (-k): Do not validate the server's certificate
• --redirect (-r): If set, follow redirects. Default is do not follow redirects.
• --timeout (-t): Timeout in seconds to wait for HTTP server response. Default is 15 seconds.
• --path (-p) and --expression: Used together. A json path and expression value to compare. Use this rather than --path and --expectedValue for making comparisons.
• --path (-p) and --expectedValue (-e): Used together. --path is the json path for retrieving a value and --expectedValue is the value to expected at the path. Use --expression instead for a more consistent interface.

Examples

Check example.com for good response

check_http --url http://www.example.com

Check example.com for good response within 2 seconds

check_http --url http://www.example.com --timeout 2

Using Expressions

Use expressions (--expression) for the ability to make comparisons other than simple string equality to a json field.

This option implements the Gval expression evaluation package to compare against a json field, yielding the ability to use ==, !=, >, <, >=, <= and probably more. These comparisons will work strings and numbers. The string or number comparison made depends on the use of double-quotes after the comparison operand.

Some examples. == "comparetothistring" gives a string comparison while == 1337 gives a number comparison. Note the use of these quotes is important because "1337" < "500" (string comparison) will yield true while 1337 < 500 (number comparison) will yield false.

Consider using --expression rather than --expectedValue.

Some examples of how to use this --expression option...

The body returned for the example URL used below is

$ curl -s -H "Accept: application/json" https://icanhazdadjoke.com/j/HeaFdiyIJe | jq '.'
{
  "id": "HeaFdiyIJe",
  "joke": "What kind of magic do cows believe in? MOODOO.",
  "status": 200
}

For starters, here's how the --expectedValue and --expression options can be equally used.

check_http --url https://icanhazdadjoke.com/j/HeaFdiyIJe --format json --path id --expectedValue HeaFdiyIJe

check_http --url https://icanhazdadjoke.com/j/HeaFdiyIJe --format json --path id --expression '== "HeaFdiyIJe"'

Note the use of double-quotes above. That's because strings are being compared. If strings were not used, it would give:

check_http --url https://icanhazdadjoke.com/j/HeaFdiyIJe --format json --path id --expression '== HeaFdiyIJe'
CheckHttp CRITICAL - Url https://icanhazdadjoke.com/j/HeaFdiyIJe responded with 200. The value found at id with value HeaFdiyIJe does not match expression "== HeaFdiyIJe"

More examples using other operators (continue to note the use of double-quotes for strings):

check_http --url https://icanhazdadjoke.com/j/HeaFdiyIJe --format json --path id --expression '<= "IeaFdiyIJe"'
CheckHttp OK - Url https://icanhazdadjoke.com/j/HeaFdiyIJe responded with 200. The value found at id with value HeaFdiyIJe and expression "<= "IeaFdiyIJe"" yields true

check_http --url https://icanhazdadjoke.com/j/HeaFdiyIJe --format json --path id --expression '>= "HeaFdiyIJd"'
CheckHttp OK - Url https://icanhazdadjoke.com/j/HeaFdiyIJe responded with 200. The value found at id with value HeaFdiyIJe and expression ">= "HeaFdiyIJd"" yields true

check_http --url https://icanhazdadjoke.com/j/HeaFdiyIJe --format json --path id --expression '!= "notequal"'
CheckHttp OK - Url https://icanhazdadjoke.com/j/HeaFdiyIJe responded with 200. The value found at id with value HeaFdiyIJe and expression "!= "notequal"" yields true

And examples using number comparisons (double-quotes not used)

check_http --url https://icanhazdadjoke.com/j/HeaFdiyIJe --format json --path status --expression '== 200'
CheckHttp OK - Url https://icanhazdadjoke.com/j/HeaFdiyIJe responded with 200. The value found at status with value 200 and expression "== 200" yields true

check_http --url https://icanhazdadjoke.com/j/HeaFdiyIJe --format json --path status --expression '>= 200'
CheckHttp OK - Url https://icanhazdadjoke.com/j/HeaFdiyIJe responded with 200. The value found at status with value 200 and expression ">= 200" yields true

check_http --url https://icanhazdadjoke.com/j/HeaFdiyIJe --format json --path status --expression '< 400'
CheckHttp OK - Url https://icanhazdadjoke.com/j/HeaFdiyIJe responded with 200. The value found at status with value 200 and expression "< 400" yields true

Finally, an example using string comparison especially for Windows users at the Command Prompt shell. Notice the --expression option is contained in double-quotes and the double-quotes inside the option are given by using two double-quotes.

check_http.exe --url https://icanhazdadjoke.com/j/HeaFdiyIJe --format json --path id --expression "== ""HeaFdiyIJe"""
CheckHttp OK - Url https://icanhazdadjoke.com/j/HeaFdiyIJe responded with 200. The value found at id with value HeaFdiyIJe and expression "== "HeaFdiyIJe"" yields true