Validate response data

This document describes how to configure an uptime check to validate the HTTP response code and the response data sent by a checked resource. By default, HTTP uptime checks verify that the response code is 2xx. Also, by default, the response data isn't validated. However, you can modify these settings. For example, you can configure an HTTP uptime check to accept 2xx and 3xx response codes. For all uptime checks, you can specify a value that the response data must, or must not, contain for the uptime check to be successful.

How to validate the response data

You can configure Cloud Monitoring to validate the response data from a checked resource when you create or edit an uptime check.

Google Cloud console

To create an uptime check that validates the response data, do the following:

1. In the navigation panel of the Google Cloud console, select Monitoring, and then select  Uptime checks:

   Go to Uptime checks

2. Click Create uptime check.
3. Enter a Title and click Next.
4. Enter the Target and click Next.

5. Configure the Response validation:

   • To validate the response data, ensure Content matching is enabled is shown, and then complete the fields related to response validation. For information about these options, see the next section of this document.
   • For the HTTP uptime checks, configure the acceptable response codes. By default, HTTP uptime checks mark any 2xx response as a successful response.

6. Click Next and complete the uptime check configuration.

Cloud Monitoring API

To configure an uptime check to validate the response data, populate the contentMatchers array of the UptimeCheckConfig object.

ContentMatcher objects contain the following fields:

• matcher: Describes how the comparison is performed. For a list of values, see ContentMatcherOption.

  Don't use the CONTENT_MATCHER_OPTION_UNSPECIFIED value.

• content: Stores the value to search for in the response data. The value is a string literal or a regular expression.

• jsonPathMatcher: Stores a JsonPathMatcher object that describes which JSONpath to search and how to perform the comparison.

  Omit this field unless the uptime check is validating a specific JSONpath.

The remainder of this document describes how to use the content-matching options.

Options to validate the response data

This section describes the string-matching strategies that you can use to validate the response sent by a checked resource. For each strategy, you specify a value and whether finding that value in the response data results in the uptime check passing or failing.

The entire response from a checked resource might not be searched:

• HTTP and HTTPS uptime checks: The first 4 MB is searched.
• TCP uptime checks: The first 1 MB is searched.

Search for a literal substring

Google Cloud console

To configure the uptime check to pass when the response data contains a a literal substring, use the following settings:

1. Select Contains in the Response content match type menu.
2. Enter the literal substring in the Response content field.
3. To verify the configuration, click Test.

To configure the uptime check to fail when the response data contains a literal substring, use the following settings:

1. Select Does not contain in the Response content match type menu.
2. Enter the literal substring in the Response content field.
3. To verify the configuration, click Test.

Cloud Monitoring API

To configure the uptime check to pass when the response data contains a a literal substring, use the following values:

...
"contentMatchers": [
    {
      "content": "Set to the string to be matched.",
      "matcher": "CONTAINS_STRING"
    }
],
...

To configure the uptime check to fail when the response data contains a a literal substring, use the following values:

...
"contentMatchers": [
    {
      "content": "Set to the string to be matched.",
      "matcher": "NOT_CONTAINS_STRING"
    }
],
...

The following table displays the uptime check status for different response data, test strings, and test types:

		Uptime check status
Response data	Test string	Contains	Doesn't contain
abcd	abcd	pass	fail
abc	abcd	fail	pass
abc	a	pass	fail
Uptime Checks	Uptime	pass	fail
Uptime Checks	uptime	fail	pass

In the previous table, the Response data column describes the data returned by the checked resource while the Test string column lists the string literal. The next two columns specify the type of test and the result of the uptime check.

Search using a regular-expression

Google Cloud console

To configure the uptime check to pass when the response data matches a regular expression, use the following settings:

1. Select Matches regex in the Response content match type menu.
2. Enter a regular expression in the Response content field.
3. To verify the configuration, click Test.

To configure the uptime check to fail when the response data matches a regular expression, use the following settings:

1. Select Does not match regex in the Response content match type menu.
2. Enter a regular expression in the Response content field.
3. To verify the configuration, click Test.

Cloud Monitoring API

To configure the uptime check to pass when the response data matches a regular expression, use the following values:

...
"contentMatchers": [
    {
      "content": "Set to the regular expression to be matched.",
      "matcher": "MATCHES_REGEX"
    }
],
...

To configure the uptime check to fail when the response data matches a regular expression, use the following values:

...
"contentMatchers": [
    {
      "content": "Set to the regular expression to be matched.",
      "matcher": "NOT_MATCHES_REGEX"
    }
],
...

The following table displays the uptime check status for different response data, regular expressions, and test types:

		Uptime check status
Response data	Regex	Matches regex	Doesn't match regex
abcd	abcd	pass	fail
Uptime Checks	[uU]ptime	pass	fail
Uptime Checks	[a-z]{6}	fail	pass
Uptime Checks	[a-zA-Z]{6}	pass	fail

In the previous table, the Response data column describes the data returned by the checked resource while the Regex column lists the regular expression. The next two columns specify the type of test and the result of the uptime check.

Search a specific field in a JSON response

You can configure an uptime check to validate a JSONpath. When you select a JSONpath test, the test compares a path value to a number, a string literal, or to a regular expression:

• Compare JSONpath to a number or string literal
• Compare JSONpath to a regular expression

When you specify a JSONpath, you must specify the root object with $. and then follow that with a specific field identifier. When the JSON response contains an array of elements, use brackets, [], to identify the specific array element to match. The following examples illustrate the path syntax:

• $.type matches the type field of a root object.
• $.[0].address.city matches the city field in the address object stored in the first array element of the JSON response.
• $.content[0].phone matches the phone field of the first array element of the content field. The content field is a child of the root object.

You can configure an uptime test to match multiple fields. Consider the following JSON:

[
  {
    ...
    "address": {
      ...
      "city": "Gwenborough",
      "geo": {
        "lat": "-37.3159",
        "lng": "81.1496"
      }
    },
  },
  ...
]

To match the entire path of the geo field in the first array element, set the JSONpath to $.[0].address.geo, and enter the complete value in the content field:

{
  "lat": "-37.3159",
  "lng": "81.1496"
}

If you are interested in experimenting with these options, then find a public website that returns a JSON response. For example, see JSON Test.

Compare JSONpath to a number or string literal

Google Cloud console

Note: In the Response content field you can enter numbers, boolean values of true and false, and strings. For a match to occur, the value you enter must match the response the uptime check receives. For example you can enter the boolean true, the number 5, or a string like "true", "5", or "hello".

To configure the uptime check to pass when a specific JSONpath in the response data matches a string literal, use the following settings:

1. Select Matches at JSONPath in the Response content match type menu.
2. Enter the path in the JSONPath field.
3. Enter the number or the string literal in the Response content field.
4. To verify the configuration, click Test.

To configure the uptime check to fail when a specific JSONpath in the response data matches a string literal, use the following settings:

1. Select Does not match at JSONPath in the Response content match type menu.
2. Enter the path in the JSONPath field.
3. Enter the number or the string literal in the Response content field.
4. To verify the configuration, click Test.

Cloud Monitoring API

Note: Because the value of the "content" field must be a string, you must wrap the value in quotes. When the value is a string, you must escape the inner quotes. For example, to match the boolean true, set the value to "true". Similarly, to match the number 5, set the value to "5". Lastly, to match the string "5", enter "\"5\"".

To configure the uptime check to pass when a specific field in the JSON-formatted response matches a number or a string literal, use the following values for the ContentMatcher object:

...
"contentMatchers": [
    {
       "content" : "Set to a number, a boolean, or the string to be matched.",
       "matcher" : "MATCHES_JSON_PATH",
       "jsonPathMatcher" : {
           "jsonPath" : "Set to the JSONpath.",
           "jsonMatcher" : "EXACT_MATCH"
    }
],
...

To configure the uptime check to fail when a specific field in the JSON-formatted response matches a number or a string literal, use the following values for the ContentMatcher object:

...
"contentMatchers": [
    {
       "content" : "Set to a number, a boolean, or the string to be matched.",
       "matcher" : "NOT_MATCHES_JSON_PATH",
       "jsonPathMatcher" : {
           "jsonPath" : "Set to the JSONpath.",
           "jsonMatcher" : "EXACT_MATCH"
    }
],
...

To illustrate how the JSONpath string-match tests operate, consider the following JSON response data:

{
    "name": "Sample Uptime Check",
    "type": "JSONpath",
    "content": [
        {
            "id": 1,
            "phone": "1234567890",
            "alias": "Exact",
            "enabled": true,
        },
        {
            "id": 2,
            "phone": "1234512345",
            "alias": "Regex",
            "enabled": false,
        }
    ]
}

The following table displays the uptime check status the previous response, but for different paths, test values, and test types:

		Uptime check status
JSONpath	Test value	JSONpath matches	JSONpath doesn't match
$.type	"JSONpath"	pass	fail
$.name	"Sample"	fail	pass
$.name	"Sample Uptime Check"	pass	fail
$.content[0].id	1	pass	fail
$.content[0].alias	"Exact"	pass	fail
$.content[0].enabled	true	pass	fail

In the previous table, the JSONpath column identifies which element to test and the Test value column lists the value. The next two columns specify the type of test and the result of the uptime check.

Compare JSONpath to a regular expression

Regular expression matches support matching a string, a number, a boolean, and null JSON values.

Note: The expression that you enter must match the entire value of the JSONpath. For example, if the value of a field is "North Pole", then .*North.* and ^North.* match the field while North and "North" don't match.

Google Cloud console

To configure the uptime check to pass when a specific JSONpath in the response data matches a regular expression, use the following settings:

1. Select Matches at JSONPath in the Response content match type menu.
2. Enter the path in the JSONPath field.
3. Enter the regular expression in the Response content field.
4. To verify the configuration, click Test.

To configure the uptime check to fail when a specific JSONpath in the response data matches a regular expression, use the following settings:

1. Select Does not match at JSONPath in the Response content match type menu.
2. Enter the path in the JSONPath field.
3. Enter the regular expression in the Response content field.
4. To verify the configuration, click Test.

Cloud Monitoring API

To configure the uptime check to pass when a specific field in the JSON-formatted response matches a regular expression, use the following values for the ContentMatcher object:

...
"contentMatchers": [
    {
       "content" : "Set to the regular expression to be matched."
       "matcher" : "MATCHES_JSON_PATH",
       "jsonPathMatcher" : {
           "jsonPath" : "Set to the JSONpath.",
           "jsonMatcher" : "REGEX_MATCH"
    }
],
...

To configure the uptime check to fail when a specific field in the JSON-formatted response matches a regular expression, use the following values for the ContentMatcher object:

...
"contentMatchers": [
    {
       "content" : "Set to the regular expression to be matched.",
       "matcher" : "NOT_MATCHES_JSON_PATH",
       "jsonPathMatcher" : {
           "jsonPath" : "Set to the JSONpath.",
           "jsonMatcher" : "REGEX_MATCH"
    }
],
...

To illustrate how the JSONpath regular-expression tests operate, consider the following JSON response data:

{
    "name": "Sample Uptime Check",
    "type": "JSONpath",
    "content": [
        {
            "id": 1,
            "phone": "1234567890",
            "alias": "Exact",
            "enabled": true,
        },
        {
            "id": 2,
            "phone": "1234512345",
            "alias": "Regex",
            "enabled": false,
        }
    ]
}

The following table displays the uptime check status the previous response, but for different paths, regular expressions, and test types:

		Uptime check status
JSONpath	Regex	JSONpath matches regex	JSONpath doesn't match regex
$.type	[A-Z]{4}Path	pass	fail
$.name	Sample	fail	pass
$.name	.*Sample.*	pass	fail
$.content[1].id	2	pass	fail
$.content[1].phone	"[12345]{2}"	pass	fail
$.content[1].enabled	f.*	pass	fail

In the previous table, the JSONpath column identifies which element to test and the Regex column lists the regular expression. The next two columns specify the type of test and the result of the uptime check.

What's next

• Create an uptime check
• Manage uptime checks
• Create alerting policies for uptime checks