Lambda function to check specific http endpoint, and report on it's availability.
Optionally, it can record metrics to CloudWatch.
All inputs are either defined as environment variables or as part of event data. Event data will take priority over environment variables
ENDPOINT - url to be checked
METHOD - http method to use, defaults to GET
PAYLOAD - http payload, if POST or PUT used as method
TIMEOUT - timeout to use for http requests, defaults to 120s
HEADERS - list of percentage sign (%) separated headers to send to target server, defaults to empty list.
USER_AGENT - If specified, will be added to the HEADERS. An example is: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:15.0) Gecko/20100101 Base2/Lambda
REPORT_RESPONSE_BODY - set to 1 if you wish to report on response body, 0
otherwise, 0 otherwise, defaults to 0
REPORT_AS_CW_METRICS - set to 1 if you wish to store reported data as CW
custom metrics, 0 otherwise, defaults to 1
CW_METRICS_NAMESPACE - if CW custom metrics are being reported, this will determine
their namespace, defaults to 'HttpCheck'
BODY_REGEX_MATCH - if CW custom metrics are being reported, this will enable ResponseBodyRegexMatch
metric to be published as well, with value determined by success of matching response body against
regular expression contained within this option
STATUS_CODE_MATCH - report whether http status code is equal to given status code or not. If this option
is not present, it won't be reported upon. Defaults to empty
FAIL_ON_STATUS_CODE_MISMATCH - if checking for status code match treat mismatch as failure, ie report Available: 0
By default, following properties will be rendered in output Json
Reason - Reason
Available - 0 or 1
TimeTaken - Time in ms it took to get response from remote server. Default timeout
is 2 minutes for http requests.
StatusCode - Http Status Code
ResponseBody - Optional, by default this won't be reported
ResponseBodyRegexMatch - Optional, if BODY_REGEX_MATCH option is provided
StatusCodeMatch - Optional, if STATUS_CODE_MATCH options is provided
Lambda function is having no external dependencies by design, so no additional packaging steps are required
for deploying it, such as doing pip install [libname]
In order to get some metrics which you can alert on, REPORT_AS_CW_METRICS and CW_METRICS_NAMESPACE environment
variables are used. Following metrics will be reported
-
Available- 0 or 1, whether response was received in timely manner, indicating problems with network, DNS lookup or server timeout -
TimeTaken- Time taken to fetch response, reported in milliseconds -
StatusCode- HTTP Status code received from server -
ResponseBodyRegexMatch- optional this will report 1 or 0 ifBODY_REGEX_MATCHoption is specified. 1 is reported if response body matches regex provided, or 0 otherwise. -
StatusCodeMatch- *optional& this will report 1 or 0 ifSTATUS_CODE_MATCHoptions is specified. 1 is reported if response status code matches code provided, or 0 otherwise
You can either deploy Lambda manually, or through AWS SAM CLI. If the SAM CLI is being chosen as method of deployments use command below, while making sure that you have setup access to your AWS account.
build the lambda
sam builddeploy the template
sam deploy --guidedIf you are setting up your Lambda function by hand, make sure it has proper IAM permissions to push Cloud Watch metrics data, and to write to CloudWatch logs
To test function locally with simple Google url (default), run following
sam local invoke Check
Optionally, for complicated example take a look at test/ipify.json file
sam local invoke Check --event test/ipify.json If you wish to see debug output for http request, set HTTP_DEBUG environment
variable to '1'. This can't be controlled through event payload.
Pull requests are welcome to serverless project to deploy CloudWatch rules in order to schedule execution of Http Checking Lambda function.