Determines the failure reason associated with an exception.

This failure reason function, the default used by the check function, uses a reason of :threw-exception for all exceptions other than:

• org.apache.http.conn.ConnectTimeoutException
• java.net.SocketTimeoutException
• java.net.ConnectException when the exception message includes “Timeout”

for which the reason is :timed-out.

In the case that this default behaviour is insufficient, an alternative failure reason function can be passed to http-endpoint-check-fn using the :failure-reason-fn option.

Returns a check function for the HTTP endpoint identified by the provided URL.

Accepts the following options in the option map:

• :method: a keyword representing the method used to check the endpoint (one of :get, :head, :post, :put, :delete, :options, :copy, :move or :patch) or a function of context that will return such a keyword; defaults to :get.
• :body: an object representing the body sent to the endpoint on check execution (supporting anything clj-http will accept) or a function of context that will return such an object; defaults to nil.
• :headers: a map of headers to be sent to the endpoint on check execution (as supported by clj-http) or a function of context that will return such a map; defaults to nil.
• :query-params: a map of query parameters to be sent to the endpoint on check execution (as supported by clj-http) or a function of context that will return such a map; defaults to nil.
• :opts: a map of additional query options (as supported by clj-http) or a function of context that will return such a map; defaults to {:throw-exceptions false} since we want response success to be deduced by the :response-result-fn rather than treating unsuccessful statuses as exceptions; note that any timeouts passed in this query options map are ignored and should be set using :connection-request-timeout, :connection-timeout and :socket-timeout.
• :connection-request-timeout: the salutem.core/duration to wait when obtaining a connection from the connection manager before considering the request failed; defaults to 5 seconds.
• :connection-timeout: the salutem.core/duration to wait when establishing an HTTP connection before considering the request failed; defaults to 5 seconds.
• :socket-timeout: the salutem.core/duration to wait while streaming response data since the last data was received before considering the request failed; defaults to 5 seconds.
• :successful-response-fn: a function of context and the response from a request to the endpoint, returning true if the response was successful, false otherwise; by default uses successful?.
• :response-result-fn: a function, of context and the response from a request to the endpoint, used to produce a result for the check; by default, a healthy result is returned if the response is successful according to :successful-response-fn, otherwise an unhealthy result is returned.
• :failure-reason-fn: a function, of context and an exception, to determine the reason for a failure; by default uses failure-reason.
• :exception-result-fn: a function, of context and an exception, used to produce a result for the check in the case that an exception is thrown; by default, an unhealthy result is returned including a :salutem/reason entry with the reason derived by :failure-reason-fn and a :salutem/exception entry containing the thrown exception.

Additionally, if the URL parameter is instead a function, it will be called with the context map at check execution time in order to obtain the endpoint URL.

If the returned check function is invoked with a context map including a :logger key with a cartus.core/Logger value, the check function will emit a number of log events whilst executing.

Returns true if the provided response has a successful status, false otherwise.

This response success function, the default used by the check function, treats status codes of 200, 201, 202, 203, 204, 205, 206, 207, 300, 301, 302, 303, 304, 307 and 308 as successful.

In the case that this default behaviour is insufficient, an alternative response success function can be passed to http-endpoint-check-fn using the :successful-response-fn option.