SWI-Prolog -- health/2

Documentation
- Reference manual
- Packages
  - SWI-Prolog HTTP support
    - The HTTP server libraries
      - library(http/http_server_health): HTTP Server health statistics
        
        server_health/1
        
        health/2
        
        hide/1

Availability::- use_module(library(http/http_server_health)).

[nondet,multifile]health(-Key, -Value)

Multifile extensible. True when Key/Value can be reported as a health statistics. Keys may be added by adding clauses to this multifile predicate. Keys may be filtered using hide/1. Predefined Key values are:

up

Defined to be true.

epoch

Starting time of the server in seconds after Jan 1, 1970 UTC.

cpu_time

Total process CPU usage in seconds.

threads

Number of active threads

workers

Number of HTTP worker threads.

requests

Number of HTTP requests processed.

bytes_sent

Number of bytes send in reply to HTTP requests.

open_files

Number of open file streams. This includes physical files as well as sockets (except for Windows). On Linux we count the file handles in /proc/self/fd. Otherwise we use stream_property/2 with the file_no(Fd) property.

loadavg

An array holding the load average over the last [1,5,15] minutes. This key is only supported on Linux machines. It is based on /proc/loadavg

heap

When compiled with TCMalloc, this provides two properties:

inuse:Bytes: Total amount of in-use memory in bytes
size:Bytes: Same as inuse, but including the TCMalloc overhead and (thus) memory that has been freed and is not (yet) reused.

`Key`	is the name of the JSON key. Must be an atom
`Value`	is the Prolog representation for a JSON (dict) value.