PublicShow sourcehttp_log.pl -- HTTP Logging module

Simple module for logging HTTP requests to a file. Logging is enabled by loading this file and ensure the setting http:logfile is not the empty atom. The default file for writing the log is httpd.log. See library(settings) for details.

The level of logging can modified using the multifile predicate http_log:nolog/1 to hide HTTP request fields from the logfile and http_log:password_field/1 to hide passwords from HTTP search specifications (e.g. /topsecret?password=secret).

Source http_log_stream(-Stream) is semidet
True when Stream is a stream to the opened HTTP log file. Opens the log file in append mode if the file is not yet open. The log file is determined from the setting http:logfile. If this setting is set to the empty atom (''), this predicate fails.

If a file error is encountered, this is reported using print_message/2, after which this predicate silently fails.

Source http_log_close(+Reason) is det
If there is a currently open HTTP logfile, close it after adding a term server(Reason, Time). to the logfile. This call is intended for cooperation with the Unix logrotate facility using the following schema:
  • Move logfile (the HTTP server keeps writing to the moved file)
  • Inform the server using an HTTP request that calls http_log_close/1
  • Compress the moved logfile
author
- Suggested by Jacco van Ossenbruggen
Source http_log(+Format, +Args) is det
Write message from Format and Args to log-stream. See format/2 for details. Succeed without side effects if logging is not enabled.
Source password_field(+Field) is semidet[multifile]
Multifile predicate that can be defined to hide passwords from the logfile.
Source nolog(+HTTPField)[multifile]
Multifile predicate that can be defined to hide request parameters from the request logfile.
 nolog_post_content_type(+Type) is semidet[multifile]
Multifile hook called with the Content-type header. If the hook succeeds, the POST data is not logged. For example, to stop logging anything but application/json messages:
:- multifile http_log:nolog_post_content_type/1.

http_log:nolog_post_content_type(Type) :-
   Type \= (application/json).
Arguments:
Type- is a term MainType/SubType
Source post_data_encoded(?Bytes:string, ?Encoded:string) is det
Encode the POST body for inclusion into the HTTP log file. The POST data is (in/de)flated using zopen/3 and base64 encoded using base64//1. The encoding makes long text messages shorter and keeps readable logfiles if binary data is posted.
Source http_logrotate(+Options) is det
Rotate the available log files. Note that there are two ways to deal with the rotation of log files:
  1. Use the OS log rotation facility. In that case the OS must (1) move the logfile and (2) have something calling http_log_close/1 to close the (moved) file and make this server create a new one on the next log message. If library(http/http_unix_daemon) is used, closing is achieved by sending SIGHUP or SIGUSR1 to the process.
  2. Call this predicate at scheduled intervals. This can be achieved by calling http_schedule_logrotate/2 in the context of library(http/http_unix_daemon) which schedules the maintenance actions.

Options:

min_size(+Bytes)
Do not rotate if the log file is smaller than Bytes. The default is 1Mbytes.
keep_logs(+Count)
Number of rotated log files to keep (default 10)
compress_logs(+Format)
Compress the log files to the given format.
background(+Boolean)
If true, rotate the log files in the background.
Source http_schedule_logrotate(When, Options)
Schedule log rotation based on maintenance broadcasts. When is one of:
daily(Hour:Min)
Run each day at Hour:Min. Min is rounded to a multitude of 5.
weekly(Day, Hour:Min)
Run at the given Day and Time each week. Day is either a number 1..7 (1 is Monday) or a weekday name or abbreviation.
monthly(DayOfTheMonth, Hour:Min)
Run each month at the given Day (1..31). Note that not all months have all days.

This must be used with a timer that broadcasts a maintenance(_,_) message (see broadcast/1). Such a timer is part of library(http/http_unix_daemon).