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 be 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).
- [semidet]http_log_stream(-Stream)
- 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. Opening is retried every minute when a new
message arrives.
Before opening the log file, the message http_log_open(Term)
is broadcasted. This message allows for creating the directory,
renaming, deleting or truncating an existing log file.
- [det]http_log_close(+Reason)
- 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
- [det]http_log(+Format,
+Args)
- Write message from Format and Args to log-stream.
See format/2 for details. Succeed without
side effects if logging is not enabled.
- [semidet,multifile]password_field(+Field)
- Multifile predicate that can be defined to hide passwords from the
logfile.
- [multifile]nolog(+HTTPField)
- Multifile predicate that can be defined to hide request parameters from
the request logfile.
- [semidet,multifile]nolog_post_content_type(+Type)
- 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).
| Type | is a term MainType/SubType |
- [det]post_data_encoded(?Bytes:string,
?Encoded:string)
- 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.
- [det]http_logrotate(+Options)
- Rotate the available log files. Note that there are two ways to deal
with the rotation of log files:
- 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.
- 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.
- 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).
