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
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
- http_log_stream(-Stream) is semidet
- True when Stream is a stream to the opened HTTP log file. Opens the
log file in
appendmode 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.
- http_log_close(+Reason) is det
- If there is a currently open HTTP logfile, close it after adding
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
- 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.
- password_field(+Field) is semidet[multifile]
- Multifile predicate that can be defined to hide passwords from the logfile.
- 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-typeheader. 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).
- 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.
- http_logrotate(+Options) is det
- 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.
- Do not rotate if the log file is smaller than Bytes. The default is 1Mbytes.
- Number of rotated log files to keep (default 10)
- Compress the log files to the given format.
true, rotate the log files in the background.
- http_schedule_logrotate(When, Options)
- Schedule log rotation based on maintenance broadcasts. When
is one of:
- 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.