xref: /freebsd/usr.sbin/fifolog/fifolog_create/fifolog.1 (revision 662cb04c254ef2fa36ddae26bbd2740d1d5727d9)

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.\" $FreeBSD$
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.Dd Feb 9, 2008
.Os FreeBSD 8.0
.Dt FIFOLOG 1
.Sh NAME
.Nm fifolog_create
.Nd Initialize storage for fifolog
.br
.Nm fifolog_write
.Nd Write data to fifolog
.br
.Nm fifolog_read
.Nd Seek and extract data from fifolog
.Sh SYNOPSIS
.Nm fifolog_create
.Op Fl l Ar record-size
.Op Fl r Ar record-count
.Op Fl s Ar size
.Ar file
.Nm fifolog_reader
.Op Fl t
.Op Fl b Ar tstart
.Op Fl B Ar Tstart
.Op Fl e Ar tend
.Op Fl E Ar Tend
.Op Fl o Ar ofile
.Op Fl R Ar regexp
.Op Fl T Ar timefmt
.Ar file
.Nm fifolog_writer
.Op Fl w Ar write-rate
.Op Fl s Ar sync-rate
.Op Fl z Ar compression
.Ar file
.Sh DESCRIPTION
Fifologs provide a compact round-robin circular storage for
recording text and binary information to permanent storage in a bounded
and predictable fashion, time and space wise.
.Pp
A fifolog can be stored either directly on a disk partition or in a
regular file.
.Pp
The input data stream is encoded, compressed and marked up with
timestamps before it is written to storage, such that it is possible
to seek out a particular time interval in the stored data, without
having to decompress the entire logfile.
.Pp
.Nm Fifolog_create
is used to initialize the first sector of a disk device
or filesystem file to make it a fifolog and should be called only
once.
.Pp
Running
.Nm
on an existing fifolog will reset it so that
.Nm fifolog_reader
and
.Nm fifolog_writer
will not see the previous contents.
(The previos contents is not physically erased, and with a bit
of hand-work, all but the first record can be easily recovered).
.Pp
If the file does not already exist
.Nm
will attempt to create and
.Xr ftruncate 3
it to the specified size, defaulting to 86400 records of 512 bytes
if the
.Fl r ,
.Fl l
or
.Fl s
arguments do not specify otherwise.
.Pp
.Nm Fifolog_writer
will read standard input and write it to the end of the fifolog
according to the parameters given.
.Pp
Writes happen whenever the output buffer is filled with compressed
data or when either of two timers expire, forcing a partially filled
buffer to be written.
.Pp
The first and faster timer,
.Fl w write-rate ,
forces available data to be written
but does not flush and reset the compression dictionary.
This timer is intended to minimize the amount of logdata lost in RAM
in case of a crash and by default it fires 10 seconds after
the previous write.
.Pp
The second and slower timer,
.Fl s sync-rate ,
forces a full flush and reset of the compression
engine and causes the next record written to be a synchronization
point with an uncompressed timestamp, making it possible to start
reading the logfile from that record.
By default this timer fires a minute after the previous sync.
.Pp
The
.Fl z compression
argument controls the
.Xr zlib 3
compression level, legal values are zero to nine which is the default.
.Pp
.Nm Fifolog_reader
will retrieve records from the fifolog according to the specified
parameters and write them either to stdout or the file specified
with
.Fl o .
.Pp
It is possible to specify a start and end time to limit the amount
of data
.Nm fifolog_reader
will report.
The lower-case variants
.Fl b
and
.Fl e
take a
.Xr time_t
value, whereas the upper-case variants
.Fl B
and
.Fl E
take human redable specifications such as "1 hour ago".
.Pp
The
.Fl t
argument forces timestamps to be formatted as "YYYYMMDDhhmmss" instead
of as time_t, and
.Fl T
allows the specification of a
.Xr strftime 3
formatting string.
.Pp
Finally, records can be filtered such that only records matching the
(REG_BASIC) regular expression specified with
.Fl R
is output.
.Sh IMPLEMENTATION NOTES
The data stored in the fifolog consists of three layers, an outher
layer that allows searches to synchronization points based on timestamps
without having to decompress and decode the actual contents, a
compression layer implemented with
.Xr zlib 3
and an inner serialization and timestamping layer.
.Pp
The exact encoding is described in the fifolog.h file.
.Pp
Fifolog is particularly well suited for use on Flash based media, where
it results in much lower write-wear, than a filesystem with regular
logfiles rotated with
.Xr newsyslog 8
etc.
.Sh EXAMPLES
Create a fifolog with 1024*1024 records of 512 bytes:
.Bd -literal
fifolog_create -r 10m /tmp/fifolog
.Ed
.Pp
Write a single record to this file:
.Bd -literal
date | fifolog_writer /tmp/fifolog
.Ed
.Pp
Read it back with human readable timestamps:
.Bd -literal
fifolog_reader -t /tmp/fifolog
.Ed
.Pp
One particular useful use of
.Nm fifolog_writer
is with
.Xr syslogd 8
using a line such as this in
.Xr /etc/syslog.conf 5 :
.Bd -literal
*.* |fifolog_writer /var/log/syslog_fifolog
.Ed
.Sh HISTORY
The fifolog tools have been liberated from an open source SCADA applications
called "measured", which monitors and controls remote radio navigation
transmitters for the Danish Air Traffic Control system.
.Sh AUTHORS
The fifolog tools were written by Poul-Henning Kamp