svlogd - runit’s service logging daemon
svlogd [-tttv] [-r c] [-R
xyz] [-l len] [-b buflen] logs
logs consists of one or more arguments,
each specifying a directory.
svlogd continuously reads log data from its
standard input, optionally filters log messages, and writes the data to
one or more automatically rotated logs.
Recent log files can automatically
be processed by an arbitrary processor program when they are rotated, and
svlogd can be told to alert selected log messages to standard error, and
svlogd runs until it sees end-of-file on standard input or is
sent a TERM signal, see below.
A log directory log contains
some number of old log files, and the current log file current. Old log
files have a file name starting with @ followed by a precise timestamp
(see the daemontools’ tai64n program), indicating when current was rotated
and renamed to this file.
A log directory additionally contains the lock
file lock, maybe state and newstate, and optionally the file config. svlogd
creates necessary files if they don’t exist.
If svlogd has trouble opening
a log directory, it prints a warning, and ignores this log directory. If
svlogd is unable to open all log directories given at the command line,
it exits with an error. This can happen on start-up or after receiving a
svlogd appends selected log messages to the
current log file. If current has size bytes or more (or there is a new-line
within the last len of size bytes), or is older than a specified amount
of time, current is rotated:
svlogd closes current, changes permission
of current to 0755, renames current to @timestamp.s, and starts with a new
empty current. If svlogd sees num or more old log files in the log directory,
it removes the oldest one. Note that this doesn’t decrease the number of
log files if there are already more than num log files, this must be done
manually, e.g. for keeping 10 log files:
ls -1 \@* |sort |sed -ne ’10,$p’ |xargs
If svlogd is told to process recent log files, it saves current
to @timestamp.u, feeds @timestamp.u through ‘‘sh -c "processor"’’ and writes the
output to @timestamp.t. If the processor finishes successfully, @timestamp.t
is renamed to @timestamp.s, and @timestamp.u is deleted; otherwise @timestamp.t
is deleted and the processor is started again. svlogd also saves any output
that the processor writes to file descriptor 5, and makes that output available
on file descriptor 4 when running processor on the next log file rotation.
A processor is run in the background. If svlogd sees a previously started
processor still running when trying to start a new one for the same log,
it blocks until the currently running processor has finished successfully.
Only the HUP signal works in that situation. Note that this may block any
program feeding its log data to svlogd.
On startup, and after receiving
a HUP signal, svlogd checks for each log directory log if the configuration
file log/config exists, and if so, reads the file line by line and adjusts
configuration for log as follows:
If the line is empty, or starts with
a ‘‘#’’, it is ignored. A line of the form
- sets the maximum file size
of current when svlogd should rotate the current log file to size bytes.
Default is 1000000. If size is zero, svlogd doesn’t rotate log files. You
should set size to at least (2 * len).
- sets the number of old log files
svlogd should maintain to num. If svlogd sees more that num old log files
in log after log file rotation, it deletes the oldest one. Default is 10.
If num is zero, svlogd doesn’t remove old log files.
- sets the minimum
number of old log files svlogd should maintain to min. min must be less
than num. If min is set, and svlogd cannot write to current because the
filesystem is full, and it sees more than min old log files, it deletes
the oldest one.
- sets the maximum age of the current log file when
svlogd should rotate the current log file to timeout seconds. If current
is timeout seconds old, and is not empty, svlogd forces log file rotation.
- tells svlogd to feed each recent log file through processor
(see above) on log file rotation. By default log files are not processed.
- tells svlogd to transmit the first len characters of selected
log messages to the IP address a.b.c.d, port number port. If port isn’t set,
the default port for syslog is used (514). len can be set through the -l
option, see below. If svlogd has trouble sending udp packets, it writes
error messages to the log directory. Attention: logging through udp is unreliable,
and should be used in private networks only.
- is the same as
the u line above, but the log messages are no longer written to the log
directory, but transmitted through udp only. Error messages from svlogd
concerning sending udp packages still go to the log directory.
svlogd to prefix each line to be written to the log directory, to standard
error, or through UDP, with prefix.
If a line starts with a -, +, e, or E,
svlogd matches the first len characters of each log message against pattern
and acts accordingly:
- the log message is deselected.
log message is selected.
- the log message is selected to be printed
to standard error.
- the log message is deselected to be printed
to standard error.
Initially each line is selected to be written to log/current.
Deselected log messages are discarded from log. Initially each line is deselected
to be written to standard err. Log messages selected for standard error
are written to standard error.
svlogd matches a log message
against the string pattern as follows:
pattern is applied to the log message
one character by one, starting with the first. A character not a star (‘‘*’’)
and not a plus (‘‘+’’) matches itself. A plus matches the next character in
pattern in the log message one or more times. A star before the end of pattern
matches any string in the log message that does not include the next character
in pattern. A star at the end of pattern matches any string.
added by svlogd are not considered part of the log message.
An svlogd pattern
is not a regular expression. For example consider a log message like this
2005-12-18_09:13:50.97618 tcpsvd: info: pid 1977 from 10.4.1.14
The following pattern doesn’t match
because the first star matches up to the first p in tcpsvd, and then the
match fails because i is not s. To match this log message, you can use a
pattern like this instead
-*: *: pid *
If svlogd is sent a HUP signal, it closes and reopens
all logs, and updates their configuration according to log/config. If svlogd
has trouble opening a log directory, it prints a warning, and discards
this log directory. If svlogd is unable to open all log directories given
at the command line, it exits with an error.
- timestamp. Prefix each selected line with a precise timestamp
(see the daemontools’ tai64n program) when writing to log or to standard
- timestamp. Prefix each selected line with a human readable, sortable
UTC timestamp of the form YYYY-MM-DD_HH:MM:SS.xxxxx when writing to log or
to standard error.
- timestamp. Prefix each selected line with a human
readable, sortable UTC timestamp of the form YYYY-MM-DDTHH:MM:SS.xxxxx when
writing to log or to standard error.
- -r c
- replace. c must be a single character.
Replace non-printable characters in log messages with c. Characters are replaced
before pattern matching is applied.
- -R xyz
- replace charset. Additionally to
non-printable characters, replace all characters found in xyz with c (default
- -l len
- line length. Pattern matching applies to the first len characters
of a log message only. Default is 1000.
- -b buflen
- buffer size. Set the size
of the buffer svlogd uses when reading from standard input and writing
to logs to buflen. Default is 1024. buflen must be greater than len. For svlogd
instances that process a lot of data in short time, the buffer size should
be increased to improve performance.
- verbose. Print verbose messages to
If svlogd is sent a TERM signal,
or if it sees end-of-file on standard input, it stops reading standard input,
processes the data in the buffer, waits for all processor subprocesses
to finish if any, and exits 0 as soon as possible.
If svlogd is sent an
ALRM signal, it forces log file rotation for all logs with a non empty
current log file.
sv(8), runsv(8), chpst(8), runit(8), runit-init(8),
Gerrit Pape <email@example.com>
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