ossp-pkg/l2/TODO
1.13
OSSP L2
=======
Improvement: return L2_ERR_XXX instead of just a single L2_ERROR
Idea:
l2_handler_t:
- function pointers
- sizeof(handler struct)
- table of config callsbacks
which use offsetof into handler struct
Auf diese Weise ist l2_channel_setparams aus API
draussen und..
Timeplan
--------
o M1
- fixed C API
- established build environment
o M2
- implemented C API
- fixed C++ API
o M3
- implemented C++ API
- documented C API
- documented C++ API
- release version 0.9.0
o M4
- release version 1.0.0
ATTENTION
---------
o hook_write's should perhaps receive a nul-termined string
instead of buf+size, because syslog else has to re-buffer it.
QUESTIONS
---------
o Should the following line copy the string or just use the reference?
L2_PARAM_SET(pa[0], ident, CHARPTR, &cfg->pszIdent);
BRAINSTORMING
-------------
Channel Handler Configuration:
o l2_handler_null
- no configuration at all
o l2_handler_fd
- mode="unix|stdio"
- fd=int|FILE*
o l2_handler_file
- mode="unix|stdio"
- path=char*
- append="yes|no"
o l2_handler_pipe
- url="prg:/path/to/program"
- fd=int
o l2_handler_socket
- url="tcp://hostname:port"
- fd=int
o l2_handler_syslog
- ident=char*
o l2_handler_filter
- pattern=char*
o l2_handler_prefix
- prefix=char*
o l2_handler_buffer
- size=size_t
o all output channels
- should they have downstream, or be true endpoints?
o l2_ch_socket
- write should handle partial send()
thus check the return of send
o l2_ch_buffer
- write() must implicitly flush() when incoming
data is larger than remaining buffer capacity
Stream Members:
o channels static array
- consider dynamic
Documentation:
o buffer
user needs to know how a buffer object behaves in
relation to up/downstream channels. When does it
pass its data to the next channel, when does it
erase, what happens to its data when it is over
written or flushed...
o syslog
many options need docu, and we should mention to
the user that more info is found in the man page
for syslog(), because after all that is what is
doing all the work in our implementation. Also,
can we really properly document these features
if they change from one system's syslog to the next?
o errors
when a channel fails during an operation, how
does it report this? How should a user interpret
the error message or other data? Do we need more
accurate or detailed error messages in the channel
code? When a channel fails, does it continue
passing data on to downstream channels? Is it
corrupt data?
Braindump:
- debugging is special case of logging
- tracing is special case of debugging
Kanalen:
o Syslog Kanal
- Trim down to what will be used, right now the
channel supports ALL functionality through syslog(3)
License:
- ISC/MIT/BSD
Sprache:
- C++
- C
Aufbau:
1. Layer C++ API log.hpp, log.cpp
2. Layer C API log.h log.c
3. Layer C Backend backend.h backend.c
- "make striptease"
- optimierung:
log(..)
{
}
:
log(....);
:
API Levels:
- PANIC (-> LOG_EMERG)
- CRITICAL (-> LOG_CRIT)
- ERROR (-> LOG_ERR)
- WARNING
- NOTICE
- INFO
- TRACE (-> LOG_DEBUG)
- DEBUG (-> LOG_DEBUG)
- ALERT
Level Entscheidungen:
>= (default)
<=
=
;
*
Backend Channels:
1 Level -> N Channels
- file (append)
- program (stdin)
- syslog
- stderr/stdout
- null (discard, nicht nur /dev/null)
- filedescriptor (escape/ext)
- callback function
Log Messages:
- raw
- optional prefixes (inclusive order):
string
facility
level
timestamp
pid
(tid)
- errno (like syslog %m)
- eigene %{foo}x mit callback function mit context
- automatisch: number -> string mapping (fuer error strings)
- __FILE__, __LINE__, (__FUNCTION__)
Configuration:
- ueber C/C++ API
- zusaetzlich Config-File
1. /etc/liblog.conf
2. (in ., .., ../..)
3. $HOME/.liblog.conf
- !debug -> !code
API C (ala MM):
- reentrant: log_xxx
- non-reentrant: Log_xxx
Message Filtering/Masking:
- facility und/oder levels und/oder wildcard pattern
API Using:
- C++:
LogManager logm;
logm.debug1("test");
logm.configure("
- C:
log lh;
lh = log_init(LOG_CFGFILE|LOG_CFGPARENT|LOG_XXX|..., "foo" (=facility));
log_configure(lh, "foo", LOG_WARN|LOG_LESSER, null);
log_cb(lh, "x", func, ctx);
int func(void *ctx, char *str, ...);
log_msg(lh, LOG_WARN, "..%{foo}x %s...%E..", cp);
log_dbg(lh, "..%{foo}x %s...%E..", cp);
log_kill(lh);
- Buffered I/O:
fuer manche channels non-buffered (debug, errors)
fuer manche andere aber buffered (access log, performance)
loesung: I/O ueber callbacks (3x: open, write, close) z.B. RRDTool
- Varargs:
log ist nur wrapper fuer vlog
- Error Handling:
o log kein Return Code
o aber error callback function (dadrin in C++: throw, in C: exit)
- Newline Handling:
option fuer channel: \r, \r\n, \n oder gleich string
und moeglichkeit gar nix (string="")
- Perhaps:
optionally reopen logfile on each write
- An optional syslog(3) compatible API for converting syslog-only based
applications (like sendmail) to (restricted) liblog-based applications.
- Ein Wort noch zu variablen Argumentlisten in cpp-Makros: gcc
unterstützt dies in in der GNU- und der C99-Ausführung. Das heißt,
der "..." Parameter kann im Makro respektive über "args" und über
"__VA_ARGS__" angesprochen werden. Wichtig ist dabei, daß "..."
nicht leer sein -- also kein Argument enthalten -- darf, da sonst
der Präprocessor an einem eventuell vorhandenen Komma scheitert.
Dies kann beim gcc durch Voranstellen von "##" vor dem "__VA_ARGS__"
umgangen werden. Ouch.
Beide Erweiterungen sind derzeit nicht aktiv, wenn mit -ansi
compiliert wird. Explizit anschalten läßt sich die standard-konforme
Erweiterung über "-std=c9x", bzw. "-std=c99" bei neueren gccs.