19 Errors and debug
19.1 Error reporting
19.1.1 Initialization
Clixon core applications typically have a command-line option controlling the logs as follows:
- -l <option>
Log on (s)yslog, std(e)rr, std(o)ut or (f)ile. Syslog is default. If foreground, then syslog and stderr is default. Filename is given after -f as follows:
-lf<file>.
An example of a clixon error as it may appear in a syslog:
Mar 24 10:30:48 Alarik clixon_restconf[3993]: clixon_restconf openssl: 3993 Started
In C-code, clixon error and logging is initialized by clixon_log_init:
clixon_log_init(h, prefix, upto, flags);
where:
prefix: appears first in the error string
upto: log priority as defined by syslog(3), eg: LOG_DEBUG, LOG_INFO,..
flags: a bitmask of where logs appear, values are:
CLIXON_LOG_STDERR,_STDOUT,_SYSLOG,_FILE.
19.1.2 Error call
An error is typically called by clixon_err() and a return value of -1 as follows:
clixon_err(category, errno, format, ...)
return -1;
where:
category is an error “category” including for example “yang”, “xml” See enum clixon_err for more examples.
errno if given, usually errors as given by
errno.hformat A variable arg string describing the error.
19.1.3 CLI Errors
There are several types of error messages in the CLI. The first class is “syntax” errors with things like:
cli> command
CLI syntax error: "foo": Unknown command
cli>
These are errors immediately detected by the CLIgen parser and are internally generated in CLIgen. Errors include command, syntax and type checking. They are shown on stderr, the CLI continues, without logging.
A second type of errors are “semantic” errors detected when processing CLI callbacks. These errors are more heavyweight than syntax errors and are declared in code using standard clixon Error call. They are logged and can be directed to syslog, and are by default printed on stderr. The CLI continues after the error message is printed. Typical places are user callbacks, backend rpc errors, validation, etc, either system-defined or user-defined callbacks. They are on the form:
cli> command
Nov 15 15:42:56: acl_get_list: 334: Yang error: no ACLs defined
CLI command error
cli>
A third class of CLI errors are similar to the previous class but quits the CLI:
cli> command
Nov 15 15:42:56: acl_get_list: 334: Yang error: no ACLs defined
sh#
These errors are typically due to system functions failing in a fatal way.
19.1.4 Error categories
An application can specialize error handling for a specific category by using clixon_err_cat_reg() and a log callback. Example:
/* Clixon error category log callback
* @param[in] handle Application-specific handle
* @param[out] cb Read log/error string into this buffer
*/
static int
my_log_cb(void *handle,
cbuf *cb)
{
cprintf(cb, "Myerror");
return 0;
}
main(){
...
/* Register error callback for category */
clixon_err_cat_reg(OE_SSL, h, openssl_cat_log_cb);
In this example, “Myerror” will appear in the log string.
19.2 Debugging
19.2.1 Debug flags
Each clixon application has a -D <level> command-line option to enable debug flags when starting a program. Levels can be combined and use either symbolic or numerical values. Example:
clixon_cli -D default -D detail
Levels are separated into subject-area and detail.
The subject-area levels are the following:
defaultDefault logsmsgIn/out messages and datastore readsinitInitializationxmlXML logsxpathXPath processing logsyangYANG processing logsbackendBackend-specific processingcliCLI-frontendnetconfNetconf-frontendrestconfRestconf-frontendsnmpSNMP-frontendnacmNetconf access control modelprocProcess handlingdatastoreDatastore handlingeventEvent handlingrpcRPC handlingrpcNotification streamsappApplication-specific handling, ie any application using clixon can use thisapp2Application-specific 2app3Application-specific 3allAll subject-area flags
The detail area levels are the following:
detailDetail loggingdetail2Extra detailsdetail3Probably more detail than you want
You can combine flags, so that, for example -D 5 means default + detailed, but no packet debugs. Similarly, some messages require multiple flags, like XML + DETAIL would be -D 20.
You can direct the debug logs using the -l <option> as follows:
s: sysloge: stderro: stdoutn: nonef: file, followed by a filename, eg-f/tmp/foo
Example:
clixon_backend -D 5 -f/tmp/log.txt
19.2.2 Change debug
You can also change debug level in run-time in different ways. For example, using netconf to change debug level in backend:
echo "<rpc username=\"root\" xmlns=\"urn:ietf:params:xml:ns:netconf:base:1.0\"><debug xmlns=\"http://clicon.org/lib\"><level>1</level></debug></rpc>]]>]]>" | clixon_netconf -q0
In this example, netconf is run using EOM encoding and does not require hello:s.
Using curl to change debug in backend via the restconf daemon:
curl -Ssik -X POST -H "Content-Type: application/yang-data+json" http://localhost/restconf/operations/clixon-lib:debug -d '{"clixon-lib:input":{"level":1}}'
19.2.3 Debugger
Enable debugging when configuring (compile-time):
./configure --enable-debug
which includes symbol table info so that you can make breakpoints on functions(output is omitted):
> sudo gdb clixon_backend
(gdb) run -FD 1 -l e
Starting program: /usr/local/sbin/clixon_backend -FD 1 -l e
(gdb) b main
Breakpoint 1 at 0x55555555bcea: file backend_main.c, line 492.
(gdb) where
#0 main (argc=5, argv=0x7fffffffe4e8) at backend_main.c:492
In the example, the backend runs in the foreground(-F), runs with debug level 1 and directs the debug messages to stderr.
19.2.4 Valgrind and callgrind
Examples of using valgrind for memeory checks:
valgrind --leak-check=full --show-leak-kinds=all clixon_netconf -qf /tmp/myconf.xml -y /tmp/my.yang
Example of using callgrind for profiling:
LD_BIND_NOW=y valgrind --tool=callgrind clixon_netconf -qf /tmp/myconf.xml -y /tmp/my.yang
sudo kcachegrind
Or massif for memory usage:
valgrind --tool=massif clixon_netconf -qf /tmp/myconf.xml -y /tmp/my.yang
massif-visualizer
19.3 Customization
Errors, logs and denugs can be customized by plugins via the ca_errmsg API.
Customized errors applies to all clixon applications. For example, logs for the backend and return output in the CLI.
The API provides a single function callback which can be used in a various ways. The example shows one simple way as described here.
First define an error message callback as part of the plugin initialization:
static clixon_plugin_api api = {
...
.ca_errmsg=example_cli_errmsg,
};
The errmsg callback has many parameters. Some are not always applicable:
h : Clixon handle
fn : name of source file (only err)
line: line of source file (only err)
type: log, err or debug (actual types called
LOG_TYPE_LOGetc)category: Error category (see Section Error categories) (only err)
suberr: Error number, eg
errno(only err)xerr: XML structure, either NETCONF (for err) or just generic XML (debug, log)
format: Format string similar to printf
ap: Variable argument list assciated with format. Similar to vprintf
cbmsg: Customized error message as output of the function. If NULL, use regular message.
A simple way to replace all error messages would be:
int
example_cli_errmsg(clixon_handle h,
const char *fn,
const int line,
enum clixon_log_type type,
int *category,
int *suberr,
cxobj *xerr,
const char *format,
va_list ap,
cbuf **cbmsg)
{
if (type != LOG_TYPE_ERR)
return 0;
if ((*cberr = cbuf_new()) == NULL){
fprintf(stderr, "cbuf_new: %s\n", strerror(errno));
return -1;
}
cprintf(*cberr, "My error message");
*category = 0;
suerr = 0;
retval = 0;
done:
return retval;
}
All error message are now:
My error message
Which may not be useful.
More logic needs to be added, for example a more advanced classification and translation/changing of error messages. Any field can be used to classify. The format string and the ap objects may be translated/converted which is out-of-scope of this document.
19.3.1 Indirection
The customized callback may also be changed dynamically. The example shows an extra indirection layer, where a new function is registered before a call, and deregistered after.
Please see the main example, where example_cli_errmsg just dispatches the call to a dynamic myerrmsg.