10:22 a.m.
On Fri, Apr 20, 2018 at 05:56:39PM +0100, Daniel P. Berrangé wrote:
Strongly recommend against use of the log_levels setting since it
creates overly verbose logs and has a serious performance impact.
Describe the log filter syntax better and mention use of shell
glob syntax. Also provide more realistic example of good settings
to use. The libvirtd example is biased towards QEMU, but when the
drivers split off each daemon can get its own more appropriate
example.
Signed-off-by: Daniel P. Berrangé <berrange(a)redhat.com>
---
[...]
Besides couple of ultra minor things, the core change looks good to me.
+# WARNING: USE OF THIS IS STRONGLY DISCOURAGED.
+#
+# WARNING: It outputs too much information to practically read.
+# WARNING: The "log_filters" setting is recommended instead.
+#
+# WARNING: Journald may employ rate limiting of the messages logged
+# WARNING: and thus lock up the libvirt daemon. To use the debug
+# WARNING: level with journald you have to specify it explicitly in
+# WARNING: 'log_outputs', otherwise only information level messages
+# WARNING: will be logged.
I see you said in your reply to Erik that you're going to reword the
above. That said ...
+# WARNING: USE OF THIS IS STRONGLY DISCOURAGED.
#log_level = 3
... the above bit reads slightly confusing, as it implies using
'log_level = 3' is discouraged, while (I think) you mean that use of
'log_level' in general is discouraged. Unless I'm misreading it.
[...]
-# Multiple filter can be defined in a single @filters, they just
need to be
-# separated by spaces.
+# Multiple filters can be defined in a single @filters, they just need to be
+# separated by spaces. Note that libvirt performs "first" match, i.e. if
+# there are concurrent filters, the first one that matches will be applied,
+# given the order in log_filters.
+#
+# For the virtlockd daemon, a typical need is to capture information
+# from the locking code and some of the utility code. Some utility
+# code is very verbose and is generally not desired. Taking the QEMU
+# hypervisor as an example, a suitable filter string for debugging
+# might be to turn off object, json & event logging, but enable the
OCD comment (applies to all occurrences of this block of text): Either
s/json/JSON to read as a sentence. Or I'd put them in single quotes:
'object', 'json' & 'event', 'util' to indicate
they're special.
+# rest of the util code:
#
-# e.g. to only get warning or errors from the remote layer and only errors
-# from the event layer:
-#log_filters="3:remote 4:event"
+#log_filters="1:locking 4:object 4:json 4:event 1:util"
# Logging outputs:
# An output is one of the places to save logging information
# The format for an output can be:
-# x:stderr
+# level:stderr
# output goes to stderr
-# x:syslog:name
+# level:syslog:name
# use syslog for the output and use the given name as the ident
-# x:file:file_path
+# level:file:file_path
# output to a file, with the given filepath
-# In all case the x prefix is the minimal level, acting as a filter
+# level:journald
+# output to journald logging system
+# In all cases 'level' is the minimal priority, acting as a filter
# 1: DEBUG
# 2: INFO
# 3: WARNING
# 4: ERROR
#
-# Multiple output can be defined, they just need to be separated by spaces.
-# e.g. to log all warnings and errors to syslog under the virtlockd ident:
+# Multiple outputs can be defined, they just need to be separated by spaces.
+# e.g. to log all warnings and errors to syslog under the libvirtd ident:
Super nit, pre-existing: s/e.g./E.g./ (Since it's the start of a sentence)
> #log_outputs="3:syslog:virtlockd"
> #
>
> diff --git a/src/logging/test_virtlogd.aug.in b/src/logging/test_virtlogd.aug.in
> index 744f3246af..a29e7e3730 100644
> --- a/src/logging/test_virtlogd.aug.in
> +++ b/src/logging/test_virtlogd.aug.in
> @@ -3,7 +3,7 @@ module Test_virtlogd =
>
> test Virtlogd.lns get conf =
> { "log_level" = "3" }
> - { "log_filters" = "3:remote 4:event" }
> + { "log_filters" = "1:logging 4:object 4:json 4:event
1:util" }
> { "log_outputs" = "3:syslog:virtlogd" }
> { "max_clients" = "1024" }
> { "admin_max_clients" = "5" }
> diff --git a/src/logging/virtlogd.conf b/src/logging/virtlogd.conf
> index c22b7737ef..f2078a730c 100644
> --- a/src/logging/virtlogd.conf
> +++ b/src/logging/virtlogd.conf
> @@ -8,49 +8,80 @@
>
> # Logging level: 4 errors, 3 warnings, 2 information, 1 debug
> # basically 1 will log everything possible
> +#
+# WARNING: USE OF THIS IS STRONGLY DISCOURAGED.
+#
+# WARNING: It outputs too much information to practically read.
+# WARNING: The "log_filters" setting is recommended instead.
+#
+# WARNING: Journald may employ rate limiting of the messages logged
+# WARNING: and thus lock up the libvirt daemon. To use the debug
+# WARNING: level with journald you have to specify it explicitly in
+# WARNING: 'log_outputs', otherwise only information level messages
+# WARNING: will be logged.
> +#
+# WARNING: USE OF THIS IS STRONGLY DISCOURAGED.
#log_level = 3
Here, too. I'll interpret the above as: "Using 'log_level' is strongly
discouraged". So probably: s/USE OF/USE OF `log_level`/
[...]
+#
+# where 'match' is a string which is matched against the category
+# given in the VIR_LOG_INIT() at the top of each libvirt source
+# file, e.g., "remote", "qemu", or "util.json". The
'match' in the
+# filter matches using shell wildcard syntax (see 'man glob(7)').
+# The 'match' is always treated a substring match. IOW a match
+# string 'foo' is equivalent to '*foo*'.
+#
+# If 'match' contains the optional "+" prefix, it tells libvirt
+# to log stack trace for each message matching name.
+#
+# 'level' is the minimal level where matching messages should
+# be logged:
+#
# 1: DEBUG
# 2: INFO
# 3: WARNING
@@ -370,22 +383,27 @@
# there are concurrent filters, the first one that matches will be applied,
# given the order in log_filters.
#
-# e.g. to only get warning or errors from the remote layer and only errors
-# from the event layer:
-#log_filters="3:remote 4:event"
+# A typical need is to capture information from a hypervisor driver,
+# public API entrypoints and some of the utility code. Some utility
Nit: s/entrypoint/entry points/
Thanks for the patch.
[...]
--
/kashyap