[libvirt] [PATCH 4/4] log: update docs for daemons to improve user understanding
Erik Skultety
eskultet at redhat.com
Mon Apr 23 06:49:00 UTC 2018
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 at redhat.com>
> ---
> src/locking/test_virtlockd.aug.in | 2 +-
> src/locking/virtlockd.conf | 70 +++++++++++++++++++++++++++----------
> src/logging/test_virtlogd.aug.in | 2 +-
> src/logging/virtlogd.conf | 73 ++++++++++++++++++++++++++++-----------
> src/remote/libvirtd.conf | 70 +++++++++++++++++++++++--------------
> src/remote/test_libvirtd.aug.in | 2 +-
> 6 files changed, 150 insertions(+), 69 deletions(-)
>
> diff --git a/src/locking/test_virtlockd.aug.in b/src/locking/test_virtlockd.aug.in
> index ad75286be6..f2f6979ef5 100644
> --- a/src/locking/test_virtlockd.aug.in
> +++ b/src/locking/test_virtlockd.aug.in
> @@ -3,7 +3,7 @@ module Test_virtlockd =
>
> test Virtlockd.lns get conf =
> { "log_level" = "3" }
> - { "log_filters" = "3:remote 4:event" }
> + { "log_filters" = "1:locking 4:object 4:json 4:event 1:util" }
> { "log_outputs" = "3:syslog:virtlockd" }
> { "max_clients" = "1024" }
> { "admin_max_clients" = "5" }
> diff --git a/src/locking/virtlockd.conf b/src/locking/virtlockd.conf
> index 1a2b27d0b9..29cefbd74a 100644
> --- a/src/locking/virtlockd.conf
> +++ b/src/locking/virtlockd.conf
> @@ -8,47 +8,79 @@
>
> # 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
So is it really worth mentioning to use debug with journal, since there are
only limitations? How about encouraging to use e.g. file for debug logs and
journald for 3+.
> +# WARNING: will be logged.
> +#
> +# WARNING: USE OF THIS IS STRONGLY DISCOURAGED.
> #log_level = 3
>
> # Logging filters:
> # A filter allows to select a different logging level for a given category
> -# of logs
> -# The format for a filter is one of:
> -# x:name
> -# x:+name
> -# where name is a string which is matched against source file name,
> -# e.g., "remote", "qemu", or "util/json", the optional "+" prefix
> -# tells libvirt to log stack trace for each message matching name,
> -# and x is the minimal level where matching messages should be logged:
> +# of logs. The format for a filter is one of:
> +#
> +# level:match
> +# level:+match
> +#
> +# 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
What about users who use libvirt from a distro package, they don't necessary
need to have the sources installed, more importantly they shouldn't really have
to care about the sources to successfully set up logging.
Reporting the categories in some consumable way that could be generated
automatically during libvirt build and shipped afterwards has been on my radar
for quite some time...
> +# 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
> # 4: ERROR
> #
> -# 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
> +# 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:
> #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
>
> # Logging filters:
> # A filter allows to select a different logging level for a given category
> -# of logs
> -# The format for a filter is one of:
> -# x:name
> -# x:+name
> -# where name is a string which is matched against source file name,
> -# e.g., "remote", "qemu", or "util/json", the optional "+" prefix
> -# tells libvirt to log stack trace for each message matching name,
> -# and x is the minimal level where matching messages should be logged:
> +# of logs. The format for a filter is one of:
> +#
> +# level:match
> +# level:+match
> +#
> +# 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
> # 4: ERROR
> #
> -# 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
> +# rest of the util code:
^This paragraph is a copy-paste from virtlockd bits, so this needs to be fixed.
> #
> -# 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:logging 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
> -# x:journald
> -# ouput to the systemd journal
> -# 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 virtlogd 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:
"under libvirt indent" - this doesn't reflect the reality below...
there's one more occurrence of this within this patch...
Erik
More information about the libvir-list
mailing list