Posts Tagged ‘facility’

How to enable HaProxy logging to a separate log /var/log/haproxy.log / prevent HAProxy duplicate messages to appear in /var/log/messages

Wednesday, February 19th, 2020

Reading Time: 9minutes

haproxy-logging-basics-how-to-log-to-separate-file-prevent-duplicate-messages-haproxy-haproxy-weblogo-squares
haproxy  logging can be managed in different form the most straight forward way is to directly use /dev/log either you can configure it to use some log management service as syslog or rsyslogd for that.

If you don't use rsyslog yet to install it: 

# apt install -y rsyslog

Then to activate logging via rsyslogd we can should add either to /etc/rsyslogd.conf or create a separte file and include it via /etc/rsyslogd.conf with following content:
 

Enable haproxy logging from rsyslogd


Log haproxy messages to separate log file you can use some of the usual syslog local0 to local7 locally used descriptors inside the conf (be aware that if you try to use some wrong value like local8, local9 as a logging facility you will get with empty haproxy.log, even though the permissions of /var/log/haproxy.log are readable and owned by haproxy user.

When logging to a local Syslog service, writing to a UNIX socket can be faster than targeting the TCP loopback address. Generally, on Linux systems, a UNIX socket listening for Syslog messages is available at /dev/log because this is where the syslog() function of the GNU C library is sending messages by default. To address UNIX socket in haproxy.cfg use:

log /dev/log local2 


If you want to log into separate log each of multiple running haproxy instances with different haproxy*.cfg add to /etc/rsyslog.conf lines like:

local2.* -/var/log/haproxylog2.log
local3.* -/var/log/haproxylog3.log


One important note to make here is since rsyslogd is used for haproxy logging you need to have enabled in rsyslogd imudp and have a UDP port listener on the machine.

E.g. somewhere in rsyslog.conf or via rsyslog include file from /etc/rsyslog.d/*.conf needs to have defined following lines:

$ModLoad imudp
$UDPServerRun 514


I prefer to use external /etc/rsyslog.d/20-haproxy.conf include file that is loaded and enabled rsyslogd via /etc/rsyslog.conf:

# vim /etc/rsyslog.d/20-haproxy.conf

$ModLoad imudp
$UDPServerRun 514​
local2.* -/var/log/haproxy2.log


It is also possible to produce different haproxy log output based on the severiy to differentiate between important and less important messages, to do so you'll need to rsyslog.conf something like:
 

# Creating separate log files based on the severity
local0.* /var/log/haproxy-traffic.log
local0.notice /var/log/haproxy-admin.log

 

Prevent Haproxy duplicate messages to appear in /var/log/messages

If you use local2 and some default rsyslog configuration then you will end up with the messages coming from haproxy towards local2 facility producing doubled simultaneous records to both your pre-defined /var/log/haproxy.log and /var/log/messages on Proxy servers that receive few thousands of simultanous connections per second.
This is a problem since doubling the log will produce too much data and on systems with smaller /var/ partition you will quickly run out of space + this haproxy requests logging to /var/log/messages makes the file quite unreadable for normal system events which are so important to track clearly what is happening on the server daily.

To prevent the haproxy duplicate messages you need to define somewhere in rsyslogd usually /etc/rsyslog.conf local2.none near line of facilities configured to log to file:

*.info;mail.none;authpriv.none;cron.none;local2.none     /var/log/messages

This configuration should work but is more rarely used as most people prefer to have haproxy log being written not directly to /dev/log which is used by other services such as syslogd / rsyslogd.

To use /dev/log to output logs from haproxy configuration in global section use config like:
 

global
        log /dev/log local2 debug
        chroot /var/lib/haproxy
        stats socket /run/haproxy/admin.sock mode 660 level admin
        stats timeout 30s
        user haproxy
        group haproxy
        daemon

The log global directive basically says, use the log line that was set in the global section for whole config till end of file. Putting a log global directive into the defaults section is equivalent to putting it into all of the subsequent proxy sections.

Using global logging rules is the most common HAProxy setup, but you can put them directly into a frontend section instead. It can be useful to have a different logging configuration as a one-off. For example, you might want to point to a different target Syslog server, use a different logging facility, or capture different severity levels depending on the use case of the backend application. 

Insetad of using /dev/log interface that is on many distributions heavily used by systemd to store / manage and distribute logs,  many haproxy server sysadmins nowdays prefer to use rsyslogd as a default logging facility that will manage haproxy logs.
Admins prefer to use some kind of mediator service to manage log writting such as rsyslogd or syslog, the reason behind might vary but perhaps most important reason is  by using rsyslogd it is possible to write logs simultaneously locally on disk and also forward logs  to a remote Logging server  running rsyslogd service.

Logging is defined in /etc/haproxy/haproxy.cfg or the respective configuration through global section but could be also configured to do a separate logging based on each of the defined Frontend Backends or default section. 
A sample exceprt from this section looks something like:

#———————————————————————
# Global settings
#———————————————————————
global
    log         127.0.0.1 local2

    chroot      /var/lib/haproxy
    pidfile     /var/run/haproxy.pid
    maxconn     4000
    user        haproxy
    group       haproxy
    daemon

    # turn on stats unix socket
    stats socket /var/lib/haproxy/stats

#———————————————————————
defaults
    mode                    tcp
    log                     global
    option                  tcplog
    #option                  dontlognull
    #option http-server-close
    #option forwardfor       except 127.0.0.0/8
    option                  redispatch
    retries                 7
    #timeout http-request    10s
    timeout queue           10m
    timeout connect         30s
    timeout client          20m
    timeout server          10m
    #timeout http-keep-alive 10s
    timeout check           30s
    maxconn                 3000

 

 

# HAProxy Monitoring Config
#———————————————————————
listen stats 192.168.0.5:8080                #Haproxy Monitoring run on port 8080
    mode http
    option httplog
    option http-server-close
    stats enable
    stats show-legends
    stats refresh 5s
    stats uri /stats                            #URL for HAProxy monitoring
    stats realm Haproxy\ Statistics
    stats auth hproxyauser:Password___          #User and Password for login to the monitoring dashboard

 

#———————————————————————
# frontend which proxys to the backends
#———————————————————————
frontend ft_DKV_PROD_WLPFO
    mode tcp
    bind 192.168.233.5:30000-31050
    option tcplog
    log-format %ci:%cp\ [%t]\ %ft\ %b/%s\ %Tw/%Tc/%Tt\ %B\ %ts\ %ac/%fc/%bc/%sc/%rc\ %sq/%bq
    default_backend Default_Bakend_Name


#———————————————————————
# round robin balancing between the various backends
#———————————————————————
backend bk_DKV_PROD_WLPFO
    mode tcp
    # (0) Load Balancing Method.
    balance source
    # (4) Peer Sync: a sticky session is a session maintained by persistence
    stick-table type ip size 1m peers hapeers expire 60m
    stick on src
    # (5) Server List
    # (5.1) Backend
    server Backend_Server1 10.10.10.1 check port 18088
    server Backend_Server2 10.10.10.2 check port 18088 backup


The log directive in above config instructs HAProxy to send logs to the Syslog server listening at 127.0.0.1:514. Messages are sent with facility local2, which is one of the standard, user-defined Syslog facilities. It’s also the facility that our rsyslog configuration is expecting. You can add more than one log statement to send output to multiple Syslog servers.

Once rsyslog and haproxy logging is configured as a minumum you need to restart rsyslog (assuming that haproxy config is already properly loaded):

# systemctl restart rsyslogd.service

To make sure rsyslog reloaded successfully:

systemctl status rsyslogd.service


Restarting HAproxy

If the rsyslogd logging to 127.0.0.1 port 514 was recently added a HAProxy restart should also be run, you can do it with:
 

# /usr/sbin/haproxy -f /etc/haproxy/haproxy.cfg -D -p /var/run/haproxy.pid -sf $(cat /var/run/haproxy.pid)


Or to restart use systemctl script (if haproxy is not used in a cluster with corosync / heartbeat).

# systemctl restart haproxy.service

You can control how much information is logged by adding a Syslog level by

    log         127.0.0.1 local2 info


The accepted values are the standard syslog security level severity:

Value Severity Keyword Deprecated keywords Description Condition
0 Emergency emerg panic System is unusable A panic condition.
1 Alert alert   Action must be taken immediately A condition that should be corrected immediately, such as a corrupted system database.
2 Critical crit   Critical conditions Hard device errors.
3 Error err error Error conditions  
4 Warning warning warn Warning conditions  
5 Notice notice   Normal but significant conditions Conditions that are not error conditions, but that may require special handling.
6 Informational info   Informational messages  
7 Debug debug   Debug-level messages Messages that contain information normally of use only when debugging a program.

 

Logging only errors / timeouts / retries and errors is done with option:

Note that if the rsyslog is configured to listen on different port for some weird reason you should not forget to set the proper listen port, e.g.:
 

  log         127.0.0.1:514 local2 info

option dontlog-normal

in defaults or frontend section.

You most likely want to enable this only during certain times, such as when performing benchmarking tests.

(or log-format-sd for structured-data syslog) directive in your defaults or frontend
 

Haproxy Logging shortly explained


The type of logging you’ll see is determined by the proxy mode that you set within HAProxy. HAProxy can operate either as a Layer 4 (TCP) proxy or as Layer 7 (HTTP) proxy. TCP mode is the default. In this mode, a full-duplex connection is established between clients and servers, and no layer 7 examination will be performed. When in TCP mode, which is set by adding mode tcp, you should also add option tcplog. With this option, the log format defaults to a structure that provides useful information like Layer 4 connection details, timers, byte count and so on.

Below is example of configured logging with some explanations:

Log-format "%ci:%cp [%t] %ft %b/%s %Tw/%Tc/%Tt %B %ts %ac/%fc/%bc/%sc/%rc %sq/%bq"

haproxy-logged-fields-explained
Example of Log-Format configuration as shown above outputted of haproxy config:

Log-format "%ci:%cp [%tr] %ft %b/%s %TR/%Tw/%Tc/%Tr/%Ta %ST %B %CC %CS %tsc %ac/%fc/%bc/%sc/%rc %sq/%bq %hr %hs %{+Q}r"

haproxy_http_log_format-explained1

To understand meaning of this abbreviations you'll have to closely read  haproxy-log-format.txt. More in depth info is to be found in HTTP Log format documentation


haproxy_logging-explained

Logging HTTP request headers

HTTP request header can be logged via:
 

 http-request capture

frontend website
    bind :80
    http-request capture req.hdr(Host) len 10
    http-request capture req.hdr(User-Agent) len 100
    default_backend webservers


The log will show headers between curly braces and separated by pipe symbols. Here you can see the Host and User-Agent headers for a request:

192.168.150.1:57190 [20/Dec/2018:22:20:00.899] website~ webservers/server1 0/0/1/0/1 200 462 – – —- 1/1/0/0/0 0/0 {mywebsite.com|Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Ubuntu Chromium/71.0.3578.80 } "GET / HTTP/1.1"

 

Haproxy Stats Monitoring Web interface


Haproxy is having a simplistic stats interface which if enabled produces some general useful information like in above screenshot, through which
you can get a very basic in browser statistics and track potential issues with the proxied traffic for all configured backends / frontends incoming outgoing
network packets configured nodes
 experienced downtimes etc.

haproxy-statistics-report-picture

The basic configuration to make the stats interface accessible would be like pointed in above config for example to enable network listener on address
 

https://192.168.0.5:8080/stats


with hproxyuser / password config would be:

# HAProxy Monitoring Config
#———————————————————————
listen stats 192.168.0.5:8080                #Haproxy Monitoring run on port 8080
    mode http
    option httplog
    option http-server-close
    stats enable
    stats show-legends
    stats refresh 5s
    stats uri /stats                            #URL for HAProxy monitoring
    stats realm Haproxy\ Statistics
    stats auth hproxyauser:Password___          #User and Password for login to the monitoring dashboard

 

 

Sessions states and disconnect errors on new application setup

Both TCP and HTTP logs include a termination state code that tells you the way in which the TCP or HTTP session ended. It’s a two-character code. The first character reports the first event that caused the session to terminate, while the second reports the TCP or HTTP session state when it was closed.

Here are some essential termination codes to track in for in the log:
 

Here are some termination code examples most commonly to see on TCP connection establishment errors:

Two-character code    Meaning
—    Normal termination on both sides.
cD    The client did not send nor acknowledge any data and eventually timeout client expired.
SC    The server explicitly refused the TCP connection.
PC    The proxy refused to establish a connection to the server because the process’ socket limit was reached while attempting to connect.


To get all non-properly exited codes the easiest way is to just grep for anything that is different from a termination code –, like that:

tail -f /var/log/haproxy.log | grep -v ' — '


This should output in real time every TCP connection that is exiting improperly.

There’s a wide variety of reasons a connection may have been closed. Detailed information about all possible termination codes can be found in the HAProxy documentation.
To get better understanding a very useful reading to haproxy Debug errors with  is in haproxy-logging.txt in that small file are collected all the cryptic error messages codes you might find in your logs when you're first time configuring the Haproxy frontend / backend and the backend application behind.

Another useful analyze tool which can be used to analyze Layer 7 HTTP traffic is halog for more on it just google around.

How to build Linux logging bash shell script write_log, logging with Named Pipe buffer, Simple Linux common log files logging with logger command

Monday, August 26th, 2019

Reading Time: 6minutes

how-to-build-bash-script-for-logging-buffer-named-pipes-basic-common-files-logging-with-logger-command

Logging into file in GNU / Linux and FreeBSD is as simple as simply redirecting the output, e.g.:
 

echo "$(date) Whatever" >> /home/hipo/log/output_file_log.txt


or with pyping to tee command

 

echo "$(date) Service has Crashed" | tee -a /home/hipo/log/output_file_log.txt


But what if you need to create a full featured logging bash robust shell script function that will run as a daemon continusly as a background process and will output
all content from itself to an external log file?
In below article, I've given example logging script in bash, as well as small example on how a specially crafted Named Pipe buffer can be used that will later store to a file of choice.
Finally I found it interesting to mention few words about logger command which can be used to log anything to many of the common / general Linux log files stored under /var/log/ – i.e. /var/log/syslog /var/log/user /var/log/daemon /var/log/mail etc.
 

1. Bash script function for logging write_log();


Perhaps the simplest method is just to use a small function routine in your shell script like this:
 

write_log()
LOG_FILE='/root/log.txt';
{
  while read text
  do
      LOGTIME=`date "+%Y-%m-%d %H:%M:%S"`
      # If log file is not defined, just echo the output
      if [ “$LOG_FILE” == “” ]; then
    echo $LOGTIME": $text";
      else
        LOG=$LOG_FILE.`date +%Y%m%d`
    touch $LOG
        if [ ! -f $LOG ]; then echo "ERROR!! Cannot create log file $LOG. Exiting."; exit 1; fi
    echo $LOGTIME": $text" | tee -a $LOG;
      fi
  done
}

 

  •  Using the script from within itself or from external to write out to defined log file

 

echo "Skipping to next copy" | write_log

 

2. Use Unix named pipes to pass data – Small intro on what is Unix Named Pipe.


Named Pipe –  a named pipe (also known as a FIFO (First In First Out) for its behavior) is an extension to the traditional pipe concept on Unix and Unix-like systems, and is one of the methods of inter-process communication (IPC). The concept is also found in OS/2 and Microsoft Windows, although the semantics differ substantially. A traditional pipe is "unnamed" and lasts only as long as the process. A named pipe, however, can last as long as the system is up, beyond the life of the process. It can be deleted if no longer used.
Usually a named pipe appears as a file, and generally processes attach to it for IPC.

 

Once named pipes were shortly explained for those who hear it for a first time, its time to say named pipe in unix / linux is created with mkfifo command, syntax is straight foward:
 

mkfifo /tmp/name-of-named-pipe


Some older Linux-es with older bash and older bash shell scripts were using mknod.
So idea behind logging script is to use a simple named pipe read input and use date command to log the exact time the command was executed, here is the script.

 

#!/bin/bash
named_pipe='/tmp/output-named-pipe';
output_named_log='
/tmp/output-named-log.txt ';

if [ -p $named_pipe ]; then
rm -f $named_pipe
fi
mkfifo $named_pipe

while true; do
read LINE <$named_pipe
echo $(date): "$LINE" >>/tmp/output-named-log.txt
done


To write out any other script output and get logged now, any of your output with a nice currentdate command generated output write out any output content to the loggin buffer like so:

 

echo 'Using Named pipes is so cool' > /tmp/output-named-pipe
echo 'Disk is full on a trigger' > /tmp/output-named-pipe

  • Getting the output with the date timestamp

# cat /tmp/output-named-log.txt
Mon Aug 26 15:21:29 EEST 2019: Using Named pipes is so cool
Mon Aug 26 15:21:54 EEST 2019: Disk is full on a trigger


If you wonder why it is better to use Named pipes for logging, they perform better (are generally quicker) than Unix sockets.

 

3. Logging files to system log files with logger

 

If you need to do a one time quick way to log any message of your choice with a standard Logging timestamp, take a look at logger (a part of bsdutils Linux package), and is a command which is used to enter messages into the system log, to use it simply invoke it with a message and it will log your specified output by default to /var/log/syslog common logfile

 

root@linux:/root# logger 'Here we go, logging'
root@linux:/root # tail -n 3 /var/log/syslog
Aug 26 15:41:01 localhost CRON[24490]: (root) CMD (chown qscand:qscand -R /var/run/clamav/ 2>&1 >/dev/null)
Aug 26 15:42:01 localhost CRON[24547]: (root) CMD (chown qscand:qscand -R /var/run/clamav/ 2>&1 >/dev/null)
Aug 26 15:42:20 localhost hipo: Here we go, logging

 

If you have took some time to read any of the init.d scripts on Debian / Fedora / RHEL / CentOS Linux etc. you will notice the logger logging facility is heavily used.

With logger you can print out message with different priorities (e.g. if you want to write an error message to mail.* logs), you can do so with:
 

 logger -i -p mail.err "Output of mail processing script"


To log a normal non-error (priority message) with logger to /var/log/mail.log system log.

 

 logger -i -p mail.notice "Output of mail processing script"


A whole list of supported facility named priority valid levels by logger (as taken of its current Linux manual) are as so:

 

FACILITIES AND LEVELS
       Valid facility names are:

              auth
              authpriv   for security information of a sensitive nature
              cron
              daemon
              ftp
              kern       cannot be generated from userspace process, automatically converted to user
              lpr
              mail
              news
              syslog
              user
              uucp
              local0
                to
              local7
              security   deprecated synonym for auth

       Valid level names are:

              emerg
              alert
              crit
              err
              warning
              notice
              info
              debug
              panic     deprecated synonym for emerg
              error     deprecated synonym for err
              warn      deprecated synonym for warning

       For the priority order and intended purposes of these facilities and levels, see syslog(3).

 


If you just want to log to Linux main log file (be it /var/log/syslog or /var/log/messages), depending on the Linux distribution, just type', even without any shell quoting:

 

logger 'The reason to reboot the server Currently was a System security Update

 

So what others is logger useful for?

 In addition to being a good diagnostic tool, you can use logger to test if all basic system logs with its respective priorities work as expected, this is especially
useful as I've seen on a Cloud Holsted OpenXEN based servers as a SAP consultant, that sometimes logging to basic log files stops to log for months or even years due to
syslog and syslog-ng problems hungs by other thirt party scripts and programs.
To test test all basic logging and priority on system logs as expected use the following logger-test-all-basic-log-logging-facilities.sh shell script.

 

#!/bin/bash
for i in {auth,auth-priv,cron,daemon,kern, \
lpr,mail,mark,news,syslog,user,uucp,local0 \
,local1,local2,local3,local4,local5,local6,local7}

do       
# (this is all one line!)

 

for k in {debug,info,notice,warning,err,crit,alert,emerg}
do

logger -p $i.$k "Test daemon message, facility $i priority $k"

done

done

Note that on different Linux distribution verions, the facility and priority names might differ so, if you get

logger: unknown facility name: {auth,auth-priv,cron,daemon,kern,lpr,mail,mark,news, \
syslog,user,uucp,local0,local1,local2,local3,local4, \
local5,local6,local7}

check and set the proper naming as described in logger man page.

 

4. Using a file descriptor that will output to a pre-set log file


Another way is to add the following code to the beginning of the script

#!/bin/bash
exec 3>&1 4>&2
trap 'exec 2>&4 1>&3' 0 1 2 3
exec 1>log.out 2>&1
# Everything below will go to the file 'log.out':

The code Explaned

  •     Saves file descriptors so they can be restored to whatever they were before redirection or used themselves to output to whatever they were before the following redirect.
    trap 'exec 2>&4 1>&3' 0 1 2 3
  •     Restore file descriptors for particular signals. Not generally necessary since they should be restored when the sub-shell exits.

          exec 1>log.out 2>&1

  •     Redirect stdout to file log.out then redirect stderr to stdout. Note that the order is important when you want them going to the same file. stdout must be redirected before stderr is redirected to stdout.

From then on, to see output on the console (maybe), you can simply redirect to &3. For example
,

echo "$(date) : Do print whatever you want logging to &3 file handler" >&3


I've initially found out about this very nice bash code from serverfault.com's post how can I fully log all bash script actions (but unfortunately on latest Debian 10 Buster Linux  that is prebundled with bash shell 5.0.3(1)-release the code doesn't behave exactly, well but still on older bash versions it works fine.

Sum it up


To shortlysummarize there is plenty of ways to do logging from a shell script logger command but using a function or a named pipe is the most classic. Sometimes if a script is supposed to write user or other script output to a a common file such as syslog, logger command can be used as it is present across most modern Linux distros.
If you have a better ways, please drop a common and I'll add it to this article.

 

Providing website search facility with Namazu indexer

Tuesday, December 29th, 2009

Reading Time: < 1minute
I’ve given a try to a nice file indexer which uses the filesystem
to provide a search engine for all your website content.
There is a now tutorial on how to install namazu on debian provided by
debian-administration.org’s website, check it outhere