The next part of the series is, Monitoring PHP and Performance Tuning
PHP is a scripting language, which is interpreted by PHP interpreter.
You may be running a PHP file either directly using PHP Interpreter [Command line]
Or By A mediator, who is telling PHP Interpreter to execute the code. This means in the case of apahce HTTP server,
running PHP as module
running PHP as cgi/fastcgi
running PHP as fpm
You can only run one version of PHP as a module. If you are running multiple version of PHP, then you can achieve that by running PHP as FPM [Fast process manager]
Monitoring PHP running as FPM
FPM is a process manager, which runs PHP process in the background.
Same as the apache process and threads, it also manages threads whose numbers can be configured.
all configuration related values are defined in www.conf file, generally located in /etc/php-fpm.d/www.conf
How to get the status ?
to get the status you need to modify www.conf
pm.status_path = /status
and add the code in one of the virtual host or apache conf file
try to access it from a public URL or command line through curl
WARNING: - These must NOT be publicly accessible as this is a security risk.
<webhost>/status?html&full
You will get the information like this.
pid
the PID of the process
state
the state of the process (Idle, Running, …)
start time
the date and time the process has started
start since
the number of seconds since the process has started
requests
the number of requests the process has served
request duration
the duration in µs [micro seconds] of the requests
request method
the request method (GET, POST, …)
request URI
the request URI with the query string
content length
the content length of the request (only with POST)
user
the user (PHP_AUTH_USER) (or ‘-‘ if not set)
script
the main script called (or ‘-‘ if not set)
last request cpu
the %cpu the last request consumed. it’s always 0 if the process is not in Idle state because CPU calculation is done when the request processing has terminated
last request memory
the max amount of memory the last request consumed. it’s always 0 if the process is not in Idle state because memory calculation is done when the request processing has terminated
How to enable slow logs ?
You can also enable access logs and slow logs. [slow logs mean script taking more than the desired time to execute]. This value can also be set
The above value defines the number of processes running PHP scripts. This can be modified on basis of your hardware resources availbility.
REMEMBER : PHP page is handled by FPM , apart from that, any static and HTML page, or the files does not have .PHP [defined extension to handle] can be directly server by webserver.
So setting Apache conifguration is differnet compare to PHP-FPM configuration
PHP performance can be improved by storing precompiled script bytecode in shared memory, thereby removing the need for PHP to load and parse scripts on each request.
Apart from monitoring server hardware and software key variable like CPU/Memory/Disk/Process, We also require monitoring of apache logs using Zabbix to monitor all from a…
A complete guide for monitoring LAMP [Linux/Apache/Mysql/PHP] application through Zabbix and setting up email notifications. In the following section, I am going to use the…
If you scale the the hardware of a machine, it does not mean that webserver will utilize the resources accordingly. Mostly web server have a default value in terms of how much resoruce they can utilize from the machine. as, In Apache default limit of connection is 150.
We always need to modify the configuration as per the availability of resources, this is the main challenge in vertical scaling.
Monitoring Apache
To figure out the Root Cause of Load, first, you should check
In apache, there are two modules that are enabled or can be enabled,
Mod Info
Mod Status
Their information can be gathered from their handler.
<server-ip>/server-info
<server-ip>/server-status
Note: please check the module config, as, by default, these are only allowed from localhost. you can configure the setting and can access it.
WARNING: - These must NOT be publicly accessible as this is a security risk.
Server Status
<Location /server-status>
SetHandler server-status
Order deny,allow
Deny from all
Allow from my-ip-address-no-port
</Location>
This will provide current server status, server load, active request, and execution time.
TIP : To refresh this page automatically, put this at end of url ?refresh=15 this will auto load page at every 15 second
Srv
Child Server number – generation
PID
OS process ID
Acc
Number of accesses this connection / this child / this slot
M
Mode of operation
CPU
CPU usage, number of seconds
SS
Seconds since beginning of most recent request
Req
Milliseconds required to process most recent request
Conn
Kilobytes transferred this connection
Child
Megabytes transferred this child
Slot
Total megabytes transferred this slot
By Checking this page during load will provide you an idea about apache status. from above image, it is visible that the server is free to process requests.
If the number of requests is equal to the number of maximum allowed requests, then further request will get the 504 error.
Server Info
<Location /server-info>
SetHandler server-info
Order deny,allow
Deny from all
Allow from my-ip-address-no-port
</Location>
This contains configuration information about the webserver.
Server SettingsServer Version: Apache/2.4.29 (Ubuntu)
Server Built: 2021-09-28T11:01:16
Server loaded APR Version: 1.6.3
Compiled with APR Version: 1.6.3
Server loaded APU Version: 1.6.1
Compiled with APU Version: 1.6.1
Module Magic Number: 20120211:68
Hostname/port: buc.melimu.com:8001
Timeouts: connection: 300 keep-alive: 5
MPM Name: prefork
MPM Information: Max Daemons: 1500 Threaded: no Forked: yes
Server Architecture: 64-bit
Server Root: /etc/apache2
Config File: /etc/apache2/apache2.conf
Server Built With: -D APR_HAS_SENDFILE -D APR_HAS_MMAP -D APR_HAVE_IPV6 (IPv4-mapped addresses enabled) -D APR_USE_SYSVSEM_SERIALIZE -D SINGLE_LISTEN_UNSERIALIZED_ACCEPT -D APR_HAS_OTHER_CHILD -D AP_HAVE_RELIABLE_PIPED_LOGS -D HTTPD_ROOT="/etc/apache2" -D SUEXEC_BIN="/usr/lib/apache2/suexec" -D DEFAULT_PIDLOG="/var/run/apache2.pid" -D DEFAULT_SCOREBOARD="logs/apache_runtime_status" -D DEFAULT_ERRORLOG="logs/error_log" -D AP_TYPES_CONFIG_FILE="mime.types" -D SERVER_CONFIG_FILE="apache2.conf"
The most important information is
Time Out,
MPM Module [prefork / evnet / worker]
MPM information
apart from that, it contains a list of modules and their config.
Server Logs
As the config file is showing the log location,
there will be at least two files
error logs: in case web server related error
access logs: for all HTTP request
To check the data for the past, logs are most important thing to analyze. You can search for 504 request or you can lookup for errors if there are any.
Goaccess is a quite handy utility to analyze the access logs and figure out the pattern. It is available from command line as well report can be exported to HTML .
Following is the command that can be used to parse apache common format logs
Once you have checked this information, then there may be two situations
Either Everything is fine
Or we need to optimize the configuration
Optimization
We may have enough hardware capabilities but apache is not using them or we just need to optimize the configuration basis on hardware allocation.
following are the steps that can be planned
Load only required module and disable the rest, this will reduce the process memory size
Apply Disk caching for static files
Modify the value of timeout or minimize that to reduce the overhead of long-running script, if somehow, your script contains forever while loops then apache does not suffer.
Modify the MPM configuration on basis of MPM module
Memory utilization
The followingscript will help you to figure out the average memory required for a process at your server so that you can calculate the total number of connections.
http://apache2buddy.pl/ it is a perl script that will provide you the optimization areas at your server.
if there is an error like “The process running on port 80 is not Apache.” then please check the output of the command “/usr/sbin/apache2 -V “. The first line of the output should be Server version: Apache/2.4.29
This kind of output will be given. This will also provide you with general improvement points that can be done on the server.
if you do not want to run this script on the server, you can use the following command to view the apache memory utilization
For the connection configuration, you must be knowing about the MPM module, accordingly, you can set the directives.
Prefork vs Worker vs Event
Prefork MPM launches multiple child processes. Each child process handle one connection at a time.Prefork is the default MPM used by Apache2 server. Prefork MPM always runs few minimum (MinSpareServers) defined processes as spare, so new requests do not need to wait for new process to start.
Worker MPM generates multiple child processes similar to prefork. Each child process runs many threads. Each thread handles one connection at a time.Worker MPM uses low memory in comparison to Prefork MPM.
Event MPM, Introduced in apache2.4. This MPM allows more requests to be served simultaneously by passing off some processing work to supporting threads. Using this MPM Apache tries to fix the ‘keep alive problem’ faced by other MPM. When a client completes the first request then the client can keep the connection open, and send further requests using the same socket, which reduces connection overload.
Warning :As PHP is not thread-safe, the common suggestion is to install Apache with the “prefork” MPM
Directives and their meaning
ServerLimit 60 # Declares the maximum number of running Apache processes
StartServers 5 # The number of processes to start initially when starting the Apache daemon
MinSpareThreads 25 # The minimum number of idle threads available to handle request spikes
MaxSpareThreads 75 # The maximum number of idle threads
ThreadsPerChild 30 # How many threads can be created per server process
MaxConnectionsPerChild 2000 # Defines the number of connections that a process can handle during its lifetime. This can be used to prevent possible Apache memory leaks (if set to 0 the lifetime is infinite)
First of all, whenever an apache is started, it will start 5 child processes which is determined by StartServers parameter.
Then each process will start 30 threads determined by ThreadsPerChild parameter so this means 5 process can service only 150 concurrent connections/clients i.e. 30×5=150.
Now if more concurrent users comes, then another child process will start, that can service another 30 users. But how many child processes can be started is controlled by ServerLimit parameter, this means that in the configuration above, I can have 60 child processes in total, with each child process can handle 30 thread, in total handling 60×30=1800 concurrent users.
One must define these directive on basis on MPM module and hardware resources, otherwise, this can floodup the server
Time Out Configuration
This directive also play a vital role in tuning the performance of the webserver.
MaxKeepAliveRequests
KeepAliveTimeout
Please visit following article to understand and tune these parameters
It is always a good idea to run Nginx in front and run apache in the background utilizing a reverse proxy, especially if you are using SSL , then offloading SSL at Nginx level will have more improvement.
Use Apache eventMPM (and not the default Prefork or Worker)
Unless you are doing development work on the server, set ExtendedStatus Off and disable mod_info as well as mod_status.
Set DirectoryIndex correctly so as to avoid content-negotiation. Here’s an example from a production server:
DirectoryIndex index.php index.html index.htm
Consider reducing the value of TimeOut to between 30 to 60 (seconds).
For the Options directive, avoid Options Multiviews as this performs a directory scan. To reduce disk I/O further use
Options -Indexes FollowSymLinks
Compression reduces response times by reducing the size of the HTTP response. Install and enable mod_deflate – refer to the documentation or man pages and Add this code to the virtual server config file within the <directory> section for the root directory (or within the .htaccess file if AllowOverrides is On):
Apart from monitoring server hardware and software key variable like CPU/Memory/Disk/Process, We also require monitoring of apache logs using Zabbix to monitor all from a…
A complete guide for monitoring LAMP [Linux/Apache/Mysql/PHP] application through Zabbix and setting up email notifications. In the following section, I am going to use the…
