====== Enabling CRIU on CloudLinux + cPanel EA4 ======
**IMPORTANT!! CRIU may cause stability issues! Enable CRIU AT YOUR OWN RISK!**
Checkpoint/Restore In Userspace, or CRIU, is an open source project which dumps all of the information of a running process to disk and restores it at the point of the dump. The LiteSpeed Enterprise Edition Web Server now supports CRIU for the CloudLinux implementation of the PHP processor.
However, generally, we don't recommend you enable CRIU unless you have a special requirement for it. CRIU uses significant server resources and may generate unusual errors while providing no performance benefits.
**We have received quite a few reports that potential bugs on the CRIU module may cause web server stability issues. Please permanently disable CRIU, or enable CRIU AT YOUR OWN RISK**.
===== Requirements =====
- CloudLinux System
- ea-apache24-mod_lsapi 1.1 on cpanel EA4 (or mod_lsapi on cPanel EA3) or above
- LiteSpeed Web Server 5.3 or above.
===== Installation =====
==== Verify CRIU is enabled on your system ====
Criu is installed with dependency to ea-apache24-mod_lsapi for cpanel EA4( or mod_lsapi for cpanel EA3) 1.1 and above package.
If you have not installed it, you should:
yum install liblsapi liblsapi-devel
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Package Arch Version Repository Size
=============================================================================================================================================================================
Installing:
liblsapi x86_64 1.1-28.el7.cloudlinux cloudlinux-x86_64-server-7 180 k
liblsapi-devel x86_64 1.1-28.el7.cloudlinux cloudlinux-x86_64-server-7 37 k
Installing for dependencies:
crit-lve x86_64 3.7-3.el7 cloudlinux-x86_64-server-7 9.6 k
criu-lve x86_64 3.7-3.el7 cloudlinux-x86_64-server-7 439 k
criu-lve-devel x86_64 3.7-3.el7 cloudlinux-x86_64-server-7 11 k
libnet x86_64 1.1.6-7.el7 cloudlinux-x86_64-server-7 58 k
protobuf-c x86_64 1.0.2-3.el7 cloudlinux-x86_64-server-7 27 k
protobuf-python x86_64 2.5.0-8.el7 cloudlinux-x86_64-server-7 129 k
python-criu-lve x86_64 3.7-3.el7 cloudlinux-x86_64-server-7 136 k
python-ipaddr noarch 2.1.11-1.el7 cloudlinux-x86_64-server-7 34 k
Transaction Summary
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Install 2 Packages (+8 Dependent packages)
yum install ea-apache24-mod_lsapi
Check CRIU whether the service is running or not. \\
ps -ef | grep criu
root 967641 1 0 19:24 ? 00:00:00 /usr/sbin/criu service -v4 -o /var/log/criu-service.log --address /var/run/criu/criu_service.socket
root 967680 965818 0 19:24 pts/1 00:00:00 grep --color=auto criu
If not, enable by following method:
systemctl enable criu
systemctl start criu
systemctl status criu
Output should be ''Active: active (running)''.
[root@globalsupport ~]# systemctl status criu
● criu.service - Checkpoint Restore in Userspace daemon
Loaded: loaded (/usr/lib/systemd/system/criu.service; disabled; vendor preset: disabled)
Active: active (running) since Mon 2018-08-20 19:24:25 UTC; 4min 23s ago
Process: 967640 ExecStartPre=/bin/mkdir -p /var/run/criu (code=exited, status=0/SUCCESS)
Main PID: 967641 (criu)
CGroup: /system.slice/criu.service
└─967641 /usr/sbin/criu service -v4 -o /var/log/criu-service.log --address /var/run/criu/criu_service.socket
Aug 20 19:24:25 globalsupport.litespeedtech.com systemd[1]: Starting Checkpoint Restore in Userspace daemon...
Aug 20 19:24:25 globalsupport.litespeedtech.com systemd[1]: Started Checkpoint Restore in Userspace daemon.
Aug 20 19:24:25 globalsupport.litespeedtech.com criu[967641]: Warn (criu/kerndat.c:660): Can't load /run/criu.kdat
====CRIU Master Switch on LSWS ====
CRIU is disabled by default. To enable it, you can go to LSWS Web Admin Console -> Server -> PHP -> PHP Global Configuration -> Enable CRIU( Again, we recommend you keep CRIU off unless you have some speical testing need only).
{{:litespeed_wiki:cloudlinux:lsws-master-criu-switch.png?800|}}
==== Check CRIU parameters====
In CloudLinux, LSPHP have been compiled with CRIU already. Please check [[https://docs.cloudlinux.com/index.html?criu_support.html|here]] \\
Use ''phpinfo()'' with parameter ''-DWITH_CRIU'' to check the LSPHP build.
====Configure the PHP environment====
Add the following necessary parameter to the PHPx.x **External App > Environment** \\
LSAPI_CRIU=1
Example for PHP56 + Enable CRUI + Set INITIAL\\
{{:litespeed_wiki:cloudlinux:criu-2.png?|}}
===Important Syntax===
^Variable^Values^Default^Description^
|LSAPI_CRIU|1/On/Off|Off|If set to On, CRIU will be performed. 1=On|
|LSAPI_INITIAL_START|A number from 1 upwards.|15|The number of consecutive calls which must be made within a single PHP instance before a dump of the instance will be made. If there’s no PHP instance running and there’s a dump on disk it will be restored on the first use.|
|LSAPI_CRIU_IMGS_DIR_PATH|Any valid, existing directory|/var/run/lsws/cl_criu/|CRIU images will start from this directory; a subdirectory named "images" will be created below and then a directory for each user's type of request. There needs to be lots of free space in this file system.|
|LSAPI_CRIU_DEBUG|On/Off|Off|If set to ''On'', messages concerning CRIU processing will be written to the stderr.log file (usually in /usr/local/apache2/logs/stderr.log)|
===== How to Verify =====
====Step 1====
- Prepare any PHP site, e.g. WordPress
====Step 2====
- Generate the dump by hitting the WordPress site
- Hit more than INITIAL_START number, e.g. 20 times
- If an image dump is generated, you should see an image folder under ''/var/run/lsws/cl_criu/''
====Step 3====
- Check the PHP process number by ps -ef | grep php
>>> user 868577 ... 10:54 0:00 lsphpL
- Kill the lsphp process via kill -9 868577
====Step 4====
- Restore the PHP by refreshing the WordPress page to regenerate it
- Verify the process number is the same as before:ps -ef | grep php
>>> user 868577 ... 10:55 0:00 lsphpThe process is **back**!!
- You can also check standard error log for something like LSCRIU: Successful CloudLinux dump of PID: 868577
LSCRIU: Successful CloudLinux restore of PID: 868577, parent: 1.
===== Logs =====
- **Error log** default located at Apache standard error log
- ''dump.log'' is in the images directory
- ''restore.log'' is in the images directory
**NOTE**: ''restore.log'' is generated even when there is no dump, so it's expected to see some related fail logs