Category: Howtos

prosody websocket behind nginx reverse proxy

Peter

Useful for kawai and other XMPP services behind the same URL (eg. for serving SSL traffic.)

WebSockets require HTTP/1.1, and prosody assumes traffic on TCP port 5280 is not secure (and trying to force it to starttls) thus requiring the configuration knob highlighted below.

prosody.cfg.lua

consider_websocket_secure = true

nginx.conf

map $http_upgrade $connection_upgrade {
    default upgrade;
    '' close;
}

server {
# ...
  location /xmpp-websocket {
    proxy_pass http://127.0.0.1:5280;
    proxy_buffering off;
    proxy_set_header Host $host;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection "upgrade";
  }
}

Boot LVM on mdraid (5, and others) on Ubuntu 14.04 on newer kernels

Peter

If you build a LVM mdraid5 on Ubuntu 14.04, and update the kernel you may be dropped into initramfs on reboot and be forced to manually activate the logical volumes on the volume group. This is due to a missing/incomplete udev rule for LVM which should be incorporated into initramfs.

/etc/udev/rules.d/85-lvm2.rules

# This file causes block devices with LVM signatures to be automatically
# added to their volume group.
# See udev(8) for syntax

SUBSYSTEM=="block", ACTION=="add|change", ENV{ID_TYPE}=="disk", \
        RUN+="watershed sh -c '/sbin/lvm vgscan; /sbin/lvm vgchange -a y'"

Once you have added this udev rule, you should update initramfs on your system:

update-initramfs -u -k all

If you need to activate the logical volume groups from initramfs, execute the following commands to boot the system:

lvm vgscan
lvm vgchange -a y
exit

QEMU agent for graceful shutdown of Windows guests under libvirt/qemu-kvm

Peter

libvirt sending an ACPI shutdown doesn't always prompt Windows guests to shutdown. That's why there is a QEMU guest agent (which is also handy for freezing/thawing guest file systems.) Installing QEMU guest agent will also cause libvirt to block on shutdown commands until the guest has terminated.

libvirt XML definition required

<channel type='unix'>
<target type='virtio' name='org.qemu.guest_agent.0'/>
<address type='virtio-serial' controller='0' bus='0' port='1'/>
</channel>

You may also have to create /var/lib/libvirt/qemu/channel/target on the KVM host.

mkdir -p /var/lib/libvirt/qemu/channel/target
chown -R libvirt-qemu:kvm /var/lib/libvirt/qemu/channel/target

virtio-win drivers distributed by the Fedora Project contain the guest-agent and required virtioserial drivers for communication between guest and host and can be downloaded as an RPM package called virtio-win.

Once you have the RPM, you can either install it or convert it to a Debian package using alien. The ISO will be installed to /usr/share/virtio-win/virtio-win.iso and can be mounted in the guest.

virsh attach-disk GuestName /usr/share/virtio-win/virtio-win.iso hdc –type cdrom –mode readonly

Once you have restarted the guest with the XML definition changes, you can complete the following steps

  • Install virtioserial driver for PCI Simple Communication Controller under Device Manager, in the vioserial folder
  • Install the guest-agent located under the guest-agent folder for your architecture in the virtio-win ISO

Intel E1G42ET (82576 controller) SR-IOV with Windows 2008 R2 guest

Peter

I've followed the Redhat Enterprise Linux 7 Using SR-IOV guide, with the following changes made for Ubuntu 14.04 and the fact that the Intel driver set (PROWinx64) doesn't install the drivers automatically.

Make sure to bring the network link state up before you start the virtual machine, or the network driver will report "Network cable unplugged" permanently. igbvf doesn't want to detach on Linux 3.10 on Ubuntu 14.04, so I have blacklisted the module.

/etc/modprobe.d/blacklist-igbvf.conf

blacklist igbvf

/etc/modprobe.d/igb.conf

options igb max_vfs=7

Download the latest Intel Virtual Function drivers from the Intel site, extract PROWinx64 with your favourite archival program. Then run the following command:

pnputil -a PRO1000\Winx64\NDIS62\v1q62x64.inf

Then you can either go to Device Manager and scan for New hardware changes or restart the virtual machine. Your guest networking should now be working.

New KVM deployment bugs and recommendations (Ubuntu 14.04: qemu 2.0, libvirt 1.2.4, Linux 3.10)

Peter

New Linux KVM qemu deployment, running on Ubuntu 14.04 with Linux 3.10 kernel and openvswitch. Hardware setup is 2 SSD in RAID1, and 2 7200RPM HDD in RAID1 using mdadm. bcache is being used as the backing cache for the HDD.

Bugs

  • hv_vapic ("vapic state='on'" in libvirt) causes Windows 2008 R2 and above VMs not to boot if CPU is an Intel IvyBridge or greater (check /sys/module/kvm_intel/parameters/enable_apicv) – Redhat Bugzilla
  • Linux 3.12 or greater (Ubuntu 14.04 ships with 3.13) have issues with virtio-net NIC and TSO (RX and TX checksuming) offloading – TCP sessions can't be established across virtual machines in certain situations (think a virtual machine as a firewall) – Debian Bugreport
  • Windows virtual machines still freeze up/high latency if you use virtio NIC, this is with the latest signed drivers available from the Fedora Project
  • Still have issues with "Russian roulette" of network interfaces with openvswitch – Blog post

Recommendations

Installed Packages

System
apt-get install haveged ntp sysstat irqbalance acpid
Linux KVM, openvswitch, virt-install, virt-top
apt-get install qemu-kvm libvirt-bin virtinst virt-top openvswitch-switch sysfsutils iotop gdisk iftop
bcache
apt-get install python-software-properties
add-apt-repository ppa:g2p/storage && apt-get update && apt-get install bcache-tools

Tuning memory, scheduler I/O subsystems for Linux KVM

Taken from RHEL 6 tuned (virtual-host)

/etc/sysctl.conf
kernel.sched_min_granularity_ns=10000000
kernel.sched_wakeup_granularity_ns=15000000
vm.dirty_ratio=10
vm.dirty_background_ratio=5
vm.swappiness=10

Disable experimental virtio-net zero copy transmit

RHEL 7 has experimental_zcopytx disabled by default.

/etc/modprobe.d/vhost-net.conf
options vhost_net  experimental_zcopytx=0

Use virtio-blk for guests, and enable Multiqueue virtio-net (except Windows)

Linux KVM page describing Multiqueue

libvirt
<devices>
  <interface type='network'>
    <model type='virtio'/>
    <driver name='vhost' queues='4'/>
  </interface>
</devices>

Where number of queues is equal to the number of virtual processors assigned to the virtual machine. Don't forget to enable the vhost_net kernel module, edit /etc/default/qemu-kvm and set VHOST_NET_ENABLED=1.

Make sure to enable Multiqueue support in the guest

ethtool -L eth0 combined 4

Use deadline scheduler, and enable transparent hugepages for KVM

/etc/default/grub
GRUB_CMDLINE_LINUX_DEFAULT="elevator=deadline transparent_hugepage=always"

Don't forget to run update-grub to make the changes persistent.

For Windows guests, take advantage of Hyper-V enlightments and use e1000 Ethernet adapter

Linux KVM presentation on Hyper-V enlightenment (slightly outdated)

  • hv_vapic (for "supported processors") for Virtual APIC
  • hv_time (aka "hypervclock") for TSC invariant timestamps passed to guest
  • hv_relaxed to prevent BSOD under high load (when a timer can't be serviced when expected)
  • hv_spinlocks let's the guest know when a virtual processor is trying to acquire a lock on the same resource as another processor
libvirt
<features>
  <acpi/>
  <apic/>
  <hyperv>
    <relaxed state='on'/>
    <vapic state='on'/>
    <spinlocks state='on' retries='4096'/>
  </hyperv>
</features>
<clock offset='localtime'>
  <timer name='hypervclock' present='yes'/>
  <timer name='hpet' present='no'/>
</clock>

Build and install longterm Linux 3.10 kernel for stability (and working openvswitch with virtio-net)

apt-get -y install build-essential
cd /usr/local/src
wget https://www.kernel.org/pub/linux/kernel/v3.x/linux-3.10.44.tar.xz
tar -Jxf linux-3.10.44.tar.xz
cd linux-3.10.44
cp /boot/config-`uname -r` .config
make olddefconfig
make -j`nproc` INSTALL_MOD_STRIP=1 deb-pkg
dpkg -i ../*.deb
apt-mark hold linux-libc-dev

Time keeping is king on FreeBSD – TSC and "how not to have time go backwards in guest"

/etc/sysctl.conf
kern.timecounter.hardware=ACPI-fast
/boot/loader.conf
virtio_load="YES"
virtio_pci_load="YES"
virtio_blk_load="YES"
if_vtnet_load="YES"
virtio_balloon_load="YES"
kern.timecounter.smp_tsc="1"
kern.timecounter.invariant_tsc="1"
libvirt
<clock offset='localtime'>
  <timer name='rtc' tickpolicy='catchup'/>
  <timer name='pit' tickpolicy='delay'/>
  <timer name='hpet' present='no'/>
</clock>