[Git] Meld - The difftool

Install meld

sudo apt-get update
sudo apt-get install meld

Setup git default diff tool as meld

git config --global diff.tool meld
git config --global --add difftool.prompt false

Examples

cd <git repo dir>
git difftool           // display file diff one by one
git difftool file_path // display one file diff
git difftool HEAD HEAD~5 filename

[Ceilometer] To collect the bandwidth of Neutron L3 router

Ceilometer component in OpenStack is a great project for me to study further in depth I think. I am not going to introduce it because it's not the scope of this post. Instead, I only want to list some resources about Ceilometer to collect the bandwith/traffic accounting of Neutron L3 router.

From this offical document: https://wiki.openstack.org/wiki/Neutron/Metering/Bandwidth
we can know that the actual implementation to collect the bandwidth of Neutron L3 router is based on iptables.

We can use the neutron command to list the related metering rules and labels
$ neutron meter-label-list
$ neutron meter-label-rule-list

The "neutron-meter-agent" will collect the traffic accounting in the iptables chain and push to oslo-messaging. So the following command can show the traffic accounting in Neutron L3 router


root@sn1:~# nova --os-project-name mickey list


root@sn1:~# nova show bb1879bd-1202-4007-9376-41be30e07ae9


root@sn1:~# neutron --os-tenant-name mickey router-list


root@node-5:~# neutron meter-label-rule-list


root@node-5:~# neutron meter-label-rule-show d31f0b9e-8824-4857-a2dc-19f237723f0c


root@node-5:~# neutron meter-label-rule-show 1ae289ef-687e-4303-8036-9a7566dd5365


So, we need to find the metering labels: "neutron-meter-l-78675a84" and "neutron-meter-l-b88c5977"

root@cn3:~#  ip netns exec qrouter-b1741371-ee12-46a1-831b-d3b35429d7c8 iptables -nL -v -x



root@cn3:~# ip netns exec qrouter-b1741371-ee12-46a1-831b-d3b35429d7c8 iptables -t nat -S




Here is the example to query the metering data in Ceilometer
$ root@node-5:~# ceilometer statistics -m bandwidth -q "resource=b88c5977-4445-4f19-9c8f-3d92809f844e;timestamp>=2016-03-01T00:00:00" --period 86400



P.S:
The following article is to introduce "Traffic Accounting with Linux IPTables" which can make us more understand it.
http://www.catonmat.net/blog/traffic-accounting-with-iptables/
https://wiki.openstack.org/wiki/Neutron/Metering/Bandwidth

[Apache2] To increase the concurrent request number of apache server

This post is just the memo for my a little task. Our web app is a Django app in Apache2 web server.
I currently tested our several RESTful APIs and found the maximum concurrent request number is not good enough (around 350) so that I try to tune it to the accepted level, for instance: more than 500.

I also found that if the concurrent request is bigger than the number (350), then I will often see the apache benchmark tool showing the error: apr_socket_recv: Connection reset by peer (104), which means web server suddenly disconnected in the middle of the session.

So, there are two things coming up to my mind: Apache2 configuration and Linux tuning.

For Apache2:
I follow this document to change the mpm_worker.conf as follows:


The defulat value:

ServerLimit 16
StartServers 2
MaxClients 150
MinSpareThreads 25
MaxSpareThreads 75
ThreadsPerChild 25

What I changed in my mpm_worker.conf
vi /etc/apache2/mods-available/mpm_worker.conf

<IfModule mpm_worker_module>
        ServerLimit              40
        StartServers             4
        MaxClients               1000
        MinSpareThreads          25
        MaxSpareThreads          75
        ThreadLimit              64
        ThreadsPerChild          25
        MaxRequestWorkers        2500
        MaxConnectionsPerChild   25
</IfModule>

For Linux tuning:
I follow this document to enlarge the system variables.

sysctl net.core.somaxconn=1024

sysctl net.core.netdev_max_backlog=2000
sysctl net.ipv4.tcp_max_syn_backlog=2048

[Django] The question of changing urlpattern dynamically

A couple of days my colleague gave me a quesiont about how to  change urlpattern dynamically in Django. Well, I indeed take some time to survey the way to do so even though we figure out alternatives to achieve the same result that we want. So, the following list is about the solution:


http://stackoverflow.com/questions/8771070/unable-dynamic-changing-urlpattern-when-changing-database
I perfer to adopt using middleware class to resolve this problem as follows:

An alternative method would be to either create a super pattern that calls a view, which in turn makes a DB call. Another approach is to handle this in a middleware class where you test for a 404 error, check if the pattern is likely to be one of your categories, and then do the DB look up there. I have done this in the past and it's not as bad as it sounds. Look at the django/contrib/flatpages code for a straightforward implementation of this approach.

For how to use middleware class, there is another link for the reference.
http://stackoverflow.com/questions/753909/django-middleware-urls

[IOMMU] The error of "VFIO group is not viable"

As my previous article mentioned, DPDK is a library to accelerate packet transmission between user space application and physical network device. Recently there is an article "Using Open vSwitch 2.4 with DPDK-2.2.0 for Inter-VM NFV Applications" that aspires me to do the similiar test environment to witness how powerful DPDK is.
But, I enounter the error of "VFIO group is not viable" when I start openvswitch daemon. After searching the information on Google, it is related with IOMMU Group issue as described below:

http://vfio.blogspot.tw/2014/08/vfiovga-faq.html
Question 1:

I get the following error when attempting to start the guest:

vfio: error, group $GROUP is not viable, please ensure all devices within the iommu_group are bound to their vfio bus driver.

Answer:

There are more devices in the IOMMU group than you're assigning, they all need to be bound to the vfio bus driver (vfio-pci) or pci-stub for the group to be viable.  See my previous post about IOMMU groups for more information.  To reduce the size of the IOMMU group, install the device into a different slot, try a platform that has better isolation support, or (at your own risk) bypass ACS using the ACS override patch.

So, the solutions are these two:
1. Install the device into a different slot
2. Bypass ACS using the ACS overrides patch

For the more explanation in details, you could see this article:
http://vfio.blogspot.tw/2014/08/iommu-groups-inside-and-out.html


The following Scripts are the summary from the article:

# Update Grub
GRUB_CMDLINE_LINUX_DEFAULT="... default_hugepagesz=1G hugepagesz=1G hugepages=16 hugepagesz=2M hugepages=2048 iommu=pt intel_iommu=on isolcpus=1-13,15-27"
update-grub

# Export Variables
export OVS_DIR=/root/soucecode/ovs
export DPDK_DIR=/root/soucecode/dpdk-2.1.0
export LC_ALL=en_US.UTF-8
export LANG=en_US.UTF-8
locale-gen "en_US.UTF-8"
dpkg-reconfigure locales

# build DPDK
curl -O http://dpdk.org/browse/dpdk/snapshot/dpdk-2.1.0.tar.gz
tar -xvzf dpdk-2.1.0.tar.gz
cd $DPDK_DIR
sed 's/CONFIG_RTE_BUILD_COMBINE_LIBS=n/CONFIG_RTE_BUILD_COMBINE_LIBS=y/' -i config/common_linuxapp
make install T=x86_64-ivshmem-linuxapp-gcc
cd $DPDK_DIR/x86_64-ivshmem-linuxapp-gcc
EXTRA_CFLAGS="-g -Ofast" make -j10

# build OVS
git clone https://github.com/openvswitch/ovs.git
cd $OVS_DIR
./boot.sh
./configure --with-dpdk="$DPDK_DIR/x86_64-ivshmem-linuxapp-gcc/" CFLAGS="-g -Ofast"
make 'CFLAGS=-g -Ofast -march=native' -j10

# Setup OVS
pkill -9 ovs
rm -rf /usr/local/var/run/openvswitch
rm -rf /usr/local/etc/openvswitch/
rm -f /usr/local/etc/openvswitch/conf.db
mkdir -p /usr/local/etc/openvswitch
mkdir -p /usr/local/var/run/openvswitch
cd $OVS_DIR
./ovsdb/ovsdb-tool create /usr/local/etc/openvswitch/conf.db ./vswitchd/vswitch.ovsschema
./ovsdb/ovsdb-server --remote=punix:/usr/local/var/run/openvswitch/db.sock --remote=db:Open_vSwitch,Open_vSwitch,manager_options --pidfile --detach
./utilities/ovs-vsctl --no-wait init

# Check IOMMU & Huge info
cat /proc/cmdline
grep Huge /proc/meminfo

# Setup Hugetable
mkdir -p /mnt/huge
mkdir -p /mnt/huge_2mb
mount -t hugetlbfs hugetlbfs /mnt/huge
mount -t hugetlbfs none /mnt/huge_2mb -o pagesize=2MB
 
# Bind Ether card
modprobe vfio-pci
cd $DPDK_DIR/tools
./dpdk_nic_bind.py --status
./dpdk_nic_bind.py --bind=vfio-pci 08:00.2

# Start OVS
modprobe openvswitch
$OVS_DIR/vswitchd/ovs-vswitchd --dpdk -c 0x2 -n 4 --socket-mem 2048 -- unix:/usr/local/var/run/openvswitch/db.sock --pidfile --detach

# Setup dpdk vhost user port
$OVS_DIR/utilities/ovs-vsctl show
$OVS_DIR/utilities/ovs-vsctl add-br br0 -- set bridge br0 datapath_type=netdev
$OVS_DIR/utilities/ovs-vsctl add-port br0 dpdk0 -- set Interface dpdk0 type=dpdk
$OVS_DIR/utilities/ovs-vsctl add-port br0 vhost-user1 -- set Interface vhost-user1 type=dpdkvhostuser
$OVS_DIR/utilities/ovs-vsctl add-port br0 vhost-user2 -- set Interface vhost-user2 type=dpdkvhostuser

find /sys/kernel/iommu_groups/ -type l

# Create VMs
qemu-system-x86_64 -m 1024 -smp 4 -cpu host -hda /tmp/vm1.qcow2 -boot c -enable-kvm -no-reboot -nographic -net none \
-chardev socket,id=char1,path=/usr/local/var/run/openvswitch/vhost-user1 \
-netdev type=vhost-user,id=mynet1,chardev=char1,vhostforce \
-device virtio-net-pci,mac=00:00:00:00:dd:01,netdev=mynet1 \
-object memory-backend-file,id=mem,size=1024M,mem-path=/dev/hugepages,share=on \
-numa node,memdev=mem -mem-prealloc
 
qemu-system-x86_64 -m 1024 -smp 4 -cpu host -hda /tmp/vm2.qcow2 -boot c -enable-kvm -no-reboot -nographic -net none \
-chardev socket,id=char1,path=/usr/local/var/run/openvswitch/vhost-user2 \
-netdev type=vhost-user,id=mynet1,chardev=char1,vhostforce \
-device virtio-net-pci,mac=00:00:00:00:dd:02,netdev=mynet1 \
-object memory-backend-file,id=mem,size=1024M,mem-path=/dev/hugepages,share=on \
-numa node,memdev=mem -mem-prealloc

[Django] How to upload a file to via Django REST Framework?

Here is an example to use Parser: MultiPartParser to parse the media type: multipart/form-data. You also can take a look at this for more in detail: http://www.django-rest-framework.org/api-guide/parsers

Client Side via curl: ( Basically you can use either PUT or POST)
Command format:
curl -X PUT -H 'Content-Type:multipart/form-data' -F 'data=@/{your_file}' -u {account}:{password} http://{your server ip address}/

for instance:
curl -X PUT -H 'Content-Type:multipart/form-data' -F 'data=@/Users/administrator/Desktop/2015.12.01.yaml' -u danny:password http://192.168.1.100:8000/api/upload_func/file/



Server side ( Django REST Framework )

in your settings.py, add the following lines
==>
    'DEFAULT_PARSER_CLASSES': (
        'rest_framework.parsers.MultiPartParser',
    )


For your_api.py, you can refer to this example as below:

class UploadAction(APIView):
    permission_classes = (IsAuthenticated, IsAdminOrReadOnly)
    parser_classes = (MultiPartParser,)

    def put(self, request, format=None):
        try:
            # Read uploaded files
            my_file = request.FILES['data']
            filename = "/tmp/" + str(my_file)
            with open(filename, 'wb+') as temp_file:
                for chunk in my_file.chunks():
                    temp_file.write(chunk)
                temp_file.close()
        except Exception as e:
            return Response(status=status.HTTP_500_INTERNAL_SERVER_ERROR)
        return Response(status=status.HTTP_201_CREATED)


P.S: Please change 'data' to others if you put the different variable name in curl command!!

Reference:
http://stackoverflow.com/questions/21012538/retrieve-json-from-request-files-in-django-without-writing-to-file

If you want to get the content of uploaded file, you can directly use the. read() api.

Something like:

if request.FILES.has_key('data'):
    file = request.Files['data']
    data = file.read()
    #you have file contents in data




[Virtual Switching] What are macvlan and macvtap?

I excerpt the content of the following URL about what macvlan and macvtap are for reference quickly.
https://www.netdev01.org/docs/netdev_tutorial_bridge_makita_150213.pdf

macvlan
VLAN using not 802.1Q tag but mac address
    • 4 types of mode
        • private
        • vepa
        • bridge
        • passthru
Using unicast filtering if supported, instead of promiscuous mode (except for passthru)
    • Unicast filtering allows

NIC to receive multiple mac addresses
    • Light weight bridge
    • No source learning
    • No STP
Only one uplink
Allow traffic between macvlans (via macvlan stack)


macvtap
with KVM has three mode
    Private
    vepa
    bridge
tap-like macvlan variant
    • packet reception
        -> file read
    • file write
        -> packet transmission



Further reading:
http://140.120.15.179/Presentation/20150203/
Virtual networking: TUN/TAP, MacVLAN, and MacVTap

[GitHub] How to rebase your branch from upstream branch?

If you fork a copy (branch) from a repository and you want to rebase your branch with this upstream repository, you can refer to the following URLs or directly see the content below.

https://help.github.com/articles/configuring-a-remote-for-a-fork/
https://help.github.com/articles/syncing-a-fork/

1. List the current configured remote repository for your fork.

   git remote -v
   # origin  https://github.com/YOUR_USERNAME/YOUR_FORK.git (fetch)
   # origin  https://github.com/YOUR_USERNAME/YOUR_FORK.git (push)
   

2. Specify a new remote upstream repository that will be synced with the fork.

   git remote add upstream https://github.com/ORIGINAL_OWNER/ORIGINAL_REPOSITORY.git
   

3. Verify the new upstream repository you've specified for your fork.

   git remote -v
   # origin    https://github.com/YOUR_USERNAME/YOUR_FORK.git (fetch)
   # origin    https://github.com/YOUR_USERNAME/YOUR_FORK.git (push)
   # upstream  https://github.com/ORIGINAL_OWNER/ORIGINAL_REPOSITORY.git (fetch)
   # upstream  https://github.com/ORIGINAL_OWNER/ORIGINAL_REPOSITORY.git (push)
   

1. Fetch the branches and their respective commits from the upstream repository. Commits tomaster will be stored in a local branch, upstream/master.

   git fetch upstream
   # remote: Counting objects: 75, done.
   # remote: Compressing objects: 100% (53/53), done.
   # remote: Total 62 (delta 27), reused 44 (delta 9)
   # Unpacking objects: 100% (62/62), done.
   # From https://github.com/ORIGINAL_OWNER/ORIGINAL_REPOSITORY
   #  * [new branch]      master     -> upstream/master
   

2. Check out your fork's local master branch.

   git checkout master
   # Switched to branch 'master'
   

3. Merge the changes from upstream/master into your local master branch. This brings your fork's master branch into sync with the upstream repository, without losing your local changes.

   git merge upstream/master
   # Updating a422352..5fdff0f
   # Fast-forward
   #  README                    |    9 -------
   #  README.md                 |    7 ++++++
   #  2 files changed, 7 insertions(+), 9 deletions(-)
   #  delete mode 100644 README
   #  create mode 100644 README.md
   

   If your local branch didn't have any unique commits, Git will instead perform a "fast-forward":

   git merge upstream/master
   # Updating 34e91da..16c56ad
   # Fast-forward
   #  README.md                 |    5 +++--
   #  1 file changed, 3 insertions(+), 2 deletions(-)