6.2. Clients and server¶
Scenarios start with clients (Tsung cluster) and server definitions:
6.2.1. Basic setup¶
For non distributed load, you can use a basic setup like:
<clients> <client host="localhost" use_controller_vm="true"/> </clients> <servers> <server host="192.168.1.1" port="80" type="tcp"></server> </servers>
This will start the load on the same host and on the same Erlang virtual machine as the controller.
The server is the entry point into the cluster. You can add several servers, by default each server will have a weight of 1, and each session will choose a server randomly according to the weight. You can set a weight for each server like this (weight can be an integer or a float):
<servers> <server host="server1" port="80" type="tcp" weight="4"></server> <server host="server2" port="80" type="tcp" weight="1"></server> </servers>
(in version older than 1.5.0, the
weight option was
not implemented and a round robin algorithm was used to choose the
Type can be
udp (for IPv6, use
udp6 ; only available in version 1.4.2 and newer)
websocket (only available in version 1.5.0 and newer))
There’s also a specific type fo BOSH:
bosh for unencrypted BOSH, and
bosh_ssl for encrypted connection
6.2.2. Advanced setup¶
The next example is more complex, and use several features for advanced distributed testing:
<clients> <client host="louxor" weight="1" maxusers="800"> <ip value="10.9.195.12"></ip> <ip value="10.9.195.13"></ip> </client> <client host="memphis" weight="3" maxusers="600" cpu="2"/> </clients> <servers> <server host="10.9.195.1" port="8080" type="tcp"></server> </servers>
Several virtual IP can be used to simulate more machines. This is very useful when a load-balancer use the client’s IP to distribute the traffic among a cluster of servers. New in 1.1.1: IP is no longer mandatory. If not specified, the default IP will be used.
New in 1.4.0: You can use
<ip scan="true" value="eth0"/> to scan for all the IP aliases on a given interface
eth0 in this example).
In this example, a second machine is used in the Tsung cluster, with a higher weight, and 2 cpus. Two Erlang virtual machines will be used to take advantage of the number of CPU.
Even if an Erlang VM is now able to handle several CPUs
(erlang SMP), benchmarks shows that it’s more efficient to use one VM
per CPU (with SMP disabled) for tsung clients. Only the controller node is using SMP
cpu should be equal to the number of cores of
your nodes. If you prefer to use erlang SMP, add the
option when starting tsung (and don’t set
cpu in the config
By default, the load is distributed uniformly on all CPU (one CPU per client by default). The weight parameter (integer) can be used to take into account the speed of the client machine. For instance, if one real client has a weight of 1 and the other client has a weight of 2, the second one will start twice the number of users as the first (the proportions will be 1/3 and 2/3). In the earlier example where for the second client has 2 CPU and weight=3, the weight is equal to 1.5 for each CPU.
18.104.22.168. direct ip¶
Sometimes, it can be a problem to use hostnames for all tsung clients (if you don’t have a DNS, you must edit /etc/hosts on all nodes). Since version in 1.7.0, you can use direct IP instead of hostnames.
To do this, you should use the -I parameter when starting Tsung,
tsung -I Your_Server_IP -f tsung.xml start
tsung -I 10.10.10.10 -f tsung.xml start
You controller node name is therefore:
For clients, put the IP like this:
<clients> <client host="10.10.10.11" maxusers="120000" cpu="7" weight="4"/> <client host="10.10.10.12" maxusers="120000" cpu="7" weight="4"/> <clients>
If you have many IPs (thousands of IPs), the
ip scan option can be
slow ; in this case you can use the
iprange tag to generate a
random IP in a given range:
<iprange version="v4" value="172.28.1-20.0-254"/>
In the given example, the third and last part of the IPv4 address will be random in the given range.
maxusers parameter is used to bypass the limit of maximum
number of sockets opened by a single process (1024 by default on many
OS) and the lack of scalability of the
select system call. When
the number of users is higher than the limit, a new erlang virtual
machine will be started to handle new users. The default value of
maxusers is 800. Nowadays, with kernel polling enable, you can and
should use a very large value for
maxusers (30000 for example)
without performance penalty (but don’t forget to raise the limit of
the OS with ulimit -n, see also Why do i have error_connect_emfile errors?).
If you are using a tsung master with slaves, the master distributes sessions to slaves. If a session contains multiples requests, a slave will execute each of these requests in order.
6.2.3. Running Tsung with a job scheduler¶
Tsung is able to get its client node list from a batch/job
scheduler. It currently handle PBS/torque, LSF and OAR. To do this,
type attribute to
<client type="batch" batch="torque" maxusers="30000">
If you need to scan IP aliases on nodes given by the batch scheduler, use scan_intf like this:
<client type="batch" batch="torque" scan_intf='eth0' maxusers="30000">