It’s just a small version bump from the now well-known 1.6 version, but ClusterShell 1.7 comes with some nice new features that we hope you’ll enjoy! Most of these features have already been tested on some very large Linux production systems.
This new version also comes with a refreshed documentation, based on the Sphinx documentation generator, available on http://clustershell.readthedocs.org.
We hope this new release will help you manage your clusters, server farms or cloud farms! Special thanks to the many of you that have sent us feedback on Github!
Version 1.7 and possible future minor versions 1.7.x are compatible with Python 2.4 up to Python 2.7 (for example: from RedHat EL5 to EL7). Upgrade from version 1.6 to 1.7 should be painless and are fully supported.
The next major version of ClusterShell will require at least Python 2.6. We will also soon start working on Python 3 support.
NodeSet class and nodeset command-line
have been improved to support multidimentional node sets with folding
capability. The use of nD naming scheme is sometimes used to map node names to
physical location like
name-<rack>-<position> or node position within the
cluster interconnect network topology.
A first example of 3D nodeset expansion is a good way to start:
$ nodeset -e gpu-[1,3]-[4-5]-[0-6/2] gpu-1-4-0 gpu-1-4-2 gpu-1-4-4 gpu-1-4-6 gpu-1-5-0 gpu-1-5-2 gpu-1-5-4 gpu-1-5-6 gpu-3-4-0 gpu-3-4-2 gpu-3-4-4 gpu-3-4-6 gpu-3-5-0 gpu-3-5-2 gpu-3-5-4 gpu-3-5-6
You’ve probably noticed the
/2 notation of the last dimension. It’s called
a step and behaves as one would expect, and is fully supported with nD
All other nodeset commands and options are supported with nD nodesets. For example, it’s always useful to have a quick way to count the number of nodes in a nodeset:
$ nodeset -c gpu-[1,3]-[4-5]-[0-6/2] 16
Then to show the most interesting new capability of the underlying
NodeSet class in version 1.7, a folding example is probably
$ nodeset -f compute-1-[1-34] compute-2-[1-34] compute-[1-2]-[1-34]
In the above example, nodeset will try to find a very compact nodesets representation whenever possible. ClusterShell is probably the first and only cluster tool capable of doing such complex nodeset folding.
Attention, as not all cluster tools are supporting this kind of complex
nodesets, even for nodeset expansion, we added an
--axis option to select
to fold along some desired dimension:
$ nodeset --axis 2 -f compute-[1-2]-[1-34] compute-1-[1-34],compute-2-[1-34]
The last dimension can also be selected using
$ nodeset --axis -1 -f compute-[1-2]-[1-34] compute-1-[1-34],compute-2-[1-34]
All set-like operations are also supported with several dimensions, for
example difference (
$ nodeset -f c-[1-10]-[1-44] -x c-[5-10]-[1-34] c-[1-4]-[1-44],c-[5-10]-[35-44]
Hard to follow? Don’t worry, ClusterShell does it for you!
File-based node groups¶
Cluster node groups have been a great success of previous version of ClusterShell and are now widely adopted. So we worked on improving it even more for version 1.7.
For those of you who use the file
/etc/clustershell/group to describe
node groups, that is still supported in 1.7 and upgrade from your 1.6 setup
should work just fine. However, for new 1.7 installations, we have put this
file in a different location by default:
$ vim /etc/clustershell/groups.d/local.cfg
Especially if you’re starting a new setup, you have also the choice to switch to a more advanced groups YAML configuration file that can define multiple sources in a single file (equivalent to separate namespaces for node groups). The YAML format possibly allows you to edit the file content with YAML tools but it’s also a file format convenient to edit just using the vim editor. To enable the example file, you need to rename it first as it needs to have the .yaml extension:
$ cd /etc/clustershell/groups.d $ mv cluster.yaml.example cluster.yaml
You can make the first dictionary found on this file (named roles) to be the
default source by changing
default: local to
default: roles in
/etc/clustershell/groups.conf (main config file for groups).
For more info about the YAML group files, please see File-based group sources.
Please also see node groups configuration for node groups configuration in general.
nodeset -L/–list-all option¶
Additionally, the nodeset command also has a new option
--list-all to list groups from all sources (
-l only lists
groups from the default source). This can be useful when configuring
ClusterShell and/or troubleshooting node group sources:
$ nodeset -LL @adm example0 @all example[2,4-5,32-159] @compute example[32-159] @gpu example[156-159] @io example[2,4-5] @racks:new example[4-5,156-159] @racks:old example[0,2,32-159] @racks:rack1 example[0,2] @racks:rack2 example[4-5] @racks:rack3 example[32-159] @racks:rack4 example[156-159] @cpu:hsw example[64-159] @cpu:ivy example[32-63]
Special group @*¶
The special group syntax
@source:* if using explicit source
selection) has been added and can be used in configuration files or with
command line tools. This special group is always available for file-based node
groups (return the content of the all group, or all groups from the source
otherwise). For external sources, it is available when either the all
upcall is defined or both map and list upcalls are defined. The all
special group is also used by
clush -a and
nodeset -a. For example,
the two following commands are equivalent:
$ nodeset -a -f example[2,4-5,32-159] $ nodeset -f @* example[2,4-5,32-159]
Version 1.7 introduces a new generic execution worker named
ExecWorker as the new base class for most exec()-based worker
classes. In practice with clush, you can now specify the worker in
command line using
-R and use exec. It also supports
special placeholders for the node (%h) or rank (%n). For example, the
following command will execute ping commands in parallel, each with a
different host from hosts cs01, etc. to cs05 as argument and then
aggregate the results:
$ clush -R exec -w cs[01-05] -bL 'ping -c1 %h >/dev/null && echo ok' cs[01-04]: ok clush: cs05: exited with exit code 1
This feature allows the system administrator to use non cluster-aware tools in
a more efficient way. You may also want to explicitly set the fanout (using
-f) to limit the number of parallel local commands launched.
Please see also clush worker selection.
Version 1.7 adds support for
rsh or any of its variants like
ssh also share a lot of common mechanisms. Worker Rsh was
added moving a lot of Worker Ssh code into it.
clush, please see clush worker selection to
rsh by default instead of
ssh at the library level, install the
provided example file named
Tree Propagation Mode¶
The ClusterShell Tree Mode allows you to send commands to target nodes through a set of predefined gateways (using ssh by default). It can be useful to access servers that are behind some other servers like bastion hosts, or to scale on very large clusters when the flat mode (eg. sliding window of ssh commands) is not enough anymore.
The tree mode is now documented, it has been improved and
is enabled by default when a
topology.conf file is found. While it is still
a work in progress, the tree mode is known to work pretty well when all gateways
are online. We’ll continue to improve it and make it more robust in the next
$XDG_CONFIG_HOME is defined, ClusterShell will use it to search for
additional configuration files.