TakTuk - a tool for large scale remote execution deployment
taktuk [-hinsvP] [-c connector] [-d limit] [-f filename] [-g duration] [-l login] [-m hostname [-[ args ... -]]] [-o stream=template] [-t timeout] [-w size] [-C separators] [-E character] [-F filename] [-L hostname] [-O separators] [-R stream=descriptor] [-T command] [-W scheme] [commands ... ]
TakTuk is a tool for broadcasting the remote execution of one ore more commands to a set of one or more distant machines. TakTuk combines local parallelization (using concurrent deployment processes) and work distribution (using an adaptive work-stealing algorithm) to achieve both scalability and efficiency.
TakTuk is especially suited to interactive tasks involving several distant machines and parallel remote executions. This is the case of clusters administration and parallel program debugging.
TakTuk also provides a basic communication layer to programs it executes.
This communication layer uses the communication infrastructure set up by
TakTuk during its deployment. It is available both for the Perl and the C
langages and is described in taktukcomm(3).
In TakTuk, options are parsed in the order given on the comand line. This is
important as some of the options change the behavior of following ones (and
only these ones - e.g. -l applies to following -m options). The
defaults settings of TakTuk can be obtained by using the --print-defaults
option. The following options are given by category in alphabetical
order.
limit is positive or null,
TakTuk uses the dynamic mode with its value as a maximal arity (0 =
no maximal arity).
A negative value for limit turns dynamic mode off.
Warning,
currently it is a bad idea to use several -d options on the same command line.
filename is the name of a file that contains remote machines names
(equivalent to several -m opions).
-l option (this is the case for ssh, the default).
hostname is the name of a remote machine on which TakTuk has to be
deployed. hostname might contain list of values specified inside brackets
and exclusion lists (see HOSTNAMES SPECIFICATION). In such case, the
depolyment will be performed on all the matching hosts.
This option can be followed by any number of arguments enclosed
between -[ and -] which will be transmitted as arguments of the remote
TakTuk that will execute on all the target hosts.
filename is the name of a file that contains additional options for TakTuk. The parsing of the file is done when encountering this option.
command is the name of the TakTuk command (default is $0, the name used to
launch TakTuk). This is the command used once connected to initiate the
remote TakTuk engine. Note that
the effect of this switch is void when using the -s option.
-F switch).
connector (errors from the connector command)error, output (error and output of remotely executed commands)info (general informations such as help summary or version)state (disabled by default, internal state of TakTuk instance)status (commands exit status)taktuk (internal messages, warnings and errors)a template is a Perl expression that should evaluate to the string eventually displayed. Within a specification, some variables might be used depending on the concerned stream:
$command (not for taktuk nor info)$count$eof$failed (connector only)$filename (taktuk only)$host$level (taktuk only)$level_name (taktuk only)$line$line_number (taktuk only)$package (taktuk only)$peer (connector only)$pid (not for taktuk nor info)$position$rank$start_date (output, error and status)$stop_date (status only)$type$user_scalarat the end of the day, the specification is evaluated for each line of the
concerned stream and the result printed on the root node.
Note that the newline has to be added explicitely as \n in the template if
needed.
WARNING: take care of your specification, if the Perl syntax is not correct lots of awfull compilation error messages will be displayed and TakTuk execution will fail.
-o option for more details about streams output.
duration the maximal interval between timeouts checks (usually checks are made more often: at each message received a timeouts check is made).
TAKTUK_COUNT and
TAKTUK_RANK are not defined in executed commands. This has the advantage of
removing the global synchronization occuring at the end of the deployment and
making the deployment more efficient.
WARNING: use this option only before any remote node specification (-m or
-f) otherwise you might get serious synchronization issues in TakTuk.
Using TakTuk point-to-point communication along with this option will
fail and produce TakTuk warnings.
ssh for instance). When the
delay expires, the connector command is simply killed.
These option are not useful for most users. They are used either internally by TakTuk itself or for development purposes.
packagename extracted from the taktuk code in
execution.
scope. The scope might be a TakTuk package name or default and the lowest the level the more verbose the output.
After the options parsing, TakTuk expects some commands either on the
remaining of the command line (batch mode) or on the standard input
(interactive mode). These commands are actions to be performed by TakTuk
using the logical network infrastructure set up during the deployment. By
default, commands might be separated by ; or newlines. For all the commands,
any non ambiguous prefix can be used instead of their full name.
In interactive mode, TakTuk has support for readline (history, command
line editing) if installed on your system.
When TakTuk commands accept arguments, they should be enclosed into matching delimiters (indicated by * below). In other words, * might be replaced either by any non alphanumeric character or by a pair of matching braces, brackets or parenthesis. These delimiters must be separated from their content (using the options separator). If the argument contains a closing delimiter preceded by a separator, then it is probably a good idea to escape it (see -E option) or to protect the whole arguments string if given on the command line.
Taktuk understands the following commands:
command line on the local machine but has no effect on the root
node. Inputs/outputs of the execution are multiplexed and fowarded to the
TakTuk root.
This command accepts optional parameters that enable the attachment of callbacks triggered by timeouts to the execution of the command. See section EXEC PARAMETERS for more details.
WARNING: this command is not atomic. If you manage somehow to initiate a file_input command from two different TakTuk instances, data will probably be interleaved. In this case you should synchronize the two instances. This is not required when spreading files only from the root node.
connecting ...
leaves.
broadcast which does not wait for nodes numbering or print_tree
which does not wait for the completion of the deployment.
exec perl
arguments have been used. The difference is that this interpreter is
previously fetched with the taktuk package that contains point-to-point
communication routines (taktuk::send and taktuk::recv, see
taktukcomm(3)).
WARNING: due to the limitations of the parser that analyses the arguments of
this command, you have to give arguments (even if empty) and to use '--' if you
give any option to the perl interpreter (and even if you give it only options).
The TakTuk command exec accepts optional parameters. These parameters are
used to attach actions triggered by timeouts to commands execution. An exec
command accepts any number of parameters. These parameters are
interpreted from left to right using the following syntax:
TAKTUK_PID that contains the pid of the timeouted
command. The given TakTuk command can be any valid TakTuk command
(without command separator).
Notice that each timeout can have any number of attached callbacks. They will be processed in the order they are given as parameters.
To change some default setting use the variable TAKTUK_NAME where NAME is
the name of the according long option in upper case and with dashes replaced by
underscores. For option taking complex value (such as --debug) just add an
underscore and the field you want to change in upper case at the end of the
name.
Using taktuk --print-defaults will give you examples of names used to change
default settings.
Note that defining in the environment a default setting not used by TakTuk
has no effect.
Hostnames given to TakTuk might be simple machine name or complex hosts lists specifications. In its general form, an hostname given to taktuk is made of an host set and an optional exclusion set separated by a slash. Each of those sets are made of constant part (characters outside brackets) and optional list parts (characters inside brackets). Each list part is a comma separated list of intervals or single values. Each interval is made of two single values separated by a dash. This is true for all hostnames given to TakTuk (both with -m or -f options).
In other words, the following expressions are valid host specifications: node1 node[19] node[1-3] node[1-3]/node2 node[1-3,5]part[a-b]/node[3-5]parta
they respectively expand to: node1 node19 node1 node2 node3 node1 node3 node1parta node1partb node2parta node2partb node3partb node5partb
Notice that these list of values are not regular expressions (node[19] is
node19 and not node1, node2, ...., node9). Intervals are implemented
using the perl magical auto increment feature, thus you can use alphanumeric
values as interval bounds (see perl documentation, operator ++ for limitations
of this auto increment).
The TakTuk command line and the taktuk::send routine accept a set
specification as destination host(s). A set specification is made of interval
specifications separated by slashes. An interval specification is made of a
single number or two numbers separated by a dash. Of course the two numbers
specifying an interval must be given in increasing order.
The remote peers included in a set specification are all the peer which logical number belong to at least one interval of the set. Here are some exemples of set specifications :
1
the peer numbered 1
2-7
the peers numbered 2,3,4,5,6 and 7
2-4/1/10
the peers numbered 1,2,3,4 an 10
The following examples illustrate the basic use of TakTuk on a few machines and the use of developper options. Notice that TakTuk is designed to scale to much more peers than the number involved in these examples.
-s. In this case, the basic remote execution of hostname on the host
toto.nowhere.com can be written :
taktuk -s -m toto.nowhere.com broadcast exec [ hostname ]
In this example, -s asks TakTuk to propagate its own code on remote
hosts. It can be removed by installing the taktuk executable on
toto.nowhere.com. By the following we will assume that TakTuk is
installed on all the remote hosts.
The -m toto.nowhere.com describe the set of remote hosts to be contacted by
TakTuk and broadcast exec [hostname] is a command that will be executed
by the TakTuk interpreter.
This example can be written in many other ways. In interactive mode, the same execution might become:
taktuk -m toto.nowhere.com
here TakTuk is blocked waiting for commands from stdin. Thus, we just have to type:
broadcast exec { hostname }
Ctrl-D
here you can notice that parameters to the exec TakTuk command (as all
commands parameters) can be enclosed in any reasonable pair of delimiters.
We might also write the list of hosts involved in the command in
a file machine that contains:
toto.nowhere.com
and the TakTuk command becomes:
taktuk -f machine broadcast exec - hostname -
We could also use another file options that contains:
-f machine
and use it as the options line given to TakTuk:
taktuk -F options broadcast exec \( hostname \)
Finally, everything could be stored in a last file command_line that
contains:
-f machine broadcast exec = hostname =
and the following command achieve the same result:
taktuk -F command_line
All of these variants have the same effect: they execute hostname on toto.nowhere.com and the output of the program is forwarded to the localhost. In this case:
toto.nowhere.com: hostname: somepid: output > toto.nowhere.com
taktuk -m localhost broadcast exec [ 'if [ $RANDOM -gt 10000 ];then echo greater;else echo lower;fi' ]
In this example, quotes are necessary to prevent the shell from interpreting
the $ and ; characters and to prevent the closing brace for if toe be
considered as closing the exec command.
In this case the variable will be interpolated
only on remote hosts. This same example can also be expressed using shortcuts
and intercative mode:
taktuk -m localhost -E%
then type:
b e [ if [ $RANDOM -gt 10000 %];then echo greater;else echo lower;fi ]
Ctrl-D
Notice the closing bracket used in the test that should not be
interpreted as the closing bracket for exec arguments. In such case, a
simpler solution is probably to use another kind of braces
taktuk -m localhost
and then: b e { if [ $RANDOM -gt 10000 ];then echo greater;else echo lower;fi } Ctrl-D
Usually, if you want to be safe, you can quote all commands parameters. Nevertheless, notice that parameters should not be quoted in interactive mode as input lines are not interpreted by the shell.
exec parameters.
For instance if you want to execute some command and send it a TERM signal
after two seconds, just type:
taktuk -m localhost broadcast exec timeout 2 [ sleep 10 ]
the callback executed when a timeout occurs can also be something else than a TERM signal. This can be another signal (KILL for instance):
taktuk -m localhost broadcast exec timeout 2 kill 9 [ sleep 10 ]
or any valid TakTuk command:
taktuk -m localhost broadcast exec timeout 2 action broadcast exec [ echo hello ] [ sleep 10 ]
or even several timeouts and several callbacks:
taktuk -m localhost b e t 2 a e [ echo hello ] k 30 t 10 k 9 [ sleep 5 ]
in this last example, the command sleep 5 is executed by TakTuk. After 2
seconds, the first timeout will be triggered, it will execute the command
echo hello and send a USR1 signal to the first command (sleep 5). The
second timeout is set to 10 seconds. Thus, it will never occur as the
sleep 5 command will be terminated before its expiration.
print_tree command to print the tree constructed by TakTuk.
Notice that it is usually a bad idea to use a too large window as it results in too much local load and bad distribution of work (something like 10 is often sufficient).
You can also force TakTuk to use more specific topologies. For instance, to
execute echo $$ using a flat-tree as deployment topology, just disable
work-stealing in TakTuk:
taktuk -d -1 -m host1 -m host2 -m host3 broadcast exec [ 'echo $$' ]
and to use a chain-like topology, either encode the topology in arguments structure:
taktuk -m host1 -[ -m host2 -[ -m host3 -] -] broadcast exec [ 'echo $$' ]
or limits the arity of the dynamic tree to 1:
taktuk -d 1 -m host1 -m host2 -m host3 broadcast exec [ 'echo $$' ]
Finally, the default will use a dynamicly constructed topology:
taktuk -d 0 -m host1 -m host2 -m host3 broadcast exec [ 'echo $$' ]
taktuk -m node1.cluster1 -[ -m node2.cluster1 -m node3.cluster1 -m node4.cluster1 -] -m node1.cluster2 -[ -m node2.cluster2 -m node3.cluster2 -m node4.cluster2 -] broadcast exec [ hostname ]
This command has the effect of deploying TakTuk on two clusters (cluster 1
and 2) made of four nodes (node 1 to 4) using node1 of each cluster to deploy
the other nodes in the same cluster. Finally, once the deployment is complete,
it executes the command hostname on all these nodes.
./taktuk -m host1 -[ exec [ hostname ] -] -m host2 -[ exec [ id ] -] -m host3 -[ exec [ 'echo $TAKTUK_RANK; ls' ] -] quit
but this could also be given using set specification (in this case logical number are used for hosts):
./taktuk -m host1 -m host3 -m host8 1 exec [ hostname ], 2 exec [ id ], 3 exec [ 'echo $TAKTUK_RANK; ls' ]
or in interactive mode:
./taktuk -m host1 -m host3 -m host8
1 exec [ hostname ]
2 exec [ id ]
3 exec [ echo $TAKTUK_RANK; ls ]
Ctrl-D
essai.pl on three hosts, knowing
that taktuk and essai.pl are only present on the root node:
taktuk -s -m host1 -m host2 -m host3
broadcast exec [ perl -- - ]
broadcast file_input [ essai.pl ]
broadcast close
message.txt to the /tmp directory of each remote
host:
taktuk -s -m host1 -m host2 -m host3
broadcast exec [ cat - >/tmp/message.txt ]
broadcast file_input [ message.txt ]
broadcast close
be careful to shell interpretation when typing everything directly on the command line (each command must be a single argument):
taktuk -s -m host1 -m host2 -m host3 broadcast exec [ 'cat - >/tmp/message.txt' ]\;broadcast file_input [ message.txt ]
communication.pl contains the following Perl script:
if ($ENV{'TAKTUK_RANK'} == 1)
{
print "I'm process 1\n";
if ($ENV{'TAKTUK_COUNT'} > 1)
{
taktuk::send(to=>2, body=>"Hello world");
}
}
elsif ($ENV{'TAKTUK_RANK'} == 2)
{
print "I'm process 2\n";
my ($to, $from, $message) = taktuk::recv();
print "Process $to received $message from $from\n";
}
then the execution of the following command:
taktuk -m localhost -m localhost broadcast taktuk_perl [ - ]\;broadcast file_input [ communication.pl ]\;broadcast close
would produce an output similar to:
Astaroth.local: taktuk_perl: 3523: output > I'm process 2
Astaroth.local: taktuk_perl: 3523: output > Process 2 received Hello world from 1
Astaroth.local: taktuk_perl: 3523: status > 0
Astaroth.local: taktuk_perl: 3524: output > I'm process 1
Astaroth.local: taktuk_perl: 3524: status > 0
if the file communication.pl was placed in the login directory of the user,
this could have also been executed by the more simple:
taktuk -m localhost -m localhost broadcast taktuk_perl [ communication.pl ]
taktuk -o status -m host1 -m host2 broadcast exec [ 'echo $TAKTUK_RANK' ]
or removing the prompt before each line of output from commands:
taktuk -o output='"$line\n"' -m host1 -m host2 broadcast exec [ 'echo $TAKTUK_RANK' ]
or even changing the prompt to make it display only the stream type:
taktuk -o default='"$type > $line\n"' -m host1 -m host2 broadcast exec [ 'echo $TAKTUK_RANK' ]
and it also possible to redirect the status to file descriptor 2 only for the second host:
taktuk -m host1 -R status=2 -m host2 broadcast exec [ 'echo $TAKTUK_RANK' ]
and so on...
debug, warning and error functions of the package diagnostic. These routines, depending on the debugging level of the package in which they are called, produce an output that is propagated up to the root node and printed on screen.
By default the debugging level of packages is set to 2 (everything is printed out except debug messages). It might be changed for each package using the -D option. For instance the following code executes true on toto.nowhere.com and prints out every bit of internal messaging:
taktuk -D default=1 -m toto.nowhere.com broadcast exec [ true ]
but one could have executed the same command keeping only messages from the scheduler package:
taktuk -D scheduler=1 -m toto.nowhere.com broadcast exec [ true ]
or ensuring an execution exempted of any warning or error messages:
taktuk -D default=4 -m toto.nowhere.com broadcast exec [ true ]
taktuk -r
Notice that in this mode the behavior of TakTuk can seem very cryptic. This is not intended for ordinary users.
The development of TakTuk is still in progress, so there are propably numbers of bugs. For now, the following characteristics (some of them are not really bugs) have been identified :
synchronize command to avoid this.
synchronize command do not allow a proper
synchronization of the print_tree command. This might change in the future
but is not in the priority list.
taktukcomm(3)
The original concept of TakTuk has been proposed by Cyrille Martin in his PhD thesis. People involved in this work include Jacques Briat, Olivier Richard, Thierry Gautier and Guillaume Huard.
The author of the perl version and current maintainer of the package is Guillaume Huard.
TakTuk is provided under the terms of the GNU General Public License version 2 or later.