TAKTUK(1)

NAME
TakTuk - a tool for large scale remote execution deployment

SYNOPSIS
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] [-S files] [-T command] [-W scheme] [commands ... ]

DESCRIPTION
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).

OPTIONS
Caution, in TakTuk options are parsed in the order given on the comand line. This means that TakTuk is not POSIX compliant regarding options order. 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.

DEPLOYMENT OPTIONS

-c connector
--connector connector
    defines the connector command used to contact the following remote machines.

-d limit
--dynamic limit
    turns dynamic mode (work stealing) on or off for the deployment of all the following remote machines specifications. If "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.

-f filename
--machines-file filename
    "filename" is the name of a file that contains remote machines names (equivalent to several "-m" opions). In each line of this file, the first word is considered as a machine name and the remaining as comments.

-l login
--login login
    sets the login name for the following hosts. This assumes that the connector command accepts "-l" option (this is the case for ssh, the default).

-m hostname
--machine hostname
    "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.

-s
--self-propagate
    propagates the TakTuk executable through the following connectors and thus eliminates the need for a TakTuk installation on remote machines.

-z
--dont-self-propagate
    cancels a preceding -s option.

-F filename
--args-file filename
    "filename" is the name of a file that contains additional options for TakTuk. The parsing of the file is done when encountering this option.

-L hostname
--localhost hostname
    changes the name of localhost as viewed by TakTuk.

-S files
--send-files files
    gives to TakTuk a list of files to be sent upon successfull remote connection. Use with caution as it will slow down deployment (the files are transfered before the end of the deployment). The intended use is NOT to transfer application data files but rather files that are necessary to perform further connections from the remote node. "files" is a comma separated list of pairs "local_file:remote_file". It behaves as the "put" command.

-T command
--taktuk-command command
    "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.

COMMAND LINE PARSING OPTIONS

-C separators set
--command-separator separators set
    replaces the default set of characters that separates successive TakTuk commands.

-E character
--escape-character character
    defines an escape character that can be used to protect any following character from TakTuk interpretation. This protection applies nearly to the whole TakTuk command line.

-O separators set
--option-separator separators set
    replaces the default set of characters that separates successive words when reading options and commands from a file (using the "-F" switch).

I/O OPTIONS

-o stream=template
--output-template stream=template
    sets an output template specification for one of output streams designed by the given name. When giving only a stream name (without template) this disables the stream. Available streams include :

    "connector" (errors from the connector command)
        this stream contains in $line informations outputed to stderr by a connector command. Relevant fields include $host, $peer and others listed below.

    "error", "output" (error and output of remotely executed commands)
        these streams contain in $line informations outputed by executed command to stdout or stderr (respectively). Relevant fields include $host, $command, $pid and others listed below.

    "info" (general informations such as help summary or version)
        this stream contains in $line informations outputed by taktuk in response to commands such as "help" or "version".

    "state" (internal state of TakTuk instance)
        this stream contains in $line the state change code matching some TakTuk events. Codes are the following:

          0 - TakTuk is ready
          1 - TakTuk is numbered
          2 - TakTuk terminated
          3 - connection failed
          4 - connection initialized
          5 - connection lost
          6 - command started
          7 - command failed
          8 - command terminated
          9 - numbering update failed
         10 - pipe input started
         11 - pipe input failed
         12 - pipe input terminated
         13 - file reception started
         14 - file reception failed
         15 - file reception terminated

        The function event_msg($) can be used in the template to translate this code into a string that describes the event. Relevant fields include $host, $position, $rank, $count and others listed below.

    "status" (commands exit status)
        this stream contains in $line the return code of executed commands. Relevant fields include $host, $pid and others listed below.

    "taktuk" (internal messages, warnings and errors)
        this stream contains in $line error, warning and debug messages outputed by TakTuk itself. Relevant fields include $line_number, $package and others listed below.

    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 (notice that $father_position and $depth that appeared in 3.2.4 are not supported anymore and that $position evolved since 3.2.5):

    $command (not for "taktuk" nor "info")
        the command line execution that generated output.

    $count
        the total number of TakTuk instances.

    $eof
        an empty string or a newline depending on what character ended command output.

    $filename ("taktuk" only)
        the file in which a TakTuk diagnostic function has been called.

    $host
        the name of the host executing the current TakTuk instance

    $init_date ("connector" and "state" only)
        the time in seconds since Jan. 1, 1970 at which the remote TakTuk instance completed its initialization (including ssh connection time and self propagation if any).

    $level ("taktuk" only)
        the level of the diagnostic function called.

    $level_name ("taktuk" only)
        the name associated with the level of the diagnostic function called.

    $line
        the raw data outputed by a command or passed to a diagnostic function, any trailing newline removed (see $eof).

    $line_number ("taktuk" only)
        the line number at which a TakTuk diagnostic function has been called.

    $package ("taktuk" only)
        the package in which a TakTuk diagnostic function has been called.

    $peer ("connector" and "state" only)
        the remote machine for which a connector command outputed information.

    $peer_position ("connector" and "state" only)
        position on the command line of the remote host. This position is expressed as a path in the hierarchy of hosts expressed on the command line (dot separated position number at each level of imbrication).

    $pid (not for "taktuk" nor "info")
        the pid of the command line executed (that produced output).

    $position
        position on the command line of the current host. This position is expressed as a path in the hierarchy of hosts expressed on the command line (dot separated position number at each level of imbrication).

    $rank
        the logical number of TakTuk instance in which output is collected.

    $reply_date ("connector" and "state" only)
        the time in seconds since Jan. 1, 1970 at which the connector command replied to the local TakTuk instance (note that this does not include the initialization exange occuring before the remote TakTuk is considered as functional).

    $start_date ("output", "error", "connector" and "status")
        the time in seconds since Jan. 1, 1970 at which the command started (taken just after the call to fork()).

    $stop_date ("connector" and "status" only)
        the time in seconds since Jan. 1, 1970 at which the command terminated (after the closing of its stdout).

    $type
        the name of the output stream (connector, error, output, ...).

    $user_scalar
        a scalar, global to the package, initially initialized to undef, that the user is free to use for any purpose.

    at 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.

-R stream=descriptor
--output-redirect stream=descriptor
    redirect a given stream output to a given file descriptor number (located at the root node). See "-o" option for more details about streams output.

PERFORMANCE TUNING OPTIONS

-B parameter=expression
--worksteal-behavior parameter=expression
    caution: this feature should be considered as experimental and could be removed from future releases. Tunes finely the behavior of the work-stealing algorithm by setting some its parameters to Perl expressions. These Perl expressions can use the variables $last_given and $available which are respectively equal to the number of tasks given to a stealer last time it stole and to the total number of remaining deployment tasks. Available parameters are :

    initial
        the number of tasks given to a remote TakTuk instance the first time it send a steal request to the local host.

    growth
        the number of tasks given to a remote TakTuk instance each time it performs a steal to the local host after the first time.

    limit
        an upper bound to the value resulting from the evaluation of "growth".

-g duration
--time-granularity duration
    sets to "duration" (in seconds) the maximal interval between timeouts checks (usually checks are made more often: at each message received a timeouts check is made).

-n
--no-numbering
    disables TakTuk logical numbering and the variables "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.

-t timeout
--timeout timeout
    sets the timeout (in seconds) for following connectors (0 = no timeout). Notice that this option override the timeout of the connector command ("ssh" for instance). When the delay expires, the connector command is simply killed.

-w size
--window size
    sets initial window to the given size (= pipeline width).

-W scheme
--window-adaptation scheme
    sets the windows adaptation scheme to number (default is 0, 0: no adaptation, 1: implementation in progress).

MISCELLANEOUS OPTIONS

-M
--my
    makes the next option local (not inherited). This means that the next option is set only for the local host and not propagated to children TakTuk instances. Has no effect if the next option is already a local one.

-h
--help
    prints a short description of TakTuk on the screen.

-i
--interactive
    forces TakTuk interactive mode even after some batch commands given on the command line.

-v
--version
    prints the TakTuk version.

-P
--print-defaults
    prints the defaults settings used by TakTuk (environment variables taken into account).

INTERNAL OPTIONS
These option are not useful for most users. They are used either internally by TakTuk itself or for development purposes.

-p packagename
--print-package packagename
    prints the content of package "packagename" extracted from the taktuk code in execution.

-r
--not-root
    current TakTuk instance is not the root node. This is an internal switch used by spawned TakTuk instances. This is usually not useful for most users.

-D scope=level
--debug scope=level
    sets debugging level (1..4) for "scope". The "scope" might be a TakTuk package name or "default" and the lowest the level the more verbose the output.

COMMANDS
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:

[ set specification ] command
    Sends the execution of command to all the peers belonging to the given set. For more details about the set specification, see section "SET SPECIFICATION".

broadcast command
    Broadcasts the execution of command on all the remote peers (not including the node initiating the broadcast).

downcast command
    Spreads the execution of command on all the children of the node initiating the downcast (not including itself).

exec parameters * command line *
    Executes the "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.

get * src * * dest *
    Copies (a) remote source(s) (present on the remote node(s)) to a destination on the node executing this command. The type of source and destination is quite similar to those accepted by the "cp -r" command (that is file or directories). This command also performs some kind of magic with its parameters: shell environment variables present in the source or destination names are replaced by their respective value on the remote and local nodes. In addition, the variables $host, $rank and $position of the remote node (which are the same as in -o option) can also be used in both names.

help
    Prints a very concise TakTuk help.

input * data *
input data * data *
    Sends the parameters as input to each command in execution on the local machine.

input close
    Closes the inputs descriptor of all executing commands on the local machine.

input file * filename *
    Sends the content of a file (which must be local to the node executing the input file) as input to each command in execution on the local machine.

    WARNING: this command is not atomic. If you manage somehow to initiate a input file 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.

input line * data *
    Sends the parameters with an additional newline as input to each command in execution on the local machine.

input pipe * data *
    Treat the parameter as a filename (which must be local to the node executing the input pipe) which behavior is the same as a pipe: data can arrive continuously. TakTuk add it as one of its input channels and send data as input to commands when available.

kill <signal>
    Sends the given signal to local commands processes groups. If no signal is given, sends a TERM signal (signal 15).

network
network state
    Prints the current TakTuk deployment tree. Numbers in parenthesis match the peer rank in the logical TakTuk numbering and the peer ready state. If the deployment is not complete, the printed tree will display "connecting ..." leaves.

network cancel
    Cancels all ongoing connections. Consequently, this causes immediate starting of the possible numbering of TakTuk instances and the execution of TakTuk commands.

network renumber
    Completely recomputes the logical numbering of TakTuk instances. This is especially useful when adding new nodes to the deployed network after initial numbering.

network update
    Updates the logical numbering of TakTuk instances without changing already existing numbers. Does not always succeed as TakTuk uses a depth first scheme for numbering. Sends an event 9 in the stream 'state' for each node of the tree that cannot be updated while keeping TakTuk numbering scheme. This is especially useful when adding new nodes to the deployed network after initial numbering.

option name * value *
option * line *
    Either changes a single option which name is given (first form) or parses an additional options line (second form) on the node(s) executing this command. See TakTuk options for more details, name can be either short or long in the first form.

    WARNING: new nodes added to TakTuk network using this command are not numbered. Further use of network renumbering or update is necessary to get TakTuk logical numbering.

put * src * * dest *
    Copies a local source (present on the node executing this command) to a destination on all the remote nodes given as prefix of the command. The type of source and destination is quite similar to those accepted by the "cp -r" command (that is file or directories). This command also performs some kind of magic with its parameters: shell environment variables present in the source or destination names are replaced by their respective value on the local and remote nodes. In addition, the variables $host, $rank and $position of the local node (which are the same as in -o option) can also be used in both names.

synchronize
    Forces the given command to wait for the completion of deployment, nodes numbering and previous commands before executing. This is usefull for commands like "broadcast" which does not wait for nodes numbering.

taktuk_perl * arguments *
    Forks a perl interpreter on the local node just as if the command "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).

version
    prints TakTuk version.

quit
    Quit the TakTuk engine and shut down the logical communication network established during the deployment.

EXEC PARAMETERS
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:

timeout value
    Creates a new timeout specification. At the end of the duration expressed by the given value, it will trigger its attached callbacks. If it has no attached callback, it will send a TERM signal to the command. If the command execution terminates before the end of the timeout duration, the timeout is canceled.

kill value
    Attach a callback to the last defined timeout. This callback send a signal, which number is the given value, to the timeouted command.

action command
    Attach a callback to the last defined timeout. This callback executes the given TakTuk command. If it executes some other command, it can use the environment variable "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.

ENVIRONMENT

Variables that change TakTuk default behavior
    Some of TakTuk defaults settings can be changed on some host using environment variables. These settings are propagated as are other options. They are overridden by propagated settings and command line options.

    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.

    You can also change some TakTuk default settings locally without propagating the change in the deployment tree. To do this, use the variable TAKTUK_MY_NAME where name is defined as above. As before, these local settings are overridden by propagated settings and command line options.

Variables set by TakTuk in remotely executed commands
    Taktuk sets the following environment variables for all the commands it executes :

    TAKTUK_CONTROL_READ, TAKTUK_CONTROL_WRITE
        File descriptors, used internally by TakTuk.

    TAKTUK_COUNT
        The total number of successfully deployed TakTuk instances

    TAKTUK_HOSTNAME
        Local node hostname as given to TakTuk (on the command line)

    TAKTUK_PIDS
        List of pids (separated by spaces) of commands executed by the local TakTuk instance.

    TAKTUK_POSITION
        Host position on the command line.

    TAKTUK_RANK
        The logical rank of the local instance

HOSTNAMES SPECIFICATION
Hostnames given to TakTuk might be simple machine name or complex hosts lists specifications. In its general form, an hostname is made of an host set and an optional exclusion set separated by a slash. Each of those sets is a comma separated list of host templates. Each of these templates is made of constant part (characters outside brackets) and optional range parts (characters inside brackets). Each range 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],otherhost/node2
    node[1-3,5]part[a-b]/node[3-5]parta,node1partb

they respectively expand to:
    node1
    node19
    node1 node2 node3
    node1 node3 otherhost
    node1parta 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).

SET SPECIFICATION
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

EXAMPLES
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.

simple deployment
    the simplest way to use TakTuk is to make it selfpropagate with option "-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

parameters braces
    notice that braces for command parameters must be separated from their content. Thus, they can contain other braces as long as no single closing brace is part of the content:

        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
    commands executed by TakTuk can be timeouted using "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.

topology
    Usually, TakTuk deploys itself using a relatively flat tree because its default window size is quite large (10 simultaneous ongoing connections). Using a smaller window size will result in a deeper tree although it also depends on the local load of the deployment nodes. You can use the TakTuk "network state" 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 $$' ]

lightweight grid deployment
    On a lightweight grid, because of locality issues (ldap cache, network topology, ...) it seems interesting to separate the deployment of each subcluster. To do this, it is possible to choose one node in each subcluster that will be deployed first and from which the rest of the cluster will be deployed:

        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.

executing a distinct command on each host
    each distinct host can be given its own command using arguments:

        ./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

script diffusion
    spreading and executing a perl script named "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 input file [ essai.pl ]
        broadcast input close
        Ctrl-D

files diffusion and collection
    since version 3.4, files transfer is supported directly by TakTuk. Notice that this transfer uses the TakTuk network (usually a tree composed of ssh connections by default). This network is not efficient for the tranfer of large files (both topologically and from a protocol point of view), so keep this in mind when using this feature.

    copying a file named "message.txt" to the "/tmp" directory of each remote host is thus as easy as:

        taktuk -s -m host1 -m host2 -m host3
        broadcast put [ message.txt ] [ /tmp ]
        Ctrl-D

    but the older method still works (and does almost the same as the previous command):

        taktuk -s -m host1 -m host2 -m host3
        broadcast exec [ cat - >/tmp/message.txt ]
        broadcast input file [ message.txt ]
        broadcast input close
        Ctrl-D

    although it reuqires to be more careful about shell interpretation when typing everything directly on the command line:

        taktuk -s -m host1 -m host2 -m host3  broadcast exec [ 'cat - >/tmp/message.txt' ]\;broadcast input file [ message.txt ]

    notice in this latter command that the "input close" is not necessary as TakTuk closes inputs of all spawned commands when quiting.

    the "get" command also makes possible things that were previously very difficult in TakTuk, files collecting. The following command gets the file "/tmp/message.txt" from each remote host and copies it locally to "message-number.txt" where "number" is the logical rank of the source node:

        taktuk -s -m host1 -m host2 -m host3
        broadcast get [ /tmp/message.txt ] [ message-$rank.txt ]
        Ctrl-D

    finally, it seems important to mention that "put/get" commands can copy directories and keep files permissions unchanged.

communication
    establishing a point-to-point communication. Assume the file "communication.pl" contains the following Perl script:

        my $rank = taktuk::get('rank');
        my $count = taktuk::get('count');
        if ($rank == 1)
          {
            print "I'm process 1\n";
            if ($count > 1)
              {
                taktuk::send(to=>2, body=>"Hello world");
              }
          }
        elsif ($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 input file [ communication.pl ]

    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 ]

output templates and redirections
    making each site echo its rank without command status information:

        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...

debugging TakTuk
    debugging in TakTuk is made using "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 ]

internal messages server
    the internal message server used in TakTuk for the management of logical network construction, commands execution and I/O forwarding can be exposed using the -r option:

        taktuk -r

    Notice that in this mode the behavior of TakTuk can seem very cryptic. This is not intended for ordinary users.

BUGS
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 :

hanged commands
    currently TakTuk do not quit (even if asked to do so) if some local commands do not terminate upon the closing of their standard input. Interrupting TakTuk actually terminate the engine but do not kill these commands. We still have to decide if this is the appropriate behavior.

command order
    broadcasts and multicast (set specifications) are not synchronized the same way in TakTuk. Thus, broadcast commands given after multicast commands might be executed before these last ones. Use the "synchronize" command to avoid this.

slow connections
    this is not really a bug : on some clusters, the connections are VERY slow when doing a large deployment (over 50 nodes) with self propagation. This result in a total time for the deployment of 50 nodes that can take several minutes (up to half an hours in some cases). I don't know what's the exact cause (ldap ? local load ? writes block ?) but it can be fixed by adding connection timeouts to connectors.

fork failures
    this is not really a bug : when a machine is highly loaded, fork may fail. If this happen to a local command, a distributed application may deadlock, because the taktuk instances numbering is correct but some instance didn't fork the local command. The simplest fix is to use timeouts on taktuk::recv().

You might also want to have a look at:

    http://taktuk.gforge.inria.fr/Bugs.txt

where all the temporary bugs are listed version by version.

SEE ALSO
taktukcomm(3)

AUTHOR
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 version 3 (perl version) and current maintainer of the package is Guillaume Huard.

COPYRIGHT
TakTuk is provided under the terms of the GNU General Public License version 2 or later.