Most often, such data can be organized in a table with rows of information, each column representing a different kind of data. For example, in the case of processes running on a computer system, rows might be sorted according to their unique process identifier, with columns containing values such as CPU usage, memory usage, owner's name, time of creation, ...
The software used to view this type of information comes in different forms and shapes. Unix users might be familiar with the top application which presents rows of process data as lines of text, whereas RMON (Remote MONitoring) SNMP software usually uses multiple windows with graphical displays, curves, pie charts, multiple configuration dialog boxes, even 3D visualization modules to visualize network traffic, connection matrices, ...
In most cases, data comes from one or more tables. A common interface, graphical with menus, drag'n'drop capability, table widgets, textual and graphical data viewers such as multiple line graphs, bar and pie charts, could be used. The user could then sort table rows, select one or more cells, rows, columns, create views such as other tables, charts, ... best suited to the way data should be presented. Once optimized, the data viewers layout and configuration could be saved for later reuse as a dashboard. In effect, what is needed is a spreadsheet tailored to dynamic data processing.
Moodss (Modular Object Oriented Dynamic SpreadSheet) is an attempt at answering these needs. It is composed of a main part (the core) and an unlimited number of modules, loaded as the application is launched or while it is running, each module interfacing to a specific type of data. The core is written in the great Tcl language (at http://www.scriptics.com/) using object oriented techniques thanks to the stooop package (at http://jfontain.free.fr/). The module function is to describe the data that it is also in charge of retrieving and formatting. Modules can be written in plain Tcl or use dynamically linked libraries written in the C language (modules are packages in the Tcl sense, so any language that can interface with Tcl is supported).
Modules are loaded when moodss is started or dynamically at a later time. Several modules can be handled concurrently (starting with moodss version 3.0). This way, you may monitor data coming from any number of heterogeneous sources. Modules are specified in the command line or dynamically loaded, and can be unloaded at any time.
Versions 4.0 and up add a dashboard functionality: the current configuration (modules, viewers, poll time, windows sizes and placement, ...) can be saved in a file at any time, for later reuse (see the -f (--file) command line switch documentation).
Versions 4.3 and up support asynchronous modules (for which no polling is needed as module data may change on its own). Note that any number of asynchronous and regular (synchronous) modules can be simultaneously loaded.
Versions 5.0 and up add a free text viewer, which can be used for comments, and which can also embed live data cells in text form.
Versions 5.3 and up support viewer type mutation through viewer icon drag'n'drop, and viewer quick destruction by a drop into the eraser icon. A new menu for empty viewer creation was also added.
Versions 6.0 and up support command line arguments per module, data table column anchoring in module configuration and automatic module discovery.
Versions 6.1 and up support HTML formatted help data for modules.
Versions 6.6 and up support automatic cross hairs with coordinates in message area for graph data viewers.
Versions 6.7 and up support contextual help (through the main window message area) on all menu items.
Versions 7.0 and up support per user (on UNIX systems) application wide preferences setting.
Versions 7.99 and up support concurrent instances of the same module.
Versions 8.1 and up support configuration settings per dashboard, with a user interface similar to the preferences interface.
Versions 8.6 and up add a stacked graph viewer.
Versions 8.8 and up allow printing in postscript to printer or a file.
Versions 8.9 and up allow printing previewing.
Versions 8.17 and up allow dynamically loading modules.
Versions 8.18 and up allow dynamically unloading modules.
Versions 8.22 and up allow swapping columns and rows in module data views.
Versions 8.26 and up include a core trace module that allows displaying message from other loaded modules.
Since module data access is entirely customizable (through C code, Tcl, HTTP, ...) and since several modules can be loaded at once, applications for moodss become limitless. For example, comparing a remote database server CPU activity and traffic load from a network probe on the same graph becomes possible.
As features are added to moodss, different ways of viewing data will be made available while the module structure will stay the same. The goal of moodss is to become a nice feature packed generic way of viewing data. Moodss can be used to monitor any type of data, since the simplest cases can fit in one table with a single row, with the most complicated requiring loading several multiple table modules.
As moodss is written in Tcl and uses well supported extensions (Tktable and BLT), it will run on Tcl/Tk supported platforms: UNIX and Windows (I do not know if Tktable and BLT are available for the MacIntosh). Obviously, some modules may be specific to a platform, but the core is guaranteed to run on them all.
After reading and understanding this document, you should be able to write your own modules in order to monitor the data that you are interested in.
Moodss is free software. You can redistribute it and/or modify it under the terms described in the COPYRIGHT file or use the main window Help Copyright menu for more information.
Unless you want to work on the moodss source code (not the modules), you can skip the rest of this section.
For the current version (8.27), the following packages must be installed before attempting to install moodss (make sure to check the INSTALL file for the latest information):
The core loads one or more modules, whose names are passed as command line parameters, come from a save file or are dynamically loaded, and starts displaying module data in one or more tables. The tables are then updated at the frequency defined by the poll time, which the user may change, or asynchronously for the relevant modules. For example, to launch moodss with the random module, just type (on a UNIX machine):
$ moodss randomAll the module code and data are kept in a separate namespace. The module data is stored is a single array including some configuration data used when the module is loaded by the core, and variable data (displayed in the application table and eventual graphical viewers). If a module is synchronous, it must start updating its data when requested by the core. If a module is asynchronous, its data may be updated at any time. The synchronous or asynchronous nature is specified in the configuration data for the module.
The initial data tables represent the first data views, from which any number of cells can be selected. Data viewers can be created by dragging and dropping cells into a graph, bar chart, pie chart, summary table or free text iconic site. In turn, these viewers can display more table cells, which when dropped into the viewer, result in the creation of corresponding data graph lines, chart bars, pie slices, table rows or text cells. Cells or rows can be removed from existing viewers, by simply selecting them and dropping them in the eraser iconic site (a pencil eraser).
Any viewer can be mutated (its type changed) by dragging from a viewer icon and dropping into it. For example, create a stacked data bar viewer from several cells, then drag the 3D pie icon into it. Any viewer can also be destroyed in one shot by dropping the eraser icon into it.
Any draggable data can be dropped in any valid drop site at any time. It is thus possible to drag several data cells from any table or any viewer into other ones, the eraser, ... even if the data comes from different modules.
All data viewers can be moved and resized at will with the help of a simple internal window manager.
The current configuration (loaded modules, tables and viewers coordinates, sizes, poll time, main window size, ...) can be saved in a file at any time, so that an identical dashboard can be relaunched at will.
The window title shows the name of the loaded module(s) along with the poll time.
When several modules of the same type are loaded (for example, CPU statistics on a group of servers), the initial data tables feature the module name followed by an instance number (module<N>), or the module identifier generated from the module code (cpustats(host.domain.org) for example). A lone module keeps his unmodified name as table titles.
Any data displayed in a table can be sorted (provided that the related module allows it) at any time by simply clicking on a column title. Clicking on the same column title again sorts the data in opposite order, thus toggling between increasing and decreasing orders.
When sorting, the selected column is used as a reference, meaning that all rows will be rearranged so that the selected column appears sorted, with values either increasing or decreasing.
A little triangular indicator is placed to the right of the reference column title label, pointing up or down depending on whether the sorting order is decreasing or increasing.
Table columns can be interactively resized by holding the first mouse button down on a column border. The mouse cursor is changed to an horizontal double arrow on column borders to show this capability.
Aside from the main tables, graphical and textual viewers can be created for monitoring table cell data over time. Viewers can also be deleted, data views (such as pie slices, curves, ...) can be added or removed from existing viewers, ... These functions are all implemented using the drag and drop functionality.
For all viewers, if a module identifier string is required (provided by the module, several instances of the same module, ...) for proper cell identification, that string will be placed first in the label. For example, data cells originating from the third instance of the random module would be labeled: "random<3>: data cell label".
Graphical viewers available at this time are BLT graph viewers (see images below), side-by-side bars charts, overlapped bars charts, stacked bars charts, 2D pie charts and 3D pie charts*. Graph viewers feature an automatic cross hair which follows the mouse pointer movements inside the plotting area. Corresponding coordinates are updated in real time in the main window message area.
*note: if you know of any other nice viewers (like 3D graphs) that work with Tcl, please let me know so I can integrate them. Many thanks in advance...
The summary table displays for each row the cell label, the current, average, minimum and maximum values since the row was created. Data cells can be inserted one or several at a time through a simple drop. Rows can be deleted by selecting any cell in the row then dropping any number of them into the eraser drop site. Data cells with missing data (could be no longer available if coming from a vanished process, for example) display the ? character.
The free text viewer is an editable Tk text widget with any number (including zero) of embedded data cell windows. Data cells can be inserted one or several at a time through a simple drop, as with the other viewers. New data cell windows are inserted at the current insertion cursor position. Data cells can be deleted by selecting then dropping any number of them into the eraser drop site. They can also be deleted using the keyboard Delete and Backspace keys, which also work on the regular text, as well as the expected other key bindings. When dropping data cells, each data cell window is preceded by a relevant label text for the cell, which can later be edited at any time.
Here is another shot featuring a free text viewer with loaded cpustats and memstats modules:
Once moodss has been launched with one or several modules and tables have been moved, resized, viewers created, moved and resized, the current configuration can be saved in a .moo file, and later reused by passing the corresponding file name with the -f (--file) command line switch.
For moodss version 4.0 and above, the following information is saved in the file (which is human readable):
Once a file name has been specified (either through the command line or the file selector dialog box), that file name is reused whenever the File Save menu is used.
Once the new module, or new instance of an already loaded module, is loaded, the application behaves as if the module had been loaded from the start.
You can choose the printout orientation (portrait or landscape), palette (color, gray scale or monochrome) and the paper size.
Due to widget and architecture limitations, the printout is pixel based. As a benefit, it is extremely WYSIWYG :-).
Also, because of design limitations, printing is disabled on Windows platforms.
The printout is sized according to the following rules:
When the print menu entry is selected, a dialog box appears, as can be seen in the screen shot below (which also shows the preview window):
Depending on the print configuration (see Preferences), either a print command line entry or a printer selection list appears below the informational message. Hitting the OK button sends the data to the selected printer or through the specified command line.
The preview functionality uses gs (also known as ghostscript), which must be installed (note: version 5.50 is required, as 5.10 is buggy). If gs cannot be found or executed, the preview button is grayed. If the gs version is below 5.20, the button is also grayed and a window tip explaining the cause is displayed when the mouse pointer is located above the button.
When the gs utility is available and of the correct version, the preview button can be depressed, in which case the print dialog temporarily disappears (so that the application main window is not obscured), and reappears along with the preview window, once the printout view has been calculated.
The preview window also features a zoom menu for resizing. If the user so desires, one or more printing parameters, such as page size, orientation, ... can be changed while the preview window remains visible. Hitting the preview button then results in both the print dialog box and the preview window to temporarily disappear while the new page look is calculated. After a short while, they both reappear with the preview updated accordingly, and having kept the same zoom ratio.
Also note that due to the implementation of the graphical layer on UNIX systems, any window or object obscuring the canvas area will also be printed, but this is unlikely, as the moodss application window will be in front when the print menu item is selected.
Furthermore, note that printing will only work if you have the dash patch (at ftp://ftp.neosoft.com/pub/tcl/sorted/packages-8.0/devel/tk8.0.5dash.patch.gz) installed in your Tcl/Tk interpreter.
You may use Tcl/Tk version 8.3, which includes the required canvas printing facilities instead, along with the corresponding moodss version (get the software and documentation at http://jfontain.free.fr/).
If there are unsaved changes (configuration, viewers created, tables or viewers moved, stacked, ...), the user is given the opportunity to save them to file (see File Save menu). The file selector dialog box is used if no save file name is currently known by the application.
Preferences choices, when applied (either by choosing Apply or OK) also affect configuration settings.
Further and up-to-date help is always provided in the different Preferences dialog box screens.
When printing to a file, you may choose its default location and name with the file browser. Note that it can be overriden in the print dialog box launched when actually printing.
When several modules are used, the minimum poll time is the greater of the minimum poll times of all modules. The default poll time (used when moodss is started) is the greater of the default poll times of all modules. The available choices in the poll time dialog box is the combination of all modules poll times.
The Poll time menu entry is available only when needed, which is not the case if all the loaded modules are asynchronous. If this case, the Options menu itself is not displayed.
This menu is only visible when not running in read-only mode (see Command line).
Only valid drop sites for the data being dragged are highlighted when the mouse cursor passes over them, thus guaranteeing error free operations (if there are no bugs, that is :).
In summary, data cells can be dragged from any table or any viewer into any viewer drop site icon, any viewer or the eraser.
Once a viewer exists, it also acts as a drop site for data cells, which may be dragged from any table or other viewers. Dropping one or more cells directly in the viewer results in corresponding lines, bars, slices or rows being created and automatically updated. Each new graphical element is assigned a new and different color.
You may delete one or more viewer elements (graph lines, bar chart bars, pie charts slices, summary table rows or free text cell window) from a viewer by selecting them (using the first mouse button) through their labels. Several elements can be selected by depressing the control key as the first mouse button is pressed. The selection can also be extended by depressing the shift key along with the first mouse button. The pie slices can also be directly selected by clicking on the slices themselves.
Then dragging from the viewer to the eraser drop site (the pencil eraser) on the upper right side of the main window and releasing the first mouse button result in the corresponding viewer elements to be destroyed. When there are no remaining elements, the viewer itself (graph, bar chart, pie or summary table) can be destroyed by dropping it into the eraser site. The free text viewer can only be deleted this way when completely emptied of any text and data cell window.
Any viewer can be deleted in one shot by dropping from the eraser icon into it.
Any viewer also acts as a drop site for viewer type data, which allows viewer mutation by just dropping from the new viewer type icon into the existing viewer. It is much quicker than destroying the existing viewer and create a new one of the new type, while remembering which data cells were monitored by the viewer of the old type.
When mutating, if some cells in the current viewer no longer exist (they may belong to a disappeared summary table), they are not made a part of the new viewer, and a warning message is flashed to the user in the message area.
Any viewer is also a drag site. It requires selecting one or more viewer elements before initiating the drag operation from any selected element in the viewer. If there are no selected elements, dragging is impossible: the mouse cursor is not changed into the drag circular cursor.
If a viewer contains no elements, then the viewer itself can be dragged and dropped into the eraser.
All viewer icons (below the menu bar) are drag sites for viewer type data, which allows quick viewer mutation (see mechanism description in Drop sites).
The eraser icon is also a drag site of the killing action type, which allows viewer destruction in one shot.
$ moodssor
$ wish moodssif the Tcl/Tk wish interpreter is not found in your PATH. You can then dynamically load modules from the File menu.
You can also just pass one or more data module names as parameters, as in:
$ wish moodss randomor, for 2 modules at once:
$ wish moodss ps cpustatsYou can specify the same module more than once and with different arguments in the command line:
$ wish moodss ps -r host.domain ps -r otherhost.domainWhen several modules of the same type are passed as argument, the initial data tables feature the module name followed by a number as title. For example "ps<2>". If the module provides an identifier string, that text will be used instead, as in "ps(host.domain)". Data cell labels include the module identifier or numbered module name as well, for proper identification.
You may eventually specify a poll time in seconds using:
$ wish moodss -p 25 randomNote that when all the specified modules are asynchronous, the poll time option specifies the preferred interval for graph viewers.
Once saved through the File Save menus (for example in save.moo), the configuration can be retrieved using:
$ wish moodss -f save.moowhich would result in the same modules being loaded, the same viewers displayed at the same positions and sizes, the same poll time being used, as well at the same application window size. New modules data displays can be added at any latter time to existing dashboards by specifying modules on the command line after the -f (--file) switch / value pair.
Command line options include:
In debug mode, when errors occur within the module namespace body or initialize procedure, the error message (either in text output when loading the module from the command line, or in a message window when dynamically loading the module) is followed by a Tcl stack trace of what was in progress when the error occured (see the Tcl error manual page for further information).
For example, the following command:
$ moodss -p 15 random --asynchronous arp --remote jdoe@foo.bar --numeric route --numericcauses the random module to update asynchronously, the arp module to collect data from the foo.bar host under the jdoe login name and not attempt to lookup symbolic names for hosts, with the last module route doing the same.
Note the setting the application poll time to 15 seconds does not interfere with the module options.
The moodss core checks the validity of module options according to the information provided by the module programmer. Any invalid option / value combination for the module is detected, reported on the standard error channel before the application exits.
Finally, it is always possible to determine the valid options for a module, using the following command:
$ moodss module --help
Changing configuration choices do not affect the Preferences choices.
Configuration entry is done through pages organized in a browsable hierarchical tree, always visible on the left side of the configuration dialog box (see picture above).
After selection of the category from the tree on the left, a related dialog interface appears, which may or may not allow immediately applying new data values.
Clicking on the OK button results in the current configuration data to be saved in memory. It will be stored in the save file when requested (see File Save and Save As menus).
Specific help can always be accessed by clicking on the bottom Help button when in a configuration page.
The default is the current screen size.
The size is immediately updated when clicking on the Apply button.
The color is immediately updated when clicking on the Apply button.
Advice: adjacent colors should be very different, colors should be visible on a black background.
Note: in a future version, creating, deleting and moving colors in the sequence will be possible.
The selected type will not be used for existing pies but for newly created ones.
On UNIX systems, preferences data is saved in each user home directory under the rc file named .moodssrc.
On Windows, data is saved in C:\.moodssrc (by default, but depends on the HOME variable).
After selection of the category from the tree on the left, a related dialog interface appears.
Help is provided for each interface, which may or may not allow immediately applying new data values.
Clicking on the OK button results in the preferences data to be written to the rc file.
The default behavior when printing can be set to either a printer or a file, but can always be overriden in the print dialog box launched when actually printing.
Various parameters, such as orientation, palette and paper size can be set.
The print command typically reads the Postscript data from its standard input and redirects it to the specified printer (for example, on UNIX, lpr -Pacme will print the canvas area on the acme printer, and lpr -P%P will allow printer selection from a listbox at printing time.
When printing to a file, you may choose its default with the file browser.
package provide random 1.1This line simply states that this is the 1.1 version of the random package. Please note that the package name must also be used as the module namespace name (see below).
Module names can be any combination of the following characters:
namespace eval random {
array set data {
...
}
proc update {} {
...
}
}
The update procedure is not needed when the module is asynchronous.
All the module configuration data is stored as array members of the array named data within the module namespace. For example:
namespace eval random {
array set data {
updates 0
0,label name 0,type ascii 0,message {user name}
1,label cpu 1,type real 1,message {cpu usage in percent}
2,label disk 2,type integer 2,message {disk usage in megabytes}
3,label command 3,type dictionary 3,message {most time consuming command} 3,anchor left
pollTimes {10 5 20 30 60 120 300}
sort {1 decreasing}
indexColumns {0 3}
helpText {
This is a simple demonstration module ...
}
}
...
}
The updates member is a counter used to keep track of the number of times that the module data was updated, and is also used by the core to detect when module data display should be updated (see variable data for more information).
The columns member is obsolete and no longer used after and including moodss version 3.5.
The n,label members define the text to be displayed as column titles. There must be as many n,label members as they are columns. The titles must contain no ? character.
The n,type members define the type of the corresponding column data. Valid types are simply those that the Tcl lsort command can handle: ascii, dictionary, integer and real. There must be as many n,type members as they are columns.
The n,message members define the text of the help message to be displayed in a floating yellow window (widget tip, balloon, also see User Interface) as the user moves the mouse pointer over column titles. It can be composed of only a few words or multiple formatted lines. There must be as many n,message members as they are columns.
The n,anchor member is optional. Column data is either centered by default, tucked to the left or right side of the column. Valid values are center, left or right.
Note that column numbers start at 0. There must not be any hole in the column numbers sequence.
The pollTimes member is a list of valid poll times (in seconds) for the module. The list is not ordered, as its first element represents the default poll time value to be used when the moodss application starts. This value may be overridden by a command line argument. The smallest value in the list is used by the core as the lowest possible poll time and checked against when the user enters a new value through the poll time dialog box. The list must not be empty.
Note that the list is also used by moodss as a set of possible choices in the dialog box used to set the new poll time. The user may still directly input any value as long as it is greater than or equal to the minimum value.
If the module is asynchronous (data can be updated at any time and not in response to update procedure invocations (no polling required)), the pollTimes member must be a single negative integer value representing the preferred time interval for viewers that require one (only graphs at this point). For example, if you wish graph viewers to have a display interval of 10 seconds, use:
namespace eval random {
array set data {
...
pollTimes -10
...
}
...
}
In this case, the graph viewers time range (knowing that they feature 100 time points) would be 1000 seconds. I guess that the value that you should specify as the pollTimes member should be the expected average update interval for your asynchronous data. Note that the graphical viewers x axis always display properly labeled absolute time ticks in any case.
When several asynchronous modules are loaded with no synchronous modules, the interval used for all relevant viewers is the average (in absolute value) of all module intervals. For example, if you load 2 asynchronous modules, one with a pollTimes member of -10 and the other of -20, then a 15 seconds interval value is retained. Note that the interval can be forced through the --poll-time command line argument.
If at least one synchronous module is loaded concurrently with any number of asynchronous modules, the actual application poll time (the one that can be set with the then available poll time dialog box) is used.
The indices member is an optional list that specifies the table columns that should be displayed. If not specified, all the table columns are visible.
Note: visibleColumns, the previous keyword for that function, is obsolete (but still supported) after moodss version 11.7.
The sort list is optional. It defines the index of the column which should be initially used as a reference for sorting the data table rows, and in which order (increasing or decreasing) the rows should be sorted. The column index for sorting works like the -index Tcl lsort command option, that is rows are sorted so that that specific column appears sorted in the specified order. The specified column must be visible (see indices member documentation above).
The indexColumns list specifies the columns required to uniquely identify a row in the table. In database talk, it represents the table key. To maintain backward compatibility, it is optional and defaults to 0, the leftmost column. The index columns are used when creating data viewer elements: their label is built by concatenating the key value for the cell row with the cell column title. The key value is the concatenation of the index column values for the cell. When specified, all the columns in the list must be visible (see indices member documentation above).
The helpText member specifies a text of any length, to be displayed when the user requests help information on the current module from within the help menu. The text can be HTML formatted or plain. HTML formatted help requires the <HTML> and <BODY> tags to be present, while tables and frames are not supported (and many other tags: stick to formatted text at the moment). The core will render HTML formatted or plain text in the module help window according to the help text contents.
The views member is optional. If specified, it defines one or more views to be used in place of the default view. One table will be displayed per view. Each view is a list of array members, suitable as an argument to an "array set" command. For each view, 2 members must be defined: indices, the sort member being optional (syntax and usage are identical to the default table members). A swap optional member may be used if the table data is to be displayed with columns and rows swapped, which is generally the case when the data table has 1 or 2 rows, or a fixed number of rows (see memstats module for an example). The swap value is a boolean and must be either 0 or 1.
The switches member is optional. If specified, it defines a list of switch / boolean pairs. A switch is a single letter or a string prepended with the - or + sign. The boolean value (0 or 1) specifies whether the switch takes an argument. If the switches member exists, an appropriate initialize procedure must be provided by the module (see Initialization). The core will take care of parsing the command line and reject any invalid switch / value combination for the module. The switches value may not be changed in the initialize procedure.
For example, a recent random module configuration is as follows:
array set data {
updates 0
0,label name 0,type ascii 0,message {user name}
1,label cpu 1,type real 1,message {cpu usage in percent}
2,label disk 2,type integer 2,message {disk usage in megabytes}
3,label memory 3,type integer 3,message {memory usage in kilobytes}
4,label command 4,type dictionary 4,message {command name}
pollTimes {10 5 20 30 60 120 300}
sort {1 decreasing}
indexColumns {0 4}
helpText {...}
views {
{indices {0 1 3 4} sort {1 decreasing}}
{indices {0 2 4} sort {2 decreasing}}
}
switches {-a 0 --asynchronous 0}
}
In this case, data is presented in 2 tables: one for the CPU and memory usage, the other for disk usage.
The identifier member is optional. It is string that uniquely identifies this module. If set, it is displayed by the core in the initial data tables title area and data cell labels in viewers. This feature can be used for example in modules that gather data from a remote host: in such a case, the identifier could be set to dataType(hostName) (the ps module uses ps(host) string). The allowed character set for the identifier is identical to the allowed set for a module name.
Note that the identifier member is usually set in the module initialize procedure, as it usually depends on the module options.
In order for a module to accept command line arguments, the initialize procedure must exist (more information below). Otherwise, if the module can take no arguments, it stays optional. In that case, it is rather redundant with inline module namespace code (namespace code outside of any module namespace procedure). When the module takes no arguments, so does the initialize procedure if it exists.
The initialize procedure is mandatory when the module supports command line arguments, and in such a case takes an array name as sole argument. The array contains the switched options values, indexed by switch. For example, if the command line was:
$ moodss random --asynchronous --other-option value -x 1234the options array will contain:
options(--asynchronous) =
options(--other-option) = value
options(-x) = 1234
Note that the --asynchronous member value is empty as that switch takes no argument. For the above example, switches would have been defined as:
switches {-a 0 --asynchronous 0 --other-option 1 -x 1}
In all cases, data members other than updates and switches can be set or updated in the initialize procedure, and successfully taken into account by the core.
Example for a module that take arguments:
proc initialize {optionsName} {
upvar $optionsName options
variable asynchronous
variable data
set asynchronous [info exists options(--asynchronous)]
if {$asynchronous} {
array set data {pollTimes -10}
}
}
The options array is accessed using the upvar Tcl command technique (used when passing arguments (such as arrays) by name). The module namespace variable asynchronous is set according to the --asynchronous command line switch existence. Then, if operating asynchronously, a preferred poll time is set in the module data.
The core waits for the initialize procedure to be completed before initializing the next module. For modules likely to initialize slowly and/or susceptible to initialization failure, it is advised to allow the user interface to be updated using the Tcl vwait command (technique used in all the remote capable modules shipped with moodss). For example:
proc initialize {optionsName} {
...
set file [open "| /usr/bin/rsh -nl $remote(user) $remote(host) cat /proc/net/arp"]
fileevent $file readable {set ::arp::remote(busy) 0}
vwait ::arp::remote(busy)
...
}
Since the file to be read sits in a remote machine on an eventual slow link, the initialize procedure is blocked until the file becomes readable, but without hanging the user interface, using the Tcl fileevent and vwait commands combination.
Similar techniques must be used in such cases within the module update procedure, so that the user interface and eventual modules running concurrently are not prevented to update. The remote capable moodss modules contain various coding techniques achieving that functionality, which I am sure you can improve on.
proc terminate {} {
# do some cleanup
}
In case of a synchronous module, the core invokes the module update procedure (which obviously must exist) when it is time to refresh the data display (tables and eventually graphical viewers). At this time, the update procedure may update the tabular data straight away (synchronous operation) or launch a request for later data update (asynchronous operation).
In case of an asynchronous module, variable data may be updated at any time. The update procedure may not exist.
For all module types, it actually does not matter when the data is updated. The core will know that fresh data is available when the updates array member is set (actually incremented as it also serves as a counter for the number of updates so far).
It is the module programmer's responsibility to increment this counter right after all tabular data has been updated.
For example, retrieving information for the processes running on a machine is a local operation that can be achieved in a reasonably small amount of time. In such a case, data would be updated immediately and the updates variable incremented at the same time.
But if the data has to be retrieved from across a network, waiting for it to come back would cause a delay that the user would certainly notice, as the application would not respond to mouse or keyboard input during the whole time that it would take to fetch the whole data. In such cases, it is easier to let the update procedure return immediately without setting the updates variable, which would be incremented at a later time, only when the data would become available. For example, when waiting for data to come across a network connection, the Tcl fileevent command could be used on a non blocking channel, where the script to be evaluated when the channel becomes readable would increment the updates array member.
For example:
namespace eval random {
...
proc update {} {
variable data
array set data "
0,0 john 0,1 1234 0,2 4567 0,3 cc
1,0 william 1,1 8901 1,2 2345 1,3 xedit
2,0 anny 2,1 6789 2,2 0123 2,3 ps
4,0 peter 4,1 4567 4,2 8901 4,3 ls
6,0 laura 6,1 2345 6,2 6789 6,3 emacs
3,0 robert 3,1 1234 3,2 5678 3,3 top
"
incr data(updates)
}
}
The tabular data array index is the row number followed by the column number separated by a comma. The column number must start from 0 up to the total number of columns minus 1 (no holes are allowed in the column sequence).
When all rows (or only those table cells that have changed) have been updated, the updates member array must be incremented so that the core knows that it can update the table data display.
The random module source code can be made to function asynchronously: please look into the random.tcl file.
package ifneeded random 1.1 "source [file join $dir random.tcl]"The line above says that if the random package is needed, the Tcl core should source the random.tcl module source code from the directory where it was installed. 1.1 is the version number for the package.
Modules can be installed at any valid place that the Tcl core allows (look at the pkg_mkIndex manual page for more information).
When you unpack moodss, you will find the sample modules in sub directories. The current directory (.) is appended to the auto_load global list variable so that sample modules can be found when moodss is run from the unpacking directory.
For example, if you unpacked moodss in /home/joe/moodss-X.x/, you will find the random module package in /home/joe/moodss-X.x/random/ so that the following will work:
$ cd /home/joe/moodss-X.x/ $ wish moodss randomYou can install your new modules in the default location: /usr/local/lib/ on Unix. For example, if you move the files in /home/joe/moodss-X.x/random/ to /usr/local/lib/random/, moodss (actually Tcl :^) will still be able to find the random module (again, look at the pkg_mkIndex manual page for more information).
Please take a look at the INSTALL file for the latest information on how to install the moodss application itself.
pushMessage "your message..." popMessage flashMessage "your message..." numberOfSecondsYour message can be any kind of string (1 line only: it should fit in a reasonably wide main window), and numberOfSeconds being optional and defaulting to 1. Note that messages sent to the message area are also displayed in the trace module table(s) if it(they) exist(s) (see below). In such cases, popping messages has no effect on trace module tables.
You also have the option of using trace tables (also see trace module) through the following API:
traceMessage "your message..."
The difference is that messages from the module are displayed in the trace module tables if they exist (there can be more than 1 trace module loaded), remain visible to the user for a longer period of time, and can be multi-line.
Finally. displaying separate (toplevel) message windows using Tk is of course always possible (if you load Tk in the module). Keep in mind that the core, not being aware of the module event that has taken place, will continue to invoke the module update procedure (unless the module is asynchronous, of course). In such a case, you may want to use an internal (to the module) busy flag so that the update procedure immediately returns until the user acknowledges the informational message. Other strategies are of course possible (let me know if you have one that you think should appear here as an example).
In the first 2 cases, specifying the module name in the error message is not necessary as the core handles it.
In such a case, no index column is required and as a matter of fact rather gets in the way. The trick is to use an empty column 0, use as index by the core by default, and to prevent it from being displayed by using 1 or more views.
Please look at the cpustats module code for a working example.
Send your comments, complaints, ... to Jean-Luc Fontaine.