'\" '\" Generated from file '' by tcllib/doctools with format 'nroff' '\" .TH "ttrace" n 2\&.8 "Tcl Threading" .\" The -*- nroff -*- definitions below are for supplemental macros used .\" in Tcl/Tk manual entries. .\" .\" .AP type name in/out ?indent? .\" Start paragraph describing an argument to a library procedure. .\" type is type of argument (int, etc.), in/out is either "in", "out", .\" or "in/out" to describe whether procedure reads or modifies arg, .\" and indent is equivalent to second arg of .IP (shouldn't ever be .\" needed; use .AS below instead) .\" .\" .AS ?type? ?name? .\" Give maximum sizes of arguments for setting tab stops. Type and .\" name are examples of largest possible arguments that will be passed .\" to .AP later. If args are omitted, default tab stops are used. .\" .\" .BS .\" Start box enclosure. From here until next .BE, everything will be .\" enclosed in one large box. .\" .\" .BE .\" End of box enclosure. .\" .\" .CS .\" Begin code excerpt. .\" .\" .CE .\" End code excerpt. .\" .\" .VS ?version? ?br? .\" Begin vertical sidebar, for use in marking newly-changed parts .\" of man pages. The first argument is ignored and used for recording .\" the version when the .VS was added, so that the sidebars can be .\" found and removed when they reach a certain age. If another argument .\" is present, then a line break is forced before starting the sidebar. .\" .\" .VE .\" End of vertical sidebar. .\" .\" .DS .\" Begin an indented unfilled display. .\" .\" .DE .\" End of indented unfilled display. .\" .\" .SO ?manpage? .\" Start of list of standard options for a Tk widget. The manpage .\" argument defines where to look up the standard options; if .\" omitted, defaults to "options". The options follow on successive .\" lines, in three columns separated by tabs. .\" .\" .SE .\" End of list of standard options for a Tk widget. .\" .\" .OP cmdName dbName dbClass .\" Start of description of a specific option. cmdName gives the .\" option's name as specified in the class command, dbName gives .\" the option's name in the option database, and dbClass gives .\" the option's class in the option database. .\" .\" .UL arg1 arg2 .\" Print arg1 underlined, then print arg2 normally. .\" .\" .QW arg1 ?arg2? .\" Print arg1 in quotes, then arg2 normally (for trailing punctuation). .\" .\" .PQ arg1 ?arg2? .\" Print an open parenthesis, arg1 in quotes, then arg2 normally .\" (for trailing punctuation) and then a closing parenthesis. .\" .\" # Set up traps and other miscellaneous stuff for Tcl/Tk man pages. .if t .wh -1.3i ^B .nr ^l \n(.l .ad b .\" # Start an argument description .de AP .ie !"\\$4"" .TP \\$4 .el \{\ . ie !"\\$2"" .TP \\n()Cu . el .TP 15 .\} .ta \\n()Au \\n()Bu .ie !"\\$3"" \{\ \&\\$1 \\fI\\$2\\fP (\\$3) .\".b .\} .el \{\ .br .ie !"\\$2"" \{\ \&\\$1 \\fI\\$2\\fP .\} .el \{\ \&\\fI\\$1\\fP .\} .\} .. .\" # define tabbing values for .AP .de AS .nr )A 10n .if !"\\$1"" .nr )A \\w'\\$1'u+3n .nr )B \\n()Au+15n .\" .if !"\\$2"" .nr )B \\w'\\$2'u+\\n()Au+3n .nr )C \\n()Bu+\\w'(in/out)'u+2n .. .AS Tcl_Interp Tcl_CreateInterp in/out .\" # BS - start boxed text .\" # ^y = starting y location .\" # ^b = 1 .de BS .br .mk ^y .nr ^b 1u .if n .nf .if n .ti 0 .if n \l'\\n(.lu\(ul' .if n .fi .. .\" # BE - end boxed text (draw box now) .de BE .nf .ti 0 .mk ^t .ie n \l'\\n(^lu\(ul' .el \{\ .\" Draw four-sided box normally, but don't draw top of .\" box if the box started on an earlier page. .ie !\\n(^b-1 \{\ \h'-1.5n'\L'|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul' .\} .el \}\ \h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\l'|0u-1.5n\(ul' .\} .\} .fi .br .nr ^b 0 .. .\" # VS - start vertical sidebar .\" # ^Y = starting y location .\" # ^v = 1 (for troff; for nroff this doesn't matter) .de VS .if !"\\$2"" .br .mk ^Y .ie n 'mc \s12\(br\s0 .el .nr ^v 1u .. .\" # VE - end of vertical sidebar .de VE .ie n 'mc .el \{\ .ev 2 .nf .ti 0 .mk ^t \h'|\\n(^lu+3n'\L'|\\n(^Yu-1v\(bv'\v'\\n(^tu+1v-\\n(^Yu'\h'-|\\n(^lu+3n' .sp -1 .fi .ev .\} .nr ^v 0 .. .\" # Special macro to handle page bottom: finish off current .\" # box/sidebar if in box/sidebar mode, then invoked standard .\" # page bottom macro. .de ^B .ev 2 'ti 0 'nf .mk ^t .if \\n(^b \{\ .\" Draw three-sided box if this is the box's first page, .\" draw two sides but no top otherwise. .ie !\\n(^b-1 \h'-1.5n'\L'|\\n(^yu-1v'\l'\\n(^lu+3n\(ul'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c .el \h'-1.5n'\L'|\\n(^yu-1v'\h'\\n(^lu+3n'\L'\\n(^tu+1v-\\n(^yu'\h'|0u'\c .\} .if \\n(^v \{\ .nr ^x \\n(^tu+1v-\\n(^Yu \kx\h'-\\nxu'\h'|\\n(^lu+3n'\ky\L'-\\n(^xu'\v'\\n(^xu'\h'|0u'\c .\} .bp 'fi .ev .if \\n(^b \{\ .mk ^y .nr ^b 2 .\} .if \\n(^v \{\ .mk ^Y .\} .. .\" # DS - begin display .de DS .RS .nf .sp .. .\" # DE - end display .de DE .fi .RE .sp .. .\" # SO - start of list of standard options .de SO 'ie '\\$1'' .ds So \\fBoptions\\fR 'el .ds So \\fB\\$1\\fR .SH "STANDARD OPTIONS" .LP .nf .ta 5.5c 11c .ft B .. .\" # SE - end of list of standard options .de SE .fi .ft R .LP See the \\*(So manual entry for details on the standard options. .. .\" # OP - start of full description for a single option .de OP .LP .nf .ta 4c Command-Line Name: \\fB\\$1\\fR Database Name: \\fB\\$2\\fR Database Class: \\fB\\$3\\fR .fi .IP .. .\" # CS - begin code excerpt .de CS .RS .nf .ta .25i .5i .75i 1i .. .\" # CE - end code excerpt .de CE .fi .RE .. .\" # UL - underline word .de UL \\$1\l'|0\(ul'\\$2 .. .\" # QW - apply quotation marks to word .de QW .ie '\\*(lq'"' ``\\$1''\\$2 .\"" fix emacs highlighting .el \\*(lq\\$1\\*(rq\\$2 .. .\" # PQ - apply parens and quotation marks to word .de PQ .ie '\\*(lq'"' (``\\$1''\\$2)\\$3 .\"" fix emacs highlighting .el (\\*(lq\\$1\\*(rq\\$2)\\$3 .. .\" # QR - quoted range .de QR .ie '\\*(lq'"' ``\\$1''\\-``\\$2''\\$3 .\"" fix emacs highlighting .el \\*(lq\\$1\\*(rq\\-\\*(lq\\$2\\*(rq\\$3 .. .\" # MT - "empty" string .de MT .QW "" .. .BS .SH NAME ttrace \- Trace-based interpreter initialization .SH SYNOPSIS package require \fBTcl 8\&.4\fR .sp package require \fBThread ?2\&.8?\fR .sp \fBttrace::eval\fR \fIarg\fR ?arg \&.\&.\&.? .sp \fBttrace::enable\fR .sp \fBttrace::disable\fR .sp \fBttrace::cleanup\fR .sp \fBttrace::update\fR ?epoch? .sp \fBttrace::getscript\fR .sp \fBttrace::atenable\fR \fIcmd\fR \fIarglist\fR \fIbody\fR .sp \fBttrace::atdisable\fR \fIcmd\fR \fIarglist\fR \fIbody\fR .sp \fBttrace::addtrace\fR \fIcmd\fR \fIarglist\fR \fIbody\fR .sp \fBttrace::addscript\fR \fIname\fR \fIbody\fR .sp \fBttrace::addresolver\fR \fIcmd\fR \fIarglist\fR \fIbody\fR .sp \fBttrace::addcleanup\fR \fIbody\fR .sp \fBttrace::addentry\fR \fIcmd\fR \fIvar\fR \fIval\fR .sp \fBttrace::getentry\fR \fIcmd\fR \fIvar\fR .sp \fBttrace::getentries\fR \fIcmd\fR ?pattern? .sp \fBttrace::delentry\fR \fIcmd\fR .sp \fBttrace::preload\fR \fIcmd\fR .sp .BE .SH DESCRIPTION This package creates a framework for on-demand replication of the interpreter state accross threads in an multithreading application\&. It relies on the mechanics of Tcl command tracing and the Tcl \fBunknown\fR command and mechanism\&. .PP The package requires Tcl threading extension but can be alternatively used stand-alone within the AOLserver, a scalable webserver from America Online\&. .PP In a nutshell, a short sample illustrating the usage of the ttrace with the Tcl threading extension: .CS % package require Ttrace 2\&.8\&.0 % set t1 [thread::create {package require Ttrace; thread::wait}] tid0x1802800 % ttrace::eval {proc test args {return test-[thread::id]}} % thread::send $t1 test test-tid0x1802800 % set t2 [thread::create {package require Ttrace; thread::wait}] tid0x1804000 % thread::send $t2 test test-tid0x1804000 .CE .PP As seen from above, the \fBttrace::eval\fR and \fBttrace::update\fR commands are used to create a thread-wide definition of a simple Tcl procedure and replicate that definition to all, already existing or later created, threads\&. .SH "USER COMMANDS" This section describes user-level commands\&. Those commands can be used by script writers to control the execution of the tracing framework\&. .TP \fBttrace::eval\fR \fIarg\fR ?arg \&.\&.\&.? This command concatenates given arguments and evaluates the resulting Tcl command with trace framework enabled\&. If the command execution was ok, it takes necessary steps to automatically propagate the trace epoch change to all threads in the application\&. For AOLserver, only newly created threads actually receive the epoch change\&. For the Tcl threading extension, all threads created by the extension are automatically updated\&. If the command execution resulted in Tcl error, no state propagation takes place\&. .sp This is the most important user-level command of the package as it wraps most of the commands described below\&. This greatly simplifies things, because user need to learn just this (one) command in order to effectively use the package\&. Other commands, as desribed below, are included mostly for the sake of completeness\&. .TP \fBttrace::enable\fR Activates all registered callbacks in the framework and starts a new trace epoch\&. The trace epoch encapsulates all changes done to the interpreter during the time traces are activated\&. .TP \fBttrace::disable\fR Deactivates all registered callbacks in the framework and closes the current trace epoch\&. .TP \fBttrace::cleanup\fR Used to clean-up all on-demand loaded resources in the interpreter\&. It effectively brings Tcl interpreter to its pristine state\&. .TP \fBttrace::update\fR ?epoch? Used to refresh the state of the interpreter to match the optional trace ?epoch?\&. If the optional ?epoch? is not given, it takes the most recent trace epoch\&. .TP \fBttrace::getscript\fR Returns a synthetized Tcl script which may be sourced in any interpreter\&. This script sets the stage for the Tcl \fBunknown\fR command so it can load traced resources from the in-memory database\&. Normally, this command is automatically invoked by other higher-level commands like \fBttrace::eval\fR and \fBttrace::update\fR\&. .PP .SH "CALLBACK COMMANDS" A word upfront: the package already includes callbacks for tracing following Tcl commands: \fBproc\fR, \fBnamespace\fR, \fBvariable\fR, \fBload\fR, and \fBrename\fR\&. Additionaly, a set of callbacks for tracing resources (object, clasess) for the XOTcl v1\&.3\&.8+, an OO-extension to Tcl, is also provided\&. This gives a solid base for solving most of the real-life needs and serves as an example for people wanting to customize the package to cover their specific needs\&. .PP Below, you can find commands for registering callbacks in the framework and for writing callback scripts\&. These callbacks are invoked by the framework in order to gather interpreter state changes, build in-memory database, perform custom-cleanups and various other tasks\&. .TP \fBttrace::atenable\fR \fIcmd\fR \fIarglist\fR \fIbody\fR Registers Tcl callback to be activated at \fBttrace::enable\fR\&. Registered callbacks are activated on FIFO basis\&. The callback definition includes the name of the callback, \fIcmd\fR, a list of callback arguments, \fIarglist\fR and the \fIbody\fR of the callback\&. Effectively, this actually resembles the call interface of the standard Tcl \fBproc\fR command\&. .TP \fBttrace::atdisable\fR \fIcmd\fR \fIarglist\fR \fIbody\fR Registers Tcl callback to be activated at \fBttrace::disable\fR\&. Registered callbacks are activated on FIFO basis\&. The callback definition includes the name of the callback, \fIcmd\fR, a list of callback arguments, \fIarglist\fR and the \fIbody\fR of the callback\&. Effectively, this actually resembles the call interface of the standard Tcl \fBproc\fR command\&. .TP \fBttrace::addtrace\fR \fIcmd\fR \fIarglist\fR \fIbody\fR Registers Tcl callback to be activated for tracing the Tcl \fBcmd\fR command\&. The callback definition includes the name of the Tcl command to trace, \fIcmd\fR, a list of callback arguments, \fIarglist\fR and the \fIbody\fR of the callback\&. Effectively, this actually resembles the call interface of the standard Tcl \fBproc\fR command\&. .TP \fBttrace::addscript\fR \fIname\fR \fIbody\fR Registers Tcl callback to be activated for building a Tcl script to be passed to other interpreters\&. This script is used to set the stage for the Tcl \fBunknown\fR command\&. Registered callbacks are activated on FIFO basis\&. The callback definition includes the name of the callback, \fIname\fR and the \fIbody\fR of the callback\&. .TP \fBttrace::addresolver\fR \fIcmd\fR \fIarglist\fR \fIbody\fR Registers Tcl callback to be activated by the overloaded Tcl \fBunknown\fR command\&. Registered callbacks are activated on FIFO basis\&. This callback is used to resolve the resource and load the resource in the current interpreter\&. .TP \fBttrace::addcleanup\fR \fIbody\fR Registers Tcl callback to be activated by the \fBtrace::cleanup\fR\&. Registered callbacks are activated on FIFO basis\&. .TP \fBttrace::addentry\fR \fIcmd\fR \fIvar\fR \fIval\fR Adds one entry to the named in-memory database\&. .TP \fBttrace::getentry\fR \fIcmd\fR \fIvar\fR Returns the value of the entry from the named in-memory database\&. .TP \fBttrace::getentries\fR \fIcmd\fR ?pattern? Returns names of all entries from the named in-memory database\&. .TP \fBttrace::delentry\fR \fIcmd\fR Deletes an entry from the named in-memory database\&. .TP \fBttrace::preload\fR \fIcmd\fR Registers the Tcl command to be loaded in the interpreter\&. Commands registered this way will always be the part of the interpreter and not be on-demand loaded by the Tcl \fBunknown\fR command\&. .PP .SH DISCUSSION Common introspective state-replication approaches use a custom Tcl script to introspect the running interpreter and synthesize another Tcl script to replicate this state in some other interpreter\&. This package, on the contrary, uses Tcl command traces\&. Command traces are registered on selected Tcl commands, like \fBproc\fR, \fBnamespace\fR, \fBload\fR and other standard (and/or user-defined) Tcl commands\&. When activated, those traces build an in-memory database of created resources\&. This database is used as a resource repository for the (overloaded) Tcl \fBunknown\fR command which creates the requested resource in the interpreter on demand\&. This way, users can update just one interpreter (master) in one thread and replicate that interpreter state (or part of it) to other threads/interpreters in the process\&. .PP Immediate benefit of such approach is the much smaller memory footprint of the application and much faster thread creation\&. By not actually loading all necessary procedures (and other resources) in every thread at the thread initialization time, but by deffering this to the time the resource is actually referenced, significant improvements in both memory consumption and thread initialization time can be achieved\&. Some tests have shown that memory footprint of an multithreading Tcl application went down more than three times and thread startup time was reduced for about 50 times\&. Note that your mileage may vary\&. Other benefits include much finer control about what (and when) gets replicated from the master to other Tcl thread/interpreters\&. .SH "SEE ALSO" thread, tpool, tsv .SH KEYWORDS command tracing, introspection