Completing the documentation is one of the tasks we're trying to
finish up before releasing 4.5. Below is the complete man page for
ns_ictl as it currently stands. We'll be releasing a lot more
information about AOLserver 4.5 over then next few weeks as we finish
things up and begin testing internally here at AOL. Stay tuned! :-)
- n
ns_ictl
NAME <http://gin.office.aol.com:8000/html/ns_ictl.n.htm#NAME>
SYNOPSIS <http://gin.office.aol.com:8000/html/ns_ictl.n.htm#SYNOPSIS>
DESCRIPTION
<http://gin.office.aol.com:8000/html/ns_ictl.n.htm#DESCRIPTION>
INTERPRETER ALLOCATION
<http://gin.office.aol.com:8000/html/ns_ictl.n.htm#INTERPRETER%20ALLOCATION>
INTERPRETER TRACES
<http://gin.office.aol.com:8000/html/ns_ictl.n.htm#INTERPRETER%20TRACES>
VIRTUAL SERVER TCL INITIALIZATION
<http://gin.office.aol.com:8000/html/ns_ictl.n.htm#VIRTUAL%20SERVER%20TCL%20INITIALIZATION>
EXAMPLES <http://gin.office.aol.com:8000/html/ns_ictl.n.htm#EXAMPLES>
SEE ALSO <http://gin.office.aol.com:8000/html/ns_ictl.n.htm#SEE%20ALSO>
KEYWORDS <http://gin.office.aol.com:8000/html/ns_ictl.n.htm#KEYWORDS>
------------------------------------------------------------------------
______________________________________________________________________________
NAME
ns_ictl − Facility to control AOLserver multi-threaded Tcl
interpreters
SYNOPSIS
*ns_ictl addmodule* /module
/*ns_ictl cancel* /thread
/*ns_ictl cleanup
ns_ictl epoch
ns_ictl get
ns_ictl getmodules
ns_ictl gettraces* /which
/*ns_ictl once* /key script
/*ns_ictl oncleanup* /script
/*ns_ictl oncreate* /script
/*ns_ictl ondelete* /script
/*ns_ictl oninit* /script
/*ns_ictl package* /?-exact? package ?version?
/*ns_ictl runtraces* /which
/*ns_ictl save* /script
/*ns_ictl threads
ns_ictl trace* /when script
/*ns_ictl update
*
_________________________________________________________________
DESCRIPTION
This command provides access to the internal facilities to control
and configure multi-threaded Tcl interpreters in the context of
AOLserver virtual servers. It is normally used in startup
initialization scripts to define how new interpreters are initialized
when created and to support cleanup and re-initalization between
transactions (e.g., HTTP connections).
*ns_ictl addmodule* /module/
Add a module to the list of modules to be initialized at startup.
This command is not normally required as each module specified in the
AOLserver modules config section for the corresponding server (e.g.,
/ns/server/server1/modules/) is automatically added to the list.
*ns_ictl cancel* /thread/
Send an asynchronous interrupt request to the specified thread,
cancelling any script currently executing on any AOLserver created
interpreter (note the interrupt is not virtual-server specific). This
command utilizes the facilities of *Tcl_AsyncMark* to mark as ready a
callback registered with *Tcl_AsyncCreate*. The callback places an
error message in the interpreter result and returns *TCL_ERROR* to
unwind the call stack. The underlying Tcl facility has limitations,
e.g., the interrupt will only be noticed when Tcl checks via
*Tcl_AsyncReady* calls between commands and the interrupt can be
caught with a *catch* command. See the man page for *Tcl_AsyncCreate*
for details.
*ns_ictl cleanup*
This command invokes any callbacks registered during a transaction
via the C-level *Ns_TclRegisterDefer* routine. Unlike callbacks
registered with the *ns_ictl trace deallocate* command or
*Ns_TclRegisterTrace* routine, these callbacks are executed only once
and there is no Tcl-level access to the underlying
*Ns_TclRegisterDefer* routine.
*ns_ictl epoch*
This command returns the unique id for the current duplication
script for the virtual server. The id starts as 0 when the virtual
server is created and is incremented each time a new script is saved
via the *ns_ictl save* command.
*ns_ictl get*
Return the current duplication script for the virtual server. This
command is useful to view the duplication script created by the
initialization script at startup.
*ns_ictl getmodules*
Return the list of modules to be initialized at startup. This list
corresponds to the names of modules specified in the virtual server
modules config section, e.g., /ns/server/server1/modules/ unless
additional modules are added via the *ns_ictl addmodule* command.
*ns_ictl gettraces* /which/
Return the list of traces which will be invoked at the specified
time. The /which/ argument can be one of /create, delete, allocate,
deallocate, getconn/, or /freeconn/. The traces are returned in the
order in which they will be executed. Script level traces are returns
as strings to evaluate and C-level traces are returned with strings
which specify the address of the underlying C procedure and argument.
*ns_ictl once* /key script/
Evaluate given script once in the virtual server. The given key is
a string name which uniquely identifies the corresponding script.
This command is useful in a Tcl package which includes one-time
initialization routines, e.g., calls to *ns_register_proc* or
initialization of shared variables using *nsv_set* (see *EXAMPLES*
below).
*ns_ictl oncleanup* /script/
This command is equivalent to *ns_ictl trace deallocate* /script/.
*ns_ictl oncreate* /script/
This command is equivalent to *ns_ictl trace create* /script/.
*ns_ictl ondelete* /script/
This command is equivalent to *ns_ictl trace delete* /script/.
*ns_ictl oninit* /script/
This command is equivalent to *ns_ictl trace allocate* /script/.
*ns_ictl package* /?-exact? package ?version?/
This command is used to require a package in the calling
interpreter and, if successfully loaded, in all other interpreters
for the virtual server. In addition to ensuring version consistency
for the package, it is equivalent to:
*set version [package require* /package ?version?/*]
ns_ictl trace allocate [list package require* /package/ *$version]*
*ns_ictl runtraces* /which/
This command runs the requested traces. The /which/ argument must
be one of *create*, *delete*, *allocate*, *deallocate*, *getconn*, or
*freeconn*. Direct calls to this command are not normally necessary
as the underlying C code will invoke the callbacks at the required
times. Exceptions include calling *ns_ictl runtraces* or testing
purposes or to mimic the normal cleanup and initialization work
performed on between transactions in a long running thread (see
*EXAMPLES* below).
*ns_ictl save* /script/
Save the given script as the duplication script, incrementing the
virtual server epoch number. This command is normally called by the
bootstrap script after constructing the script to duplicate the
procedures defined by sourcing the various module initialization
script files.
*ns_ictl threads*
Return a list of all threads with interpreters for the virtual
server. The ids return are small strings which represent the
underlying thread ids and can be passed to the *ns_ictl cancel*
command to send an asynchronous cancel request.
*ns_ictl trace create* /script/
Register /script/ to be called when an interpreter is first
created. This is useful to create procedures, require packages, or
initialize other state to be used during the lifetime of the
interpreter.
*ns_ictl trace delete* /script/
Register /script/ to be called before an interpreter is destroyed.
This is useful to free any resources which may have been allocated
for the interpreter during the lifetime of the interpreter.
*ns_ictl trace allocate* /script/
Register /script/ to be called each time an interpreter is
allocated for use by the *Ns_TclAllocateInterp* routine. This is
useful for reinitializing resources which may be used during a single
transaction in the interpreter.
*ns_ictl trace deallocate* /script/
Register /script/ to be called each time an interpreter is returned
after a transaction with the *Ns_TclDeAllocateInterp* routine. This
is useful for garbage collection, i.e., freeing any resources which
may be used during a single transaction in the interpreter.
*ns_ictl trace getconn* /script/
Register /script/ to be called each time an interpreter is returned
and associated with an HTTP connection with the *Ns_GetConnInterp*
routine. This could be useful to define variables relative to the
HTTP request.
*ns_ictl trace freeconn* /script/
Register /script/ to be called each time an HTTP connection is
closed. This could be used to log information about the request,
e.g., timing statistics. Note that the interpreter may still be
actively evaluating a script after the connection is closed, i.e.,
this is not equivalent to *ns_ictl trace deallocate* for
connection-related interpreters.
*ns_ictl update*
This command can be used to atomically compare the epoch of the
current duplication script with the epoch of the interpreter,
evaluating the script and updating the epoch in the interpreter if
they do not match. This command is generally registered as a callback
with *ns_ictl trace allocate* by the legacy initialization code.
INTERPRETER ALLOCATION
Tcl interpreter in AOLserver are available on demand with state
specific to a virtual server. These interpreters are also expected to
be reused for multiple transactions (e.g., HTTP connections,
scheduled procedures, socket callbacks).
To support reuse, AOLserver provides the C-level
*Ns_TclAllocateInterp* routine to allocate an interpreter from a
per-thread cache (creating and initializing a new interpreter if
necessary) and the *Ns_TclDeAllocateInterp* routine to return an
interpreter to the cache when no longer required. All interpreters in
the per-thread cache are destroyed when a thread exists.
In general, only C-level extension writers need to call the C-level
API’s directly; the various Tcl-level interfaces in AOLserver (e.g.,
*ADP* pages, *ns_regiseter_proc*, *ns_schedule_proc*, *ns_thread*,
etc.) allocate and reuse interpreters using the C-level API’s
automatically before invoking the cooresponding script or ADP page.
INTERPRETER TRACES
To ensure a consistent state of interpreters when allocated and
enable cleanup and reinitialization between transactions, each
virtual server maintains a list of callbacks to be invoked at various
points in the lifetime of an interpreter. These callbacks are
generally installed when the server is initialized at startup and
then called automatically by the *Ns_TclAllocateInterp* and
*Ns_TclDeAllocateInterp* API’s at the appropriate times and in
consistent order. The *Ns_TclRegisterTrace* routine can be used to
register C-level callbacks and the *ns_ictl trace* command can be
used to register Tcl script callbacks. The *ns_ictl gettraces*
command can be used to list all currently registered callbacks, both
at the Tcl script and C level.
Callbacks registered via the tracing facility are invoked in a
specific order depending on the type. Initialization style callbacks
including *create*, *allocate*, and *getconn* are invoked in FIFO
order, with all script callbacks invoked after all C-level callbacks.
This enables extension writers to utilize the facilities of
previously initialized extensions. Correspondingly, cleanup style
callbacks including *freeconn*, *deallocate*, and *delete* are
invoked in LIFO order, with all scripts callbacks invoked before
C-level callbacks. This helps avoid the possibility that a cleanup
callback utilizes features of a previously cleaned up extension.
In addition, the *ns_ictl package* command can be used to
consistently manage the loading of a Tcl package in all interpreters
for a virtual server. This feature is mostly a convenience routine
built above the generic trace framework with additional checks to
ensure version number consistency. Coupled with *ns_ictl once*, the
*ns_ictl package* command provides a clean framework to utilize Tcl
packages in multi-threaded AOLserver (see *EXAMPLES*).
VIRTUAL SERVER TCL INITIALIZATION
AOLserver also supports a Tcl initialization framework for virtual
servers based on callbacks registered by loadable modules and the
sourcing of scripts files located in corresponding directories.
Options to *ns_ictl* to support this framework include /save/, /get/,
/epoch/, and /update/ and are used in conjunction with the generic
tracing facility by the virtual server bootstrap script (normally
/bin/init.tcl/). The *ns_eval* command also relies on this framework
to support dynamic update of the state of interpreters.
This initialization framework pre-dates the Tcl package facilities
and utilizes introspection of the state of a startup interpreter at
the end of initialization to construct a single script which attempts
to duplicate the state in subsequent interpreters. Steps taken during
this initialization include:
1. Load all modules in the server’s module config section, e.g.,
/ns/server/server1/modules/. Modules with Tcl C-level extensions
typically call the legacy *Ns_TclInitInterps* routine or the more
general *Ns_TclRegisterTrace* routine with the /NS_TCL_TRACE_CREATE/
flag in their module init routine to register a callback to invoke
when new interpreters are created. The callback normally creates one
or more new commands in the interpreter with *Tcl_CreateObjCommand*
but may perform any per-interpreter initialization required, e.g.,
creating and saving private state with the *Tcl_SetAssocData*
facility. In addition, as modules are loaded, the string name of the
module is added to the list of known modules.
2. After all C modules are loaded, AOLserver creates a new Tcl
interpreter for the virtual server, executing any trace callbacks
already registered via the loaded C modules (e.g., any
*Ns_TclInitInterps* callbacks) and then sources the virtual server
bootstrap script, normally /bin/init.tcl/. This script creates a few
utility procedures and then sources all /private/ and /public/ script
files in directories which correspond to loaded modules in the order
in which they were loaded. These directories are normally relative to
the virtual server and to the AOLserver installation directory, e.g.,
initialization script files for the module /mymod/ in the /server1/
virtual server would be searched for in the
/servers/server1/modules/tcl/mymod// and /modules/tcl/mymod//. Any
/init.tcl/ file found in each directory is sourced first with all
remaining files sourced in alphabetical order. In addition, any files
in the /public/ directory with identical names to files in the
private directory are skipped as a means to enable overloading of
specific functionality on a per-server basis. In practice, most
modules only contain shared utility procedures defined in the
/public/ directories and the /private/ directories are empty or
non-existant. The script files normally contain a mix of commands to
evaluate once for server configuration (e.g., a call to
*ns_register_proc* to bind a Tcl procedure to an HTTP request URL)
with *proc* and *namespace* commands to provide additional
functionality in the interpreter.
3. After all script files have been sourced, the bootstrap script
code then uses a collection of recursive procedures to extract the
definitions of all procedures defined in all namespaces. The
definitions are used to construct a script which attempts to
duplicate the state of the initialization interpreters. This scripts
is then saved as the per-virtual server duplication script with the
*ns_ictl save* command which also increments the /epoch/ to 1. There
are limits to this approach to determine the full state, e.g., it
does not attempt to duplicate any global variables which may have
been defined in the startup scripts. Typically, startup scripts will
use *nsv_set* or other mechanisms to store such shared state.
4. The bootstrap code then uses the *ns_ictl trace allocate*
command to register a callback to the *ns_ictl update* command each
time an interpreter is allocated for use. In practice, interpreters
are created with the default /epoch/ of 0 and the first call to
*ns_ictl update* determines an out-of-date condition, evaluates the
duplication script, and increments the interpreter’s /epoch/ to 1 to
match the state created by the startup interp.
5. Subsequent calls the *ns_eval*, if any, will evaluate the
given script and then re-generate and save the duplication script
as was done at startup, incrementing the /epoch/ once again. In this
way, dynamic updates which are detected in other interpreters on
their next call to *ns_ictl update* can be supported in a limited
fashion.
In practice, while generally successful, this duplication technique
has inhibited the clean use of proper Tcl package extensions and
encouraged the use of the *ns_eval* command which is generally not
recommended for the non-deterministic manner in which it attempts to
dynamically reconfigure a server. Also, commands required to
configure the server once (e.g., calls to *ns_register_proc*) are
inter-mixed with *proc* commands designed to extend functionality in
all interpreters, complicating configuration management.
As an alternative, the example below illustrates a means to more
explicitly manage configuration through a combination of direct calls
to *ns_ictl trace create* and *ns_ictl once*. Unfortunately, the all
encompassing nature of the legacy initialization approach makes it
difficult to incrementally move to this cleaner approach because the
duplication script construction code is unable to distinguish between
state created with the newer, cleaner *ns_ictl* commands and state
created as a side effect of one or more script files being sourced.
As such, it is expected the legacy initialization framework will
remain in place until AOLserver 5.x when it will be removed entirely
in a non-backwards compatible move towards the cleaner API’s.
EXAMPLES
This example illustrates the use of *ns_ictl package* and *ns_ictl
once* to load an AOLserver-aware Tcl package into a virtual server.
The following code could be added to the virtual server bootstrap
script, /bin/init.tcl/, to load /MyPkg/ in the virtual server:
#
# Startup code in bin/init.tcl:
#
# Load MyPkg in all interps (including this one).
#
ns_ictl package require MyPkg
This call will result in the package being loaded into the startup
interpreter in the ordinary Tcl fashion (see the *package* man page
for details). Ordinary Tcl extension packages would need no
modifications but packages which utilize AOLserver-specific features
or require garbage collection between transactions could also use
*ns_ictl* for finer grained control. For example, the /init.tcl/
script specified by the *package ifneeded* command in the /MyPkg/
package’s /pkgIndex.tcl/ file could contains:
#
# Package code in lib/myPkg1.0/init.tcl:
#
#
package provide MyPkg 1.0
#
# Server init which will be executed the first time called,
# normally in the context of the startup interpreter as above.
#
ns_ictl once MyPkg {
# Register the run Tcl proc HTTP handler.
ns_register_proc /mypkg mkpkg::run
# Register a garbage collection callback.
ns_ictl trace deallocate mypkg::cleanup
}
#
# Code which will be invoked to initialize the package in
# all interpreters when required.
#
proc mypkg::run {} {
... handle /mypkg requests ...
}
proc mkpkg::cleanup {} {
... cleanup transaction resources for mypkg, e.g., db handles ...
}
SEE ALSO
Ns_TclAllocateInterp(3), Ns_TclDeAllocateInterp(3),
Ns_GetConnInterp(3), Ns_FreeConnInterp(3), Ns_TclInitInterps(3),
Ns_TclRegisterTrace(3), Ns_TclRegisterDeferred(3), ns_atclose(n),
ns_eval(n).
KEYWORDS
threads, interpreters, traces, initialization
[EMAIL PROTECTED] wrote:
How can you know exactly what variables to clean up in each
namespace? Even the cleanup for the global namespace doesn't
completely wipe out all variables.
This is exactly the problem we ran into when thinking about how we
could better support Tcl namespace variables in AOLserver 4.5. The
short answer is that there doesn't necessarily seem to be a good
way to do this automatically for you, and instead it will be up to
each developer to delete the namespace variables they have created:
ns_ictl trace deallocate {... your cleanup here ...}
In AOLserver 4.5 the callbacks have been cleaned up and now fire in
the right order, lifo for cleanups, fifo for inits. Hope that helps!
I didn't know about this "trace" option for ns_ictl, it is not
documented:
http://www.panoptic.com/wiki/aolserver/Ns_ictl
is it equivalent to:
ns_ictl oncleanup script
Registers a script to be executed at Tcl interpreter cleanup time.
-john
--
AOLserver - http://www.aolserver.com/
To Remove yourself from this list, simply send an email to
<[EMAIL PROTECTED]> with the
body of "SIGNOFF AOLSERVER" in the email message. You can leave the
Subject: field of your email blank.
--
AOLserver - http://www.aolserver.com/
To Remove yourself from this list, simply send an email to
<[EMAIL PROTECTED]> with the
body of "SIGNOFF AOLSERVER" in the email message. You can leave the
Subject: field of your email blank.
