Tcl code: /tcl/0-acs-init.tcl and /packages/acs-kernel/bootstrap.tcl
This document describes the startup (bootstrapping) process for an AOLserver running OpenACS.
Before OpenACS 3.3, the OpenACS startup process was extremely
simple: after AOLserver performed its internal initialization
(reading the configuration file, loading shared libraries and
module code, etc.) it scanned through the Tcl library directory
(generally /var/lib/aolserver/yourservername/tcl), sourcing each file in sequence.
While this overall structure for initialization is still intact, package management has thrown a wrench into the works - there are a few extra things to do during initialization, most notably:
Examine the OpenACS file tree for files that should not be present in OpenACS (i.e., that were once part of the OpenACS distribution but have since been removed).
Scan the /packages directory
for new packages.
Initialize enabled packages by sourcing their *-procs.tcl and *-init.tcl files.
This document examines in detail each of the steps involved in AOLserver/OpenACS startup.
As soon as the nsd daemon is
executed by the init process
(or otherwise), AOLserver reads its configuration file and
chroots itself if necessary. It
then loads shared libraries indicated in the .ini file (e.g., the Oracle driver and
nssock), and sources Tcl module
files (generally in /home/aol30/modules/tcl). This step is, and
has always been, the same for all AOLservers, regardless of whether
they are running OpenACS.
Next AOLserver sources, in lexicographical order, each file in
the /tcl directory. The first
such file is 0-acs-init.tcl,
which doesn't do much directly except to determine the OpenACS
path root (e.g., /var/lib/aolserver/yourservername) by trimming the
final component from the path to the Tcl library directory
(/var/lib/aolserver/yourservername/tcl).
But 0-acs-init.tcl's has an
important function, namely sourcing /packages/acs-core/bootstrap.tcl, which
does the following:
Initialize some NSVs used by the
core. These NSVs are documented in /packages/acs-core/apm-procs.tcl - no need
to worry about them unless you're an OpenACS core hacker.
Verify the deletion of obsolete
OpenACS files. The /tcl directory has evolved quite a bit over
the months and years, and a few files have come and gone. The
/www/doc/removed-files.txt file
contains a list of files which must be
deleted from the AOLserver installation, at the risk of
causing weird conflicts, e.g., having several security filters
registered. bootstrap.tcl scans
through this list, logging error messages to the log if any of
these files exist.
Source *-procs.tcl files in the OpenACS
core. We source each file matching the *-procs.tcl glob in the /packages/acs-kernel directory, in
lexicographical order. These procedure are needed to perform any of
the following steps.
Ensure that the database is available by grabbing and releasing a handle. If we can't obtain a handle, we terminate initialization (since OpenACS couldn't possibly start up the server without access to the database).
Register any new packages in the
/packages
directory. In each directory inside /packages, we look for a .info file; if we find a package that
hasn't yet been registered with the package manager (i.e.,
it's been copied there manually), we insert information about
it into the database. (The first time OpenACS starts up,
no packages will have been
registered in the database yet, so this step will registers every
single package in the /packages
directory.) Note that packages discovered here are initially
disabled; they must be manually enabled in the package manager
before they can be used.
Ensure that the acs-kernel package is
enabled. If the OpenACS core isn't initialized,
the server couldn't possibly be operational, so if there's
no enabled version of the OpenACS core we simply mark the latest
installed one as enabled.
Load *-procs.tcl files for enabled
packages, activating their APIs.
Load *-init.tcl files for enabled
packages, giving packages a chance to register
filters and procedures, initialize data structures, etc.
Verify that the core has been properly initialized by checking for the existence of an NSV created by the request processor initialization code. If it's not present, the server won't be operational, so we log an error.
At this point, bootstrap.tcl
is done executing. AOLserver proceeds to source the remaining files
in the /tcl directory (i.e.,
unpackaged libraries) and begins listening for connections.