| 8.1Script System Environment |
| 8.1.1Proxy Access |
| 8.1.2DECnet Objects |
| 8.1.3Reducing Script Latency |
| 8.1.4DECnet/OSU Startup |
| 8.2CGI |
| 8.3OSU (DECthreads) Emulation |
| 8.4User Scripts |
| ↩︎ | ↖︎ | ↑︎ | ↘︎ | ↪︎ |
"Imitation is the sincerest form of flattery" – proverb
By default WASD executes scripts within detached processes, but can also provide scripting using DECnet for the process management. DECnet scripting is not provided to generally supplant the detached process-based scripting but augment it for certain circumstances:
Any DECnet based processing incurs some overheads:
As of version 5.2 WASD provides reuse of DECnet connections for both CGI and OSU scripting, in-line with OSU v3.3 which provided reuse for OSU scripts. This means multiple script requests can be made for the cost of a single DECnet connection establishment and task object activation. Note that the OSU task procedure requires the definition of the logical name WWW_SCRIPT_MAX_REUSE representing the number of times a script may be reused. The WASD startup procedures can provide this.
In practice both the WASD CGI and OSU scripts seem to provide acceptable responsiveness.
DECnet-based scripts are mapped using the same rules as process-based scripts, using the SCRIPT and EXEC rules (Mapping User Directories in WASD Configuration) for general information on mapping rules). DECnet scripts have a DECnet node and task specification string as part of the mapping rule. There are minor variations within these to further identify it as a WASD or an OSU script (8.4 User Scripts).
The specification string follows basic VMS file system syntax (RMS), preceding the file components of the specification. The following example illustrates declaring that paths beginning with FRODO will allow the execution of scripts from the CGI-BIN:[000000] directory on DECnet node FRODO.
In similar fashion the following example illustrates a script "frodo_show" that might do a "SHOW SYSTEM" on node FRODO. Note that these rules are case-insensitive.
Both of the above examples would use the WASD CGI DECnet environment (the default if no task specification string is provided). By including task information other environments, in particular the OSU scripting enviroment, can be specified for the script to be executed within. The default task is named CGIWASD and can also be explicitly specified (although this behaviour would be the same as that in the first example)
All task specification strings may also use zero as the task abbreviation.
To execute a script within the OSU environment specify the standard OSU task executive WWWEXEC, as in the following example:
This would allow any URL beginning with "/osu/" to execute a script in the OSU environment.
By default the script process is created using the HTTPd scripting account (usually HTTP$NOBODY, although versions prior to 8.1 have used HTTP$SERVER). It is possible to specify alternate accounts for the scripts to be executed within.
The first examples are explicitly specifying an account in the script rule.
It is also possible to have scripts that have been subject to SYSUAF authorization executed within the authenticated account. The dollar symbol in the following examples directs the server to substitute the authenticated username into the access string.
The set script=as= rule used for PERSONA controlled process scripting can also be applied to DECnet scripts. This includes explicitly specified usernames as well as SYSUAF authenticated usernames. The server creates an appropriate access string when the script is activated.
User scripts can also be activated using these rules, either explicitly specifying the "~" in an access string or using the set script=as= mapping rule.
See 8.4 User Scripts for more detail.
To specify any script to execute on the same system as the HTTP server specify the node name as zero or SYS$NODE.
Mapping rules are included in the examples WASD_ROOT:[EXAMPLE] providing this. After the DECnet environment has been started any CGI script may be executed on the local system via DECnet by substituting "/decnet/" for "/cgi-bin/" as the script path, and any OSU script available by using "/osu/". Behaviour is indeterminate, though it shouldn't be catastrophic, if one is invoked using the incorrect path (i.e. an OSU script using /decnet/ or a CGI script using /osu/).
The target system must have sufficient of the WASD server environment to support the required CGI script activation and activity. If the target system is actually the same system as the HTTP server then it already exists, or if part of the local system's cluster, then providing this should be relatively straight-forward. If the target system has none of the server environment then at a minimum it must have the logical name CGI-BIN defined representing the directory containing the required DECnet object procedure and scripts. The following fragment illustrates this:
The local system must have proxy access to each target scripting system (even if that "target" system is the same system as the HTTP server). This involves creating a proxy entry in each target hosts's authorization database. The following example assumes the existance of a local HTTP$NOBODY account. If it does not exist on the target node then one must be created with the same security profile as the HTTP server's.
The zero represents the system the server is currently executing on.
It is necessary to ensure the account has permission to write into its home directory. A network process creates a NETSERVER.LOG (Phase-IV) or NET$SERVER.LOG (DECnet-Plus) file in the home directory, and will fail to start if it cannot!
To provide DECnet scripting DECnet object(s) must be specified for any system on which the scripts will be executed. The DECnet object is the program or procedure that is activated at the target system inside of a network-mode process to interact with the HTTP server.
DECnet-Plus uses the NCL utility to administer the network environment. The following NCL scripting shows the creation of a network application for the WASD CGI object:
To create a DECnet-Plus OSU WWWEXEC object:
These must be executed at each system (or server) startup, and may be executed standalone, as illustrated, or incorporated in the NCL script SYS$STARTUP:NET$APPLICATION_STARTUP.NCL for automatic creation at each system startup. Examples may be found in WASD_ROOT:[EXAMPLE]
DECnet Phase-IV uses the NCP utility to administer the network environment. The following NCP commands may be used each time during server startup to create the required DECnet objects. With Phase-IV the SET verb may be replaced with a DEFINE verb and the commands issued just once to permanently create the objects (a SET must also be done that first time to create working instances of the DEFINEd objects).
To create a DECnet CGI object:
To create a DECnet OSU WWWEXEC object:
Examples may be found in WASD_ROOT:[EXAMPLE]
Script system network process persistance may be configured using NETSERVER logical names. These can control the number and quiescent period of the server processes. These logical names must be defined in the LOGIN.COM of the HTTP server account on the target script system.
The example STARTUP.COM and STARTUP_DECNET.COM procedures found in the WASD_ROOT:[EXAMPLE] directory provide the essentials for DECnet/OSU scripting. If the INSTALL.COM startup environment is used setting the PROVIDE_DECNET symbol to 1 in STARTUP.COM will create the DECnet scripting environment during server startup.
CGI scripts that use HTTP GET (the default) may be transparently executed within the DECnet scripting environment. This means that the script is executed within a network process, on the target system (which could be the local system), instead of within a process on the local system. Other than that the WASD DECnet CGI environment behaves identically to the standard (sub)process CGI environment. CGIplus scripting is not supported and if CGIplus-only scripts are executed the behaviour is indeterminate.
Scripts that wish to use HTTP POST will need to read the request body from the NET$LINK stream, rather than from HTTP$INPUT as with (sub)process based scripts. End of body is indicated by an empty record rather than EOF. Scripts may quite simply be made to function appropriately in both environments. The following C code fragment illustrates this.
An example of making the HELP database on a system other than that hosting the HTTP server (using the CONAN script) would be done using the mapping rules
The WASD HTTP server provides an emulation of the OSU scripting environment. This is provided so that OSU-based scripts (both CGI-style and OSU-specific) may be employed by WASD with no modification. As this emulation has been designed through examining OSU code and lots of trial and error its behaviour may be incomplete or present errors. A list of OSU scripts known to work with WASD is provided at the end of this section (‘Known Working Scripts’ in 8.3 OSU (DECthreads) Emulation).
Supported scripts include only those that depend on the OSU WWWEXEC object and dialog for all functionality. Any script that uses other OSU-specific functionality is not supported. Interactions between WASD's and OSU's authentication/authorization schemes may be expected.
OSU scripts expect to get the path information unmapped, whereas WASD always additionally maps any path after the script component has been derived from the request URI. It may be necessary to ensure OSU scripts are activated with the associated path SET to provide what they expect. For example:
The author would like to know of any OSU scripts the WASD emulation barfs on, and will attempt to address the associated limitation(s) and/or problem(s).
Software necessary for supporting the OSU scripting environment (e.g. WWWEXEC.COM) and selected OSU scripts (mainly for testing purposes) have been extracted from the OSU v3.4 package and included in the WASD_ROOT:[SRC.OSU] directory. This has been done within the express OSU licensing conditions.
An example DECnet and OSU scripting startup may be found in WASD_ROOT:[EXAMPLE]. This should be called from or used within the HTTP server startup. It includes two logical definitions required for common OSU scripts. Other tailoring may be required for specific OSU scripts.
David Jones, the author of the DECthreads (OSU) HTTP server, outlines his reasons for basing OSUs scripting on DECnet (reproduced from a USENET NEWS reply to a comment this author made about DECnet-based scripting).
The OSU server's DECnet scripting is not based on arbitrary considerations. This author does not disagree with any of the concerns, and as may be seen from WASD documentation the design of WASD also directly addresses points 1, 3 and 5 with the use of persistant processes and CGIplus. Certainly DECnet-based scripting addresses the very legitimate point 4 (and also allows nodes with specific resources to participate without installing full HTTP server environments). Point 2 is not an issue with the use of detached scripting processes, or for all practical purposes addressed by adjusting account quotas to support the required number of subprocesses. Point 6 is only too true (possibly at least until Java servers and servlets become ubiquitous :^)
The following is a list of OSU-specific scripts that the WASD implementation has either been developed or tested against, and any installation notes or other WASD specifics. The author would like to know of any OSU scripts the WASD emulation has problems or works successfully with.
Comment out the Conan The Librarian mappings for the "/help" path and provide the following in WASD_CONFIG_MAP:
Yes, backward compatibility can be provided for those old OSU .HTMLX files in your new WASD environment ;^) All that is needed is a file type mapping to the script in the WASD_CONFIG_GLOBAL configuration file.
The WASD DECnet environment provides a simple mechanism for executing scripts within accounts other than the server's. This allows configured users to write and maintain scripts within their own areas and have them execute as themselves. Both standard CGI and OSU scripting may be provided for with this facility.
Of course there is always a down-side. Be careful to whom this capability is granted. User scripts are executed within a user network-mode process created by DECnet. Script actions cannot generally affect server behaviour, but they can access any WORLD-readable and modify any WORLD-writable resource in the system/cluster, opening a window for information leakage or mischievous/malicious actions. Script authors should be aware of any potential side-effects of their scripts and Web administrators vigilant against possible destructive behaviours of scripts they do not author.
User scripting is not enabled by default. To provide this facility mapping rules into the user area must be provided in much the same way as for user directories, see (Mapping User Directories in WASD Configuration).
The "EXEC" rule provides a wildcard representation of users' script paths. As part of this mapping a subdirectory specifically for the web scripts should always be included. Never map users' top-level directories. For instance if a user's account home directory was located in the area WWW_USER:[DANIEL] the following rule would potentially allow the user DANIEL to provide scripts from the home subdirectory [.WWW.CGI-BIN] using the accompanying rules (first for CGI, second for OSU scripts):
Scripts located in these directories are accessible via paths such as the following:
For each user account permitted to execute local scripts proxy access to that account must be granted to the HTTP server account.
For example, the following would allow the HTTP server to execute scripts on behalf of the username DANIEL.
| ↩︎ | ↖︎ | ↑︎ | ↘︎ | ↪︎ |