'\ '\" The contents of this file are subject to the AOLserver Public License '\" Version 1.1 (the "License"); you may not use this file except in '\" compliance with the License. You may obtain a copy of the License at '\" http://aolserver.com/. '\" '\" Software distributed under the License is distributed on an "AS IS" '\" basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See '\" the License for the specific language governing rights and limitations '\" under the License. '\" '\" The Original Code is AOLserver Code and related documentation '\" distributed by AOL. '\" '\" The Initial Developer of the Original Code is America Online, '\" Inc. Portions created by AOL are Copyright (C) 1999 America Online, '\" Inc. All Rights Reserved. '\" '\" Alternatively, the contents of this file may be used under the terms '\" of the GNU General Public License (the "GPL"), in which case the '\" provisions of GPL are applicable instead of those above. If you wish '\" to allow use of your version of this file only under the terms of the '\" GPL and not to allow others to use your version of this file under the '\" License, indicate your decision by deleting the provisions above and '\" replace them with the notice and other provisions required by the GPL. '\" If you do not delete the provisions above, a recipient may use your '\" version of this file under either the License or the GPL. '\" '\" '\" $Header: /cvsroot/aolserver/aolserver/nsproxy/ns_proxy.n,v 1.2 2006/06/26 00:28:30 jgdavidson Exp $ '\" '\" '\" The 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 '\" Start of list of standard options for a Tk widget. The '\" options follow on successive lines, in four 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. '\" '\" RCS: @(#) $Id: man.macros,v 1.1 2006/06/26 00:29:11 jgdavidson Exp $ '\" '\" # 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 .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 \\fBoptions\\fR 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 .. .de UL \\$1\l'|0\(ul'\\$2 .. .TH ns_proxy 3aolserver 4.5 AOLserver "AOLserver Built-In Commands" .BS '\" Note: do not modify the .SH NAME line immediately below! .SH NAME ns_proxy \- Proxy-process Tcl interface .SH SYNOPSIS .nf \fBns_proxy active \fIpool\fR \fBns_proxy cleanup\fR \fBns_proxy config\fR \fIpool ?-opt val -opt val ...\fR \fBns_proxy eval \fIhandle script ?timeout?\fR \fBns_proxy get\fR \fIpool ?-handle n -timeout ms? \fBns_proxy ping\fR \fIhandle\fR \fBns_proxy release \fIhandle\fR \fBns_proxy recv \fIhandle\fR \fBns_proxy send \fIhandle script\fR \fBns_proxy wait \fIhandle ?timeout?\fR .fi .BE .SH DESCRIPTION .PP This command provides a simple, robust proxy mechanism to evaluate Tcl scripts in a separate, pipe-connected process. This approach can be useful both to isolate potentially thread-unsafe code outside the address space of a multithreaded process such as AOLserver or to enable separation and timeout of potentially misbehaving, long running scripts. .PP The command is provided by the \fInsproxy\fR dynamic library which can be loaded into an interpreter via the Tcl \fBload\fR command, for example: .PP .CS load /usr/local/lib/libnsproxy.so ns_proxy ... .CE .PP It can also possible to load the library into all interpreters of an AOLserver virutal server by specifying an \fInsproxy.so\fR entry in the server's module config entry, for example: .CS ns_section ns/server/server1/modules ns_param nsproxy nsproxy.so .CE .PP When loaded, the library adds the single \fBns_proxy\fR command with takes multiple options as described below. Proxies are normally created on demand when requested and connected to the parent process via pipes used to send scripts and receive response. The processes remain active until the parent process exits, effectively closing all pipes to the slave processes. .TP \fBns_proxy active \fIpool\fR Returns a list of all currently evaluating scripts in proxies for the given \fIpool\fR. The output is a list which includes two elements, the string name of the proxy handle and the string for the script being executed. It is also possible to view the currently evaluating scripts with the Unix \fIps\fR command as the proxy slave process re-writes it's command argument space with the request script before evaluation and clears it after sending the result. .TP \fBns_proxy cleanup\fR Releases any handles from any pools currently owned by a thread. This command is intended to be used as part of a garbage collection step at the end of a transaction. Calling this command within AOLserver is not necessary as the module registers a trace to release all handles via the \fBNs_TclRegisterTrace\fR facility when interpreters are deallocated after a transaction, for example, at the end of a connection. .TP \fBns_proxy config\fR \fIpool ?-opt val -opt val ...\fR Configures options for the pool specified by \fIpool\fR. The pool is created with default options if it does not already exist. The result of \fBns_proxy config\fR is a list of the current options in the form \fI-opt val -opt val ...\fR. Configurable options include: .TP -init script Specifies a script to evaluate when proxies are started. This can be used to load additional libraries and/or source script files. The default is no script. .TP -reinit script Specifies a script to evaluate after being allocated and before being returned to the caller. This can be used to re-initalizes shared state. The default is no script. .TP -min n Sets the minimum number of proxy slave processes to pre-start before any allocations. This defaults to 0 which results in on-demand start the first time proxies are requested. Setting it to a higher number can be useful if initialization takes a significant amount of time. .TP -max n Sets the maximum number of proxy slave processes. Requests for proxies beyond the maximum will result in requesting threads waiting for existing proxies to be available instead of creating new proxy processes. Setting this value to 0 disables the pool, causing all subsequent allocation requests to fail immediately (currently allocated proxies, if any, remain valid). .TP -exec program Specifies the filename of a slave proxy program. This defaults to \fInsproxy\fR in the \fIbin\fR subdirectory of the AOLserver process. It is possible to create a custom program and enter the proxy event loop with the \fBNs_ProxyMain\fR application startup routine; see the source code for details. .TP -getimeout ms Specifies the maximum time to wait to allocate handles from the pool. The default is 500 milliseconds, i.e., 1/2 of a second. .TP -evaltimeout ms Specifies the maximum time to wait for a script to be evaluated in a proxy. This parameter can be overridden on a per-call basis with the optional \fItimeout\fR parameter to \fBns_proxy eval\fR. The default is 100 milliseconds, i.e., 1/10 of a second which assumes scripts are evaluated with minimal delay. .TP -sendtimeout ms .TP -recvtimeout ms Specifies the maximium time to wait to send a script and receive a result from a proxy. The default is 100 milliseconds, i.e., 1/10 of a second which assumes minimal delay sending and receiving reasonably sized scripts and results over the connecting pipe. .TP -waittimeout ms Specifies the maximum time to wait for a proxy to exit. The wait is performed in a dedicated reaper thread. The reaper will close the connection pipe and wait the given timeout. If the timeout is exceeded, the reaper will send a SIGTERM signal and finally a SIGKILL signal to ensure the process eventually exits. The default is 100 milliseconds which should be ample time for a graceful exit unless the process is hung executing a very long, misbehaving script, resulting in a more disruptive SIGTERM or SIGKILL. .TP \fBns_proxy eval \fIhandle script ?timeout?\fR Evalutes \fIscript\fR in the proxy specified by \fIhandle\fR. The optional \fItimeout\fR argument specifies a maximum number of milliseconds to wait for the command to complete before raising an error (see \fBERROR HANDLING\fR below for details on handling errors). .TP \fBns_proxy send \fIhandle script\fR Sends \fIscript\fR in the proxy specified by \fIhandle\fR. Unlike with \fBns_proxy eval\fR, this option will return immediately while the script continues to execute in the proxy process. A later \fBns_proxy wait\fR followed by an \fBns_proxy recv\fR is expected. .TP \fBns_proxy wait \fIhandle ?timeout?\fR Waits for a script sent via \fBns_proxy send\fR in the proxy specified by the \fIhandle\fR argument to complete. The optional \fItimeout\fR parameter specifies the number of milliseconds to wait for the script to complete, the default is an indefinite wait. .TP \fBns_proxy recv \fIhandle\fR Receives a response from a script that was sent via \fBns_proxy send\fR and waited on via \fBns_proxy wait\fR. .TP \fBns_proxy get\fR \fIpool ?-handle n -timeout ms? Returns one or more handles to proxies from the specified \fIpool\fR. The pool will be created with default options if it does not already exist. The optional \fI-handle n\fR arguments can be used to specify the number of handles to allocate, the default being 1. The optional \fI-timeout ms\fR arguments specifies the maximum amount of time in milliseconds to wait for the handles to become availale before raising an error (see \fBERROR HANDLING\fR below for details on handling errors). Requesting more than one handle in a single call if more than one handle is required is necessary as it is an error to request handles from a pool from which handles are already owned in the thread. This restriction is to avoid a possible deadlock condition and is similar to the manner in which the \fBns_db gethandles\fR command operates. .TP \fBns_proxy ping\fR \fIhandle\fR This command sends a null request to the proxy specified by the \fIhandle\fR argument. The proxy will be verified alive and restarted if necessary. This command is not normally required as the \fBns_proxy eval\fR command will also verify and restart proxies as needed. .TP \fBns_proxy release \fIhandle\fR This command can be used to release a single proxy specified by the \fIhandle\fR argument. All handles owned by a thread to the cooresponding pool must be returned before any handles can be allocated again. Within AOLserver, a call to this routine is recommended for clarity but not stricting necessary. As described above, AOLserver installs a trace to release all handles at the end of every connection during interprepter deallocation. .SH "ERROR HANDLING" .PP Errors generated by a script evaluated in a proxy interpreter are completely returned to the calling interpreter, including mapping the \fIerrorInfo\fR and \fIerrorInfo\fR global variables from the proxy to the parent if present and raising a Tcl exception. This enables proxy code to look very similar to that which may use the internal \fBeval\fR command. .PP Errors raised by a failure to communicate with the proxy process due to a timeout or unexpected process exit are also communicated back to the parent interpreter as Tcl exceptions. To distinguish between these cases, communication related errors set the \fIerrorCode\fR global variable with the first element \fBNSPROXY\fR. The second element is one of the following: .TP \fBEDeadlock\fR The interpreter attempted to allocate handles from a pool from which it already owns one or more handles. .TP \fBEExec\fR The slave program specified by the \fI-exec program\fR option could not be started. .TP \fBERange\fR Insufficient handles available in pool. .TP \fBERecv\fR There was an error receiving the result from the slave process. .TP \fBESend\fR There was an error sending the script to the slave process. .TP \fBETimeout\fR The timeout specified for the pool by the \fI-evaltimeout\fR option or as the optional argument to the current call to \fBns_proxy eval\fR was exceeded. .SH EXAMPLES .PP The following demonstrates sending a script to a remote proxy: .CS set handle [ns_proxy get myproxy] ns_proxy eval $handle {info patchlevel} ns_proxy release $handle .CE The following demonstrates an asyncronous request: .CS set handle [ns_proxy get myproxy] ns_proxy send $handle {long running script} ... continue other work ... ns_proxy wait $handle set result [ns_proxy recv $handle] ns_proxy release $handle .CE The following demonstrates using multiple proxies: .CS ns_proxy config myproxy -max 10 set handles [ns_proxy get myproxy -handle 10] foreach h $handles { ns_proxy eval $h {puts "alive: [pid]"} } ns_proxy cleanup .CE .SH "SEE ALSO" eval(n) .SH KEYWORDS threads, interpreters, proxy, initialization