Anatomy of a request - Revision history

Libjlrs at 21:11, 14 June 2016

2016-06-14T21:11:31Z

← Older revision		Revision as of 21:11, 14 June 2016
Line 1:		Line 1:
	{{AccessControl}}		{{AccessControl}}
	~~'''THIS PAGE IS UNDER CONSTRUCTION! JLRS 2014-10-23'''~~

	This is a description of how EPrints and Apache handles an incoming request.		This is a description of how EPrints and Apache handles an incoming request.
Line 176:		Line 175:
	*DOI - 5 metadata elements		*DOI - 5 metadata elements
	*40x handling		*40x handling


	~~[[Category:EPrints 3.3.12]]~~

Libjlrs: /* Flow of a request */ typo

2015-05-07T09:23:12Z

Flow of a request: typo

← Older revision		Revision as of 09:23, 7 May 2015
Line 10:		Line 10:
	Below are relevant parts of config files and perl modules that are used with when processing a request.		Below are relevant parts of config files and perl modules that are used with when processing a request.
	The request will generally be dealt with by the <code>EPrints::Apache::Rewrite</code> module, and farmed out from there.		The request will generally be dealt with by the <code>EPrints::Apache::Rewrite</code> module, and farmed out from there.
	~~Hoe~~ the request reaches this module is also explained below.		How the request reaches this module is also explained below.

	==Apache core config <code>~/cfg/apache.conf</code>==		==Apache core config <code>~/cfg/apache.conf</code>==

Libjlrs at 17:20, 28 October 2014

2014-10-28T17:20:18Z

← Older revision		Revision as of 17:20, 28 October 2014
Line 7:		Line 7:
	I will assume that you know how to locate a perl module file from the module name (e.g. <code>EPrints::Apache::Rewrite</code> will probably be <code>~/perl_lib/EPrints/Apache/Rewrite.pm</code>, although this is not always the case!).		I will assume that you know how to locate a perl module file from the module name (e.g. <code>EPrints::Apache::Rewrite</code> will probably be <code>~/perl_lib/EPrints/Apache/Rewrite.pm</code>, although this is not always the case!).

	==Flow of a request==		=Flow of a request=
	Below are relevant parts of config files and perl modules that are used with when processing a request.		Below are relevant parts of config files and perl modules that are used with when processing a request.
	The request will generally be dealt with by the <code>EPrints::Apache::Rewrite</code> module, and farmed out from there.		The request will generally be dealt with by the <code>EPrints::Apache::Rewrite</code> module, and farmed out from there.
	Hoe the request reaches this module is also explained below.		Hoe the request reaches this module is also explained below.

	===Apache core config <code>~/cfg/apache.conf</code>===		==Apache core config <code>~/cfg/apache.conf</code>==
	<source lang="apache">		<source lang="apache">

Line 23:		Line 23:
	See: http://perl.apache.org/docs/2.0/user/handlers/server.html#C_PerlPostConfigHandler_ for more info about the post_config_handler		See: http://perl.apache.org/docs/2.0/user/handlers/server.html#C_PerlPostConfigHandler_ for more info about the post_config_handler

	===Apache repository config <code>~/cfg/apache/ARCHIVEID.conf</code>===		==Apache repository config <code>~/cfg/apache/ARCHIVEID.conf</code>==
	<source lang="apache">		<source lang="apache">
	<VirtualHost *:80>		<VirtualHost *:80>
Line 33:		Line 33:

	This leads us to the backbone of EPrints - the Rewrite module - where URL_REWRITE_* triggers are called; content negotiation can happen, as well as many other wonderous things!		This leads us to the backbone of EPrints - the Rewrite module - where URL_REWRITE_* triggers are called; content negotiation can happen, as well as many other wonderous things!
	===<code>EPrints::Apache::Rewrite</code> module===		==<code>EPrints::Apache::Rewrite</code> module==
	This explanation, and line numbers are taken from a specific version of the file: https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm Obviously this file will change over time, so it's worth comparing it with the version you are using, and possibly other versions on GitHub e.g. https://github.com/eprints/eprints/blob/3.3/perl_lib/EPrints/Apache/Rewrite.pm		This explanation, and line numbers are taken from a specific version of the file: https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm Obviously this file will change over time, so it's worth comparing it with the version you are using, and possibly other versions on GitHub e.g. https://github.com/eprints/eprints/blob/3.3/perl_lib/EPrints/Apache/Rewrite.pm

	It's worth taking a few minutes to look at this file - specifically the <code>sub handler</code>.		It's worth taking a few minutes to look at this file - specifically the <code>sub handler</code>.

	====EP_TRIGGER_URL_REWRITE====		===EP_TRIGGER_URL_REWRITE===
	[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L123 Line 123] calls the 'EP_TRIGGER_URL_REWRITE' trigger:		[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L123 Line 123] calls the 'EP_TRIGGER_URL_REWRITE' trigger:
	<source lang="perl">		<source lang="perl">
Line 55:		Line 55:
	[[API:EPrints/Const#:trigger\|Information on triggers]]		[[API:EPrints/Const#:trigger\|Information on triggers]]

	====CGI scripts====		===CGI scripts===
	[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L157 Line 157] deals with CGI scripts - redirecting to HTTPS if necessary. It looks for the CGI scripts in three locations [https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L195-199 Lines 195-199]:		[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L157 Line 157] deals with CGI scripts - redirecting to HTTPS if necessary. It looks for the CGI scripts in three locations [https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L195-199 Lines 195-199]:
	*<code>~/archives/ARCHIVEID/cgi/</code>		*<code>~/archives/ARCHIVEID/cgi/</code>
Line 72:		Line 72:
	</source>		</source>

	====SWORD servicedocument====		===SWORD servicedocument===
	[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L233-258 Lines 233-258] deal with the 'Sword' service document, via the CRUD interface.		[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L233-258 Lines 233-258] deal with the 'Sword' service document, via the CRUD interface.

	====REST interface====		===REST interface===
	[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L281-290 Lines 281-290] handle the REST interface, via <code>EPrints::Apache::REST</code>		[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L281-290 Lines 281-290] handle the REST interface, via <code>EPrints::Apache::REST</code>

	====EPrints URIs====		===EPrints URIs===
	[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L292-374 Lines 292-374]: EPrint URIs are normally of the form <code><nowiki>http://repository.blah/id/...</nowiki></code>. There are three main <code>if</code> blocks in this section that use regex's to match the URI:		[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L292-374 Lines 292-374]: EPrint URIs are normally of the form <code><nowiki>http://repository.blah/id/...</nowiki></code>. There are three main <code>if</code> blocks in this section that use regex's to match the URI:
	*Line 293 <code>$uri =~ m! ^$urlpath/id/(repository\|dump)$ !x</code> matches two cases.		*Line 293 <code>$uri =~ m! ^$urlpath/id/(repository\|dump)$ !x</code> matches two cases.
Line 90:		Line 90:
	</source>		</source>

	====EPrint IDs, Documents and EP_TRIGGER_DOC_URL_REWRITE====		===EPrint IDs, Documents and EP_TRIGGER_DOC_URL_REWRITE===

	[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L377-493 Lines 377-493] This block of code looks for requests starting with e.g. <code><nowiki>http://repository.blah/123</nowiki></code> - where '123' is an EPrintID.		[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L377-493 Lines 377-493] This block of code looks for requests starting with e.g. <code><nowiki>http://repository.blah/123</nowiki></code> - where '123' is an EPrintID.
Line 148:		Line 148:
	[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L470-490 Lines 470-490] If the URL has an EPrint, but doesn't have a document, we reach this block - which updates the abstract page if necessary, and uses the EPrints templating system to render the page. It also logs the page view using <code>EPrints::Apache::LogHandler::eprint</code>.		[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L470-490 Lines 470-490] If the URL has an EPrint, but doesn't have a document, we reach this block - which updates the abstract page if necessary, and uses the EPrints templating system to render the page. It also logs the page view using <code>EPrints::Apache::LogHandler::eprint</code>.

	====Views====		===Views===
	[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L504-518 Lines 504-518] handle 'view' requests - and regenerating view pages.		[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L504-518 Lines 504-518] handle 'view' requests - and regenerating view pages.

	====auto javascript and css====		===auto javascript and css===
	[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L519-543 Lines 519-543] deal with generating the 'auto' javascript and css files		[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L519-543 Lines 519-543] deal with generating the 'auto' javascript and css files

	====Other static pages====		===Other static pages===
	[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L545-560 Lines 545-560] deals with anything else.		[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L545-560 Lines 545-560] deals with anything else.

	====Other headers====		===Other headers===
	[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L562-582 Lines 562-582] set a few headers for specific cases, and also register EPrints::Apache::Template as the handler for any .html files.		[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L562-582 Lines 562-582] set a few headers for specific cases, and also register EPrints::Apache::Template as the handler for any .html files.


			==Notes==
			*There are two 'content negotiation' functions - one in <code>EPrints::Apache::Rewrite</code>, and another in <code>EPrints::Apache::CRUD</code>.
			*[[API:EPrints/Const#:trigger]] learn about triggers ;o)
			*

	==TODO (some should be seperate pages)==		==TODO (some should be seperate pages)==

	**triggers		**triggers
	**content negotiation
	**CRUD		**CRUD
	**???		**???

Libjlrs at 13:38, 24 October 2014

2014-10-24T13:38:20Z

← Older revision		Revision as of 13:38, 24 October 2014
Line 155:		Line 155:

	====Other static pages====		====Other static pages====
	[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L545-560 Lines 545-560] ~~deal~~ with anything else.		[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L545-560 Lines 545-560] deals with anything else.

	====Other headers====		====Other headers====

Libjlrs at 13:35, 24 October 2014

2014-10-24T13:35:52Z

← Older revision		Revision as of 13:35, 24 October 2014
Line 1:		Line 1:
			{{AccessControl}}
	'''THIS PAGE IS UNDER CONSTRUCTION! JLRS 2014-10-23'''		'''THIS PAGE IS UNDER CONSTRUCTION! JLRS 2014-10-23'''

Line 89:		Line 90:
	</source>		</source>

	====EPrint IDs, Documents ====		====EPrint IDs, Documents and EP_TRIGGER_DOC_URL_REWRITE====

	~~'''Under construction!'''~~

	[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L377-493 Lines 377-493] This block of code looks for requests starting with e.g. <code><nowiki>http://repository.blah/123</nowiki></code> - where '123' is an EPrintID.		[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L377-493 Lines 377-493] This block of code looks for requests starting with e.g. <code><nowiki>http://repository.blah/123</nowiki></code> - where '123' is an EPrintID.
Line 148:		Line 147:

	[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L470-490 Lines 470-490] If the URL has an EPrint, but doesn't have a document, we reach this block - which updates the abstract page if necessary, and uses the EPrints templating system to render the page. It also logs the page view using <code>EPrints::Apache::LogHandler::eprint</code>.		[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L470-490 Lines 470-490] If the URL has an EPrint, but doesn't have a document, we reach this block - which updates the abstract page if necessary, and uses the EPrints templating system to render the page. It also logs the page view using <code>EPrints::Apache::LogHandler::eprint</code>.

			====Views====
			[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L504-518 Lines 504-518] handle 'view' requests - and regenerating view pages.

			====auto javascript and css====
			[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L519-543 Lines 519-543] deal with generating the 'auto' javascript and css files

			====Other static pages====
			[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L545-560 Lines 545-560] deal with anything else.

			====Other headers====
			[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L562-582 Lines 562-582] set a few headers for specific cases, and also register EPrints::Apache::Template as the handler for any .html files.


	==TODO (some should be seperate pages)==		==TODO (some should be seperate pages)==
	*Explain flow of Rewrite
	**triggers		**triggers
	**cgi
	**content negotiation		**content negotiation
	**CRUD		**CRUD
Line 164:		Line 175:

	[[Category:EPrints 3.3.12]]		[[Category:EPrints 3.3.12]]
	~~{{AccessControl}}~~

Libjlrs: /* EPrint IDs, Documents */

2014-10-24T12:20:01Z

EPrint IDs, Documents

@@ Line 94: / Line 94: @@
 [https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L377-493 Lines 377-493] This block of code looks for requests starting with e.g. <code><nowiki>http://repository.blah/123</nowiki></code> - where '123' is an EPrintID.
 There are some <code>redir</code>ects in this block to account for older URL that may be requested that had EPrintIDs and/or document positions zero-padded <code><nowiki>http://repository.blah/00000123</nowiki></code> or <code><nowiki>http://repository.blah/00000123/01/Document.txt</nowiki></code>.
@@ Line 101: / Line 102: @@
 <source lang="perl">$uri =~ s! ^$urlpath/(0*)([1-9][0-9]*)\b !!x</source>
 will remove the EPrintID from the start of <code>$uri</code>.
 [https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L398 Line 398]
@@ Line 125: / Line 128: @@
 *for each of the split values (referenced as $_): grep for the length of the value. This effectively strips out empty elements (length = 0, grep doesn't return the value).
 *@relationships = <code>"relationship1","relationship2","relationshipN"</code>
 ==TODO (some should be seperate pages)==

Libjlrs: /* EPrint IDs, Documents */

2014-10-24T10:23:48Z

EPrint IDs, Documents

← Older revision		Revision as of 10:23, 24 October 2014
Line 115:		Line 115:
	</source>		</source>
	They deal with document relationships - that are of the form <code>.../DocID.relationship1.relationship2.relationshipN/...</code>.		They deal with document relationships - that are of the form <code>.../DocID.relationship1.relationship2.relationshipN/...</code>.

	For documents, thumbnails are presented as related documents, the relationship is e.g. 'hassmallThumbnailVersion'.		For documents, thumbnails are presented as related documents, the relationship is e.g. 'hassmallThumbnailVersion'.

	The first line gets anything from the start of <code>$uri</code> (the DocID already having been removed by line 398), to the next '/'.		The first line gets anything from the start of <code>$uri</code> (the DocID already having been removed by line 398), to the next '/'.
	The second line takes the captured match ($1): <code>.relationship1.relationship2.relationshipN</code>
			The second line (possibly the least readable line of code in EPrints?):
			*takes the captured match ($1): <code>.relationship1.relationship2.relationshipN</code>
			*splits on '.'s: <code>"","relationship1","relationship2","relationshipN"</code>
			*for each of the split values (referenced as $_): grep for the length of the value. This effectively strips out empty elements (length = 0, grep doesn't return the value).
			*@relationships = <code>"relationship1","relationship2","relationshipN"</code>

	==TODO (some should be seperate pages)==		==TODO (some should be seperate pages)==

Libjlrs: /* EPrint IDs, Documents */

2014-10-24T10:03:45Z

EPrint IDs, Documents

@@ Line 93: / Line 93: @@
 '''Under construction!'''
-[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L377-493 Lines 377-493] This block of code looks for a request for <code><nowiki>http://repository.blah/123</nowiki></code> - '123' is EPrint ID 123.
+[https://github.com/eprints/eprints/blob/88a36fcf1f17c7a04e60455d374b617709f7461d/perl_lib/EPrints/Apache/Rewrite.pm#L377-493 Lines 377-493] This block of code looks for requests starting with e.g. <code><nowiki>http://repository.blah/123</nowiki></code> - where '123' is an EPrintID.
-$uri =~ s! ^$urlpath/(0*)([1-9][0-9]*)\b !!x
+Each subsequent match on the <code>$uri</code> consumes part of it - e.g.
 ==TODO (some should be seperate pages)==

Libjlrs: Working through Rewrite module

2014-10-23T16:12:46Z

Working through Rewrite module

@@ Line 1: / Line 1: @@
-This is a description of how EPrints and Apache handle an incoming request.
+'''THIS PAGE IS UNDER CONSTRUCTION! JLRS 2014-10-23'''
 Understanding this flow helps understand how an Access Control layer can be added to the system.
 I will assume that you know how to locate a perl module file from the module name (e.g. <code>EPrints::Apache::Rewrite</code> will probably be <code>~/perl_lib/EPrints/Apache/Rewrite.pm</code>, although this is not always the case!).
-Below are relevant parts of config files and perl modules that are used with when processing a request:
+==Flow of a request==
-*Apache core config <code>~/cfg/apache.conf</code>
+Below are relevant parts of config files and perl modules that are used with when processing a request.
 <source lang="apache">
@@ Line 15: / Line 21: @@
 The post_config_handler does some sanity checks on the EPrints setup (e.g. is Apache listening to the ports that the repositories are configured to work under)
 See: http://perl.apache.org/docs/2.0/user/handlers/server.html#C_PerlPostConfigHandler_ for more info about the post_config_handler
-*Apache repository config <code>~/cfg/apache/ARCHIVEID.conf</code>
 <source lang="apache">
 <VirtualHost *:80>
@@ Line 25: / Line 32: @@
 This leads us to the backbone of EPrints - the Rewrite module - where URL_REWRITE_* triggers are called; content negotiation can happen, as well as many other wonderous things!
-*<code>EPrints::Apache::Rewrite</code> module
+===<code>EPrints::Apache::Rewrite</code> module===
 ==TODO (some should be seperate pages)==

Libjlrs at 14:05, 13 October 2014

2014-10-13T14:05:04Z

← Older revision		Revision as of 14:05, 13 October 2014
Line 27:		Line 27:
	*<code>EPrints::Apache::Rewrite</code> module		*<code>EPrints::Apache::Rewrite</code> module

	'TODO:		==TODO (some should be seperate pages)==
	*Explain flow of Rewrite		*Explain flow of Rewrite
	**triggers		**triggers