Vmod-Dbrw User Manual
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1. 5 database user name 0005 6 debug aii ed ebyE HR een 5 debugginglevel 5 discard query S TINg 4 escape SEQUENCES susuri eee eee 5 FDL GNU Free Documentation License E 15 O 3 EEOUP we od di 6 23 initialization 0 cece eee 5 MySQL options file 6 name database 6 3 OCASE cesse i da pee 3 Options ia E AEN PA 6 options MySQL a 6 options PostgreSQL 6 Password ee 6 POLE c M APA AA 5 E AA asana conse pia 3 USE AA ieh 3 qsdiscard oig p 1 IRR ENT et 4 USD LiscfuerpereQserdek a uides 4 o o LE ma ieri ee 6 7 query string handling 3 4 redirection code cece eee eee 4 regex matching 0 004 3 regular expression case insensitive 3 regular expression case sensitive 3 result interpretation 3 LEWLILE Vio or REO ERREUR Rh 9 rewrite TUleS ooooooccccccooo 1 3 S SOLVER aida deidad 5 24 SSL connection MySQL Stat s Code scisco loc en strict matching 2 en een supported databases vmod dbrw User Manual Varnish su 2er NGA 1 vcl NIE ea an D VO TE Vera rita e PUEDES 9 VOl Synili 2 eonsvewnIrebeere e RXUpYS 10 vmod redirect ccc eee eee 10 VIMO AA Rete awe eee 10 X X VMOD DBRW Status 4 102. The simplest database structure for this purpose assuming MySQL will be CREATE TABLE redirects id INT AUTO_INCREMENT host varchar 255 NOT NULL DEFAULT url varchar 255 NOT NULL DEFAULT dest varchar 255 DEFAULT NULL PRIMARY KEY host url The columns and their purpose are id An integer uniguely identifying the row It is convenient for managing the table e g deleting the row host Host part of the incoming request url URL part of the incoming request dest Destination URL to redirect to The rewrite function is to look for a row that has host and url match ing the incoming request and to redirect it to the URL in the dest column The corresponding query is SELECT dest FROM redirects WHERE host host AND url url The variables host and url are supposed to contain the actual host and URL parts of the incoming request Handling regular expression matches is a bit trickier Your query should first return the rows that could match the request Then the vmod dbrw engine will do the rest by iterating over them and finding the one that actually does It will iterate over the rows in the order they were returned by the database server so it might be necessary to sort them by some criterion beforehand The following is an example table structure 8 vmod dbrw User Manual CREATE TABLE rewrite id INT AUTO_INCREMENT host varchar 255 NOT NULL DEFAULT
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5. not have their licenses terminated so long as such parties remain in full compliance FUTURE REVISIONS OF THIS LICENSE The Free Software Foundation may publish new revised versions of the GNU Free Documentation License from time to time Such new versions will be similar in spirit to the present version but may differ in detail to address new problems or concerns See http www gnu org copyleft Each version of the License is given a distinguishing version number If the Document specifies that a particular numbered version of this License or any later version applies to it you have the option of following the terms and conditions either of that specified version or of any later version that has been published not as a draft by the Free Software Foundation If the Document does not specify a version number of this License you may choose any version ever published not as a draft by the Free Software Foundation 22 vmod dbrw User Manual A 1 ADDENDUM How to use this License for your documents To use this License in a document you have written include a copy of the License in the document and put the following copyright and license notices just after the title page Copyright C year your name Permission is granted to copy distribute and or modify this document under the terms of the GNU Free Documentation License Version 1 2 or any later version published by the Free Software Foundation with no Invariant Secti
6. to config and returns the obtained value To do so it performs the following steps e Parameter parsing The args parameter must be a list of name value pairs separated by semicolons The function parses this string and builds a symbol table e Variable expansion Using the symbol table built in the previous stage each occurrence of name or name is replaced with the actual value of the variable name from the table Expanding an undefined variable is considered an error e Establishing the database connection Unless the connection has already been established by a prior call to rewrite the function establishes it using the parameters supplied earlier in a call to config Ifthe connection fails the function returns NULL immediately Database connections are persisting and thread specific This means that each thread keeps its own connection to the database and at tempts to re establish it if it goes down for some reason e Query execution The query is sent to the server and the resulting set collected from it e Result interpretation The resulting set is interpreted as described in result interpretation page 3 This results in a single value being returned to the caller Assuming the database structure similar to the one discussed in the previ ous chapter the following example illustrates how to use rewrite to redirect the incoming request It assumes VCL 4 0 sub vcl recv set req http X Redirect To dbrw rewr
7. 01 req http X Redirect To Redirection The vcl_error subroutine is not needed in this case Chapter 6 How to Report a Bug 13 6 How to Report a Bug Email bug reports to gray gnu org As the purpose of bug reporting is to improve software please be sure to include a detailed information when reporting a bug The minimum information needed is e Module version you use e A description of the bug e Conditions under which the bug appears e It is often helpful to send the contents of config log file along with your bug report This file is created after running configure in vmod dbrw source root directory Appendix A GNU Free Documentation License Appendix A GNU Free Documentation 15 License Version 1 2 November 2002 Copyright c 2000 2001 2002 Free Software Foundation Inc 51 Franklin Street Fifth Floor Boston MA 02110 1301 USA Everyone is permitted to copy and distribute verbatim copies of this license document but changing it is not allowed PREAMBLE The purpose of this License is to make a manual textbook or other functional and useful document free in the sense of freedom to assure everyone the effective freedom to copy and redistribute it with or with out modifying it either commercially or noncommercially Secondarily this License preserves for the author and publisher a way to get credit for their work while not being considered responsible for modifications made by others
8. Vmod Dbrw User Manual version 2 0 12 November 2014 Sergey Poznyakoff Published by the Free Software Foundation 51 Franklin Street Fifth Floor Boston MA 02110 1301 USA Copyright 2013 2014 Sergey Poznyakoff Permission is granted to copy distribute and or modify this document un der the terms of the GNU Free Documentation License Version 1 3 or any later version published by the Free Software Foundation with no Invariant Sections no Front Cover and no Back Cover texts A copy of the license is included in the section entitled GNU Free Documentation License Short Contents 1 Introduction to vmod dbrw 1 0 s 1 2 Dira o doles ice qo DANGAN dog opaco eed da 3 3 Configuration s da Quen Re donis ed b edo a wa d qr do d QUITAR es 5 4 Writing Queries sca cae ek EA x E Rao Gan e ee aes 7 5 The rewrite PINONG bado od aL ae Aca eco 9 B How to Report a Bug aa ee 13 A GNU Free Documentation License o ooooooo oo o 15 Grund s serae denga cage ea oie wig bra tie a es Es 23 Hi Table of Contents 1 Introduction to vmod dbrw 1 2 OVERVIEW 5 25 disks end ANAK dd eden 3 3 Configuration zan GANDA Ka AKA sitis iie e den 5 4 Writing Queries esses sss T 5 The rewrite Function 9 6 How to Report a Bug 13 Appendix A GNU Free Documentation License ne PPP 15 A 1 ADDENDUM How to use this Lice
9. ameters from the MySQL op tions file filename group name MySQL specific Read credentials from section name of the options file supplied with the config parameter Default section name is client cacert filename Use secure connection to the database server via SSL The filename argument is a full pathname of the certificate authority file options string Postgres specific Connection options user name Database user name password string Password to access the database query The SQL query to use It can contain variable references in the name or name which will be replaced with the actual value of the name argument to the function rewrite The example below configures vmod dbrw to use MySQL database rewrite with the user name varnish and password guessme import dbrw sub vcl_init 4 dbrw config mysql database rewrite user varnish password guessme SELECT dest FROM redirects WHERE host host AND url url Chapter 4 Writing Queries 7 4 Writing Queries The query supplied to the config function depends on the database schema and on the kind of matching required To ensure the best performance of the module it is important to design the database and the query so that the database look up be as fast as possible Suppose that you plan to use vmod dbrw to implement redirection rules based on strict matching see strict matching page 3
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12. digit from 0 through 9 is replaced with the contents of the digits parenthesized subexpression in regexp For compatibility with the traditional usage the digit notation is also allowed The resulting value is then returned to the caller Optional flags column is a comma separated list of flags that modify regular expression handling NC nocase Treat regexp as case insensitive regular expression case Treat regexp as case sensitive default 4 vmod dbrw User Manual ASA qsappend Treat the resulting value as URL append any query string from the original value to it QSD qsdiscard Treat the resulting value as URL discard any query string at tached to the original value redirect code R code On success set the X VMOD DBRW Status header to code which must be a valid HTTP status code If regexp or value is NULL strict matching is assumed see strict match ing page 3 If flags is NULL it is ignored Chapter 3 Configuration 5 3 Configuration void config string dbtype string params string query function This function configures the module and provides it with the data nec essary to connect and use the database It is normally called from the vcl_init subroutine Arguments dbtype params Type of the database to use Valid values are mysql and pgsql Database connection parameters This is a list of name value assi
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15. gnments separated with semicolons The value part can be any sequence of characters excepting white space and semicolon If any of these is to appear in it they must either be escaped by prepending them with a backslash or the entire value enclosed in a pair of single or double quotes The following escape sequences are allowed for use in value Sequence Replaced with a Audible bell character ASCII 7 b Backspace character ASCII 8 f Form feed character ASCII 12 n Newline character ASCII 10 r Carriage return character ASCII 13 t Horizontal tabulation character ASCII 9 v Vertical tabulation character ASCII 11 Table 3 1 Backslash escapes If a backslash is followed by a symbol other than listed above it is removed and the symbol following it is reproduced ver batim Valid parameters are debug n Set debugging level Argument is a decimal num ber server host Name or IP address of the database server to con nect to If not defined localhost 127 0 0 1 is assumed For MySQL databases if host be gins with a slash its value is taken to be the full pathname of the local UNIX socket to connect to vmod dbrw User Manual port n Port number on the server to connect to De fault is 3306 for MySQL and 5432 for Postgres database name The name of the database to use config filename MySQL specific Read database access creden tials and other par
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17. ite host req http Host url req url if req http X Redirect To return synth 301 Redirect 10 vmod dbrw User Manual Further handling of the 301 response should be performed in a traditional way e g import std sub vcl_synth if resp status 301 set resp http Location req http X Redirect To if req http X VMOD DBRW Status set resp status std integer req http X VMOD DBRW Status 301 return deliver The X VMOD DBRW Status header if set contains the status code to be returned to the client see X VMOD DBRW Status page 4 Notice the use of the vmod_std module to cast it to integer The example below shows the same code for VCL 3 0 import std sub vcl recv set req http X Redirect To dbrw rewrite host req http Host url req url if req http X Redirect To error 750 Redirect sub vcl_error if obj status 750 set obj http Location req http X Redirect To set obj status std integer req http X VMOD DBRW Status 301 return deliver For VCL 3 0 you can use libvmod redirect to simplify the code Chapter 5 The rewrite Function 11 import std import dbrw import redirect sub vcl recv set req http X Redirect To dbrw rewrite host req http Host url req url if req http X Redirect To error redirect location std integer req http X VMOD DBRW Status 3
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19. micolons each assignment having the form name value When called rewrite expands the SQL query registered with the prior call to config by replacing each name construct a variable reference with the corresponding value from its argument Similarly to the shell syntax the variable reference can also be written as name This lat ter form can be used in contexts where the variable reference is immediately followed by a letter digit or underscore to prevent it from being counted as a part of the name The expanded query is then sent to the database server If it returns a non empty set it is further handled depending on the number of fields it contains If the returned set has one or two columns only the first tuple is used and rewrite returns the value of its first column Otherwise if the returned set has three or more columns the regular expression matching is performed For the purpose of this discussion let s refer to the columns as follows result regexp value and flags The flags column is optional Any surplus columns are ignored For each returned tuple the value column undergoes variable expansion using the same algorithm as when preparing the query and the resulting string is matched with the regexp column which is treated as an extended POSIX regular expression If the value matches the expression the result column is expanded by replacing backreferences each occurrence of digit where digit stands for a decimal
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21. nse for your documents 22 Concept IndeX vieiras ERR ees 23 Chapter 1 Introduction to vmod dbrw 1 1 Introduction to vmod dbrw Vmod dbrw is a module for Varnish Cache which implements database driven rewrite rules These rules may be similar to RewriteRule directives implemented by mod_rewrite module in Apache or to Redirect directives of its mod_alias module What distinguishes the vmod dbrw rules from these is that they are handled by Varnish before the request reaches the httpd server and that they are stored in an SQL database which makes them easily manageable Some web sites implement thousands of rewrite rules The purpose of this module is to facilitate deploying and handling them The module can be compiled for VCL 3 0 or 4 0 l https www varnish cache org 2 http httpd apache org docs current rewrite Chapter 2 Overview 3 2 Overview Rewrite rules are stored in a MySQL or PostgreSQL database The vmod dbrw module does not impose any restrictions on its schema It only needs to know the SQL query which is to be used to retrieve data This query is supplied to the module along with the credentials for accessing the database by calling the config function in the vcl_init subroutine of the Varnish configuration file Once the module is configured the rewrite function can be called in the appropriate place of the Varnish configuration file Its argument is a list of variable assignments separated with se
22. ons no Front Cover Texts and no Back Cover Texts A copy of the license is included in the section entitled GNU Free Documentation License If you have Invariant Sections Front Cover Texts and Back Cover Texts replace the with Texts line with this with the Invariant Sections being list their titles with the Front Cover Texts being list and with the Back Cover Texts being list If you have Invariant Sections without Cover Texts or some other com bination of the three merge those two alternatives to suit the situation If your document contains nontrivial examples of program code we rec ommend releasing these examples in parallel under your choice of free soft ware license such as the GNU General Public License to permit their use in free software Concept Index Concept Index This is a general index of all issues discussed in this manual A append query string 3 backslash interpretation 5 CAC iia a end 6 Caida 3 case insensitive regular expression 3 case sensitive regular expression 3 certificate authority file SSL 6 CONE DO Senne een 5 6 configuration e yum uer ee nen 5 databases incor raros 6 database engines an 3 database name 0 a 6 database password 22222 222 0 6 database query tyit et 6 database S rver 2 cece eee eee ee 5 database server port
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26. url varchar 255 NOT NULL DEFAULT dest varchar 255 DEFAULT NULL value varchar 255 DEFAULT NULL pattern varchar 255 DEFAULT NULL flags char 64 DEFAULT NULL weight int NOT NULL DEFAULT 0 KEY source host url The meaning of id host and dest is the same as in the previous exam ple The meaning of url is described below Other columns are see regex matching page 3 value The value to be compared with the pattern pattern Regular expression to use flags Optional flags weight Relative weight of this row in the set Rows will be sorted by this column in ascending order The simplest way to select candidate rows is by their host column SELECT dest pattern value flags FROM rewrite WHERE host host ORDER BY weight One can further abridge the returned set by selecting only those rows whose url column is the prefix of the requested URL SELECT dest pattern value flags FROM rewrite WHERE host host AND LOCATE ur1 url ORDER BY weight Furthermore the url column can contain a SQL wildcard pattern in which case the query will look like SELECT dest pattern value flags FROM rewrite WHERE host host AND url like url ORDER BY weight Chapter 5 The rewrite Function 9 5 The rewrite Function string rewrite string args function This function is the working horse of the module It rewrites its argument using the database configured in the previous call
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