php-general Digest 7 Jul 2010 13:13:34 -0000 Issue 6834
php-general Digest 7 Jul 2010 13:13:34 - Issue 6834 Topics (messages 306717 through 306729): Re: communication protocol 306717 by: Ashley Sheridan 306718 by: Phpster 306723 by: Augusto Flavio 306725 by: Phpster Re: HTML in emails 306719 by: upscope 306722 by: Paul M Foster 306729 by: tedd Re: Open Source SEO tool 306720 by: Jack 306721 by: Ashley Sheridan Re: cache_control_limiter 306724 by: Guus Ellenkamp window.open access parent's JS? 306726 by: Skip Evans 306728 by: Ashley Sheridan PHP Programmer 306727 by: peeyush gulati Administrivia: To subscribe to the digest, e-mail: php-general-digest-subscr...@lists.php.net To unsubscribe from the digest, e-mail: php-general-digest-unsubscr...@lists.php.net To post to the list, e-mail: php-gene...@lists.php.net -- ---BeginMessage--- On Tue, 2010-07-06 at 18:41 -0300, Augusto Flavio wrote: Hi List, I'm looking for a chat support likes the livezilla. The livezilla is a great tool but doesn't have language supports to another language instead english and german (operator side). Then I thought that a good option would be develop my own chat support. A great solution is build the server side in PHP. The client side would be developed in PHP. For the operator side I thought that could be a Desktop Windows Application build using the Flex. I found that have a communication tool called BlazeDS for Flex that works and helps with the development of this chat support. But the BlazeDS is for Flex/Java. Is there some tool in PHP that helps the development of a server web messaging likes the BlazeDS? Thanks for all. Augusto Morais It depends what you need the chat to do. Are you looking for a full chatroom or a one-to-one chat option? You could quite easily have an AJAX front-end that queries the server every ½ second or so for new messages and display them. You could have something up and running very easily in no time at all. Thanks, Ash http://www.ashleysheridan.co.uk ---End Message--- ---BeginMessage--- Amfphp ( www.amfphp.org) is what you might be looking for. It converts php based content into the flex digestible format. Bastien Sent from my iPod On Jul 6, 2010, at 17:41, Augusto Flavio afla...@gmail.com wrote: Hi List, I'm looking for a chat support likes the livezilla. The livezilla is a great tool but doesn't have language supports to another language instead english and german (operator side). Then I thought that a good option would be develop my own chat support. A great solution is build the server side in PHP. The client side would be developed in PHP. For the operator side I thought that could be a Desktop Windows Application build using the Flex. I found that have a communication tool called BlazeDS for Flex that works and helps with the development of this chat support. But the BlazeDS is for Flex/Java. Is there some tool in PHP that helps the development of a server web messaging likes the BlazeDS? Thanks for all. Augusto Morais ---End Message--- ---BeginMessage--- Hi again, I'm thinking about in how to do the communication between web chat in browser client, the server and the operator desktop client. I'm thinking in web service likes wsdl. Is a good option? Thanks Augusto Morais ---End Message--- ---BeginMessage--- Try rest based or comet for chat Bastien Sent from my iPod On Jul 6, 2010, at 22:41, Augusto Flavio afla...@gmail.com wrote: Hi again, I'm thinking about in how to do the communication between web chat in browser client, the server and the operator desktop client. I'm thinking in web service likes wsdl. Is a good option? Thanks Augusto Morais ---End Message--- ---BeginMessage--- On Tuesday, July 06, 2010 07:03:58 am Andre Majorel wrote: On 2010-07-04 11:43 -0400, Al wrote: Seems like, from my preliminary Google searching, I should not waste time with the standard's way and just go straight to sending simple html pages since all modern browsers handle it well. And, it appears to be the way web is going. Browsers ? The web ? I thought it was about email ? If it's HTML, I have to decode and save the email to a file from my MUA and then switch a browser to read it. As you can imagine, I rarely bother. I agree, actually my filters are setup to send HTML to the trash can. Its a security risk in some cases. It use to be that we specified content-type text/html, etc. and sent both the plain ASCII and the html with boundaries and so forth. That is the only sane approach. -- Russ ---End Message--- ---BeginMessage--- On Tue, Jul 06, 2010 at 06:32:40PM +0200, Per Jessen wrote: Paul M Foster wrote: Here is the real problem with HTML email. Any straight text message will swell to many times
[PHP] PHP Programmer
Hi Every One Expert PHP programmer. Interested in Web game development ? (*Expatriate allowed) UBISoft Chengdu is seeking for talented web programmer with interest and experience in the web domain. The main responsibility of the web programmer would be to make various modules for online games. The web programmer should be capable for creating various technical solutions as per the design requirements, additionally should have understanding of various web protocols. Requirements: -Holding a Degree course in technology or any other training or equivalent. -Working experience of at least three years in PHP. -Should have clear understanding of various protocols like HTTP, AMF. -Should have good working knowledge about databases and be comfortable in using MySql or equivalent database. -Should possess excellent programming skills in web technologies like PHP, HTML, CSS, shell scripting. -Should be able to use JavaScript and similar client side technologies and have good understanding of XML. -Should be comfortable in working on Linux environment. -Should have a clear understanding of object oriented programming. -Should be flexible in organizing the work as per the requirements. -Should understand how to work in a result oriented environments and should respect commitments towards the work. -Should be a team player and has the ability to work in the constructive direction for the company, team and personal growth. -Should be capable enough to adapt to changes and get the best out of it. -Should be fluent in English and should hold good communication skills to interact with various teams -Open minded to learn to adapt in Chinese culture from experienced managers. -A passion for creating and playing games -Experience with web games is preferable. Let me know if any one interest :-) -- Thanks and Regards Peeyush Gulati
Re: [PHP] window.open access parent's JS?
On Wed, 2010-07-07 at 00:09 -0500, Skip Evans wrote: Hey all, Is there a way to have a window opened with window.open() inherit the parent windows JS environment? In other words, I call window.open() with a URL that displays a form created by a PHP script. JS code has already been loaded by the parent, and I need to be able to access that code via mouse overs and onclick calls from the code in the newly opened window. Is this possible? Thanks, Skip -- Skip Evans PenguinSites.com, LLC 503 S Baldwin St, #1 Madison WI 53703 608.250.2720 http://penguinsites.com Those of you who believe in telekinesis, raise my hand. -- Kurt Vonnegut Not really anything to do with PHP there :p What you're looking for though is window.opener which allows you to reference the window object of the frame that opened your new window, and access all of its functions and variables. Thanks, Ash http://www.ashleysheridan.co.uk
Re: [PHP] HTML in emails
At 10:09 PM -0400 7/6/10, Paul M Foster wrote: On Tue, Jul 06, 2010 at 06:32:40PM +0200, Per Jessen wrote: In principle, I agree - in practice, CPU cycles are getting cheaper by the minute, and being wasted all the time. Not using HTML is highly unlikely to have a measurable impact on anybodys CPU cycles. I keep hearing this argument. Here are what I consider similar arguments. Everyone else pours their waste into the river. Ours won't make that much difference. Our smokestack is just one of hundreds in the city. No one will notice the additional smoke. Putting paint thinner down the toilet won't make any difference. The water processing plant will clean it up. Just because everyone else wastes CPU doesn't mean you have to contribute to it, too. I keep hearing this argument too! There's always two sides to every argument -- to extend your metaphor, as a result of pollution we have the EPA and other environmental concerns who are now so focused on the rules they actually hurt the quality of life for *all* things (the recent Gulf Oil Spill is one of thousands of examples). The application of any rule-set should be tempered with how it affects the whole and not the just a part. The term Waste in the phrase Wasting CPU cycles is dependant upon what yardstick you use to measure what waste means. I do not think it a waste when you break your code into more manageable parts as compared to creating a cryptic routine that simply runs quicker. When creating code, there are things more important things to consider than CPU cycles, such as readability, maintainability, and reusability. Every programmer has to realize that Wasting CPU cycles (like wasting memory) is becoming exponentially less of a problem whereas creating reusable code is doing just the opposite. So when considering waste I hold programmer's time in more regard than CPU cycles. Just because some people write cryptic code, doesn't mean you have too. :-) Cheers, tedd -- --- http://sperling.com http://ancientstones.com http://earthstones.com -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP] window.open access parent's JS?
Yup, window.opener it is. Much thanks. I was surprised how much Googling I did and didn't find that. On 07/07/2010 04:31 AM, Ashley Sheridan wrote: Not really anything to do with PHP there :p Well, given the breadth the topics I've seen discussed on this list I thought it would slide by. But for my penance I'll ask the following: Is there a way to have a window opened with window.open() inherit the parent windows JS environment... when it resides in a much larger PHP/MySQL application? How's that for a qualifier! :) Skip -- Skip Evans PenguinSites.com, LLC 503 S Baldwin St, #1 Madison WI 53703 608.250.2720 http://penguinsites.com Those of you who believe in telekinesis, raise my hand. -- Kurt Vonnegut -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
[PHP] Multiple Access Question
Hi gang: I have *my way* of handling this problem, but I would like to hear how you guys do it. Here's the problem -- let's say you have a database containing names and addresses and you want approved users to be able to access the data. As such, a user must login before accessing an editing script that would allow them to review and edit the data -- nothing complicated about that. However, let's say you have more than one user accessing the editing script at the same time and you want to make sure that any changes made to the database are done in the most efficient manner possible. For example, if two users access the database at the same time and are editing different records, then there's no real problem. When each user finishes editing they simply click submit and their changes are recorded in the database. However, if two (or more) users want to access the same record, then how do you handle that? Cheers, tedd -- --- http://sperling.com http://ancientstones.com http://earthstones.com -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP] Multiple Access Question
tedd wrote: Hi gang: I have *my way* of handling this problem, but I would like to hear how you guys do it. Here's the problem -- let's say you have a database containing names and addresses and you want approved users to be able to access the data. As such, a user must login before accessing an editing script that would allow them to review and edit the data -- nothing complicated about that. However, let's say you have more than one user accessing the editing script at the same time and you want to make sure that any changes made to the database are done in the most efficient manner possible. For example, if two users access the database at the same time and are editing different records, then there's no real problem. When each user finishes editing they simply click submit and their changes are recorded in the database. However, if two (or more) users want to access the same record, then how do you handle that? I would provide read access whatever the case. For write access I would place a lock on the data for the first user to make the edit request. The lock would have an expiry time, and the user in possession of the lock could reset it if they need more time. Other users would be alerted that another user is currently editing the data and that the lock will expire in X minutes. If the user completes their edit before the timer expires, then the timer will be automatically cleared upon commit of the changes. Optionally, the user who doesn't get the lock could be alerted to what user currently has the lock. Additionally, if we get complicated we could allow a higher authority to steal the lock and alert the user making edits. Cheers, Rob. -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
[PHP] Re: Multiple Access Question
On 07/07/2010 11:59 AM, tedd wrote: Hi gang: I have *my way* of handling this problem, but I would like to hear how you guys do it. Here's the problem -- let's say you have a database containing names and addresses and you want approved users to be able to access the data. As such, a user must login before accessing an editing script that would allow them to review and edit the data -- nothing complicated about that. However, let's say you have more than one user accessing the editing script at the same time and you want to make sure that any changes made to the database are done in the most efficient manner possible. For example, if two users access the database at the same time and are editing different records, then there's no real problem. When each user finishes editing they simply click submit and their changes are recorded in the database. However, if two (or more) users want to access the same record, then how do you handle that? Cheers, tedd I would load up the current db values at the beginning of the edit form and store them in the session. Then on the processing page look them up again and see if they match the session values. If not, then load the edit form again with a message that says the record has recently been updated by someone else. -- Thanks! -Shawn http://www.spidean.com -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
[PHP] Creating image on-the-fly
Hello, I was wondering if there was any way I can create an image from some text with php? For Eg: I have a text box that will have a number/letter combo, I want it to dynamically gen the num/lett combo, then create say a transparent png of that number/letter combo then display it to the user. Can I take this text box and make it a png? Any pointers or insight appreciated. If anyone happens to knows of a javascript equiv., that would work too. TIA Karl DeSaulniers Design Drumm http://designdrumm.com
[PHP] State and City Database
Hi gang: Does anyone have a source for a US State and City database? Cheers, tedd -- --- http://sperling.com http://ancientstones.com http://earthstones.com -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP] Creating image on-the-fly
I was wondering if there was any way I can create an image from some text with php? Something like this? http://sgss.me/obsolete/experiments/phpfontimagegenerator2/usage.php -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP] State and City Database
Does anyone have a source for a US State and City database? This is a monster but seems to contain what you need: http://www.geonames.org/. Marc -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP] Creating image on-the-fly
On Wed, 2010-07-07 at 16:05 -0400, Marc Guay wrote: I was wondering if there was any way I can create an image from some text with php? Something like this? http://sgss.me/obsolete/experiments/phpfontimagegenerator2/usage.php One thing to bear in mind is that this introduces extra server load if the image is generated dynamically for each visit to a page. It's best to save the image once it's first created and use that file if it exists the next time round. Thanks, Ash http://www.ashleysheridan.co.uk
[PHP] Date Test...
Hello all,
I am processing an array to build an INSERT string in PHP. The code
below I build an a separate array for the TARGET fields and the VALUES.
I am trying to trap for a NULL ENTRY in a Date Input Field. Date
fields are identified with: $ffield['s']=='/'
I tried to add the !empty($fval) to the test but it is giving my
an unexpected results. In my case, I have a Data of Birth field that
keeps populating in the future: So 1941-06-16 inserts in the DB as
2041-06-16.
foreach($form_fields as $ffield){
$fval = is_array($ffield['f'])?joinFields($ffield['s'],
$ffield['f']):$_POST[$ffield['f']];
$query_values[] = '.mysql_real_escape_string($ffield['s']=='/'
!empty($fval) ?date('y-m-d',strtotime($fval)):$fval).';
}
Will anyone point out the problem with this CODE?
Don Wieland
--
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RE: [PHP] Creating image on-the-fly
-Original Message- From: Ashley Sheridan [mailto:a...@ashleysheridan.co.uk] Sent: Wednesday, July 07, 2010 1:22 PM To: Marc Guay Cc: php-general Subject: Re: [PHP] Creating image on-the-fly On Wed, 2010-07-07 at 16:05 -0400, Marc Guay wrote: I was wondering if there was any way I can create an image from some text with php? Something like this? http://sgss.me/obsolete/experiments/phpfontimagegenerator2/usage.php One thing to bear in mind is that this introduces extra server load if the image is generated dynamically for each visit to a page. It's best to save the image once it's first created and use that file if it exists the next time round. Thanks, Ash http://www.ashleysheridan.co.uk Some folks call this a cache ;-) http://en.wikipedia.org/wiki/Cache -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
RE: [PHP] Creating image on-the-fly
On Wed, 2010-07-07 at 13:43 -0700, Daevid Vincent wrote: -Original Message- From: Ashley Sheridan [mailto:a...@ashleysheridan.co.uk] Sent: Wednesday, July 07, 2010 1:22 PM To: Marc Guay Cc: php-general Subject: Re: [PHP] Creating image on-the-fly On Wed, 2010-07-07 at 16:05 -0400, Marc Guay wrote: I was wondering if there was any way I can create an image from some text with php? Something like this? http://sgss.me/obsolete/experiments/phpfontimagegenerator2/usage.php One thing to bear in mind is that this introduces extra server load if the image is generated dynamically for each visit to a page. It's best to save the image once it's first created and use that file if it exists the next time round. Thanks, Ash http://www.ashleysheridan.co.uk Some folks call this a cache ;-) http://en.wikipedia.org/wiki/Cache Yeah, well if ya wanna get all tek-nik-all! :p Thanks, Ash http://www.ashleysheridan.co.uk
Re: [PHP] Multiple Access Question
On Wed, Jul 07, 2010 at 12:59:30PM -0400, tedd wrote: Hi gang: I have *my way* of handling this problem, but I would like to hear how you guys do it. Here's the problem -- let's say you have a database containing names and addresses and you want approved users to be able to access the data. As such, a user must login before accessing an editing script that would allow them to review and edit the data -- nothing complicated about that. However, let's say you have more than one user accessing the editing script at the same time and you want to make sure that any changes made to the database are done in the most efficient manner possible. For example, if two users access the database at the same time and are editing different records, then there's no real problem. When each user finishes editing they simply click submit and their changes are recorded in the database. However, if two (or more) users want to access the same record, then how do you handle that? Use a DBMS? I'm sorry if that seems flippant, but a DBMS handles this by queuing the requests, which is one of the advantages of a client-server DBMS. So maybe I don't understand your question. Paul -- Paul M. Foster -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
[PHP] interface name file
Hi, I want to know which file name is appropriate for a interface. Today, for a PHP class I use: NAME.class.php. What about a interface? Is there a definition about it ? Thanks Augusto Morais
Re: [PHP] interface name file
*.api Application Programming Interface http://en.wikipedia.org/wiki/Application_Programming_Interface ** Hans Åhlin Tel: +46761488019 icq: 275232967 http://www.kronan-net.com/ irc://irc.freenode.net:6667 - TheCoin ** 2010/7/8 Augusto Flavio afla...@gmail.com: Hi, I want to know which file name is appropriate for a interface. Today, for a PHP class I use: NAME.class.php. What about a interface? Is there a definition about it ? Thanks Augusto Morais -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP] Multiple Access Question
On Wed, Jul 7, 2010 at 8:47 PM, Paul M Foster pa...@quillandmouse.com wrote: On Wed, Jul 07, 2010 at 12:59:30PM -0400, tedd wrote: Hi gang: I have *my way* of handling this problem, but I would like to hear how you guys do it. Here's the problem -- let's say you have a database containing names and addresses and you want approved users to be able to access the data. As such, a user must login before accessing an editing script that would allow them to review and edit the data -- nothing complicated about that. However, let's say you have more than one user accessing the editing script at the same time and you want to make sure that any changes made to the database are done in the most efficient manner possible. For example, if two users access the database at the same time and are editing different records, then there's no real problem. When each user finishes editing they simply click submit and their changes are recorded in the database. However, if two (or more) users want to access the same record, then how do you handle that? Use a DBMS? I'm sorry if that seems flippant, but a DBMS handles this by queuing the requests, which is one of the advantages of a client-server DBMS. So maybe I don't understand your question. Paul -- Paul M. Foster -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php @Paul, The OPs question is about concurrency on the record itself. How to avoid two users accessing the same record and potentially damaging each others changes My approach is the same as Rob's. Flag it locked and let the second user gets a read only copy -- Bastien Cat, the other other white meat -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP] Multiple Access Question
On Wed, Jul 07, 2010 at 10:01:05PM -0400, Bastien Koert wrote: On Wed, Jul 7, 2010 at 8:47 PM, Paul M Foster pa...@quillandmouse.com wrote: On Wed, Jul 07, 2010 at 12:59:30PM -0400, tedd wrote: Hi gang: I have *my way* of handling this problem, but I would like to hear how you guys do it. Here's the problem -- let's say you have a database containing names and addresses and you want approved users to be able to access the data. As such, a user must login before accessing an editing script that would allow them to review and edit the data -- nothing complicated about that. However, let's say you have more than one user accessing the editing script at the same time and you want to make sure that any changes made to the database are done in the most efficient manner possible. For example, if two users access the database at the same time and are editing different records, then there's no real problem. When each user finishes editing they simply click submit and their changes are recorded in the database. However, if two (or more) users want to access the same record, then how do you handle that? Use a DBMS? I'm sorry if that seems flippant, but a DBMS handles this by queuing the requests, which is one of the advantages of a client-server DBMS. So maybe I don't understand your question. Paul -- Paul M. Foster -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php @Paul, The OPs question is about concurrency on the record itself. How to avoid two users accessing the same record and potentially damaging each others changes My approach is the same as Rob's. Flag it locked and let the second user gets a read only copy I can't think of a way to do this using MySQL or PostgreSQL. And one of the biggest issues with the solution you suggest is the user who opens a record for writing and then goes out for coffee. Everyone's locked out of the record (for writes) until they come back and finish. Okay, to solve that, we start a timer. But when the locker's time is up, how do we let the locker know they're not allowed to store whatever edits they've made? And how do we fix it so that those locked out are now unlocked? Plus, they're probably in a queue, so we really only let one of them know that they can now make edits. Since this is a PHP list, I assume we're talking about a web interface. So how do we do all this back end jockeying? Javascript is about the only way. But every time you fire off one of these javascript dealies, it has to be on its own timer so that it can let the user know that the original locker is gone and now the golden ticket is yours. It essentially has to sleep and ping, sleep and ping. Actually, it's more like a spinlock. But a spinlock would eat CPU for every user, if it was running on the server. So it would have to be running on the client, and ping the server every once in a while. Then you'd have to figure out some kind of messaging infrastrucure for the DBMS, so that it would quickly answer pings without tying up a lot of CPU cycles. It would have to be something outside the normal query infrastructure. When you actually get into this, it's an incredibly complex solution. I vote instead for allowing edits to be queued, log changes to the database. If there is a true contention problem, you can look at the journal and see who made what edits in what order and resolve the situation. The best analogy I can think of is when using a DVCS like git, and trying to merge changes where two people have edited the same area of a file. Ultimately, git throws up its hands and asks a human to resolve the situation. Bottom line: I've heard about concurrency problems since I started using databases, and I've never heard of a foolproof solution for them that wasn't incredibly complex. And I don't think I've ever seen a solution in actual practice. If I'm wrong, someone show me where it's been viably solved and how. Paul -- Paul M. Foster -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP] Multiple Access Question
Paul M Foster wrote: On Wed, Jul 07, 2010 at 10:01:05PM -0400, Bastien Koert wrote: On Wed, Jul 7, 2010 at 8:47 PM, Paul M Foster pa...@quillandmouse.com wrote: On Wed, Jul 07, 2010 at 12:59:30PM -0400, tedd wrote: Hi gang: I have *my way* of handling this problem, but I would like to hear how you guys do it. Here's the problem -- let's say you have a database containing names and addresses and you want approved users to be able to access the data. As such, a user must login before accessing an editing script that would allow them to review and edit the data -- nothing complicated about that. However, let's say you have more than one user accessing the editing script at the same time and you want to make sure that any changes made to the database are done in the most efficient manner possible. For example, if two users access the database at the same time and are editing different records, then there's no real problem. When each user finishes editing they simply click submit and their changes are recorded in the database. However, if two (or more) users want to access the same record, then how do you handle that? Use a DBMS? I'm sorry if that seems flippant, but a DBMS handles this by queuing the requests, which is one of the advantages of a client-server DBMS. So maybe I don't understand your question. Paul -- Paul M. Foster -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php @Paul, The OPs question is about concurrency on the record itself. How to avoid two users accessing the same record and potentially damaging each others changes My approach is the same as Rob's. Flag it locked and let the second user gets a read only copy I can't think of a way to do this using MySQL or PostgreSQL. And one of the biggest issues with the solution you suggest is the user who opens a record for writing and then goes out for coffee. Everyone's locked out of the record (for writes) until they come back and finish. Okay, to solve that, we start a timer. But when the locker's time is up, how do we let the locker know they're not allowed to store whatever edits they've made? And how do we fix it so that those locked out are now unlocked? Plus, they're probably in a queue, so we really only let one of them know that they can now make edits. Since this is a PHP list, I assume we're talking about a web interface. So how do we do all this back end jockeying? Javascript is about the only way. But every time you fire off one of these javascript dealies, it has to be on its own timer so that it can let the user know that the original locker is gone and now the golden ticket is yours. It essentially has to sleep and ping, sleep and ping. Actually, it's more like a spinlock. But a spinlock would eat CPU for every user, if it was running on the server. So it would have to be running on the client, and ping the server every once in a while. Then you'd have to figure out some kind of messaging infrastrucure for the DBMS, so that it would quickly answer pings without tying up a lot of CPU cycles. It would have to be something outside the normal query infrastructure. When you actually get into this, it's an incredibly complex solution. I vote instead for allowing edits to be queued, log changes to the database. If there is a true contention problem, you can look at the journal and see who made what edits in what order and resolve the situation. The best analogy I can think of is when using a DVCS like git, and trying to merge changes where two people have edited the same area of a file. Ultimately, git throws up its hands and asks a human to resolve the situation. Bottom line: I've heard about concurrency problems since I started using databases, and I've never heard of a foolproof solution for them that wasn't incredibly complex. And I don't think I've ever seen a solution in actual practice. If I'm wrong, someone show me where it's been viably solved and how. I think you're overthinking the issue. The timer handles the issue of holding onto a lock for too long. As for a write queue... don't bother. If a user finds that another user has a lock then tell them when it expires. They can come back and try for the lock on their own. You can set up AJAX polling to see if the lock has been removed and indicate this to the user (if they've bothered to wait on the page) but this is optional. Queuing edits is not a good solution. Imagine document X: UserA requests X UserB requests X UserC requests X UserD requests X UserA modifies X and saves X.1 UserB modifies X and saves X.2 UserC modifies X and saves X.3 UserD modifies X and saves X.4 In this scenario all the work done by UserA, UserB, and UserC is clobbered by the submission by UserD. This can be resolved via merging such as used by versioning systems, but this makes less sense in a high traffic collaborative content system such as a wiki. In the lock scenario we
Re: [PHP] Multiple Access Question
On Wed, Jul 07, 2010 at 11:28:56PM -0400, Robert Cummings wrote: Paul M Foster wrote: snip @Paul, The OPs question is about concurrency on the record itself. How to avoid two users accessing the same record and potentially damaging each others changes My approach is the same as Rob's. Flag it locked and let the second user gets a read only copy I can't think of a way to do this using MySQL or PostgreSQL. And one of the biggest issues with the solution you suggest is the user who opens a record for writing and then goes out for coffee. Everyone's locked out of the record (for writes) until they come back and finish. Okay, to solve that, we start a timer. But when the locker's time is up, how do we let the locker know they're not allowed to store whatever edits they've made? And how do we fix it so that those locked out are now unlocked? Plus, they're probably in a queue, so we really only let one of them know that they can now make edits. Since this is a PHP list, I assume we're talking about a web interface. So how do we do all this back end jockeying? Javascript is about the only way. But every time you fire off one of these javascript dealies, it has to be on its own timer so that it can let the user know that the original locker is gone and now the golden ticket is yours. It essentially has to sleep and ping, sleep and ping. Actually, it's more like a spinlock. But a spinlock would eat CPU for every user, if it was running on the server. So it would have to be running on the client, and ping the server every once in a while. Then you'd have to figure out some kind of messaging infrastrucure for the DBMS, so that it would quickly answer pings without tying up a lot of CPU cycles. It would have to be something outside the normal query infrastructure. When you actually get into this, it's an incredibly complex solution. I vote instead for allowing edits to be queued, log changes to the database. If there is a true contention problem, you can look at the journal and see who made what edits in what order and resolve the situation. The best analogy I can think of is when using a DVCS like git, and trying to merge changes where two people have edited the same area of a file. Ultimately, git throws up its hands and asks a human to resolve the situation. Bottom line: I've heard about concurrency problems since I started using databases, and I've never heard of a foolproof solution for them that wasn't incredibly complex. And I don't think I've ever seen a solution in actual practice. If I'm wrong, someone show me where it's been viably solved and how. I think you're overthinking the issue. The timer handles the issue of holding onto a lock for too long. That's why I suggested it. As for a write queue... don't bother. If a user finds that another user has a lock then tell them when it expires. They can come back and try for the lock on their own. You can set up AJAX polling to see if the lock has been removed and indicate this to the user (if they've bothered to wait on the page) but this is optional. That's why I suggested it. Yes, we could just tell users come back later if they wanted to edit a locked page. I was just imagining a 100% complete wipe-your-butt-for-you solution. Queuing edits is not a good solution. And yet, it appears to adequate for the DBMSes I'm familiar with. Imagine document X: UserA requests X UserB requests X UserC requests X UserD requests X UserA modifies X and saves X.1 UserB modifies X and saves X.2 UserC modifies X and saves X.3 UserD modifies X and saves X.4 In this scenario all the work done by UserA, UserB, and UserC is clobbered by the submission by UserD. This can be resolved via merging such as used by versioning systems, ... if automatic merging can be done in a particular case. But there's a non-zero probability that a merge will require human intervention. Yes of course, without version/merging or some type of write-locks, there is potential contention. but this makes less sense in a high traffic collaborative content system such as a wiki. In the lock scenario we have the following: UserA requests X UserA modifies X and saves X.1 UserB requests X.1 UserB modifies X.1 and saves X.2 UserC requests X.2 UserC modifies X.2 and saves X.3 UserD requests X.3 UserD modifies X.3 and saves X.4 ... assuming UserB waits until UserA stores his edits, UserC waits until UserB stores his edits, etc. The above assumes locking, and probably versioning and merging. But a wiki is not a DBMS. And perhaps the OP was talking about a wiki. In which case, all this may be moot. I just checked, and Wikipedia does not lock pages under edit. They do versioning, but their locking is on the honor system. For a discourteous user, this would allow contention. I don't know if other wikis perform locking. I doubt it, but I could be
Re: [PHP] Multiple Access Question
Paul M Foster wrote: On Wed, Jul 07, 2010 at 11:28:56PM -0400, Robert Cummings wrote: Paul M Foster wrote: snip @Paul, The OPs question is about concurrency on the record itself. How to avoid two users accessing the same record and potentially damaging each others changes My approach is the same as Rob's. Flag it locked and let the second user gets a read only copy I can't think of a way to do this using MySQL or PostgreSQL. And one of the biggest issues with the solution you suggest is the user who opens a record for writing and then goes out for coffee. Everyone's locked out of the record (for writes) until they come back and finish. Okay, to solve that, we start a timer. But when the locker's time is up, how do we let the locker know they're not allowed to store whatever edits they've made? And how do we fix it so that those locked out are now unlocked? Plus, they're probably in a queue, so we really only let one of them know that they can now make edits. Since this is a PHP list, I assume we're talking about a web interface. So how do we do all this back end jockeying? Javascript is about the only way. But every time you fire off one of these javascript dealies, it has to be on its own timer so that it can let the user know that the original locker is gone and now the golden ticket is yours. It essentially has to sleep and ping, sleep and ping. Actually, it's more like a spinlock. But a spinlock would eat CPU for every user, if it was running on the server. So it would have to be running on the client, and ping the server every once in a while. Then you'd have to figure out some kind of messaging infrastrucure for the DBMS, so that it would quickly answer pings without tying up a lot of CPU cycles. It would have to be something outside the normal query infrastructure. When you actually get into this, it's an incredibly complex solution. I vote instead for allowing edits to be queued, log changes to the database. If there is a true contention problem, you can look at the journal and see who made what edits in what order and resolve the situation. The best analogy I can think of is when using a DVCS like git, and trying to merge changes where two people have edited the same area of a file. Ultimately, git throws up its hands and asks a human to resolve the situation. Bottom line: I've heard about concurrency problems since I started using databases, and I've never heard of a foolproof solution for them that wasn't incredibly complex. And I don't think I've ever seen a solution in actual practice. If I'm wrong, someone show me where it's been viably solved and how. I think you're overthinking the issue. The timer handles the issue of holding onto a lock for too long. That's why I suggested it. As for a write queue... don't bother. If a user finds that another user has a lock then tell them when it expires. They can come back and try for the lock on their own. You can set up AJAX polling to see if the lock has been removed and indicate this to the user (if they've bothered to wait on the page) but this is optional. That's why I suggested it. Yes, we could just tell users come back later if they wanted to edit a locked page. I was just imagining a 100% complete wipe-your-butt-for-you solution. Queuing edits is not a good solution. And yet, it appears to adequate for the DBMSes I'm familiar with. Imagine document X: UserA requests X UserB requests X UserC requests X UserD requests X UserA modifies X and saves X.1 UserB modifies X and saves X.2 UserC modifies X and saves X.3 UserD modifies X and saves X.4 In this scenario all the work done by UserA, UserB, and UserC is clobbered by the submission by UserD. This can be resolved via merging such as used by versioning systems, ... if automatic merging can be done in a particular case. But there's a non-zero probability that a merge will require human intervention. Yes of course, without version/merging or some type of write-locks, there is potential contention. but this makes less sense in a high traffic collaborative content system such as a wiki. In the lock scenario we have the following: UserA requests X UserA modifies X and saves X.1 UserB requests X.1 UserB modifies X.1 and saves X.2 UserC requests X.2 UserC modifies X.2 and saves X.3 UserD requests X.3 UserD modifies X.3 and saves X.4 ... assuming UserB waits until UserA stores his edits, UserC waits until UserB stores his edits, etc. The above assumes locking, and probably versioning and merging. No, not at all. Each user can only edit the version last saved. It only assumes locking. But a wiki is not a DBMS. And perhaps the OP was talking about a wiki. In which case, all this may be moot. I just checked, and Wikipedia does not lock pages under edit. They do versioning, but their locking is on the honor system. For a discourteous user, this would allow contention. I don't know if other
