January 2002 - Zope - Zope lists

perl (CGI) on zope in Win32
by mick polo 25 Jan '02

25 Jan '02

Hi all I want to be able to run CGI scripts on a Zope server in Windows95. Is it Possible? Do I have to install PERL into Zope somehow? I just want to be able to run CGI scripts on ZOPE can it be done in win95? thanks all Mike _________________________________________________________________ Send and receive Hotmail on your mobile device: http://mobile.msn.com

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Difference between dtml-let & dtml-in
by Gabriel Genellina 25 Jan '02

25 Jan '02

Hi This piece of code works fine: <dtml-let sql="restrictedTraverse(PathToSqlMethod)"> <dtml-in sql> <dtml-var AnyFieldName>, </dtml-in> </dtml-let> where PathToSqlMethod is a path to any SQLMethod, and AnyFieldName is a column name in that SQLMethod. Then, I didnt like the dtml-let, so I collapsed both lines, and wrote: <dtml-in "restrictedTraverse(PathToSqlMethod)"> <dtml-var AnyFieldName>, </dtml-in> and I got a KeyError in __getitem__, Error Value: 0 (zero). After several attempts I got the right way of doing it: <dtml-in "restrictedTraverse(PathToSqlMethod)()"> <dtml-var AnyFieldName>, </dtml-in> So I need to call the SQLMethod explicitly, and then it returns a sequence that <dtml-in> can handle (at least, this is what I guess.) But now, I don't understand why the ()'s arent needed using <dtml-let>, and then, why are them really necessary using <dtml-in "">. I would expect both tags to behave similarly. Perhaps someone can explain me the difference. Gabriel Genellina Softlab SRL

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Zope ans SSL
by Eugene von Niederhausern 25 Jan '02

25 Jan '02

What is the best and easiest way to setup Zope with SSL with z-server (not using apache)? regards, Eugene

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RE: [Zope] Static fail-over
by sean.upton＠uniontrib.com 24 Jan '02

24 Jan '02

In a load-distributed system (i.e. round robin, or anything that is load-balancing without detection of an out-of-service web node), you need to manage availability yourself, and this sucks for clusters of web nodes larger than 2, because you have to set them up in a ring, using IP takeover. The problem with this, say in a 3 node setup, is that if n1 fails, and n2 and n3 are still alive, one or the other of n2 or n3 will need to take on n1's load - they can't split it. In a true load-balanced arrangement, the forward LB/Proxy will detect that a box is out, and remove it from the pool. This is ideal for a lot of nodes. It sounds to me like Squid+Zope+ICP sounds like the best way to do this, of course, with the use of monitoring software like mon as well. In the case of a 2-node cluster, IP takeover is easier and cheaper; but this doesn't scale well for HTTP traffic, given the alternative of load-balancing is better. The new setup I plan on using for future projects is a pair of load-balanced proxy servers balanced with a L4 switch with direct packet return, a feature of my L4 switch which has a speed advantage over a proxied approach; the downside to this is that I have to manage availability of my proxy server boxes themselves; I do this with IP-takeover based software like heartbeat, which fills this niche very well. I also use IP takeover for my relational database, file serving, and ZEO storage server setups. The only tier of this setup that will not be managed by IP takeover clustering will be the web servers themselves, which will be managed by the 2 proxy servers acting in a capacity of a load-balancer (Squid+Zope+ICP patches). | ^ v | >[Router]< / | \ / v \ / [L4Switch ] \ Hardware Load-Balancer / | | \ DMZ | v v | ====[Cache1]:::::[Cache2] -->Squid Proxies Private | | For Caching, LoadBalancing, Netwk | | security, and availability | | of web servers _|________|_ -Clustered w/Heartbeat / | | \ [n1] [n2] [n3] [n*] -->Web Servers - Availability | | | | managed via Squid/ICP +----+----+----+ | -->Storage Svrs.(ZSS/RDB/File) | Primary and Hot Backup | Clustering w/Heartbeat [Storage1]:::::::::[Storage2] I hope this makes sense and/or is helpful in some way... I think it is a good generic blueprint for a relatively scalable setup for a large site. Sean -----Original Message----- From: Derek Simkowiak [mailto:dereks@realloc.net] Sent: Thursday, January 24, 2002 2:00 PM To: sean.upton(a)uniontrib.com Cc: zope(a)zope.org Subject: RE: [Zope] Static fail-over -> I guess what I'm saying is there are places where IP-takeover based -> clustering is appropriate, sometimes even in conjunction with forward -> traffic direction. Sean: Thanks for the I.P. Takeover info! While we're on the topic, I have a quick 'opinion' question about clusters. This applies directly to a Zope cluster I'll be building soon. A fully redundant, yet not load-balanced, H.A. system requires *almost* all the same hardware and software as a 2-node load-balanced system. That is, you need to detect a service failure and, if found, make sure traffic goes to the backup system, not the primary system. (You'd also want to send an alert, etc., and if you only have dual redundancy, you'll also want to monitor the backup to make sure it'll be there when the failover is needed.) In a load balanced system (with homogenous nodes), you need to watch all nodes for failure and, if found, fail out that particular node. But instead of the backup hardware going "wasted", just waiting for a failover, you've halved the hardware workload by distributing the work to both machines. This may result in a faster response to endusers. My question: Does it ever make sense to set up a redundant system without load balancing? After all, plopping in new nodes on an as-needed basis is a very handy feature. The only thing I can think of is this: Imagine a site that must serve 1 zillion requests per day (a zillion being a Very Big Number). If you use a simple failover system, then you buy two boxes, both capable of handling 1 zillion requests. If the site grows more popular so you must handle 2 zillion requests/day, you just upgrade both servers to handle 2 zillion requests/day. (This is a thought experiment, ignore the fact that you should have planned for the growth in the first place :) Now imagine those same two (1 zillion/day capable) boxes have been configured for load balancing. Immediately, each server is only serving .5 zillion requests/day. As the site grows to it's new 2 zillion/day load, both servers being in use means no hardware upgrade is needed. BUT --and this is a big but-- you no longer have an H.A. system. You've lost your redundancy. If one of the servers go down, about half of your customers will get an HTTP 502 "Overloaded" error message. So to keep full redundancy, you actually need THREE nodes. In fact, for however many nodes you want your cluster to be, you need to add one extra "redundant" node that would handle the traffic for any failed node (just until that failed node is repaired). So I guess I answered my own question: in a two-node load balanced system, the second node would really be nothing more than a backup node (even though it's handling traffic), and thus you'd need to upgrade your hardware (or rather, just add more nodes) as soon as your traffic exceeded the limit of (nodecount - 1) * traffic_per_node And the "traffic_per_node" you'd have to assume would be peak usage traffic, i.e. ( total_peak_traffic / (nodecount - 1) ) In the real world of public websites, however, I think a load-balanced system may actually offer extra redundancy. Because no site will get its peak load on a 24/7 basis, the load balanced system can use any extra resources (which are free because the cluster is not at 100% capacity) to fill in for the failed node -- and this would be *in addition to* your extra failover node. In a simple failover-system, you don't get this. Any additional comments would be greatly appreciated. --Derek

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RE: [Zope] Static fail-over
by sean.upton＠uniontrib.com 24 Jan '02

24 Jan '02

Ok, I've got some thoughts. Mainly, I think there are times when a cluster tier should manage its own availability, and times when it should be managed by a forward tier... >>>>>Derek Writes:>>>>> Is there a way to use URL Rewriting rules in Apache (with mod_rewrite) to test if a particular box was alive, and only if so, direct traffic there? Maybe have it look if a particular file exists (or some such)? (Also note that Apache will do much of what Squid will do using mod_proxy.) <<<<< Squid is more flexible here since it uses an external redirector script that can be written in any language that you want; redirector scripts in Squid can be as few as 4-5 lines of Python code, or an elaborate C program. In order to so this in Apache, you need to write a perl module to control mod_rewrite, I believe (a Squid redirector plugin is easier). >>>>>Derek Writes:>>>>> I.P. address take-overs are dangerous. What if the Zope processes die, but the O.S. is okay? You'll have an I.P. address conflict unless you can run a script on the primary box that tells it to shut down it's network interface. So what if the hardware locks up/loses all resources/gets into a loop of somekind? The NIC will still respond to its I.P. address, but you can't run the script to disable it. Bad situation--pray you have a watchdog card for those Zope processes. <<<<< No, you won't have an IP address conflict. IP address takeover via gratuitous/unsolicited ARP prevents an IP conflict, and its a standard documented in RFCs that switch vendors are supposed to obey. If a node running monitoring software is acting as a backup for a failed node and sees that Zope has died on its peer, it will initiate a takeover with the clustering software. Once this takeover happens, the NIC will NOT respond to its own IP address, because the switch will NOT be sending Ethernet frames to it in the first place, because switches and hosts keep ARP tables. I promise you, this stuff works. >>>>>Derek Writes:>>>>> MAC address takeovers are somewhat dangerous, because the switch that you are connected into (such as at a Data Center) may not recognize the MAC address takeover if the NIC on the primary box is still responding (as above). <<<<< Some switches behave better than others in this regard. IP address takeover is easier to deal with than MAC address takeover, and isn't so picky about hardware. Fortunately, most open source clustering software uses IP takeover, not MAC takeover. >>>>>Derek Writes:>>>>> I prefer solutions that keep all nodes (primary, backup, or any peer nodes) behind a NAT. Each node gets its own 192.168.0.x I.P. address, and the NAT box does all failover. You've now moved the I.P. takeover problem to the NAT box (with its backup), but since NAT is in the kernel (under Linux, at least) you'd be hard-pressed to find a NAT box that could respond to an ICMP or serial-port ping but not do NAT. If the kernel is running, it's running, and if it's not, it's not. <<<<< NAT isn't as flexible as proxying, though I imagine it might be faster in some cases - though in both you can bridge to a private network. Perhaps the problem of reliability of many web nodes in a cluster is best dealt with at the NAT/Proxy/L7 switch level, but there is also validity in IP address takeover. The one disadvantage in an IP address takeover, though, is that a backup server in a load-balanced arrangement will take on twice the load. Where IP takeover mechanisms might be more appropriate is in 2-box clusters for things like db/file/proxy servers. Toby's ICP patch looks __really, really cool__. My next setup is likely to use IP takeover clustering on a pair of Squid proxy servers, which themselves load-balance ZEO client nodes using ICP, with the backend storage (file/ODB/RDB) tier as a pair of storage servers also using IP takeover. The reliability of the web server nodes would be dealt with by Squid, thanks to ICP, which would free up the necessity to have a complex IP takeover arrangement for all my web servers, other than making each node have monitoring for a half-dead Zope server. I guess what I'm saying is there are places where IP-takeover based clustering is appropriate, sometimes even in conjunction with forward traffic direction. Sean

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E-Commerce Site
by miah34＠msn.com 24 Jan '02

24 Jan '02

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VirtualHost Monster -- how do I stop aquisition or namespace resolving?
by Heimo Laukkanen 24 Jan '02

24 Jan '02

This is a hypothetic question. Let's suppose I have a box, where I have different services running with VirtualHostMonster. The services are running in root folders: -service1 -service2 -service3 and the domains are in the same sense www.service1.com etc. Now if someone in service1 tries an URL www.service1.com/service2/foo - Zope tries to find -- and can access if it exists -- service2/foo. Is there a way to prevent this kind of thing happening? -huima

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Script Errors
by MarkM＠Yogananda-SRF.org 24 Jan '02

24 Jan '02

I'm trying out a website example from the beehive Zope book. I get 2 errors when typing in the code: 1. "__version__" is an invalid variable name because it starts with "_" 2. import of "MessageDialog" from "Globals" is unauthorized Why is the use of "_" an error? I can understand about the 'import error', but I don't know where "Globals" is coming from. This is probably a beehive py file? Thanks, Mark Micklich

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Confera problem
by Ismet Dere 24 Jan '02

24 Jan '02

hello all i setup a zope 2.5b2 with Confera-ZDiscussion 0.7 on Linux, Zope works fine and posting Confera messages are all fine but when i reply to a topic it appears on the main index as well as under it's parent topic, instead of only appearing under it's parent topic. does anyone know how to solve this problem? thanks for your help ismet

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Re: [Zope] Multiple Inserts Using Sybase DAV
by tgraham＠speakeasy.net 24 Jan '02

24 Jan '02

I'm not 100% sure with Sybase, but it sounds like you need to use the <dtml-var sql_delimiter> between the two insert statements. For example Insert into table_one (values) <dtml-sqlvar values type="string"> <dtml-var sql_delimiter> Insert into table_two (values) <dtml-sqlvar values type="string"> On 24 Jan 2002, Kia A. Arab wrote: > Hi, I'm creating a web application where users > can submit and retrieve library resources > online. The backend of this application is a > Sybase database. I use two tables: one that > stores a unique id, title, author, name, etc. > And another that stores keywords related to > the resource for searching purposes. All this > information is captured on one form. The > keywords are captured in a list by way of the > Python cgi module. > > The problem I'm having is inserting this > information into the two tables. I can easily > insert the title, author, etc info into one > table. But, when I try to put the keywords in > a separate table, it fails. > > Seems like a simple task but I'm at a loss. > Does anyone have any suggestions. And please > also email me directly since I'm not > subscribed to this list. Thank you, Kia > > Here is my insertAction. The appropriate > parameters are in the argument list: > > INSERT into lib_entry ( submitter, office_num, > resource_type, resource_title, > resource_author, resource_pubdate, > resource_abstract) VALUES ( <dtml-sqlvar > submitter type="string">, <dtml-sqlvar > office_num type="string">, <dtml-sqlvar > resource_type type="string">, <dtml-sqlvar > resource_title type="string">, <dtml-sqlvar > resource_author type="string">, <dtml-sqlvar > resource_pubdate type="string">, <dtml-sqlvar > resource_abstract type="string">) > > After this, how do I insert the keywords? > > _____________________________________________- > __ > Zope maillist - Zope(a)zope.org > http://lists.zope.org/mailman/listinfo/zope ** > No cross posts or HTML encoding! ** (Related > lists - http://lists.zope.org/mailman/listinf- > o/zope-announce http://lists.zope.org/mailman- > /listinfo/zope-dev )

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