tailieunhanh - ISPs Providing mod_perl Services

An ISP không thể cho phép người dùng chạy mã của họ theo mod_perl trên máy chủ chính. Có nhiều lý do cho việc này. Dưới đây là chỉ là một vài xem xét: Bộ nhớ sử dụng Một người dùng có thể tước đi những người dùng khác của bộ nhớ. Một người dùng bất cẩn của mã có thể bị rò rỉ bộ nhớ do lập trình cẩu thả | Page 800 Thursday November 18 2004 12 49 PM APPENDIX C ISPs Providing mod_perl Services This appendix proposes a few techniques for deploying mod_perl on ISP machines. Therefore it s mostly relevant to ISP technical teams and ISP users who need to convince their providers to provide them with mod_perl services. There are at least four different scenarios for deploying mod_perl-enabled Apache servers that ISPs may consider Users sharing a single web server Users sharing a single machine Giving each user a separate machine Giving each user a virtual machine This appendix covers each of those scenarios. Users Sharing a Single Web Server An ISP cannot let users run their code under mod_perl on the main server. There are many reasons for this. Here are just a few to consider Memory usage One user may deprive other users of memory. A careless user s code might leak memory due to sloppy programming. A user may use a lot of memory simply by loading a lot of modules. If one user s service is very popular and gets a lot of traffic there will be more Apache children running for that service so it s possible for that user to unintentionally consume most of the available memory even if she has a very small well-written code base with no memory leaks. Other resources It s not only memory that is shared between all users. Other important resources such as CPU the number of open files the total number of processes currently there is no easy way to control the number of mod_perl processes dedicated to each user and process priority are all shared as well. Intentionally 800 Page 801 Thursday November 18 2004 12 49 PM or not users may interfere with each other by consuming any or all of these resources. File security All users run code on the server with the same permissions . the same UID and GID . Any user who can write code for execution by the web server can read any files that are readable by the web server no matter which user owns them. Similarly any