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Introduction
Assumptions The problems with the design of 1.3 How Apache 2.0 addresses them
Assumptions
You are somewhat familiar with configuring Apache 1.3
That you understand the concept of Apache modules
The problems with 1.3
Non-standard configuration scripts Porting to new and unusual platforms is
difficult Doesn’t scale well Modules can’t interact in particularly
interesting ways
How Apache 2.0 addresses these design problems
Configuration now uses GNU autoconf The Apache Portable Runtime (APR) Multi-Processing Modules (MPMs) I/O filtering “hooks”
The build environment:Using GNU autoconf
No more APACI – now it’s the real thing No more Configuration.tmpl – everything
uses ./configure arguments (hint: look at config.nice)
Autoconf’s feature tests are nice from a developer’s perspective
The build environment:The source tree layout
Modules categorized by function, not just lumped together
Platform-specific files hidden away Vendors can add their own module
directories
The Apache Portable Runtime
Platform Abstraction Resource Management Consistency, consistency, consistency
APR: Platform abstraction
Feature tests Native OS-specific data structures hidden
behind a consistent interface
APR: Resource management
Memory allocation handled for you Resource lifetimes arranged into a tree
that’s easy to prune
APR: All about consistency
…interface to the Operating System …resource handling Naming convention! (i.e., be ready for
renames)
Multi-Processing Modules
What are they? How do you configure them? Which one is best?
MPMs defined
A module that is specialized for managing the process/thread model used by Apache on a particular platform
Each has its own target OS and scalability goals
MPM configuration
# prefork MPM
# StartServers: number of server processes to start
# MinSpareServers: minimum number of server processes which are kept spare
# MaxSpareServers: maximum number of server processes which are kept spare
# MaxClients: maximum number of server processes allowed to start
# MaxRequestsPerChild: maximum number of requests a server process serves
<IfModule prefork.c>
StartServers 5
MinSpareServers 5
MaxSpareServers 10
MaxClients 150
MaxRequestsPerChild 0
</IfModule>
MPM configuration
# worker MPM
# StartServers: initial number of server processes to start
# MaxClients: maximum number of simultaneous client connections
# MinSpareThreads: minimum number of worker threads which are kept spare
# MaxSpareThreads: maximum number of worker threads which are kept spare
# ThreadsPerChild: constant number of worker threads in each server process
# MaxRequestsPerChild: maximum number of requests a server process serves
<IfModule worker.c>
StartServers 2
MaxClients 150
MinSpareThreads 25
MaxSpareThreads 75
ThreadsPerChild 25
MaxRequestsPerChild 0
</IfModule>
MPMs: How to choose
Benchmark!! (but don’t trust ab) Consider RAM usage vs. performance,
etc. Other tunability factors too, but this is the
big one
Filtered I/O
Bucket Brigades (my specialty :) Input Filters Output Filters
Bucket Brigades
A convenient abstract data type What do they look like? How are they used? What good are they?
Input filtering
Data is “pulled” from the client through the input filters
Each filter transforms the data it hands back to its caller in some way
Order is assigned at the beginning of each request
Output filtering
The most common form – interesting things happen when old-style “handlers” get converted into output filters
Data is “pushed” to the client through the output filters
Again, each filter transforms the data that passes through it
Apache modules
The module structure itself has changed:module MODULE_VAR_EXPORT foo_module = {
STANDARD_MODULE_STUFF, foo_init_Module, /* module initializer */ foo_config_perdir_create, /* create per-dir config structures */ foo_config_perdir_merge, /* merge per-dir config structures */ foo_config_server_create, /* create per-server config structures */ foo_config_server_merge, /* merge per-server config structures */ foo_config_cmds, /* table of config file commands */ foo_config_handler, /* [#8] MIME-typed-dispatched handlers */ foo_hook_Translate, /* [#1] URI to filename translation */ foo_hook_Auth, /* [#4] validate user id from request */ foo_hook_UserCheck, /* [#5] check if the user is ok _here_ */ foo_hook_Access, /* [#3] check access by host address */ NULL, /* [#6] determine MIME type */ foo_hook_Fixup, /* [#7] pre-run fixups */ NULL, /* [#9] log a transaction */ NULL, /* [#2] header parser */ foo_init_Child, /* child_init */ NULL, /* child_exit */ foo_hook_ReadReq, /* [#0] post read-request */};
Apache modules
The module structure itself has changed:
module AP_MODULE_DECLARE_DATA foo_module = {
STANDARD20_MODULE_STUFF,
foo_config_perdir_create, /* create per-dir config structures */
foo_config_perdir_merge, /* merge per-dir config structures */
foo_config_server_create, /* create per-server config structures */
foo_config_server_merge, /* merge per-server config structures */
foo_config_cmds, /* table of configuration directives */
foo_register_hooks /* register hooks */
};
Apache modules
What happened to all the other functions? How does a module register interest in
one of those functions?
Hooks
A new, more flexible replacement for most of the module_struct’s “phases”
Order is runtime-selectable (mostly) Any module can register its own hooks –
this allows a whole new level of inter-module cooperation
Hooks: example
static void register_hooks(apr_pool_t *p)
{
APR_REGISTER_OPTIONAL_FN(ap_ssi_get_tag_and_value);
APR_REGISTER_OPTIONAL_FN(ap_ssi_parse_string);
APR_REGISTER_OPTIONAL_FN(ap_register_include_handler);
ap_hook_post_config(include_post_config, NULL, NULL,
APR_HOOK_REALLY_FIRST);
ap_hook_fixups(include_fixup, NULL, NULL,
APR_HOOK_LAST);
ap_register_output_filter("INCLUDES", includes_filter,
AP_FTYPE_RESOURCE);
}
Hooks: example cont.
static int include_post_config(apr_pool_t *p, apr_pool_t *plog, apr_pool_t *ptemp, server_rec *s){ include_hash = apr_hash_make(p);
ssi_pfn_register = APR_RETRIEVE_OPTIONAL_FN(ap_register_include_handler);
if(ssi_pfn_register) { ssi_pfn_register("if", handle_if); ssi_pfn_register("set", handle_set); ssi_pfn_register("else", handle_else); } return OK;}
Conclusion
What will I get when upgrading to Apache 2.0?
What won’t I get (yet)? Future directions
Questions?
