NAME

       Perlbal::Manual::Hooks - How Perlbal's hooks work

   VERSION
       Perlbal 1.78.

   DESCRIPTION
       Basically, a hook is a bit of code that is run at certain stages in the requests that
       Perlbal handles.There are all kinds of hooks available and they all do different things.
       Some are only applicable to some of the roles and others are applicable only to certain
       classes. Each hook is described in detail below, but first a description of the basics of
       a hook.

       In general, you define a hook by calling the "register_hook" method on a Perlbal::Service
       object. You specify what hook you are interested in and provide a reference to a
       subroutine that will be called with the parameters particular to that hook.

       There are three types of hooks:

   Global hooks
       These are hooks that are defined on a global scale. They are set like so:

           Perlbal::register_global_hook('foo', sub { return 0; });

       That would define a global hook named foo that would return 0 when it's called. (Return
       codes from hooks will be explained below)

       Global hooks are useful to define management commands. See "manage_command" under
       Perlbal::Manual::Plugins for more information.

   Service handler hooks
       A handler hook is attached to a particular service. These hooks are called one at a time
       until one hook returns 1. At that point, no further hooks are called. For example:

           $service->register_hook('bar', sub {
               # do something
               return 1;
           });

       When this hook runs, it would return 1, signalling to Perlbal that it had done what it
       needed to do and that Perlbal shouldn't call any further hooks. You can use this type of
       hook to create sets of plugins that all handle different types of requests, and when one
       hook had handled a request it wouldn't continue telling other hooks about the request.

       backend_client_assigned

       Happens right after a backend is assigned to a client, but before we've talked to the
       backend and asked it to do something. If you return a true value, the process is stopped
       and you will manually have to send the client's request to the backend, etc.

       Called in Perlbal::BackendHTTP.

       Available in role "reverse_proxy".

       backend_readable_verify

       When the backend is about to start sending the response.

       Called in Perlbal::BackendHTTP.

       Available in all roles.

       backend_response_received

       Called as soon as response headers are read from the backend. If you return a true value,
       will stop all handling at that point.

       Called in Perlbal::BackendHTTP.

       Available in all roles.

       backend_write_verify

       When the backend is ready to receive the request.

       Called in Perlbal::BackendHTTP.

       Available in all roles.

       concat_get_poststat_file_missing

       Called when a missing file was requested in a request for multiple files concatenated,
       right before sending the 404 response. Return a true value to overtake the connection.

       Called in Perlbal::ClientHTTPBase.

       Available in role "web_server".

       See also "concat_get_poststat_pre_send", "static_get_poststat_file_missing" and
       "static_get_poststat_pre_send".

       concat_get_poststat_pre_send

       Called when the resulting file of a request for multiple files concatenated is about to be
       sent, right before the 200 response code is added as a header. Return a true value to
       overtake the connection.

       Called in Perlbal::ClientHTTPBase.

       Available in role "web_server".

       See also "concat_get_poststat_file_missing", "static_get_poststat_file_missing" and
       "static_get_poststat_pre_send".

       handle_put

       Called when handling a PUT request.

       Called in Perlbal::ClientHTTP.

       Available in role "web_server".

       make_high_priority

       Called when a request is received and right before we're about to determine if this
       request is high priority or not. Return a true value to make the request high priority;
       false to leave it alone. Note that this is only called when the request isn't already high
       priority due to cookie priority scheduling, which is done inside Perlbal::Service.

       Called in Perlbal::ClientProxy.

       Available in all roles.

       make_low_priority

       Called when a request is received and right before we're about to determine if this
       request is high priority or not. Return a true value to make the request low priority;
       false to leave it alone.

       Called in Perlbal::ClientProxy.

       Available in all roles.

       modify_response_headers

       Called when we've set all the headers, and are about to serve a file. You can change or
       add response headers at this point, or cancel the process by returning a true value. You
       will have to send the response to the client yourself if you do this.

       Called in Perlbal::ClientHTTPBase.

       Available in role "web_server".

       proxy_read_request

       Called on the request before we send the request to a backend.

       Called in Perlbal::ClientProxy.

       Available in all roles.

       put_writeout

       Called when there is some put data to write out.

       Called in Perlbal::ClientHTTP.

       Available in role "web_server".

       reproxy_fh_finished

       Called when a reproxy file has completed and is about to close the file handle. You can
       cancel the process by returning a true value (in which case you will have to close the
       reproxy_fh yourself).

       Called in Perlbal::ClientHTTPBase.

       Available in role "web_server".

       reproxy_response_received

       Called as soon as response headers are read from a reproxied backend. If you return a true
       value, will stop all handling at that point.

       Called in Perlbal::ClientProxy.

       Available in role "reverse_proxy".

       return_to_base

       Called when a request has been finished, and control of the Client* object is about to be
       transferred back to ownership by a service selector. Return a true value if the perlbal
       core action in this situation should be bypassed.

       Called in Perlbal::ClientHTTPBase.

       Available in all roles.

       start_file_reproxy

       Called when we've been told to reproxy a file. If you return a true value, Perlbal will
       not perform any operations on the file and will simply return. You can also change the
       file in the scalar ref passed as the second parameter.

       Called in Perlbal::ClientProxy; receives $filename_ref, a reference to the filename.

       Available in role "reverse_proxy".

       start_http_request

       A generic hook that works for both webserver and proxy modes, run after either the
       specific "start_proxy_request" or "start_web_request" hooks below. Like those, you return
       true from this hook to takeover the connection.

       Called in Perlbal::ClientProxy and Perlbal::ClientHTTP.

       Available in roles "reverse_proxy" and "web_server".

       start_proxy_request

       Called as soon as we've read in headers from a user but right before we've requested a
       backend connection. If a true value is returned, Perlbal will not request a backend.

       Called in Perlbal::ClientProxy.

       Available in role "reverse_proxy".

       start_send_file

       Called when we've opened a file and are about to start sending it to the user using
       sendfile. Return a true value to cancel the default sending.

       Called in Perlbal::ClientHTTPBase.

       Available in role "web_server".

       start_serve_request

       Called when we're about to serve a local file, before we've done any work. You can change
       the file served by modifying $uri_ref, or cancel the process by returning a true value.

       Called in Perlbal::ClientHTTPBase; receives $uri_ref, a reference to the URI.

       Available in role "web_server".

       start_web_request

       When a service has gotten headers and is about to serve it. Return a true value to cancel
       the default handling of web requests.

       Called in Perlbal::ClientHTTP.

       Available in role "web_server".

       static_get_poststat_file_missing

       Called when a missing static single file was requested, right before sending the 404
       response. Return a true value to overtake the connection.

       Called in Perlbal::ClientHTTPBase.

       Available in role "web_server".

       See also "concat_get_poststat_file_missing", "concat_get_poststat_pre_send" and
       "static_get_poststat_pre_send".

       static_get_poststat_pre_send

       Called when a static single file is about to be sent, right before the 200 response code
       is added as a header. Return a true value to overtake the connection.

       Called in Perlbal::ClientHTTPBase.

       Available in role "web_server".

       See also "concat_get_poststat_file_missing", "concat_get_poststat_pre_send" and
       "static_get_poststat_file_missing".

   Service general hooks
       These hooks are defined the same way as above, but general hooks are all run. The return
       code is ignored. This can be useful for putting in code that records statistics about an
       action or something to that effect.

       end_proxy_request

       This hook is called when the Perlbal::ClientProxy object is being closed.

       Available in role "reverse_proxy".

   SEE ALSO
       Perlbal::Manual::Internals, Perlbal::Manual::Plugins.