=head1 NAME

Perlbal::Manual::Internals - Perlbal's architecture at a glance


=head2 VERSION

Perlbal 1.78.


=head2 DESCRIPTION

Connections come in from wherever and get to the TCPListener. It uses Service objects to determine what kind of Client* to spawn. The Client classes then handle crafting the response for the user.

                            {{ INTERNET }}
                                  |
                                  v
              [Service]<===>[TCPListener]
                          ___/    |    \___
                         v        v        v
             [ClientManage]  [ClientHTTP] [ClientProxy]
                                                ^
                                                |
                                                v
                                          [BackendHTTP]

Perlbal decides what backend to send a request to randomly (only presently supported method). If that service has idle backend connections available, configured by C<backend_persist> and C<connect_ahead>, it will reuse those connections and greatly reduce latency. See more detail in L<Perlbal::Manual::LoadBalancer>.

Perlbal also specializes in "spoonfeeding" data to slow clients. This allows backends to continue serving requests while Perlbal transfers responses back as fast as the client can read.

=head2 Classes

The following is a brief introduction/overview to the main Perlbal's classes:


=head3 Perlbal::Socket

Descends from L<Danga::Socket>.

Adds on to the base class to provide some functionality specifically useful for creating HTTP sockets.

=head4 Fields

=over 4

=item headers_string

Headers as they're being read.


=item req_headers

The final L<Perlbal::HTTPHeaders> object inbound.


=item res_headers

Response headers outbound (L<Perlbal::HTTPHeaders> object).


=item create_time

Creation time.


=item alive_time

Last time noted alive.


=item state

General purpose state; used by descendants.


=item do_die

If on, die and do no further requests.


=item read_buf

Arrayref of scalarref read from client.


=item read_ahead

Bytes sitting in read_buf.


=item read_size

Total bytes read from client, ever.

=item ditch_leading_rn

If true, the next header parsing will ignore a leading \r\n.


=item observed_ip_string

If defined, contains the observed IP string of the peer we're serving. This is intended for holding the value of the X-Forwarded-For and using it to govern ACLs.


=back


=head3 Perlbal::TCPListener

Descends from L<Perlbal::Socket>.

Very lightweight and fast connection accept class. Takes incoming connections as fast as possible and passes them off, instantiating one of the various Client* classes to handle it.

=head4 Fields

=over 4

=item service

L<Perlbal::Service>.


=item hostport

Scalar IP port of where this service is listening for new connections.


=item sslopts

The SSL Options.

    use Data::Dumper;
    warn Dumper( $tcp_listener->{'sslopts'} );

The above lines would print something like the following:

    $VAR1 = {
              'ssl' => {
                         'SSL_cipher_list' => '...',
                         'SSL_cert_file' => '...',
                         'SSL_key_file' => ',,,',
                         'SSL_ca_path' => '...',
                         'SSL_verify_mode' => '...'
                       }
            };


=item v6

Boolean value stating whether the installation of Perlbal supports IPv6 (which basically boils down to L<Danga::Socket> v1.6.1 and L<IO::Socket::INET6> being available).


=back


=head3 Perlbal::BackendHTTP

Descends from L<Perlbal::Socket>.

This class handles connections to the backend web nodes for getting data back to the user. This class is used by other classes such as L<Perlbal::ClientProxy> to send a request to an internal node.

=head4 Fields

=over 4

=item client

L<Perlbal::ClientProxy> connection, or undef.


=item service

L<Perlbal::Service>.


=item pool

L<Perlbal::Pool>; whatever pool we spawned from.


=item ip

IP scalar.


=item port

Port scalar.


=item ipport

C<$ip:$port>.


=item reportto

Object; must implement reporter interface.


=item has_attention

Has been accepted by a webserver and we know for sure we're not just talking to the TCP stack.


=item waiting_options

If true, we're waiting for an OPTIONS * response to determine when we have attention.


=item disconnect_at

Time this connection will be disconnected, if it's kept-alive and backend told us; otherwise C<undef> for unknown.


=item content_length

Length of document being transferred. Only applies when the backend server sends a content-length header.


=item content_length_remain

Bytes remaining to be read. Only applies when the backend server sends a content-length header.


=item use_count

Number of requests this backend's been used for.


=item generation

Int; counts what generation we were spawned in.


=item buffered_upload_mode

Boolean. If on, we're doing a buffered upload transmit.


=item scratch

Extra storage; plugins can use it if they want.


=back


=head3 Perlbal::HTTPHeaders

Header management. Parses headers (request and response) and stores data for further user. Also manages validation of the request line so that it conforms to HTTP specifications.

=head4 Fields

=over 4

=item headers

href; lowercase header -> comma-sep list of values.


=item origcase

Href; lowercase header -> provided case.


=item hdorder

Aref; order headers were received (canonical order).


=item method

Scalar; request method (if GET request).


=item uri

Scalar; request URI (if GET request).


=item type

C<res> or C<req>.


=item code

HTTP response status code.


=item codetext

Status text that for response code.


=item ver

Version (string) "1.1".


=item vernum

Version (number: major*1000+minor): "1.1" => 1001.


=item responseLine

First line of HTTP response (if response).


=item requestLine

First line of HTTP request (if request).


=back


=head3 Perlbal::ClientHTTPBase

Descends from L<Perlbal::Socket>.

Provides base functionality to L<Perlbal::ClientHTTP> and L<Perlbal::ClientProxy>. Notably, the ability to efficiently send files to the remote user. Also handles most of the state logic for statistics and such. Is also used for services of type C<selector>. L<Perlbal::ClientHTTPBase> then reads in the request headers, and asks the service to re-bless the client instance to a more specific type, for either a L<Perlbal::ClientProxy> or L<Perlbal::ClientHTTP> (depending on selector's mapping).

=head4 Fields

=over 4


=item service

L<Perlbal::Service> object.


=item replacement_uri

URI to send instead of the one requested; this is used to instruct C<_serve_request> to send an index file instead of trying to serve a directory and failing.


=item scratch

Extra storage; plugins can use it if they want.


=item reproxy_file

Filename the backend told us to start opening.


=item reproxy_file_size

Size of file, once we C<stat()> it.


=item reproxy_fh

If needed, L<IO::Handle> of fd.


=item reproxy_file_offset

How much we've sent from the file.


=item post_sendfile_cb

Subref to run after we're done sendfile'ing the current file.


=item requests

Number of requests this object has performed for the user.


=item selector_svc

The original service from which we came.


=item is_ssl

Whether the socket was SSL attached (restricted operations).


=back


=head3 Perlbal::ClientHTTP

Descends from L<Perlbal::ClientHTTPBase>.

Very simple and lightweight class. Handles sending files to the user without much overhead. Most of the functionality is contained in the parent class, and this class doesn't implement much new stuff.

=head4 Fields

=over 4

=item put_in_progress

1 when we're currently waiting for an async job to return.


=item put_fh

File handle to use for writing data.


=item put_fh_filename

Filename of put_fh.


=item put_pos

File offset to write next data at.


=item content_length

Length of document being transferred.


=item content_length_remain

Bytes remaining to be read.


=item chunked_upload_state

Boolean/obj: if processing a chunked upload, L<Perlbal::ChunkedUploadState> object, else undef.


=back


=head3 Perlbal::ClientProxy

Descends from L<Perlbal::ClientHTTPBase>.

Takes an incoming connection from a user and connects to a backend node (C<Perlbal::BackendHTTP>) and relays the request. The backend can then either tell the proxy to reproxy and load a file from disk, or return a file directly, or just return a status message.

=head4 Fields

=over 4

=item backend

L<Perlbal::BackendHTTP> object (or C<undef> if disconnected).


=item backend_requested

True if we've requested a backend for this request.


=item reconnect_count

Number of times we've tried to reconnect to backend.


=item high_priority

Boolean; 1 if we are or were in the high priority queue.


=item low_priority

Boolean; 1 if we are or were in the low priority queue.


=item reproxy_uris

Arrayref; URIs to reproxy to, in order.


=item reproxy_expected_size

Int: size of response we expect to get back for reproxy.


=item currently_reproxying

Arrayref; the host info and URI we're reproxying right now.


=item content_length_remain

Int: amount of data we're still waiting for.


=item responded

Bool: whether we've already sent a response to the user or not.


=item last_request_time

Int: time that we last received a request.


=item primary_res_hdrs

If defined, we are doing a transparent reproxy-URI and the headers we get back aren't necessarily the ones we want. Instead, get most headers from the provided C<res> headers object here.


=item is_buffering

Bool; if we're buffering some/all of a request to memory/disk.


=item is_writing

Bool; if on, we currently have an C<aio_write> out.


=item start_time

Hi-res time when we started getting data to upload.


=item bufh

Buffered upload filehandle object.


=item bufilename

String; buffered upload filename.


=item bureason

String; if defined, the reason we're buffering to disk.


=item buoutpos

Int; buffered output position.


=item backend_stalled

Boolean: if backend has shut off its reads because we're too slow.


=item unread_data_waiting

Boolean: if we shut off reads while we know data is yet to be read from client.


=item chunked_upload_state

Bool/obj: if processing a chunked upload, L<Perlbal::ChunkedUploadState> object, else undef.


=item request_body_length

Integer: request's body length, either as-declared, or calculated after chunked upload is complete.


=item last_upload_packet

Unixtime we last sent a UDP upload packet. For perlbal sending out UDP packets related to upload status (for xmlhttprequest upload bar).


=item upload_session

Client's self-generated upload session. For perlbal sending out UDP packets related to upload status (for xmlhttprequest upload bar).


=item retry_count

Number of times we've retried this request so far after getting C<500> errors.


=back


=head3 Perlbal::ClientManage

Descends from L<Perlbal::Socket>.

Simple interface that provides a way for users to use the management interface of Perlbal. You can connect to the management port (as defined in the config file) with a web browser or regular telnet (see L<Perlbal::Manual::Management> for more information on this).

=head4 Fields

=over 4

=item service

L<Perlbal::Service>.


=item buf

Read buffer.


=item is_http

Boolean stating whether the request is HTTP.


=item ctx

L<Perlbal::CommandContext>.


=back


=head3 Perlbal::Service

A service is a particular item that Perlbal is doing. Services can have a role which defines how they behave. Each service can also have a bunch of parameters set to further adjust its behavior. By itself, the Service class handles maintaining pools of backend connections and managing statistics about itself.

=head4 Fields

=over 4


=item name

Name of the service.


=item role

Role type (C<web_server>, C<reverse_proxy>, etc).


=item enabled

Boolean; whether we're enabled or not (enabled = listening).


=item pool

L<Perlbal::Pool> that we're using to allocate nodes if we're in proxy mode.


=item listener

L<Perlbal::TCPListener> object, when enabled.


=item reproxy_cache

L<Perlbal::Cache> object, when enabled.


=back


=head4 End-user tunables

=over 4

=item listen

C<IP:port> of where we're listening for new connections.


=item docroot

Document root for C<web_server> role.


=item dirindexing

Boolean; directory indexing (for C<web_server> role). Not async.


=item index_files

Arrayref of filenames to try for index files.


=item enable_concatenate_get

Boolean; if user can request concatenated files.


=item enable_put

Boolean; whether PUT is supported.


=item max_put_size

Max size in bytes of a put file.


=item max_chunked_request_size

Max size in bytes of a chunked request (to be written to disk first).


=item min_put_directory

Number of directories required to exist at beginning of URIs in put.


=item enable_delete

Boolean; whether DELETE is supported.


=item high_priority_cookie

Cookie name to check if the client's requests should be considered high priority.

See also C<high_priority_cookie_contents>.


=item high_priority_cookie_contents

Aforementioned cookie value must contain this substring.


=item backend_persist_cache

Max number of persistent backends to hold onto while no clients.


=item persist_client

Boolean; persistent connections for clients.


=item persist_backend

Boolean; persistent connections for backends.


=item verify_backend

Boolean; get attention of backend before giving it clients (using OPTIONS).


=item verify_backend_path

Path to check with the OPTIONS request (default is C<*>).


=item max_backend_uses

Max requests to send per kept-alive backend (default 0 = unlimited).


=item connect_ahead

Number of spare backends to connect to in advance all the time.


=item buffer_size

How much data a L<Perlbal::ClientProxy> object should buffer from a backend.


=item buffer_size_reproxy_url

Same as above but for backends that are reproxying for us.


=item queue_relief_size

Number of outstanding standard priority connections to activate pressure relief at.


=item queue_relief_chance

Int, 0-100; % chance to take a standard priority request when we're in pressure relief mode.


=item trusted_upstream_proxies

L<Net::Netmask> object containing netmasks for trusted upstreams.


=item always_trusted

Boolean; if true, always trust upstreams.


=item blind_proxy

Boolean; if true, do not modify C<X-Forwarded-For>, C<X-Host>, or C<X-Forwarded-Host> headers.


=item enable_reproxy

Boolean; if true, advertise that server will reproxy files and/or URLs.


=item reproxy_cache_maxsize

Maximum number of reproxy results to be cached. (0 is disabled and default).


=item client_sndbuf_size

Bytes for C<SO_SNDBUF>.


=item server_process

Path to server process (executable).


=item persist_client_idle_timeout

Keep-alive timeout in seconds for clients (default is 30).


=item idle_timeout

Idle timeout outside of keep-alive time (default is 30).


=back


=head4 Internal state

=over 4

=item waiting_clients

Arrayref of clients waiting for backendhttp connections.


=item waiting_clients_highpri

Arrayref of high-priority clients waiting for backendhttp connections.


=item waiting_clients_lowpri

Arrayref of low-priority clients waiting for backendhttp connections.


=item waiting_client_count

Number of clients waiting for backends.


=item waiting_client_map

Map of clientproxy fd -> 1 (if they're waiting for a connection).


=item pending_connects

Hashref of C<ip:port> -> C<$time> (only one pending connect to backend at a time).


=item pending_connect_count

Number of outstanding backend connects.


=item bored_backends

Arrayref of backends we've already connected to, but haven't got clients.


=item hooks

Hashref: hookname => [ [ plugin, ref ], [ plugin, ref ], ... ].


=item plugins

Hashref: name => 1.


=item plugin_order

Arrayref: name, name, name...


=item plugin_setters

Hashref: { plugin_name => { key_name => coderef } }.


=item extra_config

Hashref with extra config options; name => values.


=item spawn_lock

Boolean; if true, we're currently in C<spawn_backends>.


=item extra_headers

{ insert => [ [ header, value ], ... ], remove => [ header, header, ... ], set => [ [ header, value ], ... ] }.

Used in header management interface.


=item generation

Int; generation count so we can slough off backends from old pools.


=item backend_no_spawn

{ "ip:port" => 1 }.

If on, C<spawn_backends> will ignore this C<ip:port> combo.


=item buffer_backend_connect

0 if off; otherwise, number of bytes to buffer before we ask for a backend.


=item selector

CODE ref, or undef, for role C<selector> services.


=item default_service

Name of a service a selector should default to.


=item buffer_uploads

Boolean; enable/disable the buffered uploads to disk system.


=item buffer_uploads_path

Path to store buffered upload files.


=item buffer_upload_threshold_time

Int; buffer uploads estimated to take longer than this.


=item buffer_upload_threshold_size

Int; buffer uploads greater than this size (in bytes).


=item buffer_upload_threshold_rate

Int; buffer uploads uploading at less than this rate (in bytes/sec).


=item upload_status_listeners

Comma separated list of C<ip:port> of UDP upload status receivers.


=item upload_status_listeners_sockaddr

Arrayref of sockaddrs (packed ip/port).


=item enable_ssl

Boolean; whether this service speaks SSL to the client.


=item ssl_key_file

File path to key pem file.


=item ssl_cert_file

File to path to cert pem file.


=item ssl_cipher_list

OpenSSL cipher list string.


=item ssl_ca_path

Path to certificates directory.


=item ssl_verify_mode

Int; verification mode, see L<IO::Socket::SSL>.


=item enable_error_retries

Boolean; whether we should retry requests after errors.


=item error_retry_schedule

Comma-separated seconds (full or partial) to delay between retries.


=item latency

Milliseconds of latency to add to request.


=item _stat_requests

Total requests to this service.


=item _stat_cache_hits

Total requests to this service that were served via the reproxy-url cache.


=back
