Alan Kasindorf > Perlbal-1.80 > Perlbal::Manual::Internals

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NAME ^

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

VERSION

Perlbal 1.78.

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 backend_persist and connect_ahead, it will reuse those connections and greatly reduce latency. See more detail in 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.

Classes

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

Perlbal::Socket

Descends from Danga::Socket.

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

Fields

headers_string

Headers as they're being read.

req_headers

The final Perlbal::HTTPHeaders object inbound.

res_headers

Response headers outbound (Perlbal::HTTPHeaders object).

create_time

Creation time.

alive_time

Last time noted alive.

state

General purpose state; used by descendants.

do_die

If on, die and do no further requests.

read_buf

Arrayref of scalarref read from client.

read_ahead

Bytes sitting in read_buf.

read_size

Total bytes read from client, ever.

ditch_leading_rn

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

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.

Perlbal::TCPListener

Descends from 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.

Fields

service

Perlbal::Service.

hostport

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

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' => '...'
                       }
            };
v6

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

Perlbal::BackendHTTP

Descends from 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 Perlbal::ClientProxy to send a request to an internal node.

Fields

client

Perlbal::ClientProxy connection, or undef.

service

Perlbal::Service.

pool

Perlbal::Pool; whatever pool we spawned from.

ip

IP scalar.

port

Port scalar.

ipport

$ip:$port.

reportto

Object; must implement reporter interface.

has_attention

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

waiting_options

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

disconnect_at

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

content_length

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

content_length_remain

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

use_count

Number of requests this backend's been used for.

generation

Int; counts what generation we were spawned in.

buffered_upload_mode

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

scratch

Extra storage; plugins can use it if they want.

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.

Fields

headers

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

origcase

Href; lowercase header -> provided case.

hdorder

Aref; order headers were received (canonical order).

method

Scalar; request method (if GET request).

uri

Scalar; request URI (if GET request).

type

res or req.

code

HTTP response status code.

codetext

Status text that for response code.

ver

Version (string) "1.1".

vernum

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

responseLine

First line of HTTP response (if response).

requestLine

First line of HTTP request (if request).

Perlbal::ClientHTTPBase

Descends from Perlbal::Socket.

Provides base functionality to Perlbal::ClientHTTP and 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 selector. 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 Perlbal::ClientProxy or Perlbal::ClientHTTP (depending on selector's mapping).

Fields

service

Perlbal::Service object.

replacement_uri

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

scratch

Extra storage; plugins can use it if they want.

reproxy_file

Filename the backend told us to start opening.

reproxy_file_size

Size of file, once we stat() it.

reproxy_fh

If needed, IO::Handle of fd.

reproxy_file_offset

How much we've sent from the file.

post_sendfile_cb

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

requests

Number of requests this object has performed for the user.

selector_svc

The original service from which we came.

is_ssl

Whether the socket was SSL attached (restricted operations).

Perlbal::ClientHTTP

Descends from 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.

Fields

put_in_progress

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

put_fh

File handle to use for writing data.

put_fh_filename

Filename of put_fh.

put_pos

File offset to write next data at.

content_length

Length of document being transferred.

content_length_remain

Bytes remaining to be read.

chunked_upload_state

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

Perlbal::ClientProxy

Descends from Perlbal::ClientHTTPBase.

Takes an incoming connection from a user and connects to a backend node (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.

Fields

backend

Perlbal::BackendHTTP object (or undef if disconnected).

backend_requested

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

reconnect_count

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

high_priority

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

low_priority

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

reproxy_uris

Arrayref; URIs to reproxy to, in order.

reproxy_expected_size

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

currently_reproxying

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

content_length_remain

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

responded

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

last_request_time

Int: time that we last received a request.

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 res headers object here.

is_buffering

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

is_writing

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

start_time

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

bufh

Buffered upload filehandle object.

bufilename

String; buffered upload filename.

bureason

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

buoutpos

Int; buffered output position.

backend_stalled

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

unread_data_waiting

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

chunked_upload_state

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

request_body_length

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

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).

upload_session

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

retry_count

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

Perlbal::ClientManage

Descends from 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 Perlbal::Manual::Management for more information on this).

Fields

service

Perlbal::Service.

buf

Read buffer.

is_http

Boolean stating whether the request is HTTP.

ctx

Perlbal::CommandContext.

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.

Fields

name

Name of the service.

role

Role type (web_server, reverse_proxy, etc).

enabled

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

pool

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

listener

Perlbal::TCPListener object, when enabled.

reproxy_cache

Perlbal::Cache object, when enabled.

End-user tunables

listen

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

docroot

Document root for web_server role.

dirindexing

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

index_files

Arrayref of filenames to try for index files.

enable_concatenate_get

Boolean; if user can request concatenated files.

enable_put

Boolean; whether PUT is supported.

max_put_size

Max size in bytes of a put file.

max_chunked_request_size

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

min_put_directory

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

enable_delete

Boolean; whether DELETE is supported.

high_priority_cookie

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

See also high_priority_cookie_contents.

high_priority_cookie_contents

Aforementioned cookie value must contain this substring.

backend_persist_cache

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

persist_client

Boolean; persistent connections for clients.

persist_backend

Boolean; persistent connections for backends.

verify_backend

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

verify_backend_path

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

max_backend_uses

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

connect_ahead

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

buffer_size

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

buffer_size_reproxy_url

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

queue_relief_size

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

queue_relief_chance

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

trusted_upstream_proxies

Array of Net::Netmask objects containing netmasks for trusted upstreams.

always_trusted

Boolean; if true, always trust upstreams.

blind_proxy

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

enable_reproxy

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

reproxy_cache_maxsize

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

client_sndbuf_size

Bytes for SO_SNDBUF.

server_process

Path to server process (executable).

persist_client_idle_timeout

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

idle_timeout

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

Internal state

waiting_clients

Arrayref of clients waiting for backendhttp connections.

waiting_clients_highpri

Arrayref of high-priority clients waiting for backendhttp connections.

waiting_clients_lowpri

Arrayref of low-priority clients waiting for backendhttp connections.

waiting_client_count

Number of clients waiting for backends.

waiting_client_map

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

pending_connects

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

pending_connect_count

Number of outstanding backend connects.

bored_backends

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

hooks

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

plugins

Hashref: name => 1.

plugin_order

Arrayref: name, name, name...

plugin_setters

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

extra_config

Hashref with extra config options; name => values.

spawn_lock

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

extra_headers

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

Used in header management interface.

generation

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

backend_no_spawn

{ "ip:port" => 1 }.

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

buffer_backend_connect

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

selector

CODE ref, or undef, for role selector services.

default_service

Name of a service a selector should default to.

buffer_uploads

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

buffer_uploads_path

Path to store buffered upload files.

buffer_upload_threshold_time

Int; buffer uploads estimated to take longer than this.

buffer_upload_threshold_size

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

buffer_upload_threshold_rate

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

upload_status_listeners

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

upload_status_listeners_sockaddr

Arrayref of sockaddrs (packed ip/port).

enable_ssl

Boolean; whether this service speaks SSL to the client.

ssl_key_file

File path to key pem file.

ssl_cert_file

File to path to cert pem file.

ssl_cipher_list

OpenSSL cipher list string.

ssl_ca_path

Path to certificates directory.

ssl_verify_mode

Int; verification mode, see IO::Socket::SSL.

enable_error_retries

Boolean; whether we should retry requests after errors.

error_retry_schedule

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

latency

Milliseconds of latency to add to request.

server_tokens

Boolean; whether to provide a "Server" header.

_stat_requests

Total requests to this service.

_stat_cache_hits

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

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