Perlbal::Manual::Internals(3)

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.