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Manual Reference Pages  -  PERLBAL::MANUAL::INTERNALS (3)

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


Perlbal 1.78.


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        v        v
             [ClientManage]  [ClientHTTP] [ClientProxy]

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.


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


Descends from Danga::Socket.

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

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.

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.

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).

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.

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.

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.

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).

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).

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).

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.

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.

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.

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.

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).

service Perlbal::Service.
buf Read buffer.
is_http Boolean stating whether the request is HTTP.
ctx Perlbal::CommandContext.

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.

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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perl v5.20.3 PERLBAL::MANUAL::INTERNALS (3) 2011-09-03

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