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| | # -*- encoding: binary -*-
require 'thread'
# This class communicates with the MogileFS trackers.
# You should not have to use this directly unless you are developing
# support for new commands or plugins for MogileFS
class MogileFS::Backend
# Adds MogileFS commands +names+.
def self.add_command(*names)
names.each do |name|
define_method name do |*args|
do_request(name, args[0] || {}, false)
end
end
end
# adds idempotent MogileFS commands +names+, these commands may be retried
# transparently on a different tracker if there is a network/server error.
def self.add_idempotent_command(*names)
names.each do |name|
define_method name do |*args|
do_request(name, args[0] || {}, true)
end
end
end
BACKEND_ERRORS = {} # :nodoc:
# this converts an error code from a mogilefsd tracker to an exception:
#
# Examples of some exceptions that get created:
# class AfterMismatchError < MogileFS::Error; end
# class DomainNotFoundError < MogileFS::Error; end
# class InvalidCharsError < MogileFS::Error; end
def self.add_error(err_snake)
err_camel = err_snake.gsub(/(?:^|_)([a-z])/) { $1.upcase }
err_camel << 'Error' unless /Error\z/ =~ err_camel
unless const_defined?(err_camel)
const_set(err_camel, Class.new(MogileFS::Error))
end
BACKEND_ERRORS[err_snake] = const_get(err_camel)
end
def self.const_missing(name) # :nodoc:
if /Error\z/ =~ name.to_s
const_set(name, Class.new(MogileFS::Error))
else
super name
end
end
##
# The last error
attr_reader :lasterr
##
# The string attached to the last error
attr_reader :lasterrstr
##
# Creates a new MogileFS::Backend.
#
# :hosts is a required argument and must be an Array containing one or more
# 'hostname:port' pairs as Strings.
#
# :timeout adjusts the request timeout before an error is returned.
def initialize(args)
@hosts = args[:hosts]
@fail_timeout = args[:fail_timeout] || 5
raise ArgumentError, "must specify at least one host" unless @hosts
raise ArgumentError, "must specify at least one host" if @hosts.empty?
unless @hosts == @hosts.select { |h| h =~ /:\d+$/ } then
raise ArgumentError, ":hosts must be in 'host:port' form"
end
@mutex = Mutex.new
@timeout = args[:timeout] || 3
@socket = nil
@lasterr = nil
@lasterrstr = nil
@pending = []
@dead = {}
end
##
# Closes this backend's socket.
def shutdown
@mutex.synchronize { shutdown_unlocked }
end
# MogileFS::MogileFS commands
add_command :create_open
add_command :create_close
add_idempotent_command :get_paths
add_idempotent_command :noop
add_command :delete
add_idempotent_command :sleep
add_command :rename
add_idempotent_command :list_keys
add_idempotent_command :file_info
add_idempotent_command :file_debug
# MogileFS::Backend commands
add_idempotent_command :get_hosts
add_idempotent_command :get_devices
add_idempotent_command :list_fids
add_idempotent_command :stats
add_idempotent_command :get_domains
add_command :create_device
add_command :create_domain
add_command :delete_domain
add_command :create_class
add_command :update_class
add_command :updateclass
add_command :delete_class
add_command :create_host
add_command :update_host
add_command :delete_host
add_command :set_state
add_command :set_weight
add_command :replicate_now
def shutdown_unlocked(do_raise = false) # :nodoc:
@pending = []
if @socket
@socket.close rescue nil # ignore errors
@socket = nil
end
raise if do_raise
end
def dispatch_unlocked(request, timeout = @timeout) # :nodoc:
begin
io = socket
io.timed_write(request, timeout)
io
rescue SystemCallError, MogileFS::RequestTruncatedError => err
@dead[@active_host] = [ Time.now, err ]
shutdown_unlocked
retry
end
end
def pipeline_gets_unlocked(io, timeout) # :nodoc:
line = io.timed_gets(timeout) or
raise MogileFS::PipelineError,
"EOF with #{@pending.size} requests in-flight"
ready = @pending.shift
ready[1].call(parse_response(line, ready[0]))
end
def timeout_update(timeout, t0) # :nodoc:
timeout -= (Time.now - t0)
timeout < 0 ? 0 : timeout
end
# try to read any responses we have pending already before filling
# the pipeline more requests. This usually takes very little time,
# but trackers may return huge responses and we could be on a slow
# network.
def pipeline_drain_unlocked(io, timeout) # :nodoc:
set = [ io ]
while @pending.size > 0
t0 = Time.now
r = IO.select(set, set, nil, timeout)
timeout = timeout_update(timeout, t0)
if r && r[0][0]
t0 = Time.now
pipeline_gets_unlocked(io, timeout)
timeout = timeout_update(timeout, t0)
else
return timeout
end
end
timeout
end
# dispatch a request like do_request, but queue +block+ for execution
# upon receiving a response. It is the users' responsibility to ensure
# &block is executed in the correct order. Trackers with multiple
# queryworkers are not guaranteed to return responses in the same
# order they were requested.
def pipeline_dispatch(cmd, args, &block) # :nodoc:
request = make_request(cmd, args)
timeout = @timeout
@mutex.synchronize do
io = socket
timeout = pipeline_drain_unlocked(io, timeout)
# send the request out...
begin
io.timed_write(request, timeout)
@pending << [ request, block ]
rescue SystemCallError, MogileFS::RequestTruncatedError => err
@dead[@active_host] = [ Time.now, err ]
shutdown_unlocked(@pending[0])
io = socket
retry
end
@pending.size
end
end
def pipeline_wait(count = nil) # :nodoc:
@mutex.synchronize do
io = socket
count ||= @pending.size
@pending.size < count and
raise MogileFS::Error,
"pending=#{@pending.size} < expected=#{count} failed"
begin
count.times { pipeline_gets_unlocked(io, @timeout) }
rescue
shutdown_unlocked(true)
end
end
end
# Performs the +cmd+ request with +args+.
def do_request(cmd, args, idempotent = false)
no_raise = args.delete(:ruby_no_raise)
request = make_request(cmd, args)
line = nil
failed = false
@mutex.synchronize do
begin
io = dispatch_unlocked(request)
line = io.timed_gets(@timeout)
break if /\r?\n\z/ =~ line
line and raise MogileFS::InvalidResponseError,
"Invalid response from server: #{line.inspect}"
idempotent or
raise EOFError, "end of file reached after: #{request.inspect}"
# fall through to retry in loop
rescue SystemCallError,
MogileFS::InvalidResponseError # truncated response
# we got a successful timed_write, but not a timed_gets
if idempotent
failed = true
shutdown_unlocked(false)
retry
end
shutdown_unlocked(true)
rescue MogileFS::UnreadableSocketError, MogileFS::Timeout
shutdown_unlocked(true)
rescue
# we DO NOT want the response we timed out waiting for, to crop up later
# on, on the same socket, intersperesed with a subsequent request! we
# close the socket if there's any error.
shutdown_unlocked(true)
end while idempotent
shutdown_unlocked if failed
end # @mutex.synchronize
parse_response(line, no_raise ? request : nil)
end
# Makes a new request string for +cmd+ and +args+.
def make_request(cmd, args)
"#{cmd} #{url_encode args}\r\n"
end
# this converts an error code from a mogilefsd tracker to an exception
# Most of these exceptions should already be defined, but since the
# MogileFS server code is liable to change and we may not always be
# able to keep up with the changes
def error(err_snake)
BACKEND_ERRORS[err_snake] || self.class.add_error(err_snake)
end
# Turns the +line+ response from the server into a Hash of options, an
# error, or raises, as appropriate.
def parse_response(line, request = nil)
case line
when /\AOK\s+\d*\s*(\S*)\r?\n\z/
url_decode($1)
when /\AERR\s+(\w+)\s*([^\r\n]*)/
@lasterr = $1
@lasterrstr = $2 ? url_unescape($2) : nil
if request
request = " request=#{request.strip}"
@lasterrstr = @lasterrstr ? (@lasterrstr << request) : request
return error(@lasterr).new(@lasterrstr)
end
raise error(@lasterr).new(@lasterrstr)
else
raise MogileFS::InvalidResponseError,
"Invalid response from server: #{line.inspect}"
end
end
# this command is special since the cache is per-tracker, so we connect
# to all backends and not just one
def clear_cache(types = %w(all))
opts = {}
types.each { |type| opts[type] = 1 }
sockets = @hosts.map do |host|
MogileFS::Socket.start(*(host.split(/:/))) rescue nil
end
sockets.compact!
wpending = sockets
rpending = []
request = make_request("clear_cache", opts)
while wpending[0] || rpending[0]
r = IO.select(rpending, wpending, nil, @timeout) or return
rpending -= r[0]
wpending -= r[1]
r[0].each { |io| io.timed_gets(0) rescue nil }
r[1].each do |io|
begin
io.timed_write(request, 0)
rpending << io
rescue
end
end
end
nil
ensure
sockets.each { |io| io.close }
end
# Returns a socket connected to a MogileFS tracker.
def socket
return @socket if @socket and not @socket.closed?
@hosts.shuffle.each do |host|
next if dead = @dead[host] and dead[0] > (Time.now - @fail_timeout)
begin
addr, port = host.split(/:/)
@socket = MogileFS::Socket.tcp(addr, port, @timeout)
@active_host = host
rescue SystemCallError, MogileFS::Timeout => err
@dead[host] = [ Time.now, err ]
next
end
return @socket
end
errors = @dead.map { |host,(_,e)| "#{host} - #{e.message} (#{e.class})" }
raise MogileFS::UnreachableBackendError,
"couldn't connect to any tracker: #{errors.join(', ')}"
end
# Turns a url params string into a Hash.
def url_decode(str) # :nodoc:
rv = {}
str.split(/&/).each do |pair|
k, v = pair.split(/=/, 2).map! { |x| url_unescape(x) }
rv[k.freeze] = v
end
rv
end
# :stopdoc:
# TODO: see if we can use existing URL-escape/unescaping routines
# in the Ruby standard library, Perl MogileFS seems to NIH these
# routines, too
# :startdoc:
# Turns a Hash (or Array of pairs) into a url params string.
def url_encode(params) # :nodoc:
params.map do |k,v|
"#{url_escape k.to_s}=#{url_escape v.to_s}"
end.join("&")
end
# Escapes naughty URL characters.
if ''.respond_to?(:ord) # Ruby 1.9
def url_escape(str) # :nodoc:
str.gsub(/([^\w\,\-.\/\\\: ])/) { "%%%02x" % $1.ord }.tr(' ', '+')
end
else # Ruby 1.8
def url_escape(str) # :nodoc:
str.gsub(/([^\w\,\-.\/\\\: ])/) { "%%%02x" % $1[0] }.tr(' ', '+')
end
end
# Unescapes naughty URL characters.
def url_unescape(str) # :nodoc:
str.tr('+', ' ').gsub(/%([a-f0-9][a-f0-9])/i) { [$1.to_i(16)].pack 'C' }
end
end
|