Class: LS4::BasicHADB

Inherits:
Object
  • Object
show all
Defined in:
lib/ls4/service/mds_ha.rb

Overview

single node:

host1:port1

master-slave:

host1:port1,host2:port2

master-slave with read weight:

host1:port1,host2:port2;0,1

dual-master:

host1:port1--host2:port2

Constant Summary collapse

DEFAULT_WEIGHT = 
10

Instance Method Summary collapse

Constructor Details

#initialize(expr) ⇒ BasicHADB

Returns a new instance of BasicHADB.



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# File 'lib/ls4/service/mds_ha.rb', line 37

def initialize(expr)
  @dbmap = {}    # {Address => DB}
  @writers = []   # [Address]
  @readers = []   # [Address]
  @readers_rr = 0

  expr.split('--').each {|line|
    nodes, weights = line.strip.split(';',2)

    addrs = nodes.strip.split(',').map {|addr|
      parse_addr(addr)
    }

    weights = (weights||"").strip.split(',').map {|x| x.to_i }

    @writers << addrs.first

    addrs.each_with_index {|addr,i|
      weight = weights[i] ||= DEFAULT_WEIGHT
      weight.times {
        @readers << addr
      }
      @dbmap[addr] = nil
    }

    $log.info "MDS -- #{addrs.join(',')};#{weights.join(',')}"
  }

  if @dbmap.empty?
    raise "empty expression"
  end

  if @dbmap.size == 1
    # single node
    @readers = [@readers[0]]
  else
    @readers = @readers.sort_by {|addr| rand }
  end

  # open remote database
  @dbmap.keys.each {|addr|
    @dbmap[addr] = open_db(addr)
  }

rescue
  @dbmap.each_pair {|addr,db|
    if db
      close_db(db) rescue nil
    end
  }
  $log.error $!
  $log.error_backtrace $!.backtrace
  raise "MDS: invlaid address expression: #{$!}"
end

Instance Method Details

#close ⇒ Object 



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# File 'lib/ls4/service/mds_ha.rb', line 111

def close
  @dbmap.each_pair {|addr,db|
    close_db(db) rescue nil
  }
end

#read(shard_key, &block) ⇒ Object 



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# File 'lib/ls4/service/mds_ha.rb', line 103

def read(shard_key, &block)
  @readers_rr += 1
  @readers_rr = 0 if @readers_rr >= @readers.size
  ha_call(@readers, @readers_rr) {|db|
    block.call(db)
  }
end

#write(shard_key, &block) ⇒ Object 



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# File 'lib/ls4/service/mds_ha.rb', line 92

def write(shard_key, &block)
  if @writers.size == 1
    n = 0
  else
    n = hash_key(shard_key) % @writers.size
  end
  ha_call(@writers, n) {|db|
    block.call(db)
  }
end