Hunter的大杂烩 技术学习笔记

 — no backend selected yet, pick a master
 if proxy.connection.backend_ndx == 0 then
  — we don’t have a backend right now
  —
  — let’s pick a master as a good default
  —
  proxy.connection.backend_ndx = lb.idle_failsafe_rw()
 end

 — by now we should have a backend
 —
 — in case the master is down, we have to close the client connections
 — otherwise we can go on
 if proxy.connection.backend_ndx == 0 then
  return proxy.PROXY_SEND_QUERY
 end

 local s = proxy.connection.server

 — if client and server db don’t match, adjust the server-side
 —
 — skip it if we send a INIT_DB anyway
 if cmd.type ~= proxy.COM_INIT_DB and
    c.default_db and c.default_db ~= s.default_db then
  print(”    server default db: ” .. s.default_db)
  print(”    client default db: ” .. c.default_db)
  print(”    syncronizing”)
  proxy.queries:prepend(2, string.char(proxy.COM_INIT_DB) .. c.default_db, { resultset_is_needed = true })
 end

 — send to master
 if is_debug then
  if proxy.connection.backend_ndx > 0 then
   local b = proxy.global.backends[proxy.connection.backend_ndx]
   print(”  sending to backend : ” .. b.dst.name);
   print(”    is_slave         : ” .. tostring(b.type == proxy.BACKEND_TYPE_RO));
   print(”    server default db: ” .. s.default_db)
   print(”    server username  : ” .. s.username)
  end
  print(”    in_trans        : ” .. tostring(is_in_transaction))
  print(”    in_calc_found   : ” .. tostring(is_in_select_calc_found_rows))
  print(”    COM_QUERY       : ” .. tostring(cmd.type == proxy.COM_QUERY))
 end

 return proxy.PROXY_SEND_QUERY
end

—
— as long as we are in a transaction keep the connection
— otherwise release it so another client can use it
function read_query_result( inj )
 local is_debug = proxy.global.config.rwsplit.is_debug
 local res      = assert(inj.resultset)
   local flags    = res.flags

 if inj.id ~= 1 then
  — ignore the result of the USE
  — the DB might not exist on the backend, what do do ?
  —
  if inj.id == 2 then
   — the injected INIT_DB failed as the slave doesn’t have this DB
   — or doesn’t have permissions to read from it
   if res.query_status == proxy.MYSQLD_PACKET_ERR then
    proxy.queries:reset()

    proxy.response = {
     type = proxy.MYSQLD_PACKET_ERR,
     errmsg = “can’t change DB “.. proxy.connection.client.default_db ..
      ” to on slave ” .. proxy.global.backends[proxy.connection.backend_ndx].dst.name
    }

    return proxy.PROXY_SEND_RESULT
   end
  end
  return proxy.PROXY_IGNORE_RESULT
 end

 is_in_transaction = flags.in_trans
 local have_last_insert_id = (res.insert_id and (res.insert_id > 0))

 if not is_in_transaction and
    not is_in_select_calc_found_rows and
    not have_last_insert_id then
  — release the backend
  proxy.connection.backend_ndx = 0
 elseif is_debug then
  print(“(read_query_result) staying on the same backend”)
  print(”    in_trans        : ” .. tostring(is_in_transaction))
  print(”    in_calc_found   : ” .. tostring(is_in_select_calc_found_rows))
  print(”    have_insert_id  : ” .. tostring(have_last_insert_id))
 end
end

—
— close the connections if we have enough connections in the pool
—
— @return nil – close connection
—         IGNORE_RESULT – store connection in the pool
function disconnect_client()
 local is_debug = proxy.global.config.rwsplit.is_debug
 if is_debug then
  print(“[disconnect_client] ” .. proxy.connection.client.src.name)
 end

 — make sure we are disconnection from the connection
 — to move the connection into the pool
 proxy.connection.backend_ndx = 0
end