boost :: asio tcp数据库服务器

Question

I need some hints: I'm writing a tcp database server, that can hold 100 strings (I used vector of strings to hold the data). Basic functionality, achieved by me so far is:

client sends: PUT "index" "value" - string is put in the vector[index].
client sends: GET "index" - vector[index] is sent to client

I based my work on boost::asio async echo server example http://www.boost.org/doc/libs/1_39_0/doc/html/boost_asio/example/echo/async_tcp_echo_server.cpp

Right now, I want to extend the functionality of the server to:

STILL UNSOLVED 1. Be able to load the starting content of vector from file on start and save it on exit.

SOLVED 2. Put timer on database elements: lifetime of string in vector[index] should be 30 seconds, if within 30seconds of input, the new data doesn't arrive to vector[index] the content should be erased.

The only issue left, is saving/loading vector data on exit/start. Since the vector contains only 100 strings, I could simply read/write using fstream, but I have a problem with triggering the save.

My async server's main function contains: io_service.run(); How can I trigger an action by pressing a key during running server? My first guess is async_read from user input as in http://www.boost.org/doc/libs/1_51_0/doc/html/boost_asio/example/chat/posix_chat_client.cpp example. Any other ideas?

Answer 1

I'd implement the timer by saving a timestamp with the value, and on lookup, check whether the entry has expired. No need to wake up the CPU with a timer if noone asked whether the entry is still valid.

Also, as long as you have a proper abstraction between the network code and the database implementation, you can adapt your database to whatever is most suitable. If there is a maximum number of entries and they all fit into memory, then by all means a vector is fine, and SQLite is probably overkill.

Answer 2

Use Redis or Memcached because they have value time to live already. Both have C++ drivers.