TARA: Erlang tarantool connector

===== Erlang connector application to Tarantool server. Tarantool on github: https://github.com/tarantool/tarantool

Tested with Tarantool 1.7 branch, Erlang 19.0

Features:

• Multiple pools, each with its' own connection options.
• Start/stop pools dynamically or from the application env.
• Authentification.
• Autoreconnect with deamplification on connection loss or other problems.
• Both async and sync mode. The sync mode locks the caller process with gen_server:call. Worker in handle_call waits until writing to socket is completed, then tries to read some data from socket with 0 timeout and returns {noreply, State}. The worker does not wait for response for the current request, so slow operation won't block the worker, but only the caller. The case when you do a slow request from one process and then a fast one from another, and both requests are sent to the same worker of the pool, will be handled correctly - the fast one will not wait for the slow one. But 5 seconds timeout of gen_server still exists, so think about async requests for potentially slow operations.
• Can use unix domain sockets, if tarantool configured to listen on such socket. Use {local, "/tmp/sock"} as addr and 0 as port.
• select, delete, insert, call (both old 0x06 and new 0x0A), update, upsert, replace, eval operations.

Note:

• Uses Simplepool pools. You might not like it as simplepool uses quite unconventional thing - it compiles pool proc names and other data in a RAM beam module.
• If you have tarantool 1.7.2 or newer define the TARANTOOL_V172CALL macro (by default it is already defined in rebar.config). This macro would enable the new call method (0x0A) which won't convert result values to array. For earlier versions of tarantool undefine this macro. Look up the tests for difference in return value of the new and old call methods.

Build

$ rebar3 compile

If you don't have rebar3 in your path, download it from http://www.rebar3.org/ or build it from sources.

Tests

Download and make tarantool. Ensure it is stopped. Edit the test/test.config file, change the path to tarantool and the name of your terminal app. Then run

$ rebar3 ct    

Load test such as "insert 999000 records " are disabled (commented off in the test module).

Examples

• Include tara/include/tara.hrl - you may need the records and macroses from this file
• In the Sync mode operations return either {error, Error}, #tara_response{} or #tara_error{}.

• {error, Error} gets returned when the server is disconnected or authentication is not yet completed. Also, if you sent request succesfully but socket disconnected before the worker got response for this request, you will get the {error, disconnect_before_response} response.
• #tara_response{} - successful response with some data. Always contains [{?IPROTO_DATA, Data}] in the data field, where Data - list of 0 or more lists (named 'tuples' in tarantool terms, in docs and everywhere) of the result.
• #tara_error{} - tarantool error. Something went wrong - invalid parameters in request, attempt to insert the tuple which is already exists and anything like that. The error message in the message field.

• The select operation accepts optional Options parameter, with limit, index, offset, iterator integer fields. The Options can be either map or proplist. By default limit is equal to 1000 so specify some smaller value if your table potentially can have many records matching the query, and use pagination.
• Response data can be different for the vinyl backend.

Async operations have 2 additional parameters: Pid of the process which will get the result (or undefined if no process would listen for the response) and a Tag - any term, to be able to match on if you need to associate response with the request. The message will look like this: {tara, Tag, Response} where Response is either {error, Error}, #tara_response{} or #tara_error{}

rd(tara_response, {code, schema, data}).
rd(tara_error, {code, schema, message}).
TArgs = [{addr, "localhost"},
		{port, 3301},
		{username, <<"manager">>},
		{password, <<"abcdef">>}
	],
ok = tara:start_pool(pool2, [{size, 5}, {sup_flags, {one_for_one, 1, 5}}], TArgs).
%%connect is async, so right after connection it is in disconnected state. Wait for a while or poll
%%the tara:state(Pool) - see tests. Also note that connection can disconnect and reconnect again any time
timer:sleep(1000).
Tuple1 = [100, <<"a">>, 1, <<"b">>, 1.1].
#tara_response{data = [{_, [Tuple1]}]} = tara:insert(pool2, 512, Tuple1).
#tara_response{data = [{_, [Tuple1]}]} = tara:select(pool2, 512, [100]).
#tara_response{data = [{_, [Tuple1]}]} = tara:delete(pool2, 512, [100, <<"a">>]).
#tara_response{data = [{_, []}]} = tara:select(pool2, 512, [100, <<"a">>]).
ok = tara:async_delete(pool2, 512, [100, <<"a">>], self(), some_tag).
receive
    {tara, some_tag, Response} -> ok;
after 10000 -> exit(timeout)
end.

See the tests for more examples on other methods. tara.hrl contains useful macroses for the update and upsert methods. More info is there: http://tarantool.org/doc/dev_guide/box_protocol.html