Using max_taker_vol values to initiate trade sometimes results in "req funds larger than available"

[smk762]

In some cases, using the values returned from max_taker_vol to submit a trade returns "req amount is larger than balance.

Issue first encountered during AtomicDEX-Desktop testing, then checked using CLI directly with mm2 to confirm. Console output below -

curl --url "http://127.0.0.1:7783" --data "{\"userpass\":\"$userpass\",\"method\":\"version\"}"

{"result":"2.0.2422_mm2_31d1803b0_Linux_Debug","datetime":"2020-09-25T12:40:25+07:00"}

curl --url "http://127.0.0.1:7783" --data "{\"method\":\"max_taker_vol\",\"coin\":\"ZEC\",\"userpass\":\"$userpass\",\"mm2\":1}"

{"result":{"numer":"824933907","denom":"15560000000"}}

curl --url "http://127.0.0.1:7783" --data "{\"userpass\":\"$userpass\",\"method\":\"sell\",\"base\":\"ZEC\",\"rel\":\"KMD\",\"volume\":{\"numer\":\"824933907\",\"denom\":\"15560000000\"},\"price\":"\"2000\""}"

{"error":"rpc:339] lp_ordermatch:1249] taker_swap:1443] The total required ZEC amount 0.05331631793059125964010282776349614395886889460154241645244215938303341902313624678663239074550128535 is larger than available 0.05328455, balance: 0.05328455, locked by swaps: 0"}```

curl --url "http://127.0.0.1:7783" --data "{\"userpass\":\"$userpass\",\"method\":\"get_trade_fee\",\"coin\":\"ZEC\"}"

{"result":{"coin":"ZEC","amount":"0.0001","amount_fraction":{"numer":"1","denom":"10000"},"amount_rat":[[1,[1]],[1,[10000]]]}}

I've seen this with ZEC and BCH.

With BCH, after doing a swap that was half of total, doing a subsequent trade with the remainder was successful.
I've left the account with ZEC relating to the issue as is, and can provide the seed for testing if required.

[artemii235]

Thanks for report! Checking now.

[artemii235]

The problem is max_taker_vol does not take the 0.0001 min dexfee threshold into account so it returns larger number that can be actually used. I'm going to fix this now.

[smk762]

Results of latest test on fix_max_taker_vol branch:

curl --url "http://127.0.0.1:7783" --data "{"userpass":"$userpass","method":"version"}"
{"result":"31d1803b0","datetime":"2020-10-23T20:35:23+07:00"}

curl --url "http://127.0.0.1:7783" --data "{"method":"max_taker_vol","coin":"ZEC","userpass":"$userpass","mm2":1}"
{"result":{"numer":"1059691","denom":"20000000"}}

curl --url "http://127.0.0.1:7783" --data "{"userpass":"$userpass","method":"sell","base":"ZEC","rel":"KMD","volume":{"numer":"1059691","denom":"20000000"},"price":""2000""}"

{"result":{"base":"ZEC","rel":"KMD","base_amount":"0.05298455","base_amount_rat":[[1,[1059691]],[1,[20000000]]],"rel_amount":"105.9691","rel_amount_rat":[[1,[1059691]],[1,[10000]]],"action":"Sell","uuid":"88952618-c189-4a79-8002-057e79ae1721","method":"request","sender_pubkey":"f394a5c245230e9d2ee3d3fef89b2398e91621f008b6ba9256aaf98fd55c5d46","dest_pub_key":"0000000000000000000000000000000000000000000000000000000000000000","match_by":{"type":"Any"},"conf_settings":{"base_confs":3,"base_nota":false,"rel_confs":2,"rel_nota":true},"order_type":{"type":"GoodTillCancelled"}}}

curl --url "http://127.0.0.1:7783" --data "{"userpass":"$userpass","method":"get_trade_fee","coin":"ZEC"}"
{"result":{"coin":"ZEC","amount":"0.0001","amount_fraction":{"numer":"1","denom":"10000"},"amount_rat":[[1,[1]],[1,[10000]]]}}

[artemii235]

@smk762 Could you please confirm that it works fine now?

[smk762]

Tested a few times, did not encounter the "required {coin} amount {amount} is larger than available {balance}" error.
Appears to be operating as intended, thanks!