Loadgen vault close causes amountGiven or amountWanted must be greater than 0

[mhofman]

Describe the bug

After #4026 landed, the chain started to print errors in the stderr (in verbose mode) when the loadgen's create-vault task performs a vault close.

To Reproduce

Steps to reproduce the behavior:

1. Checkout agoric-sdk on revision b605a6a or more recent,
2. yarn && yarn build && make -C packages/cosmic-swingset
3. make sure agoric is in the $PATH (yarn link-cli)
4. Checkout the mhofman/report-stage-results branch of https://github.com/Agoric/testnet-load-generator/tree/mhofman/report-stage-results. The following all takes place in the testnet-load-generator directory.
5. agoric install
6. In first terminal: agoric start local-chain --verbose
7. In second terminal, after chain reaches a few blocks in height: agoric start local-solo 8000 --verbose
8. In a third terminal, after the client shows Deployed Wallet! in the output: yarn loadgen
9. In a fourth terminal, after the loadgen is ready: curl -X PUT --data '{"vault":{"interval":600}}' http://127.0.0.1:3352/config
10. During the vault task, the following error is thrown and printed in the chain output: amountGiven or amountWanted must be greater than 0: {"brand":"[Alleged: RUN brand]","value":"[0n]"} {"brand":"[Alleged: BLD brand]","value":"[0n]"}

Expected behavior

No error in output

Platform Environment

• Debian based Docker image under WSL2
• Not an usual environment it's not relevant to this bug
• agoric-sdk revision b605a6a

Additional context

Strangely the close offer succeeds, and the error is never surfaced to the client making requests.

This is the relevant create-vault code: https://github.com/Agoric/testnet-load-generator/blob/834421d023adb036f09eeb5500326b6fe9ff2499/loadgen/contract/agent-create-vault.js#L91-L105

Screenshots

The relevant output of 2 cycles run before and after the PR landed: https://gist.github.com/mhofman/a07bc58efccd7cb42f9fb31814df8fe4

This is the deliveries resulting from the relevant loadgen code above:

[
  [ 211, '211:194:deliver:ro+85:makeCloseInvitation:rp-229;[]' ],
  [
    212,
    '212:194:deliver:ro+51:withdraw:rp-230:ro+48;[{"brand":{"@qclass":"slot","iface":"Alleged: RUN brand","index":0},"value":{"@qclass":"bigint","digits":"76708106"}}]'
  ],
  [
    213,
    '213:194:deliver:ro+32:offer:rp-231:rp-229:ro+48:ro+46:rp-230;[{"@qclass":"slot","index":0},{"give":{"RUN":{"brand":{"@qclass":"slot","iface":"Alleged: RUN brand","index":1},"value":{"@qclass":"bigint","digits":"76708106"}}},"want":{"Collateral":{"brand":{"@qclass":"slot","iface":"Alleged: BLD brand","index":2},"value":{"@qclass":"bigint","digits":"0"}}}},{"RUN":{"@qclass":"slot","index":3}}]'
  ],
  [ 214, '214:194:deliver:rp-231:getPayout:rp-232;["RUN"]' ],
  [ 215, '215:194:deliver:rp-231:getPayout:rp-233;["Collateral"]' ]
]

[Chris-Hibbert]

I was unable to reproduce, and there was a suggestion that loadgen may not be useable on a Mac.

[mhofman]

I've updated instructions to avoid the loadgen runner which relies on Linux procfs

[mhofman]

FYI, I am still running into this error on master.

[Chris-Hibbert]

That error message is generated in the AMM when it receives a swap request whose want and give are both zero. IIRC, the previous code silently did an empty trade instead of complaining.

I don't see why this would be prompted by a request to close the vault. (Closing the vault shouldn't cause any interaction with the AMM.)

Perhaps the loadgen task is checking the result of the previous transaction at that time?

[Chris-Hibbert]

Ah, I see. swap is also called for price quotes. Lemme see if I can figure out who's asking for prices.

chain: Error#1: amountGiven or amountWanted must be greater than 0: {"brand":"[Alleged: RUN brand]","value":"[0n]"} {"brand":"[Alleged: BLD brand]","value":"[0n]"}
chain: Error: amountGiven or amountWanted must be greater than 0: (an object) (an object)
chain:  at construct ()
chain:  at Error (/workspaces/agoric/agoric-sdk/packages/SwingSet/src/kernel/vatManager/lockdown-subprocess-xsnap.js:8833)
chain:  at makeError (/workspaces/agoric/agoric-sdk/packages/SwingSet/src/kernel/vatManager/lockdown-subprocess-xsnap.js:3103)
chain:  at fail (/workspaces/agoric/agoric-sdk/packages/SwingSet/src/kernel/vatManager/lockdown-subprocess-xsnap.js:3231)
chain:  at baseAssert (/workspaces/agoric/agoric-sdk/packages/SwingSet/src/kernel/vatManager/lockdown-subprocess-xsnap.js:3249)
chain:  at swap (#875:194)
chain:  at (#862:33)
chain:  at getInputPrice (#915:88)
chain:  at calcAmountOut (#913:31)
chain:  at (#611:280)
chain:  at createQuote (#913:40)
chain:  at quoteGiven (#611:278)
chain:  at ()
chain:  at ()
chain: 

[Chris-Hibbert]

closeHook() calls updateUiState(). updateUiState() calls getCollateralizationRatio(), which asks the priceAuthority for the current value of the collateral (even when the collateral has been reduced to zero.) As I mentioned above, swap no longer gives a helpful answer when asked for the price of zero of the collateral. grumble

[Tartuffo]

@Chris-Hibbert For proper project planning and tracking, this needs an area label covered by one of our weekly planning meetings. Please pick the appropriate one from: agd, agoric-cli, agoric-cosmos, amm, core economy, cosmic-swingset, endo, ertp, getrun, governance, installation-bundling, metering, oracle, pegasus, run-protocol, ses, staking, swingset, swingset-runner, tc39, token economy, tooling, ui, wallet, xsnap, zoe, zoe contract

[Chris-Hibbert]

This is a bug in the AMM that is affecting loadgen.