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| Informational
| Accepted
|-
+| [[nep-23.mediawiki|23]]
+| JSON-RPC error handling and codes
+| Anna Shaleva, Roman Khimov
+| Informational
+| Accepted
+|-
|
| Dynamic Sharding
|
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+
+ NEP: 23
+ Title: Neo JSON-RPC error handling and codes
+ Author: Anna Shaleva , Roman Khimov
+ Type: Informational
+ Status: Final
+ Created: 2022-09-12
+
+
+==Abstract==
+
+This proposal describes some Neo-specific JSON-RPC interaction requirements
+along with a set of Neo-specific error codes to be used by compliant
+implementations. It allows different Neo nodes with different RPC server
+implementations to be compatible and able to interact with various RPC
+clients.
+
+==Motivation==
+
+Currently different implementations of RPC servers in Neo nodes use slightly
+different set of error codes and clients can't rely on codes to distinguish
+one error from another. Some errors were also changed on update from Legacy
+to N3. The overall set is also too coarse to be used effectively by clients,
+many different problems requiring different client actions end up with the
+same code, so clients have to parse error messages to react correctly which is
+far less reliable than using codes. At the same time JSON-RPC is too
+permissive in some of its definitions, while Neo can benefit from stricter
+definitions used.
+
+A standard set of errors and JSON-RPC conventions solve these problems by
+providing common language both for servers and clients. Servers can have a
+reference on what code should be used for what purpose and what data types
+should be used, while clients can easily check for error codes and react
+accordingly.
+
+==Specification==
+
+===General JSON-RPC conventions===
+
+JSON-RPC 2.0 specification for the Error object is augmented with
+the following compatible clauses:
+
+* code field MUST be a negative integer value ranging from -1 to -65536 that is reserved for a particular error by the specification. code field MUST be the same for each Neo node irrespective of the implementation details except for the reserved experimental implementation-defined range. code field MUST NOT be omitted.
+* message field MUST be a valid UTF-8 string value that specifies a short error description. message value MAY NOT be exactly the same across all Neo node implementations (we have code for this). message value SHOULD be limited to a concise single sentence. message field MUST NOT be omitted. message field SHOULD start with a capital letter and SHOULD NOT end with a dot.
+* data field MUST be a valid UTF-8 string value that contains any implementation-dependent textual data (including debug traces). data field MAY be omitted, however it’s RECOMMENDED for servers to return it. data value SHOULD contain additional information about error and be aimed to clarify the error reason. data value MAY NOT be exactly the same across Neo node implementations.
+
+===Error codes===
+
+Compliant server implementations can use error codes defined by JSON-RPC
+specification (from -32700 to -32600) for any calls when they're
+appropriate. The most often used one is -32602 "Invalid params", it SHOULD be
+used only when call parameters are syntactically incorrect and servers
+SHOULD give additional data like offending parameter number and why it's wrong
+in the data response field.
+
+If several codes can be used in some situations implementations SHOULD pick
+the most specific one.
+
+====Groups====
+
+Error codes are grouped. Each call can use any appropriate group and code as
+long as they fit the purpose.
+
+{|
+|+ Error code ranges
+|-
+! Range !! Usage
+|-
+| -15000...-10000 || Experimental implementation-defined range.
+|-
+| -699...-600 || Configuration and service errors.
+|-
+| -599...-500 || Inventory verification errors.
+|-
+| -399...-300 || Wallet-related errors.
+|-
+| -199...-100 || Missing/unknown items/inventories/states.
+|}
+
+Experimental codes can be used by node implementations if they're documented,
+however clients can't rely on the meaning of these codes if the version of the
+node changes or if they connect to a different node implementation. New
+proposals can set new ranges or specific codes as long as they don't conflict
+with this specification. All the remaining error codes (not listed in this
+specification or JSON-RPC 2.0) are reserved for future use and MUST NOT be
+used by compliant implementations.
+
+====Missing items====
+
+{|
+|+ Codes for missing items
+|-
+! Code !! Message !! Meaning
+|-
+| -101 || Unknown block || Call that accepts as a parameter or searches for a header or a block as a part of its job can't find it.
+|-
+| -102 || Unknown contract || Call that accepts as a parameter or searches for a contract as a part of its job can't find it.
+|-
+| -103 || Unknown transaction|| Call that accepts as a parameter or searches for a transaction as a part of its job can't find it.
+|-
+| -104 || Unknown storage item|| Call that looks for an item in the storage as part of its job can't find it.
+|-
+| -105 || Unknown script container|| Call that accepts as a parameter or searches for a script container (a block or transaction) as a part of its job can't find it (this error generalizes -101 and -103 in cases where it's needed).
+|-
+| -106 || Unknown state root || Call that accepts as a parameter or searches for a state root as a part of its job can't find it.
+|-
+| -107 || Unknown session || Call that accepts as a parameter or searches for a session as a part of its job can't find it.
+|-
+| -108 || Unknown iterator || Call that accepts as a parameter or searches for a session iterator as a part of its job can't find it.
+|-
+| -109 || Unknown height || Block or header height passed as parameter or calculated during call execution is not correct (out of the range known to the node).
+|}
+
+
+====Wallet-related problems====
+
+{|
+|+ Codes for calls that use a wallet
+|-
+! Code !! Message !! Meaning
+|-
+| -300 || Insufficient funds || Transaction that sends some assets can't be created because it fails.
+|-
+| -301 || Fee limit exceeded || Transaction requires more network fee to be paid than is allowed by settings.
+|-
+| -302 || No opened wallet || Server doesn't have any opened wallet to operate with.
+|-
+| -303 || Wallet not found || Specified (or configured) wallet file path is invalid.
+|-
+| -304 || Wallet not supported|| Specified (or configured) file can't be opened as a wallet.
+|}
+
+====Verification errors====
+
+{|
+|+ Inventory verification or verification script errors
+|-
+! Code !! Message !! Meaning
+|-
+| -500 || Unclassified verification error|| Anything that can't be expressed by other codes.
+|-
+| -501 || Inventory already exists on chain|| Block or transaction is already accepted and processed.
+|-
+| -502 || Memory pool is full|| No more transactions can be accepted into the memory pool (unless they have a priority) as its full capacity is reached.
+|-
+| -503 || Transaction already exists in the pool|| Transaction is already pooled, but not yet accepted into a block.
+|-
+| -504 || Insufficient network fee|| Transaction has incorrect (too small per Policy setting) network fee value.
+|-
+| -505 || Policy check failed|| Denied by the Policy contract (one of signers is blocked).
+|-
+| -506 || Invalid script || Transaction contains incorrect executable script.
+|-
+| -507 || Invalid attribute || Transaction contains an invalid attribute.
+|-
+| -508 || Invalid signature || One of the verification scripts failed.
+|-
+| -509 || Invalid size || Transaction or its script is too big.
+|-
+| -510 || Expired || Transaction's ValidUntilBlock value is already in the past or NotValidBefore attribute value is in future.
+|-
+| -511 || Insufficient funds || Sender doesn't have enough GAS to pay for all currently pooled transactions.
+|-
+| -512 || Invalid verification function|| Contract doesn't have a verify method or this method doesn't return proper value.
+|-
+| -513 || Conflicts || There is a conflict with another transaction already in memory pool caused by one or both of them having a Conflicts attribute.
+|}
+
+====Service and node configuration====
+
+{|
+|+ Errors related to node configuration and various services
+|-
+! Code !! Message !! Meaning
+|-
+| -600 || Access denied || Server requires authentication or has a policy not allowing request to be processed.
+|-
+| -601 || Sessions disabled || Session support is not enabled on the server.
+|-
+| -602 || Oracle service is not running|| Service is not enabled in the configuration.
+|-
+| -603 || Oracle request already finished|| The oracle request submitted is already completely processed.
+|-
+| -604 || Oracle request not found || The oracle request submitted is not known to this node.
+|-
+| -605 || Not a designated oracle node|| Oracle service is enabled, but this node is not designated to provide this functionality.
+|-
+| -606 || Old state requests are not supported|| This node can't answer requests for old state because it's configured to keep only the latest one.
+|-
+| -607 || Invalid proof || State proof verification failed.
+|-
+| -608 || Execution failed || Call made a VM execution, but it has failed.
+|}
+
+===Applicability to current calls===
+
+This table is informative, compliant implementations MAY use other codes
+specified above that fit the purpose as well if they're documented. Only
+Neo-specific codes are documented here (except -600 that can be returned
+for any call), generic JSON-RPC errors like -32602 or
+-32603 can be used by any of these methods.
+
+{|
+|+ Error codes returned from specific calls
+|-
+! Method !! Codes
+|-
+| calculatenetworkfee || -508, -512
+|-
+| closewallet ||
+|-
+| dumpprivkey || -302
+|-
+| findstates || -102, -606
+|-
+| getapplicationlog || -105
+|-
+| getblock || -101, -109
+|-
+| getblockhash || -109
+|-
+| getblockheader || -101, -109
+|-
+| getcandidates ||
+|-
+| getcommittee ||
+|-
+| getconnectioncount ||
+|-
+| getcontractstate || -102
+|-
+| getnativecontracts ||
+|-
+| getnep11balances ||
+|-
+| getnep11properties || -608
+|-
+| getnep11transfers ||
+|-
+| getnep17balances ||
+|-
+| getnep17transfers ||
+|-
+| getnewaddress || -302
+|-
+| getnextblockvalidators||
+|-
+| getpeers ||
+|-
+| getproof || -102, -104, -606
+|-
+| getrawmempool ||
+|-
+| getrawtransaction || -103
+|-
+| getstate || -102, -606
+|-
+| getstateheight ||
+|-
+| getstateroot || -106
+|-
+| getstorage || -102, -104
+|-
+| gettransactionheight|| -103
+|-
+| getunclaimedgas ||
+|-
+| getversion ||
+|-
+| getwalletbalance || -302
+|-
+| getwalletunclaimedgas|| -302
+|-
+| invokecontractverify|| -102, -512
+|-
+| invokefunction ||
+|-
+| invokescript ||
+|-
+| importprivkey || -302
+|-
+| listaddress || -302
+|-
+| listplugins ||
+|-
+| openwallet || -302, -303, -304
+|-
+| sendfrom || -300, -301, -302
+|-
+| sendmany || -300, -301, -302
+|-
+| sendtoaddress || -300, -301, -302
+|-
+| sendrawtransaction || -500, -501, -502, -503, -504, -505, -506, -507, -508, -509, -510, -511
+|-
+| submitblock || -500, -501, -502, -503, -504, -505, -506, -507, -508, -509, -510, -511
+|-
+| submitoracleresponse|| -508, -602, -603, -604, -605
+|-
+| terminatesession || -107, -601
+|-
+| traverseiterator || -107, -108, -601
+|-
+| validateaddress ||
+|-
+| verifyproof || -606, -607
+|}
+
+
+==Rationale==
+
+A large set of codes and behavior nuances is directly inhereted from current
+implementations. New ones are added where clients need more details to
+properly interpret server response. The most important changes are in the
+verification group, specific errors allow clients to adjust the behavior
+accordingly: fail, retry or wait.
+
+==Backwards Compatibility==
+
+* -100 code is gone completely, it's returned for a very wide variety of different problems at the moment, so the code itself shouldn't matter much
+* -101 and -102 errors change their meaning, they're only used in invokecontractverify call which is not very popular
+* -300 and -301 wallet-related errors are completely compatible
+* -400 error is now -302 or -600 (depending on its meaning) which may affect some applications
+* -500 error has the same meaning and is compatible
+* new codes can affect client applications that expect only old ones
+
+==References==
+
+* [https://www.jsonrpc.org/specification JSON-RPC 2.0 Specification]
+
+==Implementation==
+
+* https://pkg.go.dev/github.com/nspcc-dev/neo-go@v0.105.1/pkg/neorpc#pkg-constants and server in https://github.com/nspcc-dev/neo-go/tree/v0.105.1/pkg/services/rpcsrv
+* https://github.com/neo-project/neo-modules/pull/815