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eth/tracers/logger: use omitempty to reduce log bloat #24547

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merged 4 commits into from
Mar 29, 2022
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eth/tracers/logger: use omitempty to reduce log bloat #24547

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c792f62
eth/tracers/logger: use JSON struct tag ",omitempty" to reduce log bl…
odeke-em Mar 2, 2022
84e4daa
eth/tracers: fix review concerns
holiman Mar 16, 2022
b749723
eth/tracers/logger: apply changes at the right places
holiman Mar 16, 2022
660c1c4
eth/tracers/logger: import fix
holiman Mar 17, 2022
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2 changes: 1 addition & 1 deletion eth/tracers/logger/gen_structlog.go
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8 changes: 4 additions & 4 deletions eth/tracers/logger/logger.go
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Original file line number Diff line number Diff line change
Expand Up @@ -80,10 +80,10 @@ type StructLog struct {
type structLogMarshaling struct {
Gas math.HexOrDecimal64
GasCost math.HexOrDecimal64
Memory hexutil.Bytes
ReturnData hexutil.Bytes
OpName string `json:"opName"` // adds call to OpName() in MarshalJSON
ErrorString string `json:"error"` // adds call to ErrorString() in MarshalJSON
Memory hexutil.Bytes `json:",omitempty"`
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❯ ./evm --debug --json --code "0x60006000" run                                                                                                                                 <<<
{"pc":0,"op":96,"gas":"0x2540be400","gasCost":"0x3","memory":"0x","memSize":0,"stack":[],"returnData":"0x","depth":1,"refund":0,"opName":"PUSH1"}
{"pc":2,"op":96,"gas":"0x2540be3fd","gasCost":"0x3","memory":"0x","memSize":0,"stack":["0x0"],"returnData":"0x","depth":1,"refund":0,"opName":"PUSH1"}
{"pc":4,"op":0,"gas":"0x2540be3fa","gasCost":"0x0","memory":"0x","memSize":0,"stack":["0x0","0x0"],"returnData":"0x","depth":1,"refund":0,"opName":"STOP"}

memory and returnData still have 0x when they're empty so they're not really omitted

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@holiman holiman Mar 16, 2022 •
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Here's how I want it to work (not sure it does):

  • If you run it with memory enabled, and returndata enabled, then you get "memory":"0x" if memory is indeed blank.
  • If you run it with memory disabled, then we don't output "memory" at all.

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@holiman holiman Mar 16, 2022 •
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(not sure it does):

Narrator: And it doesn't

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The type Bytes seems to encode 0x even if the slice is nil

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I haven't studied in-dept how omitempty works. But it seems like I cannot make it differentiate between a null-slice and an empty array.

So the choice is:

  • Always output 0x as memory, even when memory disabled, or
  • Never display blank memory.

This PR currently uses option 2. Makes the output a bit less verbose.

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The type Bytes seems to encode 0x even if the slice is nil

Yes.. omitempty might just look at the encoded return value, and check if it's empty. We don't want to change the marshaller for types.Bytes, so I think we'll have to just pick one behaviour.

ReturnData hexutil.Bytes `json:",omitempty"`
OpName string `json:"opName"` // adds call to OpName() in MarshalJSON
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ErrorString string `json:"error,omitempty"` // adds call to ErrorString() in MarshalJSON
}

// OpName formats the operand name in a human-readable format.
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26 changes: 26 additions & 0 deletions eth/tracers/logger/logger_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,7 @@
package logger

import (
"encoding/json"
"math/big"
"testing"

Expand Down Expand Up @@ -72,3 +73,28 @@ func TestStoreCapture(t *testing.T) {
t.Errorf("expected %x, got %x", exp, logger.storage[contract.Address()][index])
}
}

// Tests that blank fields don't appear in logs when JSON marshalled, to reduce
// logs bloat and confusion. See https://github.com/ethereum/go-ethereum/issues/24487
func TestStructLogMarshalingOmitEmpty(t *testing.T) {
tests := []struct {
name string
log *structLogMarshaling
want string
}{
{"empty err and no fields", &structLogMarshaling{ErrorString: ""}, `{"Gas":"0x0","GasCost":"0x0","opName":""}`},
{"with err", &structLogMarshaling{ErrorString: "this failed"}, `{"Gas":"0x0","GasCost":"0x0","opName":"","error":"this failed"}`},
}

for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
blob, err := json.Marshal(tt.log)
if err != nil {
t.Fatal(err)
}
if have, want := string(blob), tt.want; have != want {
t.Fatalf("mismatched results\n\thave: %q\n\twant: %q", have, want)
}
})
}
}