rpc: implement the ADR 075 /events method (#7965)

This method implements the eventlog extension interface to expose ABCI metadata
to the log for query processing. Only the types that have ABCI events need to
implement this.

- Add an event log to the environment
- Add a sketch of the handler method
- Add an /events RPCFunc to the route map
- Implement query logic
- Subscribe to pubsub if confingured, handle termination

types/events.go

@@ -92,7 +92,13 @@ var (
 // ENCODING / DECODING
 
 // EventData is satisfied by types that can be published as event data.
+//
+// Implementations of this interface that contain ABCI event metadata should
+// also implement the eventlog.ABCIEventer extension interface to expose those
+// metadata to the event log machinery. Event data that do not contain ABCI
+// metadata can safely omit this.
 type EventData interface {
+	// The value must support encoding as a type-tagged JSON object.
 	jsontypes.Tagged
 }
 
@@ -125,6 +131,9 @@ type EventDataNewBlock struct {
 // TypeTag implements the required method of jsontypes.Tagged.
 func (EventDataNewBlock) TypeTag() string { return "tendermint/event/NewBlock" }
 
+// ABCIEvents implements the eventlog.ABCIEventer interface.
+func (e EventDataNewBlock) ABCIEvents() []abci.Event { return e.ResultFinalizeBlock.Events }
+
 type EventDataNewBlockHeader struct {
 	Header Header `json:"header"`
 
@@ -135,6 +144,9 @@ type EventDataNewBlockHeader struct {
 // TypeTag implements the required method of jsontypes.Tagged.
 func (EventDataNewBlockHeader) TypeTag() string { return "tendermint/event/NewBlockHeader" }
 
+// ABCIEvents implements the eventlog.ABCIEventer interface.
+func (e EventDataNewBlockHeader) ABCIEvents() []abci.Event { return e.ResultFinalizeBlock.Events }
+
 type EventDataNewEvidence struct {
 	Evidence Evidence `json:"evidence"`
 
@@ -152,6 +164,15 @@ type EventDataTx struct {
 // TypeTag implements the required method of jsontypes.Tagged.
 func (EventDataTx) TypeTag() string { return "tendermint/event/Tx" }
 
+// ABCIEvents implements the eventlog.ABCIEventer interface.
+func (e EventDataTx) ABCIEvents() []abci.Event {
+	base := []abci.Event{
+		eventWithAttr(TxHashKey, fmt.Sprintf("%X", Tx(e.Tx).Hash())),
+		eventWithAttr(TxHeightKey, fmt.Sprintf("%d", e.Height)),
+	}
+	return append(base, e.Result.Events...)
+}
+
 // NOTE: This goes into the replay WAL
 type EventDataRoundState struct {
 	Height int64  `json:"height,string"`
@@ -298,3 +319,16 @@ type BlockEventPublisher interface {
 type TxEventPublisher interface {
 	PublishEventTx(context.Context, EventDataTx) error
 }
+
+// eventWithAttr constructs a single abci.Event with a single attribute.
+// The type of the event and the name of the attribute are obtained by
+// splitting the event type on period (e.g., "foo.bar").
+func eventWithAttr(etype, value string) abci.Event {
+	parts := strings.SplitN(etype, ".", 2)
+	return abci.Event{
+		Type: parts[0],
+		Attributes: []abci.EventAttribute{{
+			Key: parts[1], Value: value,
+		}},
+	}
+}

types/events_test.go

@@ -7,6 +7,22 @@ import (
 	"github.com/stretchr/testify/assert"
 )
 
+// Verify that the event data types satisfy their shared interface.
+var (
+	_ EventData = EventDataBlockSyncStatus{}
+	_ EventData = EventDataCompleteProposal{}
+	_ EventData = EventDataNewBlock{}
+	_ EventData = EventDataNewBlockHeader{}
+	_ EventData = EventDataNewEvidence{}
+	_ EventData = EventDataNewRound{}
+	_ EventData = EventDataRoundState{}
+	_ EventData = EventDataStateSyncStatus{}
+	_ EventData = EventDataTx{}
+	_ EventData = EventDataValidatorSetUpdates{}
+	_ EventData = EventDataVote{}
+	_ EventData = EventDataString("")
+)
+
 func TestQueryTxFor(t *testing.T) {
 	tx := Tx("foo")
 	assert.Equal(t,