This is part of the work described by #7156.

Remove "unbuffered subscriptions" from the pubsub service.
Replace them with a dedicated blocking "observer" mechanism.
Use the observer mechanism for indexing.

Add a SubscribeWithArgs method and deprecate the old Subscribe
method. Remove SubscribeUnbuffered entirely (breaking).

Rework the Subscription interface to eliminate exposed channels.
Subscriptions now use a context to manage lifecycle notifications.

Internalize the eventbus package.

closes #2498 
solves part of #3365

Note: difficult to test the event emit in SwitchToFastSync part, might need to change `stateSyncReactor` to an interface in the `nodeImpl` struct

Adds `block_id` to the `newblock` websocket event

Closes #6028

## Description

Work towards enabling errcheck

ref #5059

* consensus: fix TestSimulateValidatorsChange

* fix selfIndex calculation

* exit from goroutine after 1 sec

* reuse the function

The PR added a new field `index` to event attribute, that will cause indexer service to index the event if set to true.

* lint: golint issue fixes

- on my local machine golint is a lot stricter than the bot so slowly going through and fixing things.

Signed-off-by: Marko Baricevic <marbar3778@yahoo.com>

* more fixes from golint

* remove isPeerPersistentFn

* add changelog entry

* libs/common: refactor libs/common 2

- move random function to there own pkg

Signed-off-by: Marko Baricevic <marbar3778@yahoo.com>

* change imports and usage throughout repo

* fix goimports

* add changelog entry

* libs/common: Refactor libs/common 01

Signed-off-by: Marko Baricevic <marbar3778@yahoo.com>

* regenerate proto files, move intslice to where its used

* update kv.KVPair(s) to kv.Pair(s)

* add changelog entry

* make intInSlice private

* Rename Tag(s) to Event(s)

- tag was replaced with event, but in some places it still mentions tag, would be easier to understand if we tried to replace it with event to not confuse people.

Signed-off-by: Marko Baricevic <marbar3778@yahoo.com>

* more  changes from tag -> event

* rename events to compositeKeys and keys

* Apply suggestions from code review

Co-Authored-By: Anton Kaliaev <anton.kalyaev@gmail.com>

* add minor documentation on how composite keys are constructed

* rename eventkey to compositekey

Co-Authored-By: Anton Kaliaev <anton.kalyaev@gmail.com>

* add changelog entry & add info to regenerate confid to changelog entry

* Pin range scope vars

* Don't disable scopelint

This PR repairs linter errors seen when running the following commands:
golangci-lint run --no-config --disable-all=true --enable=scopelint

Contributes to #3262

## PR

This PR introduces a fundamental breaking change to the structure of ABCI response and tx tags and the way they're processed. Namely, the SDK can support more complex and aggregated events for distribution and slashing. In addition, block responses can include duplicate keys in events.

    Implement new Event type. An event has a type and a list of KV pairs (ie. list-of-lists). Typical events may look like:

"rewards": [{"amount": "5000uatom", "validator": "...", "recipient": "..."}]
"sender": [{"address": "...", "balance": "100uatom"}]

The events are indexed by {even.type}.{even.attribute[i].key}/.... In this case a client would subscribe or query for rewards.recipient='...'

    ABCI response types and related types now include Events []Event instead of Tags []cmn.KVPair.
    PubSub logic now publishes/matches against map[string][]string instead of map[string]string to support duplicate keys in response events (from #1385). A match is successful if the value is found in the slice of strings.

closes: #1859
closes: #2905

## Commits:

* Implement Event ABCI type and updates responses to use events

* Update messages_test.go

* Update kvstore.go

* Update event_bus.go

* Update subscription.go

* Update pubsub.go

* Update kvstore.go

* Update query logic to handle slice of strings in events

* Update Empty#Matches and unit tests

* Update pubsub logic

* Update EventBus#Publish

* Update kv tx indexer

* Update godocs

* Update ResultEvent to use slice of strings; update RPC

* Update more tests

* Update abci.md

* Check for key in validateAndStringifyEvents

* Fix KV indexer to skip empty keys

* Fix linting errors

* Update CHANGELOG_PENDING.md

* Update docs/spec/abci/abci.md

Co-Authored-By: Federico Kunze <31522760+fedekunze@users.noreply.github.com>

* Update abci/types/types.proto

Co-Authored-By: Ethan Buchman <ethan@coinculture.info>

* Update docs/spec/abci/abci.md

Co-Authored-By: Ethan Buchman <ethan@coinculture.info>

* Update libs/pubsub/query/query.go

Co-Authored-By: Ethan Buchman <ethan@coinculture.info>

* Update match function to match if ANY value matches

* Implement TestSubscribeDuplicateKeys

* Update TestMatches to include multi-key test cases

* Update events.go

* Update Query interface godoc

* Update match godoc

* Add godoc for matchValue

* DRY-up tx indexing

* Return error from PublishWithEvents in EventBus#Publish

* Update PublishEventNewBlockHeader to return an error

* Fix build

* Update events doc in ABCI

* Update ABCI events godoc

* Implement TestEventBusPublishEventTxDuplicateKeys

* Update TestSubscribeDuplicateKeys to be table-driven

* Remove mod file

* Remove markdown from events godoc

* Implement TestTxSearchDeprecatedIndexing test

* green pubsub tests :OK:

* get rid of clientToQueryMap

* Subscribe and SubscribeUnbuffered

* start adapting other pkgs to new pubsub

* nope

* rename MsgAndTags to Message

* remove TagMap

it does not bring any additional benefits

* bring back EventSubscriber

* fix test

* fix data race in TestStartNextHeightCorrectly

```
Write at 0x00c0001c7418 by goroutine 796:
  github.com/tendermint/tendermint/consensus.TestStartNextHeightCorrectly()
      /go/src/github.com/tendermint/tendermint/consensus/state_test.go:1296 +0xad
  testing.tRunner()
      /usr/local/go/src/testing/testing.go:827 +0x162

Previous read at 0x00c0001c7418 by goroutine 858:
  github.com/tendermint/tendermint/consensus.(*ConsensusState).addVote()
      /go/src/github.com/tendermint/tendermint/consensus/state.go:1631 +0x1366
  github.com/tendermint/tendermint/consensus.(*ConsensusState).tryAddVote()
      /go/src/github.com/tendermint/tendermint/consensus/state.go:1476 +0x8f
  github.com/tendermint/tendermint/consensus.(*ConsensusState).handleMsg()
      /go/src/github.com/tendermint/tendermint/consensus/state.go:667 +0xa1e
  github.com/tendermint/tendermint/consensus.(*ConsensusState).receiveRoutine()
      /go/src/github.com/tendermint/tendermint/consensus/state.go:628 +0x794

Goroutine 796 (running) created at:
  testing.(*T).Run()
      /usr/local/go/src/testing/testing.go:878 +0x659
  testing.runTests.func1()
      /usr/local/go/src/testing/testing.go:1119 +0xa8
  testing.tRunner()
      /usr/local/go/src/testing/testing.go:827 +0x162
  testing.runTests()
      /usr/local/go/src/testing/testing.go:1117 +0x4ee
  testing.(*M).Run()
      /usr/local/go/src/testing/testing.go:1034 +0x2ee
  main.main()
      _testmain.go:214 +0x332

Goroutine 858 (running) created at:
  github.com/tendermint/tendermint/consensus.(*ConsensusState).startRoutines()
      /go/src/github.com/tendermint/tendermint/consensus/state.go:334 +0x221
  github.com/tendermint/tendermint/consensus.startTestRound()
      /go/src/github.com/tendermint/tendermint/consensus/common_test.go:122 +0x63
  github.com/tendermint/tendermint/consensus.TestStateFullRound1()
      /go/src/github.com/tendermint/tendermint/consensus/state_test.go:255 +0x397
  testing.tRunner()
      /usr/local/go/src/testing/testing.go:827 +0x162
```

* fixes after my own review

* fix formatting

* wait 100ms before kicking a subscriber out

+ a test for indexer_service

* fixes after my second review

* no timeout

* add changelog entries

* fix merge conflicts

* fix typos after Thane's review

Co-Authored-By: melekes <anton.kalyaev@gmail.com>

* reformat code

* rewrite indexer service in the attempt to fix failing test

https://github.com/tendermint/tendermint/pull/3227/#issuecomment-462316527

* Revert "rewrite indexer service in the attempt to fix failing test"

This reverts commit 0d9107a098.

* another attempt to fix indexer

* fixes after Ethan's review

* use unbuffered channel when indexing transactions

Refs https://github.com/tendermint/tendermint/pull/3227#discussion_r258786716

* add a comment for EventBus#SubscribeUnbuffered

* format code

* 2871 remove proposalHeartbeat infrastructure

* 2871 add preliminary changelog entry

This commit makes both EventNewBlock and EventNewBlockHeader emit tags
on the event bus, so subscribers can use them in queries.

* add proposer info to EventCompleteProposal

* create separate EventData structure for CompleteProposal

* cant us rs.Proposal to get BlockID because it is not guaranteed to be set yet

* copying RoundState isnt helping us here

* add Step back to make compatible with original RoundState event. update changelog

* add NewRound event

* fix test

* remove unneeded RoundState

* put height round step into a struct

* pull out ValidatorInfo struct. add ensureProposal assert

* remove height-round-state sub-struct refactor

* minor fixes from review

Refs #1916

* remove gogoproto from tools

because it's not a binary

* update protobuf version to 3.6.1 in `make get_protoc`

* update libs/common/types.pb.go and rpc/grpc/types.pb.go

* fix app tests

Refs #1861

We don't use the fee field and its likely just confusing.

We can add backwards compatible priority (instead of fee) later.

Note priority is better than fee because it lets the app do the math on how to rank order transactions, rather than forcing that into tendermint (ie. if we return fee, priority would be fee/gas)

Currently the top level directory contains basically all of the code
for the crypto package. This PR moves the crypto code into submodules
in a similar manner to what `golang/x/crypto` does. This improves code
organization.

Ref discussion: https://github.com/tendermint/tendermint/pull/1966

Closes #1956

This commit switches all usage of math/rand to cmn's rand. The only
exceptions are within the random file itself, the tools package, and the
crypto package. In tools you don't want it to lock between the go-routines.
The crypto package doesn't use it so the crypto package have no other
dependencies within tendermint/tendermint for easier portability.

Crypto/rand usage is unadjusted.

Closes #1343

Refs #693

This reverts commit d02c5d1e30.

This reverts commit 96a3502

* all: gofmt

Run 'gofmt -w .' from project root.

* Update changelog to say that I ran gofmt

* Revert "Update changelog to say that I ran gofmt"

This reverts commit 956f133ff0.

* expect all tags to be strings

Refs #1369

* port changes from https://github.com/tendermint/tmlibs/pull/204

Refs #1369

Refs #847

Refs #1369

comment out failing consensus tests for now

rewrite rpc httpclient to use new pubsub package

import pubsub as tmpubsub, query as tmquery

make event IDs constants
EventKey -> EventTypeKey

rename EventsPubsub to PubSub

mempool does not use pubsub

rename eventsSub to pubsub

new subscribe API

fix channel size issues and consensus tests bugs

refactor rpc client

add missing discardFromChan method

add mutex

rename pubsub to eventBus

remove IsRunning from WSRPCConnection interface (not needed)

add a comment in broadcastNewRoundStepsAndVotes

rename registerEventCallbacks to broadcastNewRoundStepsAndVotes

See https://dave.cheney.net/2014/03/19/channel-axioms

stop eventBuses after reactor tests

remove unnecessary Unsubscribe

return subscribe helper function

move discardFromChan to where it is used

subscribe now returns an err

this gives us ability to refuse to subscribe if pubsub is at its max
capacity.

use context for control overflow

cache queries

handle err when subscribing in replay_test

rename testClientID to testSubscriber

extract var

set channel buffer capacity to 1 in replay_file

fix byzantine_test

unsubscribe from single event, not all events

refactor httpclient to return events to appropriate channels

return failing testReplayCrashBeforeWriteVote test

fix TestValidatorSetChanges

refactor code a bit

fix testReplayCrashBeforeWriteVote

add comment

fix TestValidatorSetChanges

fixes from Bucky's review

update comment [ci skip]

test TxEventBuffer

update changelog

fix TestValidatorSetChanges (2nd attempt)

only do wg.Done when no errors

benchmark event bus

create pubsub server inside NewEventBus

only expose config params (later if needed)

set buffer capacity to 0 so we are not testing cache

new tx event format: key = "Tx" plus a tag {"tx.hash": XYZ}

This should allow to subscribe to all transactions! or a specific one
using a query: "tm.events.type = Tx and tx.hash = '013ABF99434...'"

use TimeoutCommit instead of afterPublishEventNewBlockTimeout

TimeoutCommit is the time a node waits after committing a block, before
it goes into the next height. So it will finish everything from the last
block, but then wait a bit. The idea is this gives it time to hear more
votes from other validators, to strengthen the commit it includes in the
next block. But it also gives it time to hear about new transactions.

waitForBlockWithUpdatedVals

rewrite WAL crash tests

Task:
test that we can recover from any WAL crash.

Solution:
the old tests were relying on event hub being run in the same thread (we
were injecting the private validator's last signature).

when considering a rewrite, we considered two possible solutions: write
a "fuzzy" testing system where WAL is crashing upon receiving a new
message, or inject failures and trigger them in tests using something
like https://github.com/coreos/gofail.

remove sleep

no cs.Lock around wal.Save

test different cases (empty block, non-empty block, ...)

comments

add comments

test 4 cases: empty block, non-empty block, non-empty block with smaller part size, many blocks

fixes as per Bucky's last review

reset subscriptions on UnsubscribeAll

use a simple counter to track message for which we panicked

also, set a smaller part size for all test cases