Merge pull request #1618 from tendermint/1494-production-notes

[docs] notes about running a production system

docs/index.rst

@@ -58,6 +58,7 @@ Tendermint 102
    subscribing-to-events-via-websocket.rst
    indexing-transactions.rst
    how-to-read-logs.rst
+   running-in-production.rst
 
 Tendermint 201
 --------------

docs/running-in-production.rst

@@ -0,0 +1,203 @@
+Running in production
+=====================
+
+Logging
+-------
+
+Default logging level (``main:info,state:info,*:``) should suffice for normal
+operation mode. Read `this post
+<https://blog.cosmos.network/one-of-the-exciting-new-features-in-0-10-0-release-is-smart-log-level-flag-e2506b4ab756>`__
+for details on how to configure ``log_level`` config variable. Some of the
+modules can be found `here <./how-to-read-logs.html#list-of-modules>`__. If
+you're trying to debug Tendermint or asked to provide logs with debug logging
+level, you can do so by running tendermint with ``--log_level="*:debug"``.
+
+DOS Exposure and Mitigation
+---------------------------
+
+Validators are supposed to setup `Sentry Node Architecture
+<https://blog.cosmos.network/tendermint-explained-bringing-bft-based-pos-to-the-public-blockchain-domain-f22e274a0fdb>`__
+to prevent Denial-of-service attacks. You can read more about it `here
+<https://github.com/tendermint/aib-data/blob/develop/medium/TendermintBFT.md>`__.
+
+P2P
+~~~
+
+The core of the Tendermint peer-to-peer system is ``MConnection``. Each
+connection has ``MaxPacketMsgPayloadSize``, which is the maximum packet size
+and bounded send & receive queues. One can impose restrictions on send &
+receive rate per connection (``SendRate``, ``RecvRate``).
+
+RPC
+~~~
+
+Endpoints returning multiple entries are limited by default to return 30
+elements (100 max).
+
+Rate-limiting and authentication are another key aspects to help protect
+against DOS attacks. While in the future we may implement these features, for
+now, validators are supposed to use external tools like `NGINX
+<https://www.nginx.com/blog/rate-limiting-nginx/>`__ or `traefik
+<https://docs.traefik.io/configuration/commons/#rate-limiting>`__ to achieve
+the same things.
+
+Debugging Tendermint
+--------------------
+
+If you ever have to debug Tendermint, the first thing you should probably do is
+to check out the logs. See `"How to read logs" <./how-to-read-logs.html>`__,
+where we explain what certain log statements mean.
+
+If, after skimming through the logs, things are not clear still, the second
+TODO is to query the `/status` RPC endpoint. It provides the necessary info:
+whenever the node is syncing or not, what height it is on, etc.
+
+```
+$ curl http(s)://{ip}:{rpcPort}/status
+```
+
+`/dump_consensus_state` will give you a detailed overview of the consensus
+state (proposer, lastest validators, peers states). From it, you should be able
+to figure out why, for example, the network had halted.
+
+```
+$ curl http(s)://{ip}:{rpcPort}/dump_consensus_state
+```
+
+There is a reduced version of this endpoint - `/consensus_state`, which
+returns just the votes seen at the current height.
+
+- `Github Issues <https://github.com/tendermint/tendermint/issues>`__
+- `StackOverflow questions <https://stackoverflow.com/questions/tagged/tendermint>`__
+
+Monitoring Tendermint
+---------------------
+
+Each Tendermint instance has a standard `/health` RPC endpoint, which responds
+with 200 (OK) if everything is fine and 500 (or no response) - if something is
+wrong.
+
+Other useful endpoints include mentioned earlier `/status`, `/net_info` and
+`/validators`.
+
+We have a small tool, called tm-monitor, which outputs information from the
+endpoints above plus some statistics. The tool can be found `here
+<https://github.com/tendermint/tools/tree/master/tm-monitor>`__.
+
+What happens when my app dies?
+------------------------------
+
+You are supposed to run Tendermint under a `process supervisor
+<https://en.wikipedia.org/wiki/Process_supervision>`__ (like systemd or runit).
+It will ensure Tendermint is always running (despite possible errors).
+
+Getting back to the original question, if your application dies, Tendermint
+will panic. After a process supervisor restarts your application, Tendermint
+should be able to reconnect successfully. The order of restart does not matter
+for it.
+
+Signal handling
+---------------
+
+We catch SIGINT and SIGTERM and try to clean up nicely. For other signals we
+use the default behaviour in Go: `Default behavior of signals in Go programs
+<https://golang.org/pkg/os/signal/#hdr-Default_behavior_of_signals_in_Go_programs>`__.
+
+Hardware
+--------
+
+Processor and Memory
+~~~~~~~~~~~~~~~~~~~~
+
+While actual specs vary depending on the load and validators count, minimal requirements are:
+
+- 1GB RAM
+- 25GB of disk space
+- 1.4 GHz CPU
+
+SSD disks are preferable for applications with high transaction throughput.
+
+Recommended:
+
+- 2GB RAM
+- 100GB SSD
+- x64 2.0 GHz 2v CPU
+
+While for now, Tendermint stores all the history and it may require significant
+disk space over time, we are planning to implement state syncing (See `#828
+<https://github.com/tendermint/tendermint/issues/828>`__). So, storing all the
+past blocks will not be necessary.
+
+Operating Systems
+~~~~~~~~~~~~~~~~~
+
+Tendermint can be compiled for a wide range of operating systems thanks to Go
+language (the list of $OS/$ARCH pairs can be found `here
+<https://golang.org/doc/install/source#environment>`__).
+
+While we do not favor any operation system, more secure and stable Linux server
+distributions (like Centos) should be preferred over desktop operation systems
+(like Mac OS).
+
+Misc.
+~~~~~
+
+NOTE: if you are going to use Tendermint in a public domain, make sure you read
+`hardware recommendations (see "4. Hardware")
+<https://cosmos.network/validators>`__ for a validator in the Cosmos network.
+
+Configuration parameters
+------------------------
+
+- ``p2p.flush_throttle_timeout``
+  ``p2p.max_packet_msg_payload_size``
+  ``p2p.send_rate``
+  ``p2p.recv_rate``
+
+If you are going to use Tendermint in a private domain and you have a private
+high-speed network among your peers, it makes sense to lower flush throttle
+timeout and increase other params.
+
+::
+
+    [p2p]
+
+    send_rate=20000000 # 2MB/s
+    recv_rate=20000000 # 2MB/s
+    flush_throttle_timeout=10
+    max_packet_msg_payload_size=10240 # 10KB
+
+- ``mempool.recheck``
+
+After every block, Tendermint rechecks every transaction left in the mempool to
+see if transactions committed in that block affected the application state, so
+some of the transactions left may become invalid. If that does not apply to
+your application, you can disable it by setting ``mempool.recheck=false``.
+
+- ``mempool.broadcast``
+
+Setting this to false will stop the mempool from relaying transactions to other
+peers until they are included in a block. It means only the peer you send the
+tx to will see it until it is included in a block.
+
+- ``consensus.skip_timeout_commit``
+
+We want skip_timeout_commit=false when there is economics on the line because
+proposers should wait to hear for more votes. But if you don't care about that
+and want the fastest consensus, you can skip it. It will be kept false by
+default for public deployments (e.g. `Cosmos Hub
+<https://cosmos.network/intro/hub>`__) while for enterprise applications,
+setting it to true is not a problem.
+
+- ``consensus.peer_gossip_sleep_duration``
+
+You can try to reduce the time your node sleeps before checking if theres something to send its peers.
+
+- ``consensus.timeout_commit``
+
+You can also try lowering ``timeout_commit`` (time we sleep before proposing the next block).
+
+- ``consensus.max_block_size_txs``
+
+By default, the maximum number of transactions per a block is 10_000. Feel free
+to change it to suit your needs.

docs/spec/consensus/wal.md

@@ -0,0 +1,33 @@
+# WAL
+
+Consensus module writes every message to the WAL (write-ahead log).
+
+It also issues fsync syscall through
+[File#Sync](https://golang.org/pkg/os/#File.Sync) for messages signed by this
+node (to prevent double signing).
+
+Under the hood, it uses
+[autofile.Group](https://godoc.org/github.com/tendermint/tmlibs/autofile#Group),
+which rotates files when those get too big (> 10MB).
+
+The total maximum size is 1GB. We only need the latest block and the block before it,
+but if the former is dragging on across many rounds, we want all those rounds.
+
+## Replay
+
+Consensus module will replay all the messages of the last height written to WAL
+before a crash (if such occurs).
+
+The private validator may try to sign messages during replay because it runs
+somewhat autonomously and does not know about replay process.
+
+For example, if we got all the way to precommit in the WAL and then crash,
+after we replay the proposal message, the private validator will try to sign a
+prevote. But it will fail. That's ok because we’ll see the prevote later in the
+WAL. Then it will go to precommit, and that time it will work because the
+private validator contains the `LastSignBytes` and then we’ll replay the
+precommit from the WAL.
+
+Make sure to read about [WAL
+corruption](https://tendermint.readthedocs.io/projects/tools/en/master/specification/corruption.html#wal-corruption)
+and recovery strategies.

docs/spec/reactors/block_sync/reactor.md

@@ -47,3 +47,13 @@ type bcStatusResponseMessage struct {
 ## Protocol
 
 TODO
+
+## Channels
+
+Defines `maxMsgSize` for the maximum size of incoming messages,
+`SendQueueCapacity` and `RecvBufferCapacity` for maximum sending and
+receiving buffers respectively. These are supposed to prevent amplification
+attacks by setting up the upper limit on how much data we can receive & send to
+a peer.
+
+Sending incorrectly encoded data will result in stopping the peer.

docs/spec/reactors/consensus/consensus-reactor.md

@@ -342,3 +342,11 @@ It broadcasts `NewRoundStepMessage` or `CommitStepMessage` upon new round state
 broadcasting these messages does not depend on the PeerRoundState; it is sent on the StateChannel. 
 Upon receiving VoteMessage it broadcasts `HasVoteMessage` message to its peers on the StateChannel. 
 `ProposalHeartbeatMessage` is sent the same way on the StateChannel.
+
+## Channels
+
+Defines 4 channels: state, data, vote and vote_set_bits. Each channel
+has  `SendQueueCapacity` and `RecvBufferCapacity` and
+`RecvMessageCapacity` set to `maxMsgSize`.
+
+Sending incorrectly encoded data will result in stopping the peer.

docs/spec/reactors/evidence/reactor.md

@@ -0,0 +1,10 @@
+# Evidence Reactor
+
+## Channels
+
+[#1503](https://github.com/tendermint/tendermint/issues/1503)
+
+Sending invalid evidence will result in stopping the peer.
+
+Sending incorrectly encoded data or data exceeding `maxMsgSize` will result
+in stopping the peer.

docs/spec/reactors/mempool/reactor.md

@@ -0,0 +1,14 @@
+# Mempool Reactor
+
+## Channels
+
+[#1503](https://github.com/tendermint/tendermint/issues/1503)
+
+Mempool maintains a cache of the last 10000 transactions to prevent
+replaying old transactions (plus transactions coming from other
+validators, who are continually exchanging transactions). Read [Replay
+Protection](https://tendermint.readthedocs.io/projects/tools/en/master/app-development.html?#replay-protection)
+for details.
+
+Sending incorrectly encoded data or data exceeding `maxMsgSize` will result
+in stopping the peer.

docs/spec/reactors/pex/reactor.md

@@ -0,0 +1,12 @@
+# PEX Reactor
+
+## Channels
+
+Defines only `SendQueueCapacity`. [#1503](https://github.com/tendermint/tendermint/issues/1503)
+
+Implements rate-limiting by enforcing minimal time between two consecutive
+`pexRequestMessage` requests. If the peer sends us addresses we did not ask,
+it is stopped.
+
+Sending incorrectly encoded data or data exceeding `maxMsgSize` will result
+in stopping the peer.