tendermint/docs/running-in-production.md

Running in production

Logging

Default logging level (main:info,state:info,*:) should suffice for normal operation mode. Read this post for details on how to configure log_level config variable. Some of the modules can be found here. 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 to prevent Denial-of-service attacks. You can read more about it here.

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 or traefik 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", 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
• StackOverflow questions

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.

Tendermint also can report and serve Prometheus metrics. See Metrics.

What happens when my app dies?

You are supposed to run Tendermint under a process supervisor (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.

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 this issue). 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).

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).

Miscellaneous

NOTE: if you are going to use Tendermint in a public domain, make sure you read hardware recommendations (see "4. Hardware") 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) 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.

• p2p.addr_book_strict

By default, Tendermint checks whenever a peer's address is routable before saving it to the address book. The address is considered as routable if the IP is valid and within allowed ranges.

This may not be the case for private networks, where your IP range is usually strictly limited and private. If that case, you need to set addr_book_strict to false (turn off).

• rpc.max_open_connections

By default, the number of simultaneous connections is limited because most OS give you limited number of file descriptors.

If you want to accept greater number of connections, you will need to increase these limits.

Sysctls to tune the system to be able to open more connections

...for N connections, such as 50k:

kern.maxfiles=10000+2*N         # BSD
kern.maxfilesperproc=100+2*N    # BSD
kern.ipc.maxsockets=10000+2*N   # BSD
fs.file-max=10000+2*N           # Linux
net.ipv4.tcp_max_orphans=N      # Linux

# For load-generating clients.
net.ipv4.ip_local_port_range="10000  65535"  # Linux.
net.inet.ip.portrange.first=10000  # BSD/Mac.
net.inet.ip.portrange.last=65535   # (Enough for N < 55535)
net.ipv4.tcp_tw_reuse=1         # Linux
net.inet.tcp.maxtcptw=2*N       # BSD

# If using netfilter on Linux:
net.netfilter.nf_conntrack_max=N
echo $((N/8)) > /sys/module/nf_conntrack/parameters/hashsize

The similar option exists for limiting the number of gRPC connections - rpc.grpc_max_open_connections.