tendermint/docs/tendermint-core/configuration.md

---
order: 3
---

# Configuration

Tendermint Core can be configured via a TOML file in
`$TMHOME/config/config.toml`. Some of these parameters can be overridden by
command-line flags. For most users, the options in the `##### main base configuration options #####` are intended to be modified while config options
further below are intended for advance power users.

## Options

The default configuration file create by `tendermint init` has all
the parameters set with their default values. It will look something
like the file below, however, double check by inspecting the
`config.toml` created with your version of `tendermint` installed:

```toml
# This is a TOML config file.
# For more information, see https://github.com/toml-lang/toml

# NOTE: Any path below can be absolute (e.g. "/var/myawesomeapp/data") or
# relative to the home directory (e.g. "data"). The home directory is
# "$HOME/.tendermint" by default, but could be changed via $TMHOME env variable
# or --home cmd flag.

##### main base config options #####

# TCP or UNIX socket address of the ABCI application,
# or the name of an ABCI application compiled in with the Tendermint binary
proxy_app = "tcp://127.0.0.1:26658"

# A custom human readable name for this node
moniker = "anonymous"

# If this node is many blocks behind the tip of the chain, FastSync
# allows them to catchup quickly by downloading blocks in parallel
# and verifying their commits
fast_sync = true

# Database backend: goleveldb | cleveldb | boltdb | rocksdb | badgerdb
# * goleveldb (github.com/syndtr/goleveldb - most popular implementation)
#   - pure go
#   - stable
# * cleveldb (uses levigo wrapper)
#   - fast
#   - requires gcc
#   - use cleveldb build tag (go build -tags cleveldb)
# * boltdb (uses etcd's fork of bolt - github.com/etcd-io/bbolt)
#   - EXPERIMENTAL
#   - may be faster is some use-cases (random reads - indexer)
#   - use boltdb build tag (go build -tags boltdb)
# * rocksdb (uses github.com/tecbot/gorocksdb)
#   - EXPERIMENTAL
#   - requires gcc
#   - use rocksdb build tag (go build -tags rocksdb)
# * badgerdb (uses github.com/dgraph-io/badger)
#   - EXPERIMENTAL
#   - use badgerdb build tag (go build -tags badgerdb)
db_backend = "goleveldb"

# Database directory
db_dir = "data"

# Output level for logging, including package level options
log_level = "main:info,state:info,*:error"

# Output format: 'plain' (colored text) or 'json'
log_format = "plain"

##### additional base config options #####

# Path to the JSON file containing the initial validator set and other meta data
genesis_file = "config/genesis.json"

# Path to the JSON file containing the private key to use as a validator in the consensus protocol
priv_validator_file = "config/priv_validator.json"

# TCP or UNIX socket address for Tendermint to listen on for
# connections from an external PrivValidator process
priv_validator_laddr = ""

# Path to the JSON file containing the private key to use for node authentication in the p2p protocol
node_key_file = "config/node_key.json"

# Mechanism to connect to the ABCI application: socket | grpc
abci = "socket"

# TCP or UNIX socket address for the profiling server to listen on
prof_laddr = ""

# If true, query the ABCI app on connecting to a new peer
# so the app can decide if we should keep the connection or not
filter_peers = false

##### advanced configuration options #####

##### rpc server configuration options #####
[rpc]

# TCP or UNIX socket address for the RPC server to listen on
laddr = "tcp://0.0.0.0:26657"

# A list of origins a cross-domain request can be executed from
# Default value '[]' disables cors support
# Use '["*"]' to allow any origin
cors_allowed_origins = []

# A list of methods the client is allowed to use with cross-domain requests
cors_allowed_methods = ["HEAD", "GET", "POST"]

# A list of non simple headers the client is allowed to use with cross-domain requests
cors_allowed_headers = ["Origin", "Accept", "Content-Type", "X-Requested-With", "X-Server-Time"]

# TCP or UNIX socket address for the gRPC server to listen on
# NOTE: This server only supports /broadcast_tx_commit
grpc_laddr = ""

# Maximum number of simultaneous connections.
# Does not include RPC (HTTP&WebSocket) connections. See max_open_connections
# If you want to accept a larger number than the default, make sure
# you increase your OS limits.
# 0 - unlimited.
# Should be < {ulimit -Sn} - {MaxNumInboundPeers} - {MaxNumOutboundPeers} - {N of wal, db and other open files}
# 1024 - 40 - 10 - 50 = 924 = ~900
grpc_max_open_connections = 900

# Activate unsafe RPC commands like /dial_seeds and /unsafe_flush_mempool
unsafe = false

# Maximum number of simultaneous connections (including WebSocket).
# Does not include gRPC connections. See grpc_max_open_connections
# If you want to accept a larger number than the default, make sure
# you increase your OS limits.
# 0 - unlimited.
# Should be < {ulimit -Sn} - {MaxNumInboundPeers} - {MaxNumOutboundPeers} - {N of wal, db and other open files}
# 1024 - 40 - 10 - 50 = 924 = ~900
max_open_connections = 900

# Maximum number of unique clientIDs that can /subscribe
# If you're using /broadcast_tx_commit, set to the estimated maximum number
# of broadcast_tx_commit calls per block.
max_subscription_clients = 100

# Maximum number of unique queries a given client can /subscribe to
# If you're using GRPC (or Local RPC client) and /broadcast_tx_commit, set to
# the estimated # maximum number of broadcast_tx_commit calls per block.
max_subscriptions_per_client = 5

# How long to wait for a tx to be committed during /broadcast_tx_commit.
# WARNING: Using a value larger than 10s will result in increasing the
# global HTTP write timeout, which applies to all connections and endpoints.
# See https://github.com/tendermint/tendermint/issues/3435
timeout_broadcast_tx_commit = "10s"

# Maximum size of request body, in bytes
max_body_bytes = {{ .RPC.MaxBodyBytes }}

# Maximum size of request header, in bytes
max_header_bytes = {{ .RPC.MaxHeaderBytes }}

# The path to a file containing certificate that is used to create the HTTPS server.
# Migth be either absolute path or path related to tendermint's config directory.
# If the certificate is signed by a certificate authority,
# the certFile should be the concatenation of the server's certificate, any intermediates,
# and the CA's certificate.
# NOTE: both tls_cert_file and tls_key_file must be present for Tendermint to create HTTPS server. Otherwise, HTTP server is run.
tls_cert_file = ""

# The path to a file containing matching private key that is used to create the HTTPS server.
# Migth be either absolute path or path related to tendermint's config directory.
# NOTE: both tls_cert_file and tls_key_file must be present for Tendermint to create HTTPS server. Otherwise, HTTP server is run.
tls_key_file = ""

##### peer to peer configuration options #####
[p2p]

# Address to listen for incoming connections
laddr = "tcp://0.0.0.0:26656"

# Address to advertise to peers for them to dial
# If empty, will use the same port as the laddr,
# and will introspect on the listener or use UPnP
# to figure out the address.
external_address = ""

# Comma separated list of seed nodes to connect to
seeds = ""

# Comma separated list of nodes to keep persistent connections to
persistent_peers = ""

# UPNP port forwarding
upnp = false

# Path to address book
addr_book_file = "config/addrbook.json"

# Set true for strict address routability rules
# Set false for private or local networks
addr_book_strict = true

# Maximum number of inbound peers
max_num_inbound_peers = 40

# Maximum number of outbound peers to connect to, excluding persistent peers
max_num_outbound_peers = 10

# Time to wait before flushing messages out on the connection
flush_throttle_timeout = "100ms"

# Maximum size of a message packet payload, in bytes
max_packet_msg_payload_size = 1024

# Rate at which packets can be sent, in bytes/second
send_rate = 5120000

# Rate at which packets can be received, in bytes/second
recv_rate = 5120000

# Set true to enable the peer-exchange reactor
pex = true

# Seed mode, in which node constantly crawls the network and looks for
# peers. If another node asks it for addresses, it responds and disconnects.
#
# Does not work if the peer-exchange reactor is disabled.
seed_mode = false

# Comma separated list of peer IDs to keep private (will not be gossiped to other peers)
private_peer_ids = ""

# Toggle to disable guard against peers connecting from the same ip.
allow_duplicate_ip = false

# Peer connection configuration.
handshake_timeout = "20s"
dial_timeout = "3s"

##### mempool configuration options #####
[mempool]

recheck = true
broadcast = true
wal_dir = ""

# Maximum number of transactions in the mempool
size = 5000

# Limit the total size of all txs in the mempool.
# This only accounts for raw transactions (e.g. given 1MB transactions and
# max_txs_bytes=5MB, mempool will only accept 5 transactions).
max_txs_bytes = 1073741824

# Size of the cache (used to filter transactions we saw earlier) in transactions
cache_size = 10000

# Maximum size of a single transaction.
# NOTE: the max size of a tx transmitted over the network is {max_tx_bytes} + {amino overhead}.
max_tx_bytes = 1048576

##### fast sync configuration options #####
[fastsync]

# Fast Sync version to use:
#   1) "v0" (default) - the legacy fast sync implementation
#   2) "v1" - refactor of v0 version for better testability
#   2) "v2" - complete redesign of v0, optimized for testability & readability
version = "v0"

##### consensus configuration options #####
[consensus]

wal_file = "data/cs.wal/wal"

timeout_propose = "3s"
timeout_propose_delta = "500ms"
timeout_prevote = "1s"
timeout_prevote_delta = "500ms"
timeout_precommit = "1s"
timeout_precommit_delta = "500ms"
timeout_commit = "1s"

# Make progress as soon as we have all the precommits (as if TimeoutCommit = 0)
skip_timeout_commit = false

# EmptyBlocks mode and possible interval between empty blocks
create_empty_blocks = true
create_empty_blocks_interval = "0s"

# Reactor sleep duration parameters
peer_gossip_sleep_duration = "100ms"
peer_query_maj23_sleep_duration = "2s"

# Block time parameters. Corresponds to the minimum time increment between consecutive blocks.
blocktime_iota = "1s"

##### transactions indexer configuration options #####
[tx_index]

# What indexer to use for transactions
#
# Options:
#   1) "null"
#   2) "kv" (default) - the simplest possible indexer, backed by key-value storage (defaults to levelDB; see DBBackend).
indexer = "kv"

# Comma-separated list of compositeKeys to index (by default the only key is "tx.hash")
# Remember that Event has the following structure: type.key
# type: [
#  key: value,
#  ...
# ]
#
# You can also index transactions by height by adding "tx.height" event here.
#
# It's recommended to index only a subset of keys due to possible memory
# bloat. This is, of course, depends on the indexer's DB and the volume of
# transactions.
index_keys = ""

# When set to true, tells indexer to index all compositeKeys (predefined keys:
# "tx.hash", "tx.height" and all keys from DeliverTx responses).
#
# Note this may be not desirable (see the comment above). IndexEvents has a
# precedence over IndexAllEvents (i.e. when given both, IndexEvents will be
# indexed).
index_all_keys = false

##### instrumentation configuration options #####
[instrumentation]

# When true, Prometheus metrics are served under /metrics on
# PrometheusListenAddr.
# Check out the documentation for the list of available metrics.
prometheus = false

# Address to listen for Prometheus collector(s) connections
prometheus_listen_addr = ":26660"

# Maximum number of simultaneous connections.
# If you want to accept a larger number than the default, make sure
# you increase your OS limits.
# 0 - unlimited.
max_open_connections = 3

# Instrumentation namespace
namespace = "tendermint"
```

## Empty blocks VS no empty blocks

### create_empty_blocks = true

If `create_empty_blocks` is set to `true` in your config, blocks will be
created ~ every second (with default consensus parameters). You can regulate
the delay between blocks by changing the `timeout_commit`. E.g. `timeout_commit = "10s"` should result in ~ 10 second blocks.

### create_empty_blocks = false

In this setting, blocks are created when transactions received.

Note after the block H, Tendermint creates something we call a "proof block"
(only if the application hash changed) H+1. The reason for this is to support
proofs. If you have a transaction in block H that changes the state to X, the
new application hash will only be included in block H+1. If after your
transaction is committed, you want to get a light-client proof for the new state
(X), you need the new block to be committed in order to do that because the new
block has the new application hash for the state X. That's why we make a new
(empty) block if the application hash changes. Otherwise, you won't be able to
make a proof for the new state.

Plus, if you set `create_empty_blocks_interval` to something other than the
default (`0`), Tendermint will be creating empty blocks even in the absence of
transactions every `create_empty_blocks_interval`. For instance, with
`create_empty_blocks = false` and `create_empty_blocks_interval = "30s"`,
Tendermint will only create blocks if there are transactions, or after waiting
30 seconds without receiving any transactions.

## Consensus timeouts explained

There's a variety of information about timeouts in [Running in
production](./running-in-production.md)

You can also find more detailed technical explanation in the spec: [The latest
gossip on BFT consensus](https://arxiv.org/abs/1807.04938).

```toml
[consensus]
...

timeout_propose = "3s"
timeout_propose_delta = "500ms"
timeout_prevote = "1s"
timeout_prevote_delta = "500ms"
timeout_precommit = "1s"
timeout_precommit_delta = "500ms"
timeout_commit = "1s"
```

Note that in a successful round, the only timeout that we absolutely wait no
matter what is `timeout_commit`.

Here's a brief summary of the timeouts:

- `timeout_propose` = how long we wait for a proposal block before prevoting
  nil
- `timeout_propose_delta` = how much timeout_propose increases with each round
- `timeout_prevote` = how long we wait after receiving +2/3 prevotes for
  anything (ie. not a single block or nil)
- `timeout_prevote_delta` = how much the timeout_prevote increases with each
  round
- `timeout_precommit` = how long we wait after receiving +2/3 precommits for
  anything (ie. not a single block or nil)
- `timeout_precommit_delta` = how much the timeout_precommit increases with
  each round
- `timeout_commit` = how long we wait after committing a block, before starting
  on the new height (this gives us a chance to receive some more precommits,
  even though we already have +2/3)