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  1. # Using Tendermint
  2. This is a guide to using the `tendermint` program from the command line.
  3. It assumes only that you have the `tendermint` binary installed and have
  4. some rudimentary idea of what Tendermint and ABCI are.
  5. You can see the help menu with `tendermint --help`, and the version
  6. number with `tendermint version`.
  7. ## Directory Root
  8. The default directory for blockchain data is `~/.tendermint`. Override
  9. this by setting the `TMHOME` environment variable.
  10. ## Initialize
  11. Initialize the root directory by running:
  12. tendermint init
  13. This will create a new private key (`priv_validator.json`), and a
  14. genesis file (`genesis.json`) containing the associated public key, in
  15. `$TMHOME/config`. This is all that's necessary to run a local testnet
  16. with one validator.
  17. For more elaborate initialization, see the tesnet command:
  18. tendermint testnet --help
  19. ## Run
  20. To run a Tendermint node, use
  21. tendermint node
  22. By default, Tendermint will try to connect to an ABCI application on
  23. [127.0.0.1:26658](127.0.0.1:26658). If you have the `kvstore` ABCI app
  24. installed, run it in another window. If you don't, kill Tendermint and
  25. run an in-process version of the `kvstore` app:
  26. tendermint node --proxy_app=kvstore
  27. After a few seconds you should see blocks start streaming in. Note that
  28. blocks are produced regularly, even if there are no transactions. See
  29. *No Empty Blocks*, below, to modify this setting.
  30. Tendermint supports in-process versions of the `counter`, `kvstore` and
  31. `nil` apps that ship as examples with `abci-cli`. It's easy to compile
  32. your own app in-process with Tendermint if it's written in Go. If your
  33. app is not written in Go, simply run it in another process, and use the
  34. `--proxy_app` flag to specify the address of the socket it is listening
  35. on, for instance:
  36. tendermint node --proxy_app=/var/run/abci.sock
  37. ## Transactions
  38. To send a transaction, use `curl` to make requests to the Tendermint RPC
  39. server, for example:
  40. curl http://localhost:26657/broadcast_tx_commit?tx=\"abcd\"
  41. We can see the chain's status at the `/status` end-point:
  42. curl http://localhost:26657/status | json_pp
  43. and the `latest_app_hash` in particular:
  44. curl http://localhost:26657/status | json_pp | grep latest_app_hash
  45. Visit http://localhost:26657> in your browser to see the list of other
  46. endpoints. Some take no arguments (like `/status`), while others specify
  47. the argument name and use `_` as a placeholder.
  48. ### Formatting
  49. The following nuances when sending/formatting transactions should be
  50. taken into account:
  51. With `GET`:
  52. To send a UTF8 string byte array, quote the value of the tx pramater:
  53. curl 'http://localhost:26657/broadcast_tx_commit?tx="hello"'
  54. which sends a 5 byte transaction: "h e l l o" \[68 65 6c 6c 6f\].
  55. Note the URL must be wrapped with single quoes, else bash will ignore
  56. the double quotes. To avoid the single quotes, escape the double quotes:
  57. curl http://localhost:26657/broadcast_tx_commit?tx=\"hello\"
  58. Using a special character:
  59. curl 'http://localhost:26657/broadcast_tx_commit?tx="€5"'
  60. sends a 4 byte transaction: "€5" (UTF8) \[e2 82 ac 35\].
  61. To send as raw hex, omit quotes AND prefix the hex string with `0x`:
  62. curl http://localhost:26657/broadcast_tx_commit?tx=0x01020304
  63. which sends a 4 byte transaction: \[01 02 03 04\].
  64. With `POST` (using `json`), the raw hex must be `base64` encoded:
  65. curl --data-binary '{"jsonrpc":"2.0","id":"anything","method":"broadcast_tx_commit","params": {"tx": "AQIDBA=="}}' -H 'content-type:text/plain;' http://localhost:26657
  66. which sends the same 4 byte transaction: \[01 02 03 04\].
  67. Note that raw hex cannot be used in `POST` transactions.
  68. ## Reset
  69. **WARNING: UNSAFE** Only do this in development and only if you can
  70. afford to lose all blockchain data!
  71. To reset a blockchain, stop the node, remove the `~/.tendermint/data`
  72. directory and run
  73. tendermint unsafe_reset_priv_validator
  74. This final step is necessary to reset the `priv_validator.json`, which
  75. otherwise prevents you from making conflicting votes in the consensus
  76. (something that could get you in trouble if you do it on a real
  77. blockchain). If you don't reset the `priv_validator.json`, your fresh
  78. new blockchain will not make any blocks.
  79. ## Configuration
  80. Tendermint uses a `config.toml` for configuration. For details, see [the
  81. config specification](./specification/configuration.html).
  82. Notable options include the socket address of the application
  83. (`proxy_app`), the listening address of the Tendermint peer
  84. (`p2p.laddr`), and the listening address of the RPC server
  85. (`rpc.laddr`).
  86. Some fields from the config file can be overwritten with flags.
  87. ## No Empty Blocks
  88. This much requested feature was implemented in version 0.10.3. While the
  89. default behaviour of `tendermint` is still to create blocks
  90. approximately once per second, it is possible to disable empty blocks or
  91. set a block creation interval. In the former case, blocks will be
  92. created when there are new transactions or when the AppHash changes.
  93. To configure Tendermint to not produce empty blocks unless there are
  94. transactions or the app hash changes, run Tendermint with this
  95. additional flag:
  96. tendermint node --consensus.create_empty_blocks=false
  97. or set the configuration via the `config.toml` file:
  98. [consensus]
  99. create_empty_blocks = false
  100. Remember: because the default is to *create empty blocks*, avoiding
  101. empty blocks requires the config option to be set to `false`.
  102. The block interval setting allows for a delay (in seconds) between the
  103. creation of each new empty block. It is set via the `config.toml`:
  104. [consensus]
  105. create_empty_blocks_interval = 5
  106. With this setting, empty blocks will be produced every 5s if no block
  107. has been produced otherwise, regardless of the value of
  108. `create_empty_blocks`.
  109. ## Broadcast API
  110. Earlier, we used the `broadcast_tx_commit` endpoint to send a
  111. transaction. When a transaction is sent to a Tendermint node, it will
  112. run via `CheckTx` against the application. If it passes `CheckTx`, it
  113. will be included in the mempool, broadcasted to other peers, and
  114. eventually included in a block.
  115. Since there are multiple phases to processing a transaction, we offer
  116. multiple endpoints to broadcast a transaction:
  117. /broadcast_tx_async
  118. /broadcast_tx_sync
  119. /broadcast_tx_commit
  120. These correspond to no-processing, processing through the mempool, and
  121. processing through a block, respectively. That is, `broadcast_tx_async`,
  122. will return right away without waiting to hear if the transaction is
  123. even valid, while `broadcast_tx_sync` will return with the result of
  124. running the transaction through `CheckTx`. Using `broadcast_tx_commit`
  125. will wait until the transaction is committed in a block or until some
  126. timeout is reached, but will return right away if the transaction does
  127. not pass `CheckTx`. The return value for `broadcast_tx_commit` includes
  128. two fields, `check_tx` and `deliver_tx`, pertaining to the result of
  129. running the transaction through those ABCI messages.
  130. The benefit of using `broadcast_tx_commit` is that the request returns
  131. after the transaction is committed (i.e. included in a block), but that
  132. can take on the order of a second. For a quick result, use
  133. `broadcast_tx_sync`, but the transaction will not be committed until
  134. later, and by that point its effect on the state may change.
  135. ## Tendermint Networks
  136. When `tendermint init` is run, both a `genesis.json` and
  137. `priv_validator.json` are created in `~/.tendermint/config`. The
  138. `genesis.json` might look like:
  139. {
  140. "validators" : [
  141. {
  142. "pub_key" : {
  143. "value" : "h3hk+QE8c6QLTySp8TcfzclJw/BG79ziGB/pIA+DfPE=",
  144. "type" : "tendermint/PubKeyEd25519"
  145. },
  146. "power" : 10,
  147. "name" : ""
  148. }
  149. ],
  150. "app_hash" : "",
  151. "chain_id" : "test-chain-rDlYSN",
  152. "genesis_time" : "0001-01-01T00:00:00Z"
  153. }
  154. And the `priv_validator.json`:
  155. {
  156. "last_step" : 0,
  157. "last_round" : "0",
  158. "address" : "B788DEDE4F50AD8BC9462DE76741CCAFF87D51E2",
  159. "pub_key" : {
  160. "value" : "h3hk+QE8c6QLTySp8TcfzclJw/BG79ziGB/pIA+DfPE=",
  161. "type" : "tendermint/PubKeyEd25519"
  162. },
  163. "last_height" : "0",
  164. "priv_key" : {
  165. "value" : "JPivl82x+LfVkp8i3ztoTjY6c6GJ4pBxQexErOCyhwqHeGT5ATxzpAtPJKnxNx/NyUnD8Ebv3OIYH+kgD4N88Q==",
  166. "type" : "tendermint/PrivKeyEd25519"
  167. }
  168. }
  169. The `priv_validator.json` actually contains a private key, and should
  170. thus be kept absolutely secret; for now we work with the plain text.
  171. Note the `last_` fields, which are used to prevent us from signing
  172. conflicting messages.
  173. Note also that the `pub_key` (the public key) in the
  174. `priv_validator.json` is also present in the `genesis.json`.
  175. The genesis file contains the list of public keys which may participate
  176. in the consensus, and their corresponding voting power. Greater than 2/3
  177. of the voting power must be active (i.e. the corresponding private keys
  178. must be producing signatures) for the consensus to make progress. In our
  179. case, the genesis file contains the public key of our
  180. `priv_validator.json`, so a Tendermint node started with the default
  181. root directory will be able to make progress. Voting power uses an int64
  182. but must be positive, thus the range is: 0 through 9223372036854775807.
  183. Because of how the current proposer selection algorithm works, we do not
  184. recommend having voting powers greater than 10\^12 (ie. 1 trillion) (see
  185. [Proposals section of Byzantine Consensus
  186. Algorithm](./specification/byzantine-consensus-algorithm.html#proposals)
  187. for details).
  188. If we want to add more nodes to the network, we have two choices: we can
  189. add a new validator node, who will also participate in the consensus by
  190. proposing blocks and voting on them, or we can add a new non-validator
  191. node, who will not participate directly, but will verify and keep up
  192. with the consensus protocol.
  193. ### Peers
  194. #### Seed
  195. A seed node is a node who relays the addresses of other peers which they know
  196. of. These nodes constantly crawl the network to try to get more peers. The
  197. addresses which the seed node relays get saved into a local address book. Once
  198. these are in the address book, you will connect to those addresses directly.
  199. Basically the seed nodes job is just to relay everyones addresses. You won't
  200. connect to seed nodes once you have received enough addresses, so typically you
  201. only need them on the first start. The seed node will immediately disconnect
  202. from you after sending you some addresses.
  203. #### Persistent Peer
  204. Persistent peers are people you want to be constantly connected with. If you
  205. disconnect you will try to connect directly back to them as opposed to using
  206. another address from the address book. On restarts you will always try to
  207. connect to these peers regardless of the size of your address book.
  208. All peers relay peers they know of by default. This is called the peer exchange
  209. protocol (PeX). With PeX, peers will be gossipping about known peers and forming
  210. a network, storing peer addresses in the addrbook. Because of this, you don't
  211. have to use a seed node if you have a live persistent peer.
  212. #### Connecting to Peers
  213. To connect to peers on start-up, specify them in the
  214. `$TMHOME/config/config.toml` or on the command line. Use `seeds` to
  215. specify seed nodes, and
  216. `persistent_peers` to specify peers that your node will maintain
  217. persistent connections with.
  218. For example,
  219. tendermint node --p2p.seeds "f9baeaa15fedf5e1ef7448dd60f46c01f1a9e9c4@1.2.3.4:26656,0491d373a8e0fcf1023aaf18c51d6a1d0d4f31bd@5.6.7.8:26656"
  220. Alternatively, you can use the `/dial_seeds` endpoint of the RPC to
  221. specify seeds for a running node to connect to:
  222. curl 'localhost:26657/dial_seeds?seeds=\["f9baeaa15fedf5e1ef7448dd60f46c01f1a9e9c4@1.2.3.4:26656","0491d373a8e0fcf1023aaf18c51d6a1d0d4f31bd@5.6.7.8:26656"\]'
  223. Note, with PeX enabled, you
  224. should not need seeds after the first start.
  225. If you want Tendermint to connect to specific set of addresses and
  226. maintain a persistent connection with each, you can use the
  227. `--p2p.persistent_peers` flag or the corresponding setting in the
  228. `config.toml` or the `/dial_peers` RPC endpoint to do it without
  229. stopping Tendermint core instance.
  230. tendermint node --p2p.persistent_peers "429fcf25974313b95673f58d77eacdd434402665@10.11.12.13:26656,96663a3dd0d7b9d17d4c8211b191af259621c693@10.11.12.14:26656"
  231. curl 'localhost:26657/dial_peers?persistent=true&peers=\["429fcf25974313b95673f58d77eacdd434402665@10.11.12.13:26656","96663a3dd0d7b9d17d4c8211b191af259621c693@10.11.12.14:26656"\]'
  232. ### Adding a Non-Validator
  233. Adding a non-validator is simple. Just copy the original `genesis.json`
  234. to `~/.tendermint/config` on the new machine and start the node,
  235. specifying seeds or persistent peers as necessary. If no seeds or
  236. persistent peers are specified, the node won't make any blocks, because
  237. it's not a validator, and it won't hear about any blocks, because it's
  238. not connected to the other peer.
  239. ### Adding a Validator
  240. The easiest way to add new validators is to do it in the `genesis.json`,
  241. before starting the network. For instance, we could make a new
  242. `priv_validator.json`, and copy it's `pub_key` into the above genesis.
  243. We can generate a new `priv_validator.json` with the command:
  244. tendermint gen_validator
  245. Now we can update our genesis file. For instance, if the new
  246. `priv_validator.json` looks like:
  247. {
  248. "address" : "5AF49D2A2D4F5AD4C7C8C4CC2FB020131E9C4902",
  249. "pub_key" : {
  250. "value" : "l9X9+fjkeBzDfPGbUM7AMIRE6uJN78zN5+lk5OYotek=",
  251. "type" : "tendermint/PubKeyEd25519"
  252. },
  253. "priv_key" : {
  254. "value" : "EDJY9W6zlAw+su6ITgTKg2nTZcHAH1NMTW5iwlgmNDuX1f35+OR4HMN88ZtQzsAwhETq4k3vzM3n6WTk5ii16Q==",
  255. "type" : "tendermint/PrivKeyEd25519"
  256. },
  257. "last_step" : 0,
  258. "last_round" : "0",
  259. "last_height" : "0"
  260. }
  261. then the new `genesis.json` will be:
  262. {
  263. "validators" : [
  264. {
  265. "pub_key" : {
  266. "value" : "h3hk+QE8c6QLTySp8TcfzclJw/BG79ziGB/pIA+DfPE=",
  267. "type" : "tendermint/PubKeyEd25519"
  268. },
  269. "power" : 10,
  270. "name" : ""
  271. },
  272. {
  273. "pub_key" : {
  274. "value" : "l9X9+fjkeBzDfPGbUM7AMIRE6uJN78zN5+lk5OYotek=",
  275. "type" : "tendermint/PubKeyEd25519"
  276. },
  277. "power" : 10,
  278. "name" : ""
  279. }
  280. ],
  281. "app_hash" : "",
  282. "chain_id" : "test-chain-rDlYSN",
  283. "genesis_time" : "0001-01-01T00:00:00Z"
  284. }
  285. Update the `genesis.json` in `~/.tendermint/config`. Copy the genesis
  286. file and the new `priv_validator.json` to the `~/.tendermint/config` on
  287. a new machine.
  288. Now run `tendermint node` on both machines, and use either
  289. `--p2p.persistent_peers` or the `/dial_peers` to get them to peer up.
  290. They should start making blocks, and will only continue to do so as long
  291. as both of them are online.
  292. To make a Tendermint network that can tolerate one of the validators
  293. failing, you need at least four validator nodes (e.g., 2/3).
  294. Updating validators in a live network is supported but must be
  295. explicitly programmed by the application developer. See the [application
  296. developers guide](./app-development.html) for more details.
  297. ### Local Network
  298. To run a network locally, say on a single machine, you must change the
  299. `_laddr` fields in the `config.toml` (or using the flags) so that the
  300. listening addresses of the various sockets don't conflict. Additionally,
  301. you must set `addrbook_strict=false` in the `config.toml`, otherwise
  302. Tendermint's p2p library will deny making connections to peers with the
  303. same IP address.
  304. ### Upgrading
  305. The Tendermint development cycle currently includes a lot of breaking changes.
  306. Upgrading from an old version to a new version usually means throwing
  307. away the chain data. Try out the
  308. [tm-migrate](https://github.com/hxzqlh/tm-tools) tool written by
  309. [@hxzqlh](https://github.com/hxzqlh) if you are keen to preserve the
  310. state of your chain when upgrading to newer versions.