Debugging

tendermint debug kill

Tendermint comes with a debug sub-command that allows you to kill a live Tendermint process while collecting useful information in a compressed archive. The information includes the configuration used, consensus state, network state, the node' status, the WAL, and even the stack trace of the process before exit. These files can be useful to examine when debugging a faulty Tendermint process.

Copy tendermint debug kill <pid> </path/to/out.zip> --home=</path/to/app.d>

will write debug info into a compressed archive. The archive will contain the following:

Copy ├── config.toml ├── consensus_state.json ├── net_info.json ├── stacktrace.out ├── status.json └── wal

Under the hood, debug kill fetches info from /status, /net_info, and /dump_consensus_state HTTP endpoints, and kills the process with -6, which catches the go-routine dump.

Tendermint debug dump

Also, the debug dump sub-command allows you to dump debugging data into compressed archives at a regular interval. These archives contain the goroutine and heap profiles in addition to the consensus state, network info, node status, and even the WAL.

Copy tendermint debug dump </path/to/out> --home=</path/to/app.d>

will perform similarly to kill except it only polls the node and dumps debugging data every frequency seconds to a compressed archive under a given destination directory. Each archive will contain:

Copy ├── consensus_state.json ├── goroutine.out ├── heap.out ├── net_info.json ├── status.json └── wal

Note: goroutine.out and heap.out will only be written if a profile address is provided and is operational. This command is blocking and will log any error.

Tendermint Inspect

Tendermint includes an inspect command for querying Tendermint's state store and block store over Tendermint RPC.

When the Tendermint consensus engine detects inconsistent state, it will crash the entire Tendermint process. While in this inconsistent state, a node running Tendermint's consensus engine will not start up. The inspect command runs only a subset of Tendermint's RPC endpoints for querying the block store and state store. inspect allows operators to query a read-only view of the stage. inspect does not run the consensus engine at all and can therefore be used to debug processes that have crashed due to inconsistent state.

Running inspect

Start up the inspect tool on the machine where Tendermint crashed using:

Copy tendermint inspect --home=</path/to/app.d>

inspect will use the data directory specified in your Tendermint configuration file. inspect will also run the RPC server at the address specified in your Tendermint configuration file.

Using inspect

With the inspect server running, you can access RPC endpoints that are critically important for debugging. Calling the /status, /consensus_state and /dump_consensus_state RPC endpoint will return useful information about the Tendermint consensus state.

To start the inspect process, run

Copy tendermint inspect

RPC endpoints

The list of available RPC endpoints can be found by making a request to the RPC port. For an inspect process running on 127.0.0.1:26657, navigate your browser to http://127.0.0.1:26657/ to retrieve the list of enabled RPC endpoints.

Additional information on the Tendermint RPC endpoints can be found in the rpc documentation (opens new window).