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| # Debugging LND | ||
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| 1. [Overview](debugging_lnd.md#overview) | ||
| 2. [Debug Logging](debugging_lnd.md#debug-logging) | ||
| 3. [Capturing pprof data with `lnd`](debugging_lnd.md#capturing-pprof-data-with-lnd) | ||
| 1. [Overview](debugging\_lnd.md#overview) | ||
| 2. [Debug Logging](debugging\_lnd.md#debug-logging) | ||
| 3. [Capturing pprof data with `lnd`](debugging\_lnd.md#capturing-pprof-data-with-lnd) | ||
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| ## Overview | ||
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| `lnd` ships with a few useful features for debugging, such as a built-in profiler and tunable logging levels. If you need to submit a bug report for `lnd`, it may be helpful to capture debug logging and performance data ahead of time. | ||
| `LND` ships with a few useful features for debugging, such as a built-in profiler and tunable logging levels. If you need to submit a bug report for `LND`, it may be helpful to capture debug logging and performance data ahead of time. | ||
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| ## Debug Logging | ||
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| You can enable debug logging in `lnd` by passing the `--debuglevel` flag. For example, to increase the log level from `info` to `debug`: | ||
| Logging is useful for security and operating purposes. LND logs can typically be found on Linux at `~/.lnd/logs/bitcoin/mainnet/lnd.log`, on macOS at `~/Library/Application Support/Lnd/logs/bitcoin/mainnet` or in their specified location using the`--logdir` flag at startup. | ||
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| ```text | ||
| ⛰ lnd --debuglevel=debug | ||
| ``` | ||
| By default, LND will log 10MB worth of its history, and additionally keep three blocks of logs around, compressed with gzip as `lnd.log.<i>.gz` in the same directory. | ||
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| You may also specify logging per-subsystem, like this: | ||
| You can adjust the location of your log files as well their maximum size (in MB) and how many historical log files you expect LND to keep, in your `lnd.conf` file. | ||
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| ```text | ||
| ⛰ lnd --debuglevel=<subsystem>=<level>,<subsystem2>=<level>,... | ||
| ``` | ||
| `logdir=~/.lnd/logs`\ | ||
| `maxlogfiles=3`\ | ||
| `maxlogfilesize=10`\ | ||
| `debuglevel=debug,PEER=info` | ||
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| Additionally, the debuglevel can be overridden and adjusted without requiring a restart using the command `lncli debuglevel –-level=` | ||
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| The available debug levels are, in order of descending detail: `trace`, `debug`, `info`, `warn`, `error`, `critical`, `off` | ||
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| Example usage: | ||
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| `lncli debuglevel –-level=debug` | ||
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| Additionally, the log level can be adjusted for each individual subsystem. A list of the subsystem can also be obtained with the command `lncli debuglevel --show` | ||
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| Varying debug levels for multiple subsystems can be chained together with commands. | ||
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| Example usage: | ||
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| `debuglevel --level=BTCN=trace,LNWL=debug` | ||
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| Subsystems: | ||
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| | LNWL | lnwallet | Lightning Wallet | | ||
| | ---- | --------------- | --------------------- | | ||
| | DISC | discovery | Discovery | | ||
| | NTFN | chainntnfs | Chain Notifications | | ||
| | CHDB | channeldb | Channel database | | ||
| | HSWC | htlcswitch | HTLC Switch | | ||
| | CMGR | connmgr | Connection Manager | | ||
| | BTCN | neutrino | Neutrino | | ||
| | CNCT | contractcourt | Contract Court | | ||
| | UTXN | contractcourt | Contract Court | | ||
| | BRAR | contractcourt | Contract Court | | ||
| | SPHX | sphinx | Sphinx | | ||
| | SWPR | sweep | Sweep Transactions | | ||
| | SGNR | signrpc | Signature RPC | | ||
| | WLKT | walletrpc | Wallet RPC | | ||
| | ARPC | autopilotrpc | Autopilot RPC | | ||
| | INVC | invoices | Invoices | | ||
| | NANN | netann | Network Announcements | | ||
| | WTWR | watchtower | Watchtower | | ||
| | NTFR | chainrpc | Chain RPC | | ||
| | IRPC | invoicesrpc | Invoices RPC | | ||
| | CHNF | channelnotifier | Channel Notifier | | ||
| | CHBU | chanbackup | Channel backup | | ||
| | PROM | monitoring | Monitoring | | ||
| | WTCL | wtclient | Watch Tower Client | | ||
| | PRNF | peernotifier | Peer Notifier | | ||
| | CHFD | chanfunding | Channel Funding | | ||
| | PEER | peer | Peer | | ||
| | CHCL | chancloser | Channel Closer | | ||
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| ## Capturing pprof data with `lnd` | ||
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| `lnd` has a built-in feature which allows you to capture profiling data at runtime using [pprof](https://golang.org/pkg/runtime/pprof/), a profiler for Go. The profiler has negligible performance overhead during normal operations \(unless you have explicitly enabled CPU profiling\). | ||
| `lnd` has a built-in feature which allows you to capture profiling data at runtime using [pprof](https://golang.org/pkg/runtime/pprof/), a profiler for Go. The profiler has negligible performance overhead during normal operations (unless you have explicitly enabled CPU profiling). | ||
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| To enable this ability, start `lnd` with the `--profile` option using a free port. | ||
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| ```text | ||
| ``` | ||
| ⛰ lnd --profile=9736 | ||
| ``` | ||
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| Now, with `lnd` running, you can use the pprof endpoint on port 9736 to collect runtime profiling data. You can fetch this data using `curl` like so: | ||
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| ```text | ||
| ``` | ||
| ⛰ curl http://localhost:9736/debug/pprof/goroutine?debug=1 | ||
| ... | ||
| ``` | ||
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