# Developer guide

This document is the entry point for developers who wish to work on Etn-sc. Developers are people who are interested to build, develop, debug, submit a bug report or pull request or otherwise contribute to the Etn-sc source code.

Please see [Contributing](/etn-sc-client/developers/contributing.md) for the Etn-sc contribution guidelines.

## Building and Testing <a href="#building-and-testing" id="building-and-testing"></a>

Developers should use a recent version of Go for building and testing. We use the go toolchain for development, which you can get from the [Go downloads page](https://golang.org/doc/install). Etn-sc is a Go module, and uses the [Go modules system](https://github.com/golang/go/wiki/Modules) to manage dependencies. Using `GOPATH` is not required to build electroneum-sc.

### Building Executables <a href="#building-executables" id="building-executables"></a>

Switch to the electroneum-sc repository root directory. All code can be built using the go tool, placing the resulting binary in `$GOPATH/bin`.

```sh
go install -v ./...
```

electroneum-sc executables can be built individually. To build just etn-sc, use:

```sh
go install -v ./cmd/etn-sc
```

Cross compilation is not recommended, please build Etn-sc for the host architecture.

### Testing <a href="#testing" id="testing"></a>

Testing a package:

```sh
go test -v ./eth
```

Running an individual test:

```sh
go test -v ./eth -run TestMethod
```

{% hint style="info" %}
**Note**: here all tests with prefix *TestMethod* will be run, so if TestMethod and TestMethod1 both exist then both tests will run.
{% endhint %}

Running benchmarks, eg.:

```sh
go test -v -bench . -run BenchmarkJoin
```

For more information, see the [go test flags](https://golang.org/cmd/go/#hdr-Testing_flags) documentation.

### Getting Stack Traces <a href="#getting-stack-traces" id="getting-stack-traces"></a>

A stack trace provides a very detailed look into the current state of the etn-sc node. It helps us to debug issues easier as it contains information about what is currently done by the node. Stack traces can be created by running `debug.stacks()` in the Etn-sc console. If the node was started without the `console` command or with a script in the background, the following command can be used to dump the stack trace into a file.

```sh
etn-sc attach <path-to-etn-sc.ipc> --exec "debug.stacks()" > stacktrace.txt
```

Etn-sc logs the location of the IPC endpoint on startup. It is typically under `/home/user/.electroneum-sc/etn-sc.ipc` or `/tmp/etn-sc.ipc`.

`debug.stacks()` also takes an optional `filter` argument. Passing a package name or filepath to `filter` restricts the output to stack traces involving only that package/file. For example:

```sh
debug.stacks("enode")
```

returns data that looks like:

```
INFO [11-04|16:15:54.486] Expanded filter expression               filter=enode   expanded="`enode` in Value"
goroutine 121 [chan receive, 3 minutes]:
github.com/ethereum/go-ethereum/p2p/enode.(*FairMix).nextFromAny(...)
	github.com/ethereum/go-ethereum/p2p/enode/iter.go:241
github.com/ethereum/go-ethereum/p2p/enode.(*FairMix).Next(0xc0008c6060)
	github.com/ethereum/go-ethereum/p2p/enode/iter.go:215 +0x2c5
github.com/ethereum/go-ethereum/p2p.(*dialScheduler).readNodes(0xc00021c2c0, {0x18149b0, 0xc0008c6060})
	github.com/ethereum/go-ethereum/p2p/dial.go:321 +0x9f
created by github.com/ethereum/go-ethereum/p2p.newDialScheduler
	github.com/ethereum/go-ethereum/p2p/dial.go:179 +0x425
```

and

```sh
debug.stacks("consolecmd.go")
```

returns data that looks like:

```
INFO [11-04|16:16:47.141] Expanded filter expression               filter=consolecmd.go expanded="`consolecmd.go` in Value"
goroutine 1 [chan receive]:
github.com/ethereum/go-ethereum/internal/jsre.(*JSRE).Do(0xc0004223c0, 0xc0003c00f0)
	github.com/ethereum/go-ethereum/internal/jsre/jsre.go:230 +0xf4
github.com/ethereum/go-ethereum/internal/jsre.(*JSRE).Evaluate(0xc00033eb60?, {0xc0013c00a0, 0x1e}, {0x180d720?, 0xc000010018})
	github.com/ethereum/go-ethereum/internal/jsre/jsre.go:289 +0xb3
github.com/ethereum/go-ethereum/console.(*Console).Evaluate(0xc0005366e0, {0xc0013c00a0?, 0x0?})
	github.com/ethereum/go-ethereum/console/console.go:353 +0x6d
github.com/ethereum/go-ethereum/console.(*Console).Interactive(0xc0005366e0)
	github.com/ethereum/go-ethereum/console/console.go:481 +0x691
main.localConsole(0xc00026d580?)
	github.com/ethereum/go-ethereum/cmd/geth/consolecmd.go:109 +0x348
github.com/ethereum/go-ethereum/internal/flags.MigrateGlobalFlags.func2.1(0x20b52c0?)
	github.com/ethereum/go-ethereum/internal/flags/helpers.go:91 +0x36
github.com/urfave/cli/v2.(*Command).Run(0x20b52c0, 0xc000313540)
	github.com/urfave/cli/v2@v2.17.2-0.20221006022127-8f469abc00aa/command.go:177 +0x719
github.com/urfave/cli/v2.(*App).RunContext(0xc0005501c0, {0x1816128?, 0xc000040110}, {0xc00003c180, 0x3, 0x3})
	github.com/urfave/cli/v2@v2.17.2-0.20221006022127-8f469abc00aa/app.go:387 +0x1035
github.com/urfave/cli/v2.(*App).Run(...)
	github.com/urfave/cli/v2@v2.17.2-0.20221006022127-8f469abc00aa/app.go:252
main.main()
	github.com/ethereum/go-ethereum/cmd/geth/main.go:266 +0x47

goroutine 159 [chan receive, 4 minutes]:
github.com/ethereum/go-ethereum/node.(*Node).Wait(...)
	github.com/ethereum/go-ethereum/node/node.go:529
main.localConsole.func1()
	github.com/ethereum/go-ethereum/cmd/geth/consolecmd.go:103 +0x2d
created by main.localConsole
	github.com/ethereum/go-ethereum/cmd/geth/consolecmd.go:102 +0x32e
```

If Etn-sc is started with the `--pprof` option, a debugging HTTP server is made available on port 6060. Navigating to <http://localhost:6060/debug/pprof> displays the heap, running routines etc. By clicking "full goroutine stack dump" a trace can be generated that is useful for debugging.

Note that if multiple instances of Etn-sc exist, port 6060 will only work for the first instance that was launched. To generate stacktraces for other instances, they should be started up with alternative pprof ports. Ensure `stderr` is being redirected to a logfile.

```sh
etn-sc -port=30300 -verbosity 5 --pprof --pprof.port 6060 2>> /tmp/00.glog
etn-sc -port=30301 -verbosity 5 --pprof --pprof.port 6061 2>> /tmp/01.glog
etn-sc -port=30302 -verbosity 5 --pprof --pprof.port 6062 2>> /tmp/02.glog
```

Alternatively to kill the clients (in case they hang or stalled syncing, etc) and have the stacktrace too, use the `-QUIT` signal with `kill`:

```sh
killall -QUIT etn-sc
```

This will dump stack traces for each instance to their respective log file.

## Where to go next <a href="#where-next" id="where-next"></a>

Read the remaining pages in the Etn-sc developer section, and get building!


---

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