libbeat: global init state prevents multiple instances of filebeat receiver

While looking into testcases for the new beats receivers I encountered an issue that happens when creating multiple filebeat receivers via a factory:

panic: plugin parse_aws_vpc_flow_log registration fail parse_aws_vpc_flow_log exists already [recovered]
    panic: plugin parse_aws_vpc_flow_log registration fail parse_aws_vpc_flow_log exists already

Here is a test that reproduces this issue:

TestInstantiateReceiverFromFactory

```go func TestReceiverFactory(t *testing.T) { factory := NewFactory() cfg := Config{ Beatconfig: map[string]interface{}{ "filebeat": map[string]interface{}{ "inputs": []map[string]interface{}{ { "type": "benchmark", "enabled": true, "message": "test", "count": 1, }, }, }, "output": map[string]interface{}{ "otelconsumer": map[string]interface{}{}, }, "logging": map[string]interface{}{ "level": "debug", "selectors": []string{ "*", }, }, "path.home": t.TempDir(), }, } for i := 0; i < 5; i++ { // For collector packages < v0.112.0 this is `factory.CreateLogsReceiver` receiver, err := factory.CreateLogs(nil, receivertest.NewNopSettings(), &cfg, nil) assert.NoError(t, err) assert.NotNil(t, receiver) assert.NoError(t, receiver.Start(context.Background(), componenttest.NewNopHost())) assert.NoError(t, receiver.Shutdown(context.Background())) } } ``` The test output: ``` === RUN TestReceiverFactory --- FAIL: TestReceiverFactory (0.02s) panic: plugin parse_aws_vpc_flow_log registration fail parse_aws_vpc_flow_log exists already [recovered] panic: plugin parse_aws_vpc_flow_log registration fail parse_aws_vpc_flow_log exists already goroutine 67 [running]: testing.tRunner.func1.2({0x73e27c0, 0xc0020898e0}) /home/mauri870/git/go/src/testing/testing.go:1706 +0x21c testing.tRunner.func1() /home/mauri870/git/go/src/testing/testing.go:1709 +0x35e panic({0x73e27c0?, 0xc0020898e0?}) /home/mauri870/git/go/src/runtime/panic.go:787 +0x132 github.com/elastic/beats/v7/libbeat/processors.RegisterPlugin({0x7c5b471, 0x16}, 0x7e991e8) /home/mauri870/git/elastic/beats/libbeat/processors/registry.go:60 +0x125 github.com/elastic/beats/v7/x-pack/filebeat/processors/aws_vpcflow.InitializeModule() /home/mauri870/git/elastic/beats/x-pack/filebeat/processors/aws_vpcflow/parse_aws_vpc_flow_log.go:29 +0x26 github.com/elastic/beats/v7/x-pack/filebeat/include.InitializeModule() /home/mauri870/git/elastic/beats/x-pack/filebeat/include/list.go:64 +0x18 github.com/elastic/beats/v7/libbeat/cmd/instance.NewBeat({0x7c184d7, 0x8}, {0x0, 0x0}, {0x0, 0x0}, 0x1, {0xc0010055c0, 0x4, 0x6}) /home/mauri870/git/elastic/beats/libbeat/cmd/instance/beat.go:245 +0x72 github.com/elastic/beats/v7/libbeat/cmd/instance.NewBeatReceiver({{0x7c184d7, 0x8}, {0x0, 0x0}, {0x0, 0x0}, 0x1, 0x1, {{0x0, 0x0}, ...}, ...}, ...) /home/mauri870/git/elastic/beats/libbeat/cmd/instance/beat.go:292 +0xbe github.com/elastic/beats/v7/x-pack/filebeat/fbreceiver.createReceiver({0xc0011aff20?, 0x7e982b0?}, {{{{0x7c0f18c, 0x3}}, {0xc001315320, 0x24}}, {0xc000aefe80, {0x84d9f30, 0xc0011aff00}, {0x84d9f08, ...}, ...}, ...}, ...) /home/mauri870/git/elastic/beats/x-pack/filebeat/fbreceiver/factory.go:45 +0x50e go.opentelemetry.io/collector/receiver.CreateLogsFunc.CreateLogs(...) /home/mauri870/go/pkg/mod/go.opentelemetry.io/collector/receiver@v0.112.0/receiver.go:133 github.com/elastic/beats/v7/x-pack/filebeat/fbreceiver.TestReceiverFactory(0xc001302fc0) /home/mauri870/git/elastic/beats/x-pack/filebeat/fbreceiver/receiver_test.go:289 +0x6d9 testing.tRunner(0xc001302fc0, 0x7e97870) /home/mauri870/git/go/src/testing/testing.go:1764 +0xf4 created by testing.(*T).Run in goroutine 1 /home/mauri870/git/go/src/testing/testing.go:1823 +0x409 FAIL github.com/elastic/beats/v7/x-pack/filebeat/fbreceiver 0.052s ```

According to @leehinman this is likely a global state issue in libbeat

https://github.com/elastic/beats/blob/6ae50388e8ffa5d74f7f2984ee36b3d93f768787/libbeat/processors/registry.go#L40-L53

elastic / beats

libbeat: global init state prevents multiple instances of filebeat receiver #41475