panic: invalid memory addresss

[joastonish]

这次是真的了。。。推了2个流到livego ，前端是http + flv.js 1.不知道为啥出来的比较慢。 2.打开2个的时候第二个死活出不来，再打开就报了一个panic:runtime error:invalid memory address or nil pointer dereference 然后程序崩溃

[gwuhaolin]

请提供错误详细堆栈

[joastonish]

2017/06/16 10:20:37 writer.go:159: http flv closed panic: runtime error: invalid memory address or nil pointer dereference [signal SIGSEGV: segmentation violation code=0x1 addr=0x20 pc=0x501558]

goroutine 4988871 [running]: bufio.(Writer).Flush(0xc420012b00, 0xc422c98d44, 0x6e9) /usr/local/Cellar/go/1.8.3/libexec/src/bufio/bufio.go:566 +0x58 bufio.(Writer).Write(0xc420012b00, 0xc422c98d44, 0x2620, 0x622bc, 0xb, 0x0, 0x0) /usr/local/Cellar/go/1.8.3/libexec/src/bufio/bufio.go:602 +0xdf net/http.(response).write(0xc420180540, 0x2620, 0xc422c98d44, 0x2620, 0x622bc, 0x0, 0x0, 0xb, 0x0, 0x0) /usr/local/Cellar/go/1.8.3/libexec/src/net/http/server.go:1525 +0x150 net/http.(response).Write(0xc420180540, 0xc422c98d44, 0x2620, 0x622bc, 0xb, 0x0, 0x0) /usr/local/Cellar/go/1.8.3/libexec/src/net/http/server.go:1495 +0x64 github.com/gwuhaolin/livego/protocol/httpflv.(*FLVWriter).SendPacket(0xc4200f6240, 0x0, 0x0) /Users/halwu/go/src/github.com/gwuhaolin/livego/protocol/httpflv/writer.go:134 +0x20c github.com/gwuhaolin/livego/protocol/httpflv.NewFLVWriter.func1(0xc4200f6240) /Users/halwu/go/src/github.com/gwuhaolin/livego/protocol/httpflv/writer.go:47 +0x2f created by github.com/gwuhaolin/livego/protocol/httpflv.NewFLVWriter /Users/halwu/go/src/github.com/gwuhaolin/livego/protocol/httpflv/writer.go:52 +0x387

[joastonish]

我找到重现的方法了。一直调用，用火狐测试大概是27个小时多一点的时候，就会出现这个错误。

[YuJuncen]

看起来有点像是 flvWriter.SendPacket 和 flvWriter.Close 的竞争条件，这里给一个推测，不一定正确：

1. Go 的 http 库会在 Handler 返回的时候，调用 response.finishRequest 方法，这个方法会调用 response 内部的 bufio.Writer 的 Reset(nil)。
2. 一般而言，httpflv/server.handleConn 会等待 flvWriter 结束。
3. flvWriter.Close 会关闭 packetQueue 和 closedChan，后者让 handleConn 结束，前者让 SendPacket 结束。

但是，SendPacket 在发送之前并不会检查自身是否已经结束： https://github.com/gwuhaolin/livego/blob/bf65635cef7355fd828b352e61beeedc6467991d/protocol/httpflv/writer.go#L140-L146 所以，假如说有以下的执行序列：

1. 某处调用 flvWriter.Close。
2. handleConn 发现 closedChan 关闭，返回；http 库执行 finishRequest。
3. 此时，SendPacket 进入了这个分支： https://github.com/gwuhaolin/livego/blob/bf65635cef7355fd828b352e61beeedc6467991d/protocol/httpflv/writer.go#L110-L130
4. 在执行到 https://github.com/gwuhaolin/livego/blob/bf65635cef7355fd828b352e61beeedc6467991d/protocol/httpflv/writer.go#L140 或者 https://github.com/gwuhaolin/livego/blob/bf65635cef7355fd828b352e61beeedc6467991d/protocol/httpflv/writer.go#L144 的时候，就可能会遇到往空 io.Writer 写数据的 panic。

[sduqlsc]

@gwuhaolin 这个问题解决了吗？

[22125236]

panic: runtime error: invalid memory address or nil pointer dereference [signal 0xc0000005 code=0x0 addr=0x18 pc=0x63f603]

goroutine 77131459 [running]: bufio.(Writer).Flush(0xc004717800, 0xc00579f94e, 0x61) c:/go/src/bufio/bufio.go:591 +0x63 bufio.(Writer).Write(0xc004717800, 0xc00579f94e, 0x1dd, 0x236b2, 0xb, 0x0, 0x0) c:/go/src/bufio/bufio.go:627 +0x101 net/http.(response).write(0xc0002b6c40, 0x1dd, 0xc00579f94e, 0x1dd, 0x236b2, 0x0, 0x0, 0xb, 0x0, 0x0) c:/go/src/net/http/server.go:1578 +0x2dc net/http.(response).Write(0xc0002b6c40, 0xc00579f94e, 0x1dd, 0x236b2, 0xb, 0x0, 0x0) c:/go/src/net/http/server.go:1547 +0x5d github.com/gwuhaolin/livego/protocol/httpflv.(*FLVWriter).SendPacket(0xc001420000, 0xa8bb28, 0xc00324f1e0) C:/Users/renzo/code/nslive/protocol/httpflv/writer.go:144 +0x198 github.com/gwuhaolin/livego/protocol/httpflv.NewFLVWriter.func1(0xc001420000) C:/Users/renzo/code/nslive/protocol/httpflv/writer.go:49 +0x36 created by github.com/gwuhaolin/livego/protocol/httpflv.NewFLVWriter C:/Users/renzo/code/nslive/protocol/httpflv/writer.go:48 +0x362

使用6路推流原画时，当推流速度很小的情况下（测试时约为0.6x），会出现以上错误

[litterGuy]

时不时会出现这个问题，但是没找到出现的规律。这个问题有解决方案了吗？ ` panic: runtime error: invalid memory address or nil pointer dereference [signal SIGSEGV: segmentation violation code=0x1 addr=0x18 pc=0x50ada2]

goroutine 153 [running]: bufio.(Writer).Flush(0xc0000d5bc0, 0xc0011dfbef, 0x7f5) G:/Program Files/Go/src/bufio/bufio.go:607 +0x62 bufio.(Writer).Write(0xc0000d5bc0, 0xc0011dfbef, 0x2981, 0x5b411, 0xb, 0x0, 0x0) G:/Program Files/Go/src/bufio/bufio.go:643 +0xfc net/http.(response).write(0xc00021c2a0, 0x2981, 0xc0011dfbef, 0x2981, 0x5b411, 0x0, 0x0, 0xb, 0x0, 0x0) G:/Program Files/Go/src/net/http/server.go:1615 +0x38a net/http.(response).Write(0xc00021c2a0, 0xc0011dfbef, 0x2981, 0x5b411, 0xb, 0x0, 0x0) G:/Program Files/Go/src/net/http/server.go:1573 +0x56 github.com/gwuhaolin/livego/protocol/httpflv.(*FLVWriter).SendPacket(0xc0000c4000, 0x7fc2f1b3f028, 0xc0000765a0) E:/go/src/livego/protocol/httpflv/writer.go:151 +0x198 github.com/gwuhaolin/livego/protocol/httpflv.NewFLVWriter.func1(0xc0000c4000) E:/go/src/livego/protocol/httpflv/writer.go:55 +0x2f created by github.com/gwuhaolin/livego/protocol/httpflv.NewFLVWriter E:/go/src/livego/protocol/httpflv/writer.go:54 +0x35f `