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Created Debugging (markdown)

Christian Schwarz 2019-09-08 09:47:31 +02:00
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## Memory Leaks & Goroutine Leaks
A good example for a goroutine & memory leak caused by not draining a channel is
[3bfe0c16d0233cac66a01a6f89959c34ef01c663](https://github.com/zrepl/zrepl/commit/3bfe0c16d0233cac66a01a6f89959c34ef01c663d) ("rpc/dataconn/stream: fix goroutine leaks & transitive buffer leaks")
1. Run zrepl with autostarted pprof server: `ZREPL_DAEMON_AUTOSTART_PPROF_SERVER=:12345 zrepl daemon`
(We will assume the address is 192.168.124.252)
2. `watch 'curl 192.168.124.252:22345/metrics | grep -v "#" | grep memstats'`<br/>
=> `go_memstats_heap_inuse_bytes` or `go_memstats_heap_alloc_bytes` should be rising
3. `watch curl http://192.168.124.252:12345/debug/pprof/goroutine?debug=1`
```
9 @ 0x469db0 0x43d5f4 0x43d5ca 0x43d355 0xc767b0 0x498f51
# 0xc767af github.com/zrepl/zrepl/rpc/dataconn/stream.doWriteStream.func1+0x2ff /mnt/zrepl /rpc/dataconn/stream/stream.go:92
```
=> 9 kept increasing to higher numbers over time => look at `doWriteStream` impl and fix goroutine leak (see commit)