Fix race condition - #69

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Fix race condition #69
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@bshafiee

@bshafiee bshafiee commented Apr 1, 2019

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When multiple IndexWriter instances call Flush concurrently, they hit race or index out of range for sortTmp since it's getting modified from multiple go routines.
example:

goroutine 59 [running]:
github.com/meerkat/vendor/github.com/google/codesearch/index.sortPost(0xc023ab0000, 0x32f2, 0x800000)
	/Users/behrooz/go/src/github.com/meerkat/vendor/github.com/google/codesearch/index/write.go:648 +0x298
github.com/meerkat/vendor/github.com/google/codesearch/index.(*IndexWriter).mergePost(0xc0000d62c0, 0xc001e8e300)
	/Users/behrooz/go/src/github.com/meerkat/vendor/github.com/google/codesearch/index/write.go:291 +0x13c
github.com/meerkat/vendor/github.com/google/codesearch/index.(*IndexWriter).Flush(0xc0000d62c0)
	/Users/behrooz/go/src/github.com/meerkat/vendor/github.com/google/codesearch/index/write.go:210 +0x1f1
github.com/meerkat/index.(*indexer).Index(0xc00011e000, 0x13a56e0, 0xc001fb4060, 0x0, 0x0)
	/Users/behrooz/go/src/github.com/meerkat/index/indexer.go:239 +0x429
main.main.func1(0xc0002c4280, 0xc001e4e6d0, 0xc00011c000, 0x30, 0x13a25a0, 0xc00011e000, 0xc00039b800)
	/Users/behrooz/go/src/github.com/meerkat/main.go:88 +0x206
created by main.main
	/Users/behrooz/go/src/github.com/meerkat/main.go:76 +0x334
panic: runtime error: index out of range
goroutine 181 [running]:
github.com/meerkat/vendor/github.com/google/codesearch/index.sortPost(0xc01fab0000, 0x3b65, 0x800000)
	/Users/behrooz/go/src/github.com/meerkat/vendor/github.com/google/codesearch/index/write.go:628 +0x29f
github.com/meerkat/vendor/github.com/google/codesearch/index.(*IndexWriter).mergePost(0xc0011d2000, 0xc0000a6240)
	/Users/behrooz/go/src/github.com/meerkat/vendor/github.com/google/codesearch/index/write.go:291 +0x13c
github.com/meerkat/vendor/github.com/google/codesearch/index.(*IndexWriter).Flush(0xc0011d2000)
	/Users/behrooz/go/src/github.com/meerkat/vendor/github.com/google/codesearch/index/write.go:210 +0x1f1
github.com/meerkat/index.(*indexer).Index(0xc00011e000, 0x13a56e0, 0xc0003a7ae0, 0x0, 0x0)
	/Users/behrooz/go/src/github.com/meerkat/index/indexer.go:239 +0x429
main.main.func1(0xc0002c4280, 0xc001e4e6d0, 0xc00011c000, 0x30, 0x13a25a0, 0xc00011e000, 0xc00039b500)
	/Users/behrooz/go/src/github.com/meerkat/main.go:88 +0x206
created by main.main
	/Users/behrooz/go/src/github.com/meerkat/main.go:76 +0x334

This fix simply moves global unprotected vars to local func scope. We could alternatively include them in IndexWriter struct too.

Behrooz Shafiee


 this causes race condition when multiple IndexWriter Flush is called,...

f089c2f

... the fix simply moves global unprotected vars to local func scope

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