Subgraph: Segfault in GetUids() #5472
Description
What version of Dgraph are you using?
v20.03.2 and cc97957
Have you tried reproducing the issue with the latest release?
No
What is the hardware spec (RAM, OS)?
N/A
Steps to reproduce the issue (command/config used to run Dgraph).
Run https://github.com/dgraph-io/flock and the issues shows up after some time.
The issue might not be reproducible easily.
Update - This issue shows up always within 10 minutes of running flock.
Expected behaviour and actual result.
I expected No crash.
I0519 11:22:52.637364 20 mvcc.go:80] Rolled up 136000 keys
I0519 11:23:01.269323 20 mvcc.go:80] Rolled up 137000 keys
I0519 11:23:10.957573 20 mvcc.go:80] Rolled up 138000 keys
I0519 11:23:17.025191 20 draft.go:1424] Num pending txns: 4
I0519 11:23:17.093727 20 draft.go:892] [0x1] Set Raft progress to index: 135829.
I0519 11:23:25.601400 20 mvcc.go:80] Rolled up 139000 keys
I0519 11:23:39.138569 20 mvcc.go:80] Rolled up 140000 keys
I0519 11:23:45.018406 20 mvcc.go:80] Rolled up 141000 keys
I0519 11:23:50.043304 20 mvcc.go:80] Rolled up 142000 keys
I0519 11:24:00.137204 20 mvcc.go:80] Rolled up 143000 keys
I0519 11:24:05.373182 20 mvcc.go:80] Rolled up 144000 keys
I0519 11:24:17.025183 20 draft.go:1424] Num pending txns: 4
I0519 11:24:17.064221 20 draft.go:892] [0x1] Set Raft progress to index: 140582.
I0519 11:24:21.175987 20 mvcc.go:80] Rolled up 145000 keys
unexpected fault address 0x0
fatal error: fault
[signal SIGSEGV: segmentation violation code=0x80 addr=0x0 pc=0x15eefab]
goroutine 862934 [running]:
runtime.throw(0x1b8660b, 0x5)
/usr/local/go/src/runtime/panic.go:774 +0x72 fp=0xc02d602b38 sp=0xc02d602b08 pc=0xa3cff2
runtime.sigpanic()
/usr/local/go/src/runtime/signal_unix.go:401 +0x3de fp=0xc02d602b68 sp=0xc02d602b38 pc=0xa534ee
github.com/dgraph-io/dgraph/query.(*SubGraph).formResult(0xc07e463b00, 0xc049e17c80, 0xc02c090340, 0x0, 0x0)
/home/ibrahim/Projects/go/src/github.com/dgraph-io/dgraph/query/groupby.go:226 +0x18b fp=0xc02d602cc0 sp=0xc02d602b68 pc=0x15eefab
github.com/dgraph-io/dgraph/query.(*SubGraph).processGroupBy(0xc07e463b00, 0xc03d69e8a0, 0xc094616530, 0x1, 0x2, 0x7f02bd06b940, 0xc02d602d98)
/home/ibrahim/Projects/go/src/github.com/dgraph-io/dgraph/query/groupby.go:376 +0x78 fp=0xc02d602d30 sp=0xc02d602cc0 pc=0x15f0078
github.com/dgraph-io/dgraph/query.(*SubGraph).valueVarAggregation(0xc07e463b00, 0xc03d69e8a0, 0xc094616530, 0x1, 0x2, 0xc07e463800, 0x0, 0x0)
/home/ibrahim/Projects/go/src/github.com/dgraph-io/dgraph/query/query.go:1136 +0xe42 fp=0xc02d602fc0 sp=0xc02d602d30 pc=0x16077a2
github.com/dgraph-io/dgraph/query.(*SubGraph).populatePostAggregation(0xc07e463b00, 0xc03d69e8a0, 0xc094616530, 0x2, 0x2, 0xc07e463800, 0x0, 0x1)
/home/ibrahim/Projects/go/src/github.com/dgraph-io/dgraph/query/query.go:1241 +0x1a9 fp=0xc02d603020 sp=0xc02d602fc0 pc=0x1607a09
github.com/dgraph-io/dgraph/query.(*SubGraph).populatePostAggregation(0xc07e463800, 0xc03d69e8a0, 0xc0944e8900, 0x1, 0x1, 0x0, 0x0, 0x1)
/home/ibrahim/Projects/go/src/github.com/dgraph-io/dgraph/query/query.go:1235 +0xcd fp=0xc02d603080 sp=0xc02d603020 pc=0x160792d
github.com/dgraph-io/dgraph/query.(*Request).ProcessQuery(0xc02d603530, 0x1de1840, 0xc0624a2810, 0xc049634000, 0x7f02f11ecb28)
/home/ibrahim/Projects/go/src/github.com/dgraph-io/dgraph/query/query.go:2710 +0xd61 fp=0xc02d603240 sp=0xc02d603080 pc=0x1612cc1
github.com/dgraph-io/dgraph/query.(*Request).Process(0xc02d603530, 0x1de1840, 0xc0624a2810, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, ...)
/home/ibrahim/Projects/go/src/github.com/dgraph-io/dgraph/query/query.go:2741 +0x7c fp=0xc02d6032d0 sp=0xc02d603240 pc=0x161323c
github.com/dgraph-io/dgraph/edgraph.processQuery(0x1de1840, 0xc0624a2810, 0xc02ce46320, 0x0, 0x0, 0x14)
/home/ibrahim/Projects/go/src/github.com/dgraph-io/dgraph/edgraph/server.go:919 +0x241 fp=0xc02d6037a8 sp=0xc02d6032d0 pc=0x162b431
github.com/dgraph-io/dgraph/edgraph.(*Server).doQuery(0x2946028, 0x1de1840, 0xc0624a2810, 0xc034b0c540, 0x0, 0x0, 0x0, 0x0)
/home/ibrahim/Projects/go/src/github.com/dgraph-io/dgraph/edgraph/server.go:850 +0x4e9 fp=0xc02d6039d0 sp=0xc02d6037a8 pc=0x162a929
github.com/dgraph-io/dgraph/edgraph.(*Server).Query(0x2946028, 0x1de1840, 0xc0624a2690, 0xc034b0c540, 0x2946028, 0xc0624a2690, 0xc08b1d4a80)
/home/ibrahim/Projects/go/src/github.com/dgraph-io/dgraph/edgraph/server.go:763 +0xa6 fp=0xc02d603a20 sp=0xc02d6039d0 pc=0x162a386
github.com/dgraph-io/dgo/v200/protos/api._Dgraph_Query_Handler(0x1ac3940, 0x2946028, 0x1de1840, 0xc0624a2690, 0xc02ce3d440, 0x0, 0x1de1840, 0xc0624a2690, 0xc05d810480, 0x166)
/home/ibrahim/Projects/go/pkg/mod/github.com/dgraph-io/dgo/v200@v200.0.0-20200401175452-e463f9234453/protos/api/api.pb.go:1604 +0x217 fp=0xc02d603a90 sp=0xc02d603a20 pc=0xf519b7
google.golang.org/grpc.(*Server).processUnaryRPC(0xc000484160, 0x1df08e0, 0xc04bd3fb00, 0xc0384de000, 0xc03ee42960, 0x272ad38, 0x0, 0x0, 0x0)
/home/ibrahim/Projects/go/pkg/mod/google.golang.org/grpc@v1.23.0/server.go:995 +0x460 fp=0xc02d603e18 sp=0xc02d603a90 pc=0xf344c0
google.golang.org/grpc.(*Server).handleStream(0xc000484160, 0x1df08e0, 0xc04bd3fb00, 0xc0384de000, 0x0)
/home/ibrahim/Projects/go/pkg/mod/google.golang.org/grpc@v1.23.0/server.go:1275 +0xd97 fp=0xc02d603f48 sp=0xc02d603e18 pc=0xf38427
google.golang.org/grpc.(*Server).serveStreams.func1.1(0xc04c65ed50, 0xc000484160, 0x1df08e0, 0xc04bd3fb00, 0xc0384de000)
/home/ibrahim/Projects/go/pkg/mod/google.golang.org/grpc@v1.23.0/server.go:710 +0xbb fp=0xc02d603fb8 sp=0xc02d603f48 pc=0xf4538b
runtime.goexit()
/usr/local/go/src/runtime/asm_amd64.s:1357 +0x1 fp=0xc02d603fc0 sp=0xc02d603fb8 pc=0xa6dc81
created by google.golang.org/grpc.(*Server).serveStreams.func1
/home/ibrahim/Projects/go/pkg/mod/google.golang.org/grpc@v1.23.0/server.go:708 +0xa1