Persistent buffers using 100% of available space causes the job to fail

[jsteel44]

We can use 99% (technically 100% minus one unit of granularity) of available space however when we create a buffer to consume the remaining space, it looks to be created successfully but then squeue reports:

             JOBID PARTITION     NAME     USER ST       TIME  NODES NODELIST(REASON)
                20     debug create-p    test2 PD       0:00      1 (burst_buffer/datawarp: setup: panic: runtime error: index out of range [recovered]
        panic: runtime error: index out of range

goroutine 1 [running]:
main.main.func1()
        /home/circleci/data-acc/cmd/dacctl/main.go:187 +0xb9
panic(0xb0d7c0, 0x12394c0)
        /usr/local/go/src/runtime/panic.go:522 +0x1b5
github.com/RSE-Cambridge/data-acc/internal/pkg/dacctl/workflow_impl.sessionFacade.doAllocationAndWriteSession(0xce3440, 0xc000176d00, 0xcdf780, 0xc000179560, 0xce0e80, 0xc00017c750, 0xcccf
60, 0x126c0c8, 0x7ffff8268d30, 0x2, ...)
        /home/circleci/data-acc/internal/pkg/dacctl/workflow_impl/session.go:166 +0x6ee
github.com/RSE-Cambridge/data-acc/internal/pkg/dacctl/workflow_impl.sessionFacade.CreateSession.func1(0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, ...)
        /home/circleci/data-acc/internal/pkg/dacctl/workflow_impl/session.go:110 +0xfb
github.com/RSE-Cambridge/data-acc/internal/pkg/dacctl/workflow_impl.sessionFacade.submitJob(0xce3440, 0xc000176d00, 0xcdf780, 0xc000179560, 0xce0e80, 0xc00017c750, 0xcccf60, 0x126c0c8, 0x7
ffff8268d30, 0x2, ...)
        /home/circleci/data-acc/internal/pkg/dacctl/workflow_impl/session.go:53 +0x3e8
github.com/RSE-Cambridge/data-acc/internal/pkg/dacctl/workflow_impl.sessionFacade.CreateSession(0xce3440, 0xc000176d00, 0xcdf780, 0xc000179560, 0xce0e80, 0xc00017c750, 0xcccf60, 0x126c0c8,
 0x7ffff8268d30, 0x2, ...)
        /home/circleci/data-acc/internal/pkg/dacctl/workflow_impl/session.go:107 +0x1b4
github.com/RSE-Cambridge/data-acc/internal/pkg/dacctl/actions_impl.(*dacctlActions).CreatePerJobBuffer(0xc000179580, 0xcdcac0, 0xc0000e71e0, 0xc000179580, 0x0)
        /home/circleci/data-acc/internal/pkg/dacctl/actions_impl/job.go:93 +0x6f5
main.setup(0xc0000e71e0, 0x0, 0x0)
        /home/circleci/data-acc/cmd/dacctl/actions.go:92 +0xa3
github.com/urfave/cli.HandleAction(0xade2a0, 0xc15140, 0xc0000e71e0, 0xc0000e71e0, 0x0)
        /go/pkg/mod/github.com/urfave/cli@v1.21.0/app.go:514 +0xbe
github.com/urfave/cli.Command.Run(0xbe38a2, 0x5, 0x0, 0x0, 0x0, 0x0, 0x0, 0xc0a8db, 0x47, 0x0, ...)
        /go/pkg/mod/github.com/urfave/cli@v1.21.0/command.go:171 +0x4d2
github.com/urfave/cli.(*App).Run(0xc0000dc540, 0xc0000b4000, 0xe, 0xf, 0x0, 0x0)
        /go/pkg/mod/github.com/urfave/cli@v1.21.0/app.go:265 +0x733
main.runCli(0xc0000b4000, 0xf, 0xf, 0xbe21f8, 0x1)
        /home/circleci/data-acc/cmd/dacctl/main.go:172 +0x1255
main.main()
        /home/circleci/data-acc/cmd/dacctl/main.go:194 +0x1f1
)

At this point everything looks normal with the buffers with now 0 FreeSpace as expected:

Name=datawarp DefaultPool=default Granularity=1600GiB TotalSpace=24000GiB FreeSpace=0 UsedSpace=24000GiB
  Flags=EnablePersistent,PrivateData
  StageInTimeout=3600 StageOutTimeout=3600 ValidateTimeout=5 OtherTimeout=3600
  GetSysState=/usr/local/bin/dacctl
  GetSysStatus=/usr/local/bin/dacctl
  Allocated Buffers:
    Name=small CreateTime=2019-10-02T14:24:55 Pool=default Size=3200GiB State=allocated UserID=test2(1002)
    Name=full CreateTime=2019-10-02T14:23:14 Pool=default Size=20800GiB State=allocated UserID=test2(1002)
  Per User Buffer Use:
    UserID=test2(1002) Used=24000GiB

[jsteel44]

This seems to only affect persistent buffers, a per-job buffer can request 100% of the space without issue.