Error panic: runtime error: slice bounds out of range

[mcortinas]

Hi,
I booted a weave instance and I can see this error:

INFO: 2017/07/17 17:16:51.167079 Command line options: map[docker-bridge:docker0 ipalloc-default-subnet:x.y.z.0/24 nickname:PREFIX_NODE-236.SUFIX_DATACENTER plugin:true datapath:datapath dns-effective-listen-address:172.17.0.1 dns-listen-address:172.17.0.1:53 http-addr:127.0.0.1:6784 port:6783 resolv-conf:/var/run/weave/etc/resolv.conf H:[unix:///var/run/weave/weave.sock] host-root:/host ipalloc-range:x.y.z.0/24 proxy:true trusted-subnets:10.2.160.0/19 weave-bridge:weave dns-domain:service.bcn1.sdisc.odigeo.com. status-addr:10.2.160.102:7070]
INFO: 2017/07/17 17:16:51.167153 weave  git-448518d50090
INFO: 2017/07/17 17:16:51.168630 Docker API on unix:///var/run/docker.sock: &[Version=17.03.1-ce ApiVersion=1.27 MinAPIVersion=1.12 GitCommit=c6d412e Os=linux Arch=amd64 KernelVersion=3.10.0-514.26.2.el7.x86_64 GoVersion=go1.7.5 BuildTime=2017-03-24T00:36:45.846383257+00:00]
INFO: 2017/07/17 17:16:51.168822 Using docker bridge IP for DNS: 172.17.0.1
INFO: 2017/07/17 17:16:51.172817 proxy listening on unix:///var/run/weave/weave.sock
INFO: 2017/07/17 17:16:51.175151 Bridge type is bridged_fastdp
INFO: 2017/07/17 17:16:51.175174 Communication between peers via untrusted networks is encrypted.
INFO: 2017/07/17 17:16:51.231989 Our name is 9e:1f:d3:7e:72:ef(PREFIX_NODE-236.SUFIX_DATACENTER)
INFO: 2017/07/17 17:16:51.232021 Launch detected - using supplied peer list: []
INFO: 2017/07/17 17:16:51.233269 Docker API on unix:///var/run/docker.sock: &[Version=17.03.1-ce GitCommit=c6d412e GoVersion=go1.7.5 Arch=amd64 BuildTime=2017-03-24T00:36:45.846383257+00:00 ApiVersion=1.27 MinAPIVersion=1.12 Os=linux KernelVersion=3.10.0-514.26.2.el7.x86_64]
INFO: 2017/07/17 17:16:51.233706 Checking for pre-existing addresses on weave bridge
INFO: 2017/07/17 17:16:51.234806 weave bridge has address x.y.z.17/24
INFO: 2017/07/17 17:16:51.255198 [allocator 9e:1f:d3:7e:72:ef] Initialising with persisted data
INFO: 2017/07/17 17:16:51.255242 Assuming quorum size of 1
panic: runtime error: slice bounds out of range
goroutine 1 [running]:
github.com/weaveworks/weave/ipam.(*Allocator).tryOps(0xc42148c140, 0xc42148c1e0)
        /go/src/github.com/weaveworks/weave/ipam/allocator.go:255 +0x1b0
github.com/weaveworks/weave/ipam.(*Allocator).Start(0xc42148c140)
        /go/src/github.com/weaveworks/weave/ipam/allocator.go:174 +0x23c
main.createAllocator(0xc420014c80, 0x7fffd4042dc5, 0xc, 0x7fffd4042ed5, 0xc, 0x0, 0x0, 0x0, 0x0, 0x0, ...)
        /go/src/github.com/weaveworks/weave/prog/weaver/main.go:617 +0x3cd
main.main()
        /go/src/github.com/weaveworks/weave/prog/weaver/main.go:391 +0x2ec3

[31267:31263 2:749] 19:17:09 Mon Jul 17 [root@PREFIX_NODE-236.SUFIX_DATACENTER: +1] ~ 
(1:749)# Jul 17 19:17:37 PREFIX_NODE-236.SUFIX_DATACENTER clean_weave_stop.sh[7950]: /usr/bin/docker rm 6e362a553c06
Jul 17 19:17:37 PREFIX_NODE-236.SUFIX_DATACENTER clean_weave_stop.sh[7950]: 6e362a553c06
Jul 17 19:17:37 PREFIX_NODE-236.SUFIX_DATACENTER clean_weave_stop.sh[7950]: /usr/bin/docker rm a67b96ad3da5
Jul 17 19:17:37 PREFIX_NODE-236.SUFIX_DATACENTER clean_weave_stop.sh[7950]: a67b96ad3da5
Jul 17 19:17:37 PREFIX_NODE-236.SUFIX_DATACENTER clean_weave_stop.sh[7950]: /usr/bin/docker rm 7b2a165600c8
Jul 17 19:17:37 PREFIX_NODE-236.SUFIX_DATACENTER clean_weave_stop.sh[7950]: 7b2a165600c8
Job for weave.service failed because the control process exited with error code. See "systemctl status weave.service" and "journalctl -xe" for details.

Let me share my environment

[31267:31263 1:753] 19:26:01 Mon Jul 17 [root@nodeSUFIX_DATACENTER: +1] ~ 
(1:753)# /usr/local/bin/weave version
weave script unreleased
weave git-448518d50090

[31267:31263 1:754] 19:26:11 Mon Jul 17 [root@nodeSUFIX_DATACENTER: +1] ~ 
(1:754)# docker version
Client:
 Version:      17.03.1-ce
 API version:  1.27
 Go version:   go1.7.5
 Git commit:   c6d412e
 Built:        Fri Mar 24 00:36:45 2017
 OS/Arch:      linux/amd64

Server:
 Version:      17.03.1-ce
 API version:  1.27 (minimum version 1.12)
 Go version:   go1.7.5
 Git commit:   c6d412e
 Built:        Fri Mar 24 00:36:45 2017
 OS/Arch:      linux/amd64
 Experimental: false

[31267:31263 1:755] 19:26:14 Mon Jul 17 [root@nodeSUFIX_DATACENTER: +1] ~ 
(1:755)# cat /etc/redhat-release 
CentOS Linux release 7.3.1611 (Core) 

[31267:31263 1:756] 19:26:17 Mon Jul 17 [root@nodeSUFIX_DATACENTER: +1] ~ 
(1:756)# uname -a
Linux nodeSUFIX_DATACENTER 3.10.0-514.26.2.el7.x86_64 #1 SMP Tue Jul 4 15:04:05 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux

[bboreham]

It seems it loaded persisted data, but the persisted data was empty, and the logic doesn't account for that case.

The call sequence leading to the crash is:

Allocator.Start()
Allocator.tryOps()
Claim.Try()
Allocator.establishRing()
Allocator.createRing()
Allocator.ringUpdated()
Allocator.tryPendingOps()
Allocator.tryOps()

So this is very similar to #2892.

I cannot see a code path where it would persist an empty data set, so I don't know how it got into this state.

To remove the persisted data as a work-around do docker rm -v weavedb, or just weave reset and launch again.