juju restore fails with "/var/lib/juju/agents: No such file or directory"

I have the same error when I restore the envirionments.

juju version I am using is 1.21.3

Yeah, this looks a lot like lp:1434437.

This is different: For what I see the error in this case happens when updating the units. restore script ssh's into each unit and updates the agent.conf to point to the newly created API server.
Perhaps this should just be logged as an error and the script continue with the updating to get as much machines updates as possible since we cannot go back at this point.
As a side note, if /var/lib/juju/agents is not there, something is broken in the unit, perhaps it is still coming up?

Yes, there is no /var/lib/juju/agents in machines side.
Therefore juju status shows all of machines are "down" status

Can you please list me the contents of /var/lib/juju if any? I am a bit puzzled by the fact that there is no /var/lib/juju/agents (in the context of this error, this actually happened in one of the units)

The juju-core version I tested before is deprecated.
Now it's already released in 1.22 and tested backup and restore again.

The result looks same as before.

Backup is fine and it has errors while restoring. The logs are as below

Installing package: cloud-image-utils
Fetching tools: curl -sSfw 'tools from %{url_effective} downloaded: HTTP %{http_code}; time %{time_total}s; size %{size_download} bytes; speed %{speed_download} bytes/s ' --retry 10 -o $bin/tools.tar.gz <[https://streams.canonical.com/juju/tools/releases/juju-1.22.0-trusty-amd64.tgz]>
Bootstrapping Juju machine agent
Starting Juju machine agent (jujud-machine-0)
2015-04-07 02:02:41 INFO juju.cmd cmd.go:113 Bootstrap complete
connecting to newly bootstrapped instance
2015-04-07 02:02:41 DEBUG juju.environs utils.go:93 StateServerInstances returned: [/MAAS/api/1.0/nodes/node-2389fbd2-d28f-11e4-8436-525400b3849e/]
2015-04-07 02:02:41 INFO juju.api apiclient.go:252 dialing "wss://bootstrap03.maas:17070/"
2015-04-07 02:02:41 DEBUG juju.api apiclient.go:258 error dialing "wss://bootstrap03.maas:17070/", will retry: websocket.Dial wss://bootstrap03.maas:17070/: dial tcp 10.100.1.151:17070: connection refused
.......................................................................................... ==> same error
2015-04-07 02:14:04 INFO juju.api apiclient.go:260 error dialing "wss://10.100.1.151:17070/": websocket.Dial wss://10.100.1.151:17070/: dial tcp 10.100.1.151:17070: connection refused
opening state
error: cannot connect to api server: unable to connect to "wss://10.100.1.151:17070/"

And this is the log for juju state machine
015-04-07 02:29:11 DEBUG juju.mongo open.go:122 TLS handshake failed: x509: certificate is valid for localhost, juju-apiserver, bootstrap05.maas, not juju-mongodb

it's same error as above I updated before.

ubuntu@bootstrap03:~$ ls /var/lib/juju
agents db nonce.txt server.pem shared-secret system-identity tools

There is no directory for juju in machines
ubuntu@ceph01:~$ ls /var/lib/juju
ls: cannot access /var/lib/juju: No such file or directory

I have checked on an openstack deployed with juju 1.20.14 I checked all of the ceph nodes and allof them had a /var/lib/juju directory.
I used:
 juju run --service=ceph 'ls -l /var/lib/juju/agents/'
nevertheless I will add an exception for this, we should not stop restoring because one of the machines is not in shape since this is beyond the point of no return and we should try to do as much as we can given that there are many factors why the machine could be in a weird state and it is very possible that the integrity of the services is ok and that our backup has machines that where removed after.

As indicated in lp:1434437, the following line from the log indicates a bug that has been fixed in 1.22.1:

015-04-07 02:29:11 DEBUG juju.mongo open.go:122 TLS handshake failed: x509: certificate is valid for localhost, juju-apiserver, bootstrap05.maas, not juju-mongodb

@ericsnowcurrently indeed, I was talking about the initial bug of this report.

Proposed http://reviews.vapour.ws/r/1850/ and http://reviews.vapour.ws/r/1851/ as fixes