Magnum Troubleshooting Guide

This guide is intended for users who use Magnum to deploy and manage clusters of hosts for a Container Orchestration Engine. It describes common failure conditions and techniques for troubleshooting. To help the users quickly identify the relevant information, the guide is organized as a list of failure symptoms: each has some suggestions with pointers to the details for troubleshooting.

A separate section for developers describes useful techniques such as debugging unit tests and gate tests.

Failure symptoms

My cluster-create takes a really long time

If you are using devstack on a small VM, cluster-create will take a long time and may eventually fail because of insufficient resources. Another possible reason is that a process on one of the nodes is hung and heat is still waiting on the signal. In this case, it will eventually fail with a timeout, but since heat has a long default timeout, you can look at the heat stacks and check the WaitConditionHandle resources.

My cluster-create fails with error: “Failed to create trustee XXX in domain XXX”

Check the trustee for cluster

Kubernetes cluster-create fails

Check the heat stacks, log into the master nodes and check the Kubernetes services and etcd service.

I get the error “Timed out waiting for a reply” when deploying a pod

Verify the Kubernetes services and etcd service are running on the master nodes.

I deploy pods on Kubernetes cluster but the status stays “Pending”

The pod status is “Pending” while the Docker image is being downloaded, so if the status does not change for a long time, log into the minion node and check for Cluster internet access.

I deploy pods and services on Kubernetes cluster but the app is not working

The pods and services are running and the status looks correct, but if the app is performing communication between pods through services, verify Kubernetes networking.

I get a “Protocol violation” error when deploying a container

For Kubernetes, check the Kubernetes services to verify that kube-apiserver is running to accept the request. Check TLS and Barbican service.

My cluster-create fails with a resource error on docker_volume

Check for available volume space on Cinder and the request volume size in the heat template. Run “nova volume-list” to check the volume status.

Troubleshooting details

Heat stacks

To be filled in

A cluster is deployed by a set of heat stacks: one top level stack and several nested stack. The stack names are prefixed with the cluster name and the nested stack names contain descriptive internal names like kube_masters, kube_minions.

To list the status of all the stacks for a cluster:

heat stack-list -n | grep cluster-name

If the cluster has failed, then one or more of the heat stacks would have failed. From the stack list above, look for the stacks that failed, then look for the particular resource(s) that failed in the failed stack by:

heat resource-list failed-stack-name | grep “FAILED”

The resource_type of the failed resource should point to the OpenStack service, e.g. OS::Cinder::Volume. Check for more details on the failure by:

heat resource-show failed-stack-name failed-resource-name

The resource_status_reason may give an indication on the failure, although in some cases it may only say “Unknown”.

If the failed resource is OS::Heat::WaitConditionHandle, this indicates that one of the services that are being started on the node is hung. Log into the node where the failure occurred and check the respective Kubernetes services. If the failure is in other scripts, look for them as Heat software resource scripts.

Trustee for cluster

When a user creates a cluster, Magnum will dynamically create a service account for the cluster. The service account will be used by the cluster to access the OpenStack services (i.e. Neutron, Swift, etc.). A trust relationship will be created between the user who created the cluster (the “trustor”) and the service account created for the cluster (the “trustee”).

If Magnum fails to create the trustee, check the magnum config file (usually in /etc/magnum/magnum.conf). Make sure ‘trustee_*’ and ‘www_authenticate_uri’ are set and their values are correct:

[keystone_authtoken] www_authenticate_uri = http://controller:5000/v3 …

[trust] trustee_domain_admin_password = XXX trustee_domain_admin_id = XXX trustee_domain_id = XXX

If the ‘trust’ group is missing, you might need to create the trustee domain and the domain admin:

. /opt/stack/devstack/accrc/admin/admin
export OS_IDENTITY_API_VERSION=3
unset OS_AUTH_TYPE
openstack domain create magnum
openstack user create trustee_domain_admin --password secret \
    --domain magnum
openstack role add --user=trustee_domain_admin --user-domain magnum \
    --domain magnum admin

. /opt/stack/devstack/functions
export MAGNUM_CONF=/etc/magnum/magnum.conf
iniset $MAGNUM_CONF trust trustee_domain_id \
    $(openstack domain show magnum | awk '/ id /{print $4}')
iniset $MAGNUM_CONF trust trustee_domain_admin_id \
    $(openstack user show trustee_domain_admin | awk '/ id /{print $4}')
iniset $MAGNUM_CONF trust trustee_domain_admin_password secret

Then, restart magnum-api and magnum-cond to pick up the new configuration. If the problem still exists, you might want to manually verify your domain admin credential to ensure it has the right privilege. To do that, run the script below with the credentials replaced (you must use the IDs where specified). If it fails, that means the credential you provided is invalid.

from keystoneauth1.identity import v3 as ka_v3
from keystoneauth1 import session as ka_session
from keystoneclient.v3 import client as kc_v3

auth = ka_v3.Password(
    auth_url=YOUR_AUTH_URI,
    user_id=YOUR_TRUSTEE_DOMAIN_ADMIN_ID,
    domain_id=YOUR_TRUSTEE_DOMAIN_ID,
    password=YOUR_TRUSTEE_DOMAIN_ADMIN_PASSWORD)

session = ka_session.Session(auth=auth)
domain_admin_client = kc_v3.Client(session=session)
user = domain_admin_client.users.create(
    name='anyname',
    password='anypass')

TLS

In production deployments, operators run the OpenStack APIs using ssl certificates and in private clouds it is common to use self-signed or certificates signed from CAs that they are usually not included in the systems’ default CA-bundles. Magnum clusters with TLS enabled have their own CA but they need to make requests to the OpenStack APIs for several reasons. Eg Get the cluster CA and sign node certificates (Keystone, Magnum), signal the Heat API for stack completion, create resources (volumes, load balancers) or get information for each node (Cinder, Neutron, Nova). In these cases, the cluster nodes need the CA used for to run the APIs.

To pass the OpenStack CA bundle to the nodes you can set the CA using the openstack_ca_file option in the drivers section of Magnum’s configuration file (usually /etc/magnum/magnum.conf). The default drivers in magnum install this CA in the system and set it in all the places it might be needed (eg when configuring the kubernetes cloud provider or for the heat-agents.)

The cluster nodes will validate the Certificate Authority by default when making requests to the OpenStack APIs (Keystone, Magnum, Heat). If you need to disable CA validation, the configuration parameter verify_ca can be set to False. More information on CA Validation.

Barbican service

To be filled in

Cluster internet access

The nodes for Kubernetes are connected to a private Neutron network, so to provide access to the external internet, a router connects the private network to a public network. With devstack, the default public network is “public”, but this can be replaced by the parameter “external-network” in the ClusterTemplate. The “public” network with devstack is actually not a real external network, so it is in turn routed to the network interface of the host for devstack. This is configured in the file local.conf with the variable PUBLIC_INTERFACE, for example:

PUBLIC_INTERFACE=eth1

If the route to the external internet is not set up properly, the ectd discovery would fail (if using public discovery) and container images cannot be downloaded, among other failures.

First, check for connectivity to the external internet by pinging an external IP (the IP shown here is an example; use an IP that works in your case):

ping 8.8.8.8

If the ping fails, there is no route to the external internet. Check the following:

• Is PUBLIC_INTERFACE in devstack/local.conf the correct network interface? Does this interface have a route to the external internet?

• If “external-network” is specified in the ClusterTemplate, does this network have a route to the external internet?

• Is your devstack environment behind a firewall? This can be the case for some enterprises or countries. In this case, consider using a proxy server.

• Is the traffic blocked by the security group? Check the rules of security group.

• Is your host NAT’ing your internal network correctly? Check your host iptables.

• Use tcpdump for networking troubleshooting. You can run tcpdump on the interface docker0, flannel0 and eth0 on the node and then run ping to see the path of the message from the container.

If ping is successful, check that DNS is working:

wget google.com

If DNS works, you should get back a few lines of HTML text.

If the name lookup fails, check the following:

• Is the DNS entry correct in the subnet? Try “neutron subnet-show <subnet-id>” for the private subnet and check dns_nameservers. The IP should be either the default public DNS 8.8.8.8 or the value specified by “dns-nameserver” in the ClusterTemplate.

• If you are using your own DNS server by specifying “dns-nameserver” in the ClusterTemplate, is it reachable and working?

• More help on DNS troubleshooting.

Kubernetes networking

The networking between pods is different and separate from the neutron network set up for the cluster. Kubernetes presents a flat network space for the pods and services and uses different network drivers to provide this network model.

It is possible for the pods to come up correctly and be able to connect to the external internet, but they cannot reach each other. In this case, the app in the pods may not be working as expected. For example, if you are trying the redis example, the key:value may not be replicated correctly. In this case, use the following steps to verify the inter-pods networking and pinpoint problems.

Since the steps are specific to the network drivers, refer to the particular driver being used for the cluster.

Using Flannel as network driver

Flannel is the default network driver for Kubernetes clusters. Flannel is an overlay network that runs on top of the neutron network. It works by encapsulating the messages between pods and forwarding them to the correct node that hosts the target pod.

First check the connectivity at the node level. Log into two different minion nodes, e.g. node A and node B, run a docker container on each node, attach to the container and find the IP.

For example, on node A:

sudo docker run -it alpine
# ip -f inet -o a | grep eth0 | awk '{print $4}'
10.100.54.2/24

Similarly, on node B:

sudo docker run -it alpine
# ip -f inet -o a | grep eth0 | awk '{print $4}'
10.100.49.3/24

Check that the containers can see each other by pinging from one to another.

On node A:

# ping 10.100.49.3
PING 10.100.49.3 (10.100.49.3): 56 data bytes
64 bytes from 10.100.49.3: seq=0 ttl=60 time=1.868 ms
64 bytes from 10.100.49.3: seq=1 ttl=60 time=1.108 ms

Similarly, on node B:

# ping 10.100.54.2
PING 10.100.54.2 (10.100.54.2): 56 data bytes
64 bytes from 10.100.54.2: seq=0 ttl=60 time=2.678 ms
64 bytes from 10.100.54.2: seq=1 ttl=60 time=1.240 ms

If the ping is not successful, check the following:

• Is neutron working properly? Try pinging between the VMs.

• Are the docker0 and flannel0 interfaces configured correctly on the nodes? Log into each node and find the Flannel CIDR by:

  cat /run/flannel/subnet.env | grep FLANNEL_SUBNET
  FLANNEL_SUBNET=10.100.54.1/24
  

  Then check the interfaces by:

  ifconfig flannel0
  ifconfig docker0
  

  The correct configuration should assign flannel0 with the “0” address in the subnet, like 10.100.54.0, and docker0 with the “1” address, like 10.100.54.1.

• Verify the IP’s assigned to the nodes as found above are in the correct Flannel subnet. If this is not correct, the docker daemon is not configured correctly with the parameter –bip. Check the systemd service for docker.

• Is Flannel running properly? check the Running Flannel.

• Ping and try tcpdump on each network interface along the path between two nodes to see how far the message is able to travel. The message path should be as follows:

  1. Source node: docker0

  2. Source node: flannel0

  3. Source node: eth0

  4. Target node: eth0

  5. Target node: flannel0

  6. Target node: docker0

If ping works, this means the flannel overlay network is functioning correctly.

The containers created by Kubernetes for pods will be on the same IP subnet as the containers created directly in Docker as above, so they will have the same connectivity. However, the pods still may not be able to reach each other because normally they connect through some Kubernetes services rather than directly. The services are supported by the kube-proxy and rules inserted into the iptables, therefore their networking paths have some extra hops and there may be problems here.

To check the connectivity at the Kubernetes pod level, log into the master node and create two pods and a service for one of the pods. You can use the examples provided in the directory /etc/kubernetes/examples/ for the first pod and service. This will start up an nginx container and a Kubernetes service to expose the endpoint. Create another manifest for a second pod to test the endpoint:

cat > alpine.yaml << END
apiVersion: v1
kind: Pod
metadata:
  name: alpine
spec:
  containers:
  - name: alpine
    image: alpine
    args:
    - sleep
    - "1000000"
END

kubectl create -f /etc/kubernetes/examples/pod-nginx-with-label.yaml
kubectl create -f /etc/kubernetes/examples/service.yaml
kubectl create -f alpine.yaml

Get the endpoint for the nginx-service, which should route message to the pod nginx:

kubectl describe service nginx-service | grep -e IP: -e Port:
IP:                     10.254.21.158
Port:                   <unnamed>       8000/TCP

Note the IP and port to use for checking below. Log into the node where the alpine pod is running. You can find the hosting node by running this command on the master node:

kubectl get pods -o wide  | grep alpine | awk '{print $6}'
k8-gzvjwcooto-0-gsrxhmyjupbi-kube-minion-br73i6ans2b4

To get the IP of the node, query Nova on devstack:

nova list

On this hosting node, attach to the alpine container:

export DOCKER_ID=`sudo docker ps | grep k8s_alpine | awk '{print $1}'`
sudo docker exec -it $DOCKER_ID sh

From the alpine pod, you can try to reach the nginx pod through the nginx service using the IP and Port found above:

wget 10.254.21.158:8000

If the connection is successful, you should receive the file index.html from nginx.

If the connection is not successful, you will get an error message like::xs

wget: can’t connect to remote host (10.100.54.9): No route to host

In this case, check the following:

• Is kube-proxy running on the nodes? It runs as a container on each node. check by logging in the minion nodes and run:

  sudo docker ps | grep k8s_kube-proxy
  

• Check the log from kube-proxy by running on the minion nodes:

  export PROXY=`sudo docker ps | grep "hyperkube proxy" | awk '{print $1}'`
  sudo docker logs $PROXY
  

• Try additional service debugging. To see what’s going during provisioning:

  kubectl get events
  

  To get information on a service in question:

  kubectl describe services <service_name>
  

etcd service

The etcd service is used by many other components for key/value pair management, therefore if it fails to start, these other components will not be running correctly either. Check that etcd is running on the master nodes by:

sudo service etcd status -l

If it is running correctly, you should see that the service is successfully deployed:

Active: active (running) since ....

The log message should show the service being published:

etcdserver: published {Name:10.0.0.5 ClientURLs:[http://10.0.0.5:2379]} to cluster 3451e4c04ec92893

In some cases, the service may show as active but may still be stuck in discovery mode and not fully operational. The log message may show something like:

discovery: waiting for other nodes: error connecting to https://discovery.etcd.io, retrying in 8m32s

If this condition persists, check for Cluster internet access.

If the daemon is not running, the status will show the service as failed, something like:

Active: failed (Result: timeout)

In this case, try restarting etcd by:

sudo service etcd start

If etcd continues to fail, check the following:

• Check the log for etcd:

  sudo journalctl -u etcd
  

• etcd requires discovery, and the default discovery method is the public discovery service provided by etcd.io; therefore, a common cause of failure is that this public discovery service is not reachable. Check by running on the master nodes:

  . /etc/sysconfig/heat-params
  curl $ETCD_DISCOVERY_URL
  

  You should receive something like:

  {"action":"get",
   "node":{"key":"/_etcd/registry/00a6b00064174c92411b0f09ad5466c6",
           "dir":true,
           "nodes":[
             {"key":"/_etcd/registry/00a6b00064174c92411b0f09ad5466c6/7d8a68781a20c0a5",
              "value":"10.0.0.5=http://10.0.0.5:2380",
              "modifiedIndex":978239406,
              "createdIndex":978239406}],
           "modifiedIndex":978237118,
           "createdIndex":978237118}
  }
  

  The list of master IP is provided by Magnum during cluster deployment, therefore it should match the current IP of the master nodes. If the public discovery service is not reachable, check the Cluster internet access.

Running Flannel

When deploying a COE, Flannel is available as a network driver for certain COE type. Magnum currently supports Flannel for a Kubernetes cluster.

Flannel provides a flat network space for the containers in the cluster: they are allocated IP in this network space and they will have connectivity to each other. Therefore, if Flannel fails, some containers will not be able to access services from other containers in the cluster. This can be confirmed by running ping or curl from one container to another.

The Flannel daemon is run as a systemd service on each node of the cluster. To check Flannel, run on each node:

sudo service flanneld status

If the daemon is running, you should see that the service is successfully deployed:

Active: active (running) since ....

If the daemon is not running, the status will show the service as failed, something like:

Active: failed (Result: timeout) ....

or:

Active: inactive (dead) ....

Flannel daemon may also be running but not functioning correctly. Check the following:

• Check the log for Flannel:

  sudo journalctl -u flanneld
  

• Since Flannel relies on etcd, a common cause for failure is that the etcd service is not running on the master nodes. Check the etcd service. If the etcd service failed, once it has been restored successfully, the Flannel service can be restarted by:

  sudo service flanneld restart
  

• Magnum writes the configuration for Flannel in a local file on each master node. Check for this file on the master nodes by:

  cat /etc/sysconfig/flannel-network.json
  

  The content should be something like:

  {
    "Network": "10.100.0.0/16",
    "Subnetlen": 24,
    "Backend": {
      "Type": "udp"
    }
  }
  

  where the values for the parameters must match the corresponding parameters from the ClusterTemplate.

  Magnum also loads this configuration into etcd, therefore, verify the configuration in etcd by running etcdctl on the master nodes:

  . /etc/sysconfig/flanneld
  etcdctl get $FLANNEL_ETCD_KEY/config
  

• Each node is allocated a segment of the network space. Check for this segment on each node by:

  grep FLANNEL_SUBNET /run/flannel/subnet.env
  

  The containers on this node should be assigned an IP in this range. The nodes negotiate for their segment through etcd, and you can use etcdctl on the master node to query the network segment associated with each node:

  . /etc/sysconfig/flanneld
  for s in `etcdctl ls $FLANNEL_ETCD_KEY/subnets`
  do
  echo $s
  etcdctl get $s
  done
  
  /atomic.io/network/subnets/10.100.14.0-24
  {"PublicIP":"10.0.0.5"}
  /atomic.io/network/subnets/10.100.61.0-24
  {"PublicIP":"10.0.0.6"}
  /atomic.io/network/subnets/10.100.92.0-24
  {"PublicIP":"10.0.0.7"}
  

  Alternatively, you can read the full record in ectd by:

  curl http://<master_node_ip>:2379/v2/keys/coreos.com/network/subnets
  

  You should receive a JSON snippet that describes all the segments allocated.

• This network segment is passed to Docker via the parameter –bip. If this is not configured correctly, Docker would not assign the correct IP in the Flannel network segment to the container. Check by:

  cat /run/flannel/docker
  ps -aux | grep docker
  

• Check the interface for Flannel:

  ifconfig flannel0
  

  The IP should be the first address in the Flannel subnet for this node.

• Flannel has several different backend implementations and they have specific requirements. The udp backend is the most general and have no requirement on the network. The vxlan backend requires vxlan support in the kernel, so ensure that the image used does provide vxlan support. The host-gw backend requires that all the hosts are on the same L2 network. This is currently met by the private Neutron subnet created by Magnum; however, if other network topology is used instead, ensure that this requirement is met if host-gw is used.

Current known limitation: the image fedora-21-atomic-5.qcow2 has Flannel version 0.5.0. This version has known bugs that prevent the backend vxland and host-gw to work correctly. Only the backend udp works for this image. Version 0.5.3 and later should work correctly. The image fedora-21-atomic-7.qcow2 has Flannel version 0.5.5.

Kubernetes services

To be filled in

(How to introspect k8s when heat works and k8s does not)

Additional Kubernetes troubleshooting section is available in the Monitoring, Logging, and Debugging section.

Barbican issues

To be filled in

Docker CLI

To be filled in

Request volume size

To be filled in

Heat software resource scripts

To be filled in

For Developers

This section is intended to help with issues that developers may run into in the course of their development adventures in Magnum.

Troubleshooting in Gate

Simulating gate tests

1. Boot a VM

2. Provision this VM like so:

   apt-get update \
   && apt-get upgrade \ # Kernel upgrade, as recommended by README, select to keep existing grub config
   && apt-get install git tmux vim \
   && git clone https://git.openstack.org/openstack-infra/system-config \
   && system-config/install_puppet.sh && system-config/install_modules.sh \
   && puppet apply \
   --modulepath=/root/system-config/modules:/etc/puppet/modules \
   -e "class { openstack_project::single_use_slave: install_users => false,
   ssh_key => \"$( cat .ssh/authorized_keys | awk '{print $2}' )\" }" \
   && echo "jenkins ALL=(ALL) NOPASSWD:ALL" >> /etc/sudoers \
   && cat ~/.ssh/authorized_keys >> /home/jenkins/.ssh/authorized_keys
   

3. Compare ~/.ssh/authorized_keys and /home/jenkins/.ssh/authorized_keys. Your original public SSH key should now be in /home/jenkins/.ssh/authorized_keys. If it’s not, explicitly copy it (this can happen if you spin up a using --key-name <name>, for example).

4. Assuming all is well up to this point, now it’s time to reboot into the latest kernel

5. Once you’re done booting into the new kernel, log back in as jenkins user to continue with setting up the simulation.

6. Now it’s time to set up the workspace:

   export REPO_URL=https://git.openstack.org
   export WORKSPACE=/home/jenkins/workspace/testing
   export ZUUL_URL=/home/jenkins/workspace-cache2
   export ZUUL_REF=HEAD
   export ZUUL_BRANCH=master
   export ZUUL_PROJECT=openstack/magnum
   mkdir -p $WORKSPACE
   git clone $REPO_URL/$ZUUL_PROJECT $ZUUL_URL/$ZUUL_PROJECT \
   && cd $ZUUL_URL/$ZUUL_PROJECT \
   && git checkout remotes/origin/$ZUUL_BRANCH
   

7. At this point, you may be wanting to test a specific change. If so, you can pull down the changes in $ZUUL_URL/$ZUUL_PROJECT directory:

   cd $ZUUL_URL/$ZUUL_PROJECT \
   && git fetch https://review.openstack.org/openstack/magnum refs/changes/83/247083/12 && git checkout FETCH_HEAD
   

8. Now you’re ready to pull down the devstack-gate scripts that will let you run the gate job on your own VM:

   cd $WORKSPACE \
   && git clone --depth 1 $REPO_URL/openstack-infra/devstack-gate
   

9. And now you can kick off the job using the following script (the devstack-gate documentation suggests just copying from the job which can be found in the project-config repository), naturally it should be executable (chmod u+x <filename>):

   #!/bin/bash -xe
   cat > clonemap.yaml << EOF
   clonemap:
     - name: openstack-infra/devstack-gate
       dest: devstack-gate
   EOF
   /usr/zuul-env/bin/zuul-cloner -m clonemap.yaml --cache-dir /opt/git \
       https://git.openstack.org \
       openstack-infra/devstack-gate
   export PYTHONUNBUFFERED=true
   export DEVSTACK_GATE_TIMEOUT=240 # bump this if you see timeout issues.  Default is 120
   export DEVSTACK_GATE_TEMPEST=0
   export DEVSTACK_GATE_NEUTRON=1
   # Enable tempest for tempest plugin
   export ENABLED_SERVICES=tempest
   export BRANCH_OVERRIDE="default"
   if [ "$BRANCH_OVERRIDE" != "default" ] ; then
       export OVERRIDE_ZUUL_BRANCH=$BRANCH_OVERRIDE
   fi
   export PROJECTS="openstack/magnum $PROJECTS"
   export PROJECTS="openstack/python-magnumclient $PROJECTS"
   export PROJECTS="openstack/barbican $PROJECTS"
   export DEVSTACK_LOCAL_CONFIG="enable_plugin magnum https://git.openstack.org/openstack/magnum"
   export DEVSTACK_LOCAL_CONFIG+=$'\n'"enable_plugin ceilometer https://git.openstack.org/openstack/ceilometer"
   # Keep localrc to be able to set some vars in post_test_hook
   export KEEP_LOCALRC=1
   function gate_hook {
        cd /opt/stack/new/magnum/
       ./magnum/tests/contrib/gate_hook.sh api # change this to k8s to run kubernetes functional tests
   }
   export -f gate_hook
   function post_test_hook {
       . $BASE/new/devstack/accrc/admin/admin
       cd /opt/stack/new/magnum/
       ./magnum/tests/contrib/post_test_hook.sh api # change this to k8s to run kubernetes functional tests
   }
   export -f post_test_hook
   cp devstack-gate/devstack-vm-gate-wrap.sh ./safe-devstack-vm-gate-wrap.sh
   ./safe-devstack-vm-gate-wrap.sh