This topic will discuss general approaches for test and debug of cloud-init on deployed instances.
Occasionally instances don't appear as performant as we would like and cloud-init packages a simple facility to inspect what operations took cloud-init the longest during boot and setup.
The script /usr/bin/cloud-init has an analyze sub-command analyze which parses any cloud-init.log file into formatted and sorted events. It allows for detailed analysis of the most costly cloud-init operations are to determine the long-pole in cloud-init configuration and setup. These subcommands default to reading /var/log/cloud-init.log.
analyze show
Parse and organize cloud-init.log events by stage and include each sub-stage granularity with time delta reports.
$ cloud-init analyze show -i my-cloud-init.log
-- Boot Record 01 --
The total time elapsed since completing an event is printed after the "@"
character.
The time the event takes is printed after the "+" character.
Starting stage: modules-config
|`->config-emit_upstart ran successfully @05.47600s +00.00100s
|`->config-snap_config ran successfully @05.47700s +00.00100s
|`->config-ssh-import-id ran successfully @05.47800s +00.00200s
|`->config-locale ran successfully @05.48000s +00.00100s
...
analyze dump
Parse cloud-init.log into event records and return a list of dictionaries that can be consumed for other reporting needs.
$ cloud-init analyze dump -i my-cloud-init.log
[
{
"description": "running config modules",
"event_type": "start",
"name": "modules-config",
"origin": "cloudinit",
"timestamp": 1510807493.0
},...
analyze blame
Parse cloud-init.log into event records and sort them based on highest time cost for quick assessment of areas of cloud-init that may need improvement.
$ cloud-init analyze blame -i my-cloud-init.log
-- Boot Record 11 --
00.01300s (modules-final/config-scripts-per-boot)
00.00400s (modules-final/config-final-message)
00.00100s (modules-final/config-rightscale_userdata)
...
analyze boot
Make subprocess calls to the kernel in order to get relevant pre-cloud-init timestamps, such as the kernel start, kernel finish boot, and cloud-init start.
$ cloud-init analyze boot
-- Most Recent Boot Record --
Kernel Started at: 2019-06-13 15:59:55.809385
Kernel ended boot at: 2019-06-13 16:00:00.944740
Kernel time to boot (seconds): 5.135355
Cloud-init start: 2019-06-13 16:00:05.738396
Time between Kernel boot and Cloud-init start (seconds): 4.793656
To quickly obtain a cloud-init log try using lxc on any ubuntu system:
$ lxc init ubuntu-daily:xenial x1
$ lxc start x1
$ # Take lxc's cloud-init.log and pipe it to the analyzer
$ lxc file pull x1/var/log/cloud-init.log - | cloud-init analyze dump -i -
$ lxc file pull x1/var/log/cloud-init.log - | \
python3 -m cloudinit.analyze dump -i -
To quickly analyze a KVM a cloud-init log:
- Download the current cloud image
$ wget https://cloud-images.ubuntu.com/daily/server/xenial/current/xenial-server-cloudimg-amd64.img
- Create a snapshot image to preserve the original cloud-image
$ qemu-img create -b xenial-server-cloudimg-amd64.img -f qcow2 \
test-cloudinit.qcow2
- Create a seed image with metadata using cloud-localds
$ cat > user-data <<EOF
#cloud-config
password: passw0rd
chpasswd: { expire: False }
EOF
$ cloud-localds my-seed.img user-data
- Launch your modified VM
$ kvm -m 512 -net nic -net user -redir tcp:2222::22 \
-drive file=test-cloudinit.qcow2,if=virtio,format=qcow2 \
-drive file=my-seed.img,if=virtio,format=raw
- Analyze the boot (blame, dump, show)
$ ssh -p 2222 ubuntu@localhost 'cat /var/log/cloud-init.log' | \
cloud-init analyze blame -i -
This subcommand is not called by the init system. It can be called manually to
load the configured datasource and run a single cloud-config module once using
the cached userdata and metadata after the instance has booted. Each
cloud-config module has a module FREQUENCY configured: PER_INSTANCE, PER_BOOT,
PER_ONCE or PER_ALWAYS. When a module is run by cloud-init, it stores a
semaphore file in
/var/lib/cloud/instance/sem/config_<module_name>.<frequency>
which marks
when the module last successfully ran. Presence of this semaphore file
prevents a module from running again if it has already been run. To ensure that
a module is run again, the desired frequency can be overridden on the
commandline:
$ sudo cloud-init single --name cc_ssh --frequency always
...
Generating public/private ed25519 key pair
...
Inspect cloud-init.log for output of what operations were performed as a result.