157 lines
7.4 KiB
Markdown
157 lines
7.4 KiB
Markdown
# Generating chaos in a test GitLab instance
|
|
|
|
As [Werner Vogels](https://twitter.com/Werner), the CTO at Amazon Web Services, famously put it, **Everything fails, all the time**.
|
|
|
|
As a developer, it's as important to consider the failure modes in which your software will operate as much as normal operation. Doing so can mean the difference between a minor hiccup leading to a scattering of `500` errors experienced by a tiny fraction of users and a full site outage that affects all users for an extended period.
|
|
|
|
To paraphrase [Tolstoy](https://en.wikipedia.org/wiki/Anna_Karenina_principle), _all happy servers are alike, but all failing servers are failing in their own way_. Luckily, there are ways we can attempt to simulate these failure modes, and the chaos endpoints are tools for assisting in this process.
|
|
|
|
Currently, there are four endpoints for simulating the following conditions:
|
|
|
|
- Slow requests.
|
|
- CPU-bound requests.
|
|
- Memory leaks.
|
|
- Unexpected process crashes.
|
|
|
|
## Enabling chaos endpoints
|
|
|
|
For obvious reasons, these endpoints are not enabled by default on `production`.
|
|
They are enabled by default on **development** environments.
|
|
|
|
DANGER: **Danger:**
|
|
It is required that you secure access to the chaos endpoints using a secret token.
|
|
You should not enable them in production unless you absolutely know what you're doing.
|
|
|
|
A secret token can be set through the `GITLAB_CHAOS_SECRET` environment variable.
|
|
For example, when using the [GDK](https://gitlab.com/gitlab-org/gitlab-development-kit)
|
|
this can be done with the following command:
|
|
|
|
```shell
|
|
GITLAB_CHAOS_SECRET=secret gdk run
|
|
```
|
|
|
|
Replace `secret` with your own secret token.
|
|
|
|
## Invoking chaos
|
|
|
|
Once you have enabled the chaos endpoints and restarted the application, you can start testing using the endpoints.
|
|
|
|
By default, when invoking a chaos endpoint, the web worker process which receives the request will handle it. This means, for example, that if the Kill
|
|
operation is invoked, the Puma or Unicorn worker process handling the request will be killed. To test these operations in Sidekiq, the `async` parameter on
|
|
each endpoint can be set to `true`. This will run the chaos process in a Sidekiq worker.
|
|
|
|
## Memory leaks
|
|
|
|
To simulate a memory leak in your application, use the `/-/chaos/leakmem` endpoint.
|
|
|
|
NOTE: **Note:**
|
|
The memory is not retained after the request finishes. Once the request has completed, the Ruby garbage collector will attempt to recover the memory.
|
|
|
|
```plaintext
|
|
GET /-/chaos/leakmem
|
|
GET /-/chaos/leakmem?memory_mb=1024
|
|
GET /-/chaos/leakmem?memory_mb=1024&duration_s=50
|
|
GET /-/chaos/leakmem?memory_mb=1024&duration_s=50&async=true
|
|
```
|
|
|
|
| Attribute | Type | Required | Description |
|
|
| ------------ | ------- | -------- | ------------------------------------------------------------------------------------ |
|
|
| `memory_mb` | integer | no | How much memory, in MB, should be leaked. Defaults to 100MB. |
|
|
| `duration_s` | integer | no | Minimum duration_s, in seconds, that the memory should be retained. Defaults to 30s. |
|
|
| `async` | boolean | no | Set to true to leak memory in a Sidekiq background worker process |
|
|
|
|
```shell
|
|
curl http://localhost:3000/-/chaos/leakmem?memory_mb=1024&duration_s=10 --header 'X-Chaos-Secret: secret'
|
|
curl http://localhost:3000/-/chaos/leakmem?memory_mb=1024&duration_s=10&token=secret
|
|
```
|
|
|
|
## CPU spin
|
|
|
|
This endpoint attempts to fully utilise a single core, at 100%, for the given period.
|
|
|
|
Depending on your rack server setup, your request may timeout after a predetermined period (normally 60 seconds).
|
|
If you're using Unicorn, this is done by killing the worker process.
|
|
|
|
```plaintext
|
|
GET /-/chaos/cpu_spin
|
|
GET /-/chaos/cpu_spin?duration_s=50
|
|
GET /-/chaos/cpu_spin?duration_s=50&async=true
|
|
```
|
|
|
|
| Attribute | Type | Required | Description |
|
|
| ------------ | ------- | -------- | --------------------------------------------------------------------- |
|
|
| `duration_s` | integer | no | Duration, in seconds, that the core will be utilized. Defaults to 30s |
|
|
| `async` | boolean | no | Set to true to consume CPU in a Sidekiq background worker process |
|
|
|
|
```shell
|
|
curl http://localhost:3000/-/chaos/cpu_spin?duration_s=60 --header 'X-Chaos-Secret: secret'
|
|
curl http://localhost:3000/-/chaos/cpu_spin?duration_s=60&token=secret
|
|
```
|
|
|
|
## DB spin
|
|
|
|
This endpoint attempts to fully utilise a single core, and interleave it with DB request, for the given period.
|
|
This endpoint can be used to model yielding execution to another threads when running concurrently.
|
|
|
|
Depending on your rack server setup, your request may timeout after a predetermined period (normally 60 seconds).
|
|
If you're using Unicorn, this is done by killing the worker process.
|
|
|
|
```plaintext
|
|
GET /-/chaos/db_spin
|
|
GET /-/chaos/db_spin?duration_s=50
|
|
GET /-/chaos/db_spin?duration_s=50&async=true
|
|
```
|
|
|
|
| Attribute | Type | Required | Description |
|
|
| ------------ | ------- | -------- | --------------------------------------------------------------------------- |
|
|
| `interval_s` | float | no | Interval, in seconds, for every DB request. Defaults to 1s |
|
|
| `duration_s` | integer | no | Duration, in seconds, that the core will be utilized. Defaults to 30s |
|
|
| `async` | boolean | no | Set to true to perform the operation in a Sidekiq background worker process |
|
|
|
|
```shell
|
|
curl http://localhost:3000/-/chaos/db_spin?interval_s=1&duration_s=60 --header 'X-Chaos-Secret: secret'
|
|
curl http://localhost:3000/-/chaos/db_spin?interval_s=1&duration_s=60&token=secret
|
|
```
|
|
|
|
## Sleep
|
|
|
|
This endpoint is similar to the CPU Spin endpoint but simulates off-processor activity, such as network calls to backend services. It will sleep for a given duration_s.
|
|
|
|
As with the CPU Spin endpoint, this may lead to your request timing out if duration_s exceeds the configured limit.
|
|
|
|
```plaintext
|
|
GET /-/chaos/sleep
|
|
GET /-/chaos/sleep?duration_s=50
|
|
GET /-/chaos/sleep?duration_s=50&async=true
|
|
```
|
|
|
|
| Attribute | Type | Required | Description |
|
|
| ------------ | ------- | -------- | ---------------------------------------------------------------------- |
|
|
| `duration_s` | integer | no | Duration, in seconds, that the request will sleep for. Defaults to 30s |
|
|
| `async` | boolean | no | Set to true to sleep in a Sidekiq background worker process |
|
|
|
|
```shell
|
|
curl http://localhost:3000/-/chaos/sleep?duration_s=60 --header 'X-Chaos-Secret: secret'
|
|
curl http://localhost:3000/-/chaos/sleep?duration_s=60&token=secret
|
|
```
|
|
|
|
## Kill
|
|
|
|
This endpoint will simulate the unexpected death of a worker process using a `kill` signal.
|
|
|
|
NOTE: **Note:**
|
|
Since this endpoint uses the `KILL` signal, the worker is not given a chance to cleanup or shutdown.
|
|
|
|
```plaintext
|
|
GET /-/chaos/kill
|
|
GET /-/chaos/kill?async=true
|
|
```
|
|
|
|
| Attribute | Type | Required | Description |
|
|
| ------------ | ------- | -------- | ---------------------------------------------------------------------- |
|
|
| `async` | boolean | no | Set to true to kill a Sidekiq background worker process |
|
|
|
|
```shell
|
|
curl http://localhost:3000/-/chaos/kill --header 'X-Chaos-Secret: secret'
|
|
curl http://localhost:3000/-/chaos/kill?token=secret
|
|
```
|