244 lines
9.8 KiB
Markdown
244 lines
9.8 KiB
Markdown
---
|
|
stage: none
|
|
group: unassigned
|
|
info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/product/ux/technical-writing/#assignments
|
|
---
|
|
|
|
# Generating chaos in a test GitLab instance
|
|
|
|
<!-- vale gitlab.Spelling = NO -->
|
|
|
|
As [Werner Vogels](https://twitter.com/Werner), the CTO at Amazon Web Services, famously put it, **Everything fails, all the time**.
|
|
|
|
<!-- vale gitlab.Spelling = NO -->
|
|
|
|
As a developer, it's as important to consider the failure modes in which your software may 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.
|
|
|
|
WARNING:
|
|
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 start
|
|
```
|
|
|
|
Replace `secret` with your own secret token.
|
|
|
|
## Invoking chaos
|
|
|
|
After 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 handles it. This means, for example, that if the Kill
|
|
operation is invoked, the Puma worker process handling the request is killed. To test these operations in Sidekiq, the `async` parameter on
|
|
each endpoint can be set to `true`. This runs the chaos process in a Sidekiq worker.
|
|
|
|
## Memory leaks
|
|
|
|
To simulate a memory leak in your application, use the `/-/chaos/leakmem` endpoint.
|
|
|
|
The memory is not retained after the request finishes. After the request has completed, the Ruby garbage collector attempts 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 use 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).
|
|
|
|
```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 is used. 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 use 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).
|
|
|
|
```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 is used. 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 sleeps 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 sleeps 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 simulates the unexpected death of a worker process using the `KILL` signal.
|
|
|
|
Because this endpoint uses the `KILL` signal, the process isn't given an
|
|
opportunity to clean up or shut down.
|
|
|
|
```plaintext
|
|
GET /-/chaos/kill
|
|
GET /-/chaos/kill?async=true
|
|
```
|
|
|
|
| Attribute | Type | Required | Description |
|
|
| ------------ | ------- | -------- | ---------------------------------------------------------------------- |
|
|
| `async` | boolean | no | Set to true to signal 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"
|
|
```
|
|
|
|
## Quit
|
|
|
|
This endpoint simulates the unexpected death of a worker process using the `QUIT` signal.
|
|
Unlike `KILL`, the `QUIT` signal will also attempt to write a core dump.
|
|
See [core(5)](https://man7.org/linux/man-pages/man5/core.5.html) for more information.
|
|
|
|
```plaintext
|
|
GET /-/chaos/quit
|
|
GET /-/chaos/quit?async=true
|
|
```
|
|
|
|
| Attribute | Type | Required | Description |
|
|
| ------------ | ------- | -------- | ---------------------------------------------------------------------- |
|
|
| `async` | boolean | no | Set to true to signal a Sidekiq background worker process |
|
|
|
|
```shell
|
|
curl "http://localhost:3000/-/chaos/quit" --header 'X-Chaos-Secret: secret'
|
|
curl "http://localhost:3000/-/chaos/quit?token=secret"
|
|
```
|
|
|
|
## Run garbage collector
|
|
|
|
This endpoint triggers a GC run on the worker handling the request and returns its worker ID
|
|
plus GC stats as JSON. This is mostly useful when running Puma in standalone mode, since
|
|
otherwise the worker handling the request will not be known upfront.
|
|
|
|
Endpoint:
|
|
|
|
```plaintext
|
|
POST /-/chaos/gc
|
|
```
|
|
|
|
Example request:
|
|
|
|
```shell
|
|
curl --request POST "http://localhost:3000/-/chaos/gc" \
|
|
--header 'X-Chaos-Secret: secret'
|
|
curl --request POST "http://localhost:3000/-/chaos/gc?token=secret"
|
|
```
|
|
|
|
Example response:
|
|
|
|
```json
|
|
{
|
|
"worker_id": "puma_1",
|
|
"gc_stat": {
|
|
"count": 94,
|
|
"heap_allocated_pages": 9077,
|
|
"heap_sorted_length": 9077,
|
|
"heap_allocatable_pages": 0,
|
|
"heap_available_slots": 3699720,
|
|
"heap_live_slots": 2827510,
|
|
"heap_free_slots": 872210,
|
|
"heap_final_slots": 0,
|
|
"heap_marked_slots": 2827509,
|
|
"heap_eden_pages": 9077,
|
|
"heap_tomb_pages": 0,
|
|
"total_allocated_pages": 9077,
|
|
"total_freed_pages": 0,
|
|
"total_allocated_objects": 14229357,
|
|
"total_freed_objects": 11401847,
|
|
"malloc_increase_bytes": 8192,
|
|
"malloc_increase_bytes_limit": 30949538,
|
|
"minor_gc_count": 71,
|
|
"major_gc_count": 23,
|
|
"compact_count": 0,
|
|
"remembered_wb_unprotected_objects": 41685,
|
|
"remembered_wb_unprotected_objects_limit": 83370,
|
|
"old_objects": 2617806,
|
|
"old_objects_limit": 5235612,
|
|
"oldmalloc_increase_bytes": 8192,
|
|
"oldmalloc_increase_bytes_limit": 122713697
|
|
}
|
|
}
|
|
```
|