garage/script/jepsen.garage/README.md

# jepsen.garage

Jepsen checking of Garage consistency properties.

## Usage

Requirements:

- vagrant
- VirtualBox, configured so that nodes can take an IP in a private network `192.168.56.0/24`
- a user that can create VirtualBox VMs
- leiningen
- gnuplot

Set up VMs:

```
vagrant up
```

Run tests (this one should fail):

```
lein run test --nodes-file nodes.vagrant --time-limit 64 --concurrency 50 --rate 50 --workload reg
```

These ones are working:

```
lein run test --nodes-file nodes.vagrant --time-limit 64 --rate 50  --concurrency 50 --workload set1
lein run test --nodes-file nodes.vagrant --time-limit 64 --rate 50  --concurrency 50 --workload set2
```

## Results

### Register linear, without timestamp patch

Command: `lein run test --nodes-file nodes.vagrant --time-limit 60 --rate 20  --concurrency 20 --workload reg --ops-per-key 100`

Results: fails with a simple clock-scramble nemesis.

Explanation: without the timestamp patch, nodes will create objects using their
local clock only as a timestamp, so the ordering will be all over the place if
clocks are scrambled.

### Register linear, with timestamp patch

Command: `lein run test --nodes-file nodes.vagrant --time-limit 60 --rate 20  --concurrency 20 --workload reg --ops-per-key 100 -I`

Results:

- No failure with clock-scramble nemesis
- Fails with clock-scramble nemesis + partition nemesis

Explanation: S3 objects are not meant to behave like linearizable registers. TODO explain using a counter-example

### Read-after-write CRDT register model

TODO: determine the expected semantics of such a register, code a checker and show that results are correct

### Set, basic test (write some items, then read)

Command: `lein run test --nodes-file nodes.vagrant --time-limit 60 --rate 100  --concurrency 100 --workload set1 --ops-per-key 100`

Results:

- For now, no failures with clock-scramble nemesis + partition nemesis

### Set, continuous test (interspersed reads and writes)

TODO

TODO: nemesis that reconfigures the cluster with a different subset of nodes, to have requests that occur during a resync period.


## Investigating (and fixing) wierd behavior

### Segfaults

They are due to the download being interrupted in the middle (^C during first launch on clean VMs), the `garage` binary is truncated.
Add `:force?` to the `cached-wget!` call in `daemon.clj` to re-download the binary.

### In `jepsen.garage`: prefix wierdness

In `store/garage set1/20231019T163358.615+0200`:

```
INFO [2023-10-19 16:35:20,977] clojure-agent-send-off-pool-207 - jepsen.garage.set list results for prefix set20/ : (set13/0 set13/1 set13/10 set13/11 set13/12 set13/13 set13/14 set13/15 set13/16 set13/17 set13/18 set13/19 set13/2 set13/20 set13/21 set13/22 set13/23 set13/24 set13/25 set13/26 set13/27 set13/28 set13/29 set13/3 set13/30 set13/31 set13/32 set13/33 set13/34 set13/35 set13/36 set13/37 set13/38 set13/39 set13/4 set13/40 set13/41 set13/42 set13/43 set13/44 set13/45 set13/46 set13/47 set13/48 set13/49 set13/5 set13/50 set13/51 set13/52 set13/53 set13/54 set13/55 set13/56 set13/57 set13/58 set13/59 set13/6 set13/60 set13/61 set13/62 set13/63 set13/64 set13/65 set13/66 set13/67 set13/68 set13/69 set13/7 set13/70 set13/71 set13/72 set13/73 set13/74 set13/75 set13/76 set13/77 set13/78 set13/79 set13/8 set13/80 set13/81 set13/82 set13/83 set13/84 set13/85 set13/86 set13/87 set13/88 set13/89 set13/9 set13/90 set13/91 set13/92 set13/93 set13/94 set13/95 set13/96 set13/97 set13/98 set13/99)  (node: http://192.168.56.25:3900 )
```

After inspecting, the actual S3 call made was with prefix "set13/", so at least this is not an error in Garage itself but in the jepsen code.

Finally found out that this was due to closures not correctly capturing their context in the list function in s3api.clj (wtf clojure?)
Not sure exactly where it came from but it seems to have been fixed by making list-inner a separate function and not a sub-function,
and passing all values that were previously in the context (creds and prefix) as additional arguments.

## License

Copyright © 2023 Alex Auvolat

This program and the accompanying materials are made available under the
terms of the GNU Affero General Public License v3.0.