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initial DELVING.md document.

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# Delving into the unknown
This write-up summarises how to debug what appears to be a mischievous Lotus
instance during our Testground tests. It also goes enumerates which assets are
useful to report suspicious behaviours upstream, in a way that they are
actionable.
## Querying the Lotus RPC API
The `local:docker` and `cluster:k8s` map ports that you specify in the
composition.toml, so you can access them externally.
All our compositions should carry this fragment:
```toml
[global.run_config]
exposed_ports = ["6060", "1234", "2345"]
```
This tells Testground to expose the following ports:
* `6060` => Go pprof.
* `1234` => Lotus full node RPC.
* `2345` => Lotus storage miner RPC.
### local:docker
1. Install the `lotus` binary on your host.
2. Find the container that you want to connect to in `docker ps`.
* Note that our _container names_ are slightly long, and they're the last
field on every line, so if your terminal is wrapping text, the port
numbers will end up ABOVE the friendly/recognizable container name (e.g. `tg-lotus-soup-deals-e2e-acfc60bc1727-miners-1`).
* The testground output displays the _container ID_ inside coloured angle
brackets, so if you spot something spurious in a particular node, you can
hone in on that one, e.g. `<< 54dd5ad916b2 >>`.
```
⟩ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
54dd5ad916b2 be3c18d7f0d4 "/testplan" 10 seconds ago Up 8 seconds 0.0.0.0:32788->1234/tcp, 0.0.0.0:32783->2345/tcp, 0.0.0.0:32773->6060/tcp, 0.0.0.0:32777->6060/tcp tg-lotus-soup-deals-e2e-acfc60bc1727-clients-2
53757489ce71 be3c18d7f0d4 "/testplan" 10 seconds ago Up 8 seconds 0.0.0.0:32792->1234/tcp, 0.0.0.0:32790->2345/tcp, 0.0.0.0:32781->6060/tcp, 0.0.0.0:32786->6060/tcp tg-lotus-soup-deals-e2e-acfc60bc1727-clients-1
9d3e83b71087 be3c18d7f0d4 "/testplan" 10 seconds ago Up 8 seconds 0.0.0.0:32791->1234/tcp, 0.0.0.0:32789->2345/tcp, 0.0.0.0:32779->6060/tcp, 0.0.0.0:32784->6060/tcp tg-lotus-soup-deals-e2e-acfc60bc1727-clients-0
7bd60e75ed0e be3c18d7f0d4 "/testplan" 10 seconds ago Up 8 seconds 0.0.0.0:32787->1234/tcp, 0.0.0.0:32782->2345/tcp, 0.0.0.0:32772->6060/tcp, 0.0.0.0:32776->6060/tcp tg-lotus-soup-deals-e2e-acfc60bc1727-miners-1
dff229d7b342 be3c18d7f0d4 "/testplan" 10 seconds ago Up 9 seconds 0.0.0.0:32778->1234/tcp, 0.0.0.0:32774->2345/tcp, 0.0.0.0:32769->6060/tcp, 0.0.0.0:32770->6060/tcp tg-lotus-soup-deals-e2e-acfc60bc1727-miners-0
4cd67690e3b8 be3c18d7f0d4 "/testplan" 11 seconds ago Up 8 seconds 0.0.0.0:32785->1234/tcp, 0.0.0.0:32780->2345/tcp, 0.0.0.0:32771->6060/tcp, 0.0.0.0:32775->6060/tcp tg-lotus-soup-deals-e2e-acfc60bc1727-bootstrapper-0
aeb334adf88d iptestground/sidecar:edge "testground sidecar …" 43 hours ago Up About an hour 0.0.0.0:32768->6060/tcp testground-sidecar
c1157500282b influxdb:1.8 "/entrypoint.sh infl…" 43 hours ago Up 25 seconds 0.0.0.0:8086->8086/tcp testground-influxdb
99ca4c07fecc redis "docker-entrypoint.s…" 43 hours ago Up About an hour 0.0.0.0:6379->6379/tcp testground-redis
bf25c87488a5 bitnami/grafana "/run.sh" 43 hours ago Up 26 seconds 0.0.0.0:3000->3000/tcp testground-grafana
cd1d6383eff7 goproxy/goproxy "/goproxy" 45 hours ago Up About a minute 8081/tcp testground-goproxy
```
3. Take note of the port mapping. Imagine in the output above, we want to query
`54dd5ad916b2`. We'd use `localhost:32788`, as it forwards to the container's
1234 port (Lotus Full Node RPC).
4. Run your Lotus CLI command setting the `FULLNODE_API_INFO` env variable,
which is a multiaddr:
```sh
$ FULLNODE_API_INFO=":/ip4/127.0.0.1/tcp/$port/http" lotus chain list
[...]
```
### cluster:k8s
WIP @nonsense.
### Useful commands / checks
* **Making sure miners are on the same chain:** compare outputs of `lotus chain list`.
* **Checking deals:** `lotus client list-deals`.
* **Sector queries:** WIP @nonsense.
## Viewing logs of a particular container (local:docker)
This works for both started and stopped containers. Just get the container ID
(in double angle brackets in Testground output, on every log line), and do a:
```shell script
$ docker logs $container_id
```
## Accessing the golang instrumentation
Testground exposes a pprof endpoint under local port 6060, which both
`local:docker` and `cluster:k8s` map.
For `local:docker`, see above to figure out which host port maps to the
container's 6060 port.
## Acquiring a goroutine dump
When things appear to be stuck, get a goroutine dump.
```shell script
$ wget -o goroutine.out http://localhost:${pprof_port}/debug/pprof/goroutine?debug=2
```
You can use whyrusleeping/stackparse to extract a summary:
```shell script
$ go get https://github.com/whyrusleeping/stackparse
$ stackparse --summary goroutine.out
```
## Acquiring a CPU profile
When the CPU appears to be spiking/rallying, grab a CPU profile.
```shell script
$ wget -o profile.out http://localhost:${pprof_port}/debug/pprof/profile
```
Analyse it using `go tool pprof`. Usually, generating a `png` graph is useful:
```shell script
$ go tool pprof profile.out
File: testground
Type: cpu
Time: Jul 3, 2020 at 12:00am (WEST)
Duration: 30.07s, Total samples = 2.81s ( 9.34%)
Entering interactive mode (type "help" for commands, "o" for options)
(pprof) png
Generating report in profile003.png
```
## Submitting actionable reports / findings
This is useful both internally (within the Oni team, so that peers can help) and
externally (when submitting a finding upstream).
We don't need to play the full bug-hunting game on Lotus, but it's tremendously
useful to provide the necessary data so that any reports are actionable.
These include:
* test outputs (use `testground collect`).
* stack traces that appear in logs (whether panics or not).
* output of relevant Lotus CLI commands.
* if this is some kind of blockage / deadlock, goroutine dumps.
* if this is a CPU hotspot, a CPU profile would be useful.
* if this is a memory issue, a heap dump would be useful.