Add IPFS node guide

README.md

@@ -21,7 +21,7 @@ Demo instance: https://mitra.social/ (invite-only)
 
 - Rust 1.51+
 - PostgreSQL 10.2+
-- IPFS node (optional)
+- IPFS node (optional, see [guide](./docs/ipfs.md))
 - Ethereum node (optional)
 
 ## Development

docs/ipfs.md

@@ -0,0 +1,62 @@
+# Running IPFS node
+
+This guide explains how to run IPFS node in resource-constrained environment (such as cheap VPS or single-board computer).
+
+The recommended IPFS implementation is [go-ipfs](https://github.com/ipfs/go-ipfs), version 0.11 or higher. Normally go-ipfs requires at least 2 GB RAM, but after tweaking it can run on a machine with only 512 MB.
+
+## Configuration profiles
+
+IPFS configuration should be initialized with `server` profile if your node is running on a cloud server:
+
+```
+ipfs init --profile server
+```
+
+If you're running it on single-board computer, the recommended profile is `lowpower`.
+
+Documentation on configuration profiles: https://github.com/ipfs/go-ipfs/blob/master/docs/config.md#profiles.
+
+## Configuration options
+
+- `Gateway.NoFetch`. Configures gateway to not fetch files from the network. Recommended value is `true`.
+- `RelayService.Enabled`. Enables providing p2p relay service to other peers on the network. Recommended value is `false`.
+- `Routing.Type`. Should be set to `dht` otherwise the node will not respond to requests from other peers.
+- `Swarm.ConnMgr.LowWater`. Recommended value is `10`.
+- `Swarm.ConnMgr.HighWater`. Recommended value is `20`.
+- `Swarm.ConnMgr.GracePeriod`. Recommended value is `15s`.
+- `Swarm.DisableBandwidthMetrics`. Disabling bandwidth metrics can slightly improve performance. Recommended value is `true`.
+
+Documentation: https://github.com/ipfs/go-ipfs/blob/master/docs/config.md
+
+## Systemd service
+
+When go-ipfs starts, its memory usage is around 100 MB and then it slowly increases. To keep memory usage within reasonable bounds the service needs to be restarted regularly.
+
+This can be achieved by using systemd process supervison features:
+
+```
+[Unit]
+Description=InterPlanetary File System (IPFS) daemon
+
+[Service]
+ExecStart=/usr/local/bin/ipfs daemon
+User=ipfs
+Group=ipfs
+
+# Terminate service every 20 minutes and restart automatically
+RuntimeMaxSec=1200
+Restart=on-failure
+
+# Specify the absolute limit on memory usage
+# If memory usage cannot be contained under the limit, out-of-memory killer is invoked
+MemoryMax=250M
+MemorySwapMax=0
+
+[Install]
+WantedBy=default.target
+```
+
+Documentation:
+
+- https://www.freedesktop.org/software/systemd/man/systemd.service.html
+- https://www.freedesktop.org/software/systemd/man/systemd.resource-control.html