Add portal config format example

network-rfc/12_portal_config.md

@@ -0,0 +1,53 @@
+# Portal config format
+
+Each portal instance is passed a config file that specifies the datasets it should serve.
+
+The config is a YAML file with the following structure:
+
+```yaml
+sqd_network:
+  datasets: https://cdn.subsquid.io/sqd-network/datasets.yml
+  serve: "all"  # only support "all" for now
+
+datasets:
+  "ethereum-mainnet":  # the "default name" of the dataset
+    aliases: ["eth-main", "eth"]  # optional
+    sqd_network:
+      dataset_name: "ethereum-mainnet"
+      # Or
+      # dataset_id: "s3://ethereum-mainnet-2"  # explicitly specifies the dataset version, should rarely be used
+
+  "arbitrum-one":
+    aliases: ["arbitrum-mainnet", "arbitrum-main"]
+    # If `sqd-network` is not specified, uses the network dataset with the same name (if any)
+
+  "solana-mainnet":
+    sqd_network:
+      dataset_name: "solana-mainnet"
+    real_time:
+      kind: solana
+      data_sources:
+        - "https://..."
+      retention:
+        # If dataset is present in the network, the historical blocks will also be removed from hotblocks storage
+        from_block: 250000000
+        # Or
+        # head: 2000
+
+  "my-devnet":
+    real_time:
+      kind: evm
+      data_sources:
+        - "http://localhost:8000/hotblocks"
+      retention:
+        head: 100
+
+  # The rest of the datasets are used from the mapping file
+
+hotblocks:
+  db: /data/hotblocks
+
+hostname: http://0.0.0.0:8000  # used for building legacy API urls
+```
+
+All the fields with their default values may be found in the [source code](https://github.com/subsquid/sqd-portal/blob/master/src/config.rs)