docker: make the shard count configurable, defaulting to conway's 8

docker/.env.production.template

@@ -3,7 +3,12 @@
 # Normally written for you by scripts/deploy-validator.sh, which fills in
 # DOMAIN, ACME_EMAIL, GENESIS_URL, GENESIS_BUCKET, GENESIS_PATH_PREFIX,
 # VALIDATOR_KEY, VALIDATOR_NAME, HOSTNAME, LINERA_VALIDATOR_IMAGE,
-# LINERA_CLIENT_IMAGE and NUM_SHARDS.
+# LINERA_CLIENT_IMAGE, NUM_SHARDS and COMPOSE_PROFILES.
+#
+# COMPOSE_PROFILES enables shard-4..7; shard-0..3 always run. Docker Compose
+# reads it from this file, so editing it changes how many shards start - which
+# will not match the shard list in server.json. Use --num-shards at deploy time
+# instead; see docs/DOCKER-COMPOSE.md#changing-the-shard-count.
 # See https://docs.infra.linera.net/QUICKSTART/. This template is the
 # reference for manual setup and for tuning an existing deployment.
 #
@@ -189,6 +194,14 @@ HOSTNAME=your-domain.example.com
 #LIMIT_MEM_SHARD_2=6G
 #LIMIT_CPUS_SHARD_3=2.00
 #LIMIT_MEM_SHARD_3=6G
+#LIMIT_CPUS_SHARD_4=2.00
+#LIMIT_MEM_SHARD_4=6G
+#LIMIT_CPUS_SHARD_5=2.00
+#LIMIT_MEM_SHARD_5=6G
+#LIMIT_CPUS_SHARD_6=2.00
+#LIMIT_MEM_SHARD_6=6G
+#LIMIT_CPUS_SHARD_7=2.00
+#LIMIT_MEM_SHARD_7=6G
 
 # Observability stack
 #LIMIT_CPUS_ALLOY=0.50

docker/alloy-config.river

@@ -17,34 +17,44 @@ prometheus.scrape "proxy_metrics" {
   scrape_timeout  = "10s"
 }
 
+// Discover the shards instead of listing them, so the shard count is
+// configurable without editing this file. Mirrors the docker_sd_configs block
+// in prometheus.yaml — the two scrape paths must agree on job and shard.
+discovery.relabel "shard_metrics" {
+  targets = discovery.docker.containers.targets
+
+  // Every shard service carries linera.shard; nothing else does.
+  rule {
+    source_labels = ["__meta_docker_container_label_linera_shard"]
+    regex         = ".+"
+    action        = "keep"
+  }
+
+  rule {
+    source_labels = ["__meta_docker_network_ip"]
+    target_label  = "__address__"
+    replacement   = "$1:21100"
+  }
+
+  rule {
+    source_labels = ["__meta_docker_container_label_linera_shard"]
+    target_label  = "shard"
+  }
+
+  rule {
+    target_label = "job"
+    replacement  = "linera-shard"
+  }
+
+  rule {
+    target_label = "instance"
+    replacement  = env("HOSTNAME")
+  }
+}
+
 // Scrape metrics from all shard services
 prometheus.scrape "shard_metrics" {
-  targets = [
-    {
-      __address__ = "docker-shard-1:21100",
-      job         = "linera-shard",
-      shard       = "0",
-      instance    = env("HOSTNAME"),
-    },
-    {
-      __address__ = "docker-shard-2:21100",
-      job         = "linera-shard",
-      shard       = "1",
-      instance    = env("HOSTNAME"),
-    },
-    {
-      __address__ = "docker-shard-3:21100",
-      job         = "linera-shard",
-      shard       = "2",
-      instance    = env("HOSTNAME"),
-    },
-    {
-      __address__ = "docker-shard-4:21100",
-      job         = "linera-shard",
-      shard       = "3",
-      instance    = env("HOSTNAME"),
-    },
-  ]
+  targets = discovery.relabel.shard_metrics.output
 
   forward_to = [otelcol.receiver.prometheus.default.receiver]
 

docker/docker-compose.local-monitoring.yaml

@@ -140,6 +140,8 @@ services:
       # Prometheus fails to start on a missing rule file.
       - ./recording.rules.yaml:/etc/prometheus/recording.rules.yaml:ro
       - ${PROMETHEUS_DATA_DIR:-./data/prometheus}:/prometheus
+      # Read-only: docker_sd_configs discovers the shards through it.
+      - /var/run/docker.sock:/var/run/docker.sock:ro
     ports:
       - "${PROMETHEUS_PORT:-9090}:9090"
     deploy:

docker/docker-compose.remote-scylla.yaml

@@ -46,3 +46,16 @@ services:
   shard-3:
     extra_hosts:
       - "scylla=${SCYLLA_HOST:?set SCYLLA_HOST to the address of your ScyllaDB host}"
+
+  shard-4:
+    extra_hosts:
+      - "scylla=${SCYLLA_HOST:?set SCYLLA_HOST to the address of your ScyllaDB host}"
+  shard-5:
+    extra_hosts:
+      - "scylla=${SCYLLA_HOST:?set SCYLLA_HOST to the address of your ScyllaDB host}"
+  shard-6:
+    extra_hosts:
+      - "scylla=${SCYLLA_HOST:?set SCYLLA_HOST to the address of your ScyllaDB host}"
+  shard-7:
+    extra_hosts:
+      - "scylla=${SCYLLA_HOST:?set SCYLLA_HOST to the address of your ScyllaDB host}"