diff --git a/docs/writing-plugins.md b/docs/writing-plugins.md
index e3a00183..367922f1 100644
--- a/docs/writing-plugins.md
+++ b/docs/writing-plugins.md
@@ -230,11 +230,11 @@ Communicating with Factorio
 
 For pushing data into Factorio there's RCON, which lets you send
 arbitrary Lua commands to invoke whatever code you want in the game.
-This is done by calling the `sendRcon` method on the instance's server object.
+This is done by calling the `sendRcon` method on the plugin object.
 For example:
 
     async onStart() {
-        let response = await this.instance.server.sendRcon(
+        let response = await this.sendRcon(
             "/sc rcon.print('data')"
         );
 
diff --git a/packages/lib/plugin.js b/packages/lib/plugin.js
index f5447f3a..3a461fea 100644
--- a/packages/lib/plugin.js
+++ b/packages/lib/plugin.js
@@ -192,6 +192,10 @@ class BaseInstancePlugin {
 	 * @param {string} event.name - Name of the player that joined/left.
 	 */
 	async onPlayerEvent(event) { }
+
+	async sendRcon(message, expectEmpty) {
+		return await this.instance.sendRcon(message, expectEmpty, this.info.name);
+	}
 }
 
 /**
diff --git a/packages/slave/slave.js b/packages/slave/slave.js
index dfaff915..3345b68f 100755
--- a/packages/slave/slave.js
+++ b/packages/slave/slave.js
@@ -36,12 +36,21 @@ const libConfig = require("@clusterio/lib/config");
 const libSharedCommands = require("@clusterio/lib/shared_commands");
 
 
-const instanceRconCommandsCounter = new libPrometheus.Counter(
-	"clusterio_instance_rcon_commands_total",
-	"How many commands have been sent to the instance",
+const instanceRconCommandDuration = new libPrometheus.Histogram(
+	"clusterio_instance_rcon_command_duration_seconds",
+	"Histogram of the RCON command duration from request to response.",
 	{ labels: ["instance_id"] }
 );
 
+const instanceRconCommandSize = new libPrometheus.Histogram(
+	"clusterio_instance_rcon_command_size_bytes",
+	"Histogram of the RCON command sizes that are sent.",
+	{
+		labels: ["instance_id", "plugin"],
+		buckets: libPrometheus.Histogram.exponential(16, 2, 12),
+	}
+);
+
 const instanceFactorioCpuTime = new libPrometheus.Gauge(
 	"clusterio_instance_factorio_cpu_time_total",
 	"Factorio CPU time spent in seconds.",
@@ -61,7 +70,7 @@ const instanceFactorioAutosaveSize = new libPrometheus.Gauge(
 );
 
 function applyAsConfig(name) {
-	return async function action(server, value) {
+	return async function action(instance, value) {
 		if (name === "tags" && value instanceof Array) {
 			// Replace spaces with non-break spaces and delimit by spaces.
 			// This does change the defined tags, but there doesn't seem to
@@ -69,7 +78,7 @@ function applyAsConfig(name) {
 			value = value.map(tag => tag.replace(/ /g, "\u00a0")).join(" ");
 		}
 		try {
-			await server.sendRcon(`/config set ${name} ${value}`);
+			await instance.sendRcon(`/config set ${name} ${value}`);
 		} catch (err) {
 			console.error(`Error applying server setting ${name}`, err);
 		}
@@ -91,11 +100,11 @@ const serverSettingsActions = {
 	"game_password": applyAsConfig("password"),
 	"require_user_verification": applyAsConfig("require-user-verification"),
 	"tags": applyAsConfig("tags"),
-	"visibility": async (server, value) => {
+	"visibility": async (instance, value) => {
 		for (let scope of ["lan", "public", "steam"]) {
 			try {
 				let enabled = Boolean(value[scope]);
-				await server.sendRcon(`/config set visibility-${scope} ${enabled}`);
+				await instance.sendRcon(`/config set visibility-${scope} ${enabled}`);
 			} catch (err) {
 				console.error(`Error applying visibility ${scope}`, err);
 			}
@@ -149,12 +158,6 @@ class Instance extends libLink.Link{
 			factorioDir, this._dir, serverOptions
 		);
 
-		let originalSendRcon = this.server.sendRcon;
-		this.server.sendRcon = (...args) => {
-			instanceRconCommandsCounter.labels(String(this.config.get("instance.id"))).inc();
-			return originalSendRcon.call(this.server, ...args);
-		};
-
 		this.server.on("output", (output) => {
 			libLink.messages.instanceOutput.send(this, { instance_id: this.config.get("instance.id"), output });
 
@@ -180,6 +183,17 @@ class Instance extends libLink.Link{
 		});
 	}
 
+	async sendRcon(message, expectEmpty, plugin = "") {
+		let instanceId = String(this.config.get("instance.id"));
+		let observeDuration = instanceRconCommandDuration.labels(instanceId).startTimer();
+		try {
+			return await this.server.sendRcon(message, expectEmpty);
+		} finally {
+			observeDuration();
+			instanceRconCommandSize.labels(instanceId, plugin).observe(Buffer.byteLength(message, "utf8"));
+		}
+	}
+
 	async _autosave(name) {
 		let stat = await fs.stat(this.path("saves", `${name}.zip`));
 		instanceFactorioAutosaveSize.labels(String(this.config.get("instance.id"))).set(stat.size);
@@ -519,7 +533,7 @@ class Instance extends libLink.Link{
 	async updateInstanceData() {
 		let name = libLuaTools.escapeString(this.config.get("instance.name"));
 		let id = this.config.get("instance.id");
-		await this.server.sendRcon(`/sc clusterio_private.update_instance(${id}, "${name}")`, true);
+		await this.sendRcon(`/sc clusterio_private.update_instance(${id}, "${name}")`, true);
 	}
 
 	async updateFactorioSettings(current, previous) {
@@ -528,7 +542,7 @@ class Instance extends libLink.Link{
 
 		for (let [key, action] of Object.entries(serverSettingsActions)) {
 			if (current[key] !== undefined && !util.isDeepStrictEqual(current[key], previous[key])) {
-				await action(this.server, current[key]);
+				await action(this, current[key]);
 			}
 		}
 	}
@@ -541,18 +555,18 @@ class Instance extends libLink.Link{
 	 */
 	async updateFactorioWhitelist(enable) {
 		if (!enable) {
-			await this.server.sendRcon("/whitelist disable");
+			await this.sendRcon("/whitelist disable");
 		}
 
 		if (this.config.get("factorio.sync_whitelist")) {
-			await this.server.sendRcon("/whitelist clear");
+			await this.sendRcon("/whitelist clear");
 			for (let player of this._slave.whitelist) {
-				await this.server.sendRcon(`/whitelist ${player}`);
+				await this.sendRcon(`/whitelist ${player}`);
 			}
 		}
 
 		if (enable) {
-			await this.server.sendRcon("/whitelist enable");
+			await this.sendRcon("/whitelist enable");
 		}
 	}
 
@@ -563,7 +577,7 @@ class Instance extends libLink.Link{
 
 		let { name, admin } = message.data;
 		let command = admin ? `/promote ${name}` : `/demote ${name}`;
-		await this.server.sendRcon(command);
+		await this.sendRcon(command);
 	}
 
 	async banlistUpdateEventHandler(message) {
@@ -573,7 +587,7 @@ class Instance extends libLink.Link{
 
 		let { name, banned, reason } = message.data;
 		let command = banned ? `/ban ${name} ${reason}` : `/unban ${name}`;
-		await this.server.sendRcon(command);
+		await this.sendRcon(command);
 	}
 
 	async whitelistUpdateEventHandler(message) {
@@ -583,7 +597,7 @@ class Instance extends libLink.Link{
 
 		let { name, whitelisted } = message.data;
 		let command = whitelisted ? `/whitelist add ${name}` : `/whiteliste remove ${name}`;
-		await this.server.sendRcon(command);
+		await this.sendRcon(command);
 	}
 
 
@@ -723,7 +737,7 @@ class Instance extends libLink.Link{
 	}
 
 	async sendRconRequestHandler(message) {
-		let result = await this.server.sendRcon(message.data.command);
+		let result = await this.sendRcon(message.data.command);
 		return { result };
 	}
 
diff --git a/plugins/global_chat/instance.js b/plugins/global_chat/instance.js
index 65e994fc..ff996788 100644
--- a/plugins/global_chat/instance.js
+++ b/plugins/global_chat/instance.js
@@ -33,7 +33,7 @@ class InstancePlugin extends libPlugin.BaseInstancePlugin {
 	async chatEventHandler(message) {
 		// TODO check if cross server chat is enabled
 		let content = `[${message.data.instance_name}] ${removeTags(message.data.content)}`;
-		await this.instance.server.sendRcon(`/sc game.print('${libLuaTools.escapeString(content)}')`, true);
+		await this.sendRcon(`/sc game.print('${libLuaTools.escapeString(content)}')`, true);
 	}
 
 	sendChat(message) {
diff --git a/plugins/research_sync/instance.js b/plugins/research_sync/instance.js
index c8bef0fb..e495db3c 100644
--- a/plugins/research_sync/instance.js
+++ b/plugins/research_sync/instance.js
@@ -29,7 +29,7 @@ class InstancePlugin extends libPlugin.BaseInstancePlugin {
 
 	async progressEventHandler(message) {
 		let techsJson = libLuaTools.escapeString(JSON.stringify(message.data.technologies));
-		await this.instance.server.sendRcon(`/sc research_sync.update_progress("${techsJson}")`, true);
+		await this.sendRcon(`/sc research_sync.update_progress("${techsJson}")`, true);
 	}
 
 	async researchFinished(tech) {
@@ -38,13 +38,13 @@ class InstancePlugin extends libPlugin.BaseInstancePlugin {
 
 	async finishedEventHandler(message) {
 		let { name, level, researched } = message.data;
-		await this.instance.server.sendRcon(
+		await this.sendRcon(
 			`/sc research_sync.research_technology("${libLuaTools.escapeString(name)}", ${level})`, true
 		);
 	}
 
 	async onStart() {
-		let dumpJson = await this.instance.server.sendRcon("/sc research_sync.dump_technologies()");
+		let dumpJson = await this.sendRcon("/sc research_sync.dump_technologies()");
 		let techsToSend = [];
 		let instanceTechs = new Map();
 		for (let tech of JSON.parse(dumpJson)) {
@@ -74,7 +74,7 @@ class InstancePlugin extends libPlugin.BaseInstancePlugin {
 
 		if (techsToSync.length) {
 			let syncJson = libLuaTools.escapeString(JSON.stringify(techsToSync));
-			await this.instance.server.sendRcon(`/sc research_sync.sync_technologies("${syncJson}")`, true);
+			await this.sendRcon(`/sc research_sync.sync_technologies("${syncJson}")`, true);
 		}
 	}
 }
diff --git a/plugins/statistics_exporter/instance.js b/plugins/statistics_exporter/instance.js
index d95dd9c7..002e51f6 100644
--- a/plugins/statistics_exporter/instance.js
+++ b/plugins/statistics_exporter/instance.js
@@ -30,7 +30,7 @@ class InstancePlugin extends libPlugin.BaseInstancePlugin {
 	}
 
 	async gatherMetrics() {
-		let string = await this.instance.server.sendRcon("/sc statistics_exporter.export()");
+		let string = await this.sendRcon("/sc statistics_exporter.export()");
 		let stats;
 		try {
 			stats = JSON.parse(string);
diff --git a/plugins/subspace_storage/instance.js b/plugins/subspace_storage/instance.js
index 7b5daaba..6250517d 100644
--- a/plugins/subspace_storage/instance.js
+++ b/plugins/subspace_storage/instance.js
@@ -22,7 +22,7 @@ class InstancePlugin extends libPlugin.BaseInstancePlugin {
 
 	async onStart() {
 		this.pingId = setInterval(() => {
-			this.instance.server.sendRcon(
+			this.sendRcon(
 				"/sc __subspace_storage__ global.ticksSinceMasterPinged = 0", true
 			).catch(unexpectedError);
 		}, 5000);
@@ -30,7 +30,7 @@ class InstancePlugin extends libPlugin.BaseInstancePlugin {
 		let response = await this.info.messages.getStorage.send(this.instance);
 		// TODO Diff with dump of invdata produce minimal command to sync
 		let itemsJson = libLuaTools.escapeString(JSON.stringify(response.items));
-		await this.instance.server.sendRcon(`/sc __subspace_storage__ UpdateInvData("${itemsJson}", true)`, true);
+		await this.sendRcon(`/sc __subspace_storage__ UpdateInvData("${itemsJson}", true)`, true);
 	}
 
 	onExit() {
@@ -68,7 +68,7 @@ class InstancePlugin extends libPlugin.BaseInstancePlugin {
 		}
 
 		let itemsJson = libLuaTools.escapeString(JSON.stringify(response.items));
-		await this.instance.server.sendRcon(`/sc __subspace_storage__ Import("${itemsJson}")`, true);
+		await this.sendRcon(`/sc __subspace_storage__ Import("${itemsJson}")`, true);
 	}
 
 	// combinator signals ---------------------------------------------------------
@@ -87,7 +87,7 @@ class InstancePlugin extends libPlugin.BaseInstancePlugin {
 		items.push(["signal-unixtime", Math.floor(Date.now()/1000)]);
 
 		let itemsJson = libLuaTools.escapeString(JSON.stringify(items));
-		await this.instance.server.sendRcon(`/sc __subspace_storage__ UpdateInvData("${itemsJson}")`, true);
+		await this.sendRcon(`/sc __subspace_storage__ UpdateInvData("${itemsJson}")`, true);
 	}
 }
 
diff --git a/test/mock.js b/test/mock.js
index c8cddfbb..8d0c0812 100644
--- a/test/mock.js
+++ b/test/mock.js
@@ -92,6 +92,10 @@ class MockInstance extends libLink.Link {
 			},
 		};
 	}
+
+	async sendRcon(command, expectEmpty, plugin) {
+		return await this.server.sendRcon(command);
+	}
 }
 
 class MockSlave extends libLink.Link {