Merge pull request #5878 from carlosalbertorg/feat/log-viewer

feat: Add a Logs viewer to the admin UI

backend/internal/log-viewer.js

@@ -0,0 +1,229 @@
+import fs from "node:fs";
+import errs from "../lib/error.js";
+import internalDeadHost from "./dead-host.js";
+import internalProxyHost from "./proxy-host.js";
+import internalRedirectionHost from "./redirection-host.js";
+import internalStream from "./stream.js";
+
+const SYSTEM_LOG_FILE = "/data/logs/backend.log";
+const LETSENCRYPT_LOG_FILE = "/data/logs/letsencrypt.log";
+
+// Matches the access_log/error_log paths written by the nginx templates
+// (see backend/templates/{proxy_host,redirection_host,dead_host,stream}.conf).
+// This is a fixed, server-side lookup table - a host log path is always derived
+// from a validated `host_type` enum + numeric `host_id`, never from a client-supplied
+// path or filename, so there is no path-traversal surface here.
+const HOST_FILE_PREFIX = {
+	proxy: "proxy-host",
+	redirection: "redirection-host",
+	dead: "dead-host",
+	stream: "stream",
+};
+
+const DEFAULT_LINES = 200;
+const MAX_LINES = 1000;
+const CHUNK_SIZE = 64 * 1024;
+// Never scan further back than this, regardless of how many lines were requested,
+// so a huge or pathological log file can't turn a single request into unbounded I/O.
+const MAX_SCAN_BYTES = 5 * 1024 * 1024;
+
+/**
+ * Reads at most `maxLines` lines from the end of a file, without loading the
+ * whole file into memory. Reads backwards in fixed-size chunks until enough
+ * newlines have been seen, the start of the file is reached, or the hard
+ * MAX_SCAN_BYTES ceiling is hit.
+ *
+ * @param   {String} filePath
+ * @param   {Number} maxLines
+ * @returns {Promise<{lines: String[], size: Number, truncated: Boolean}>}
+ */
+const readLastLines = async (filePath, maxLines) => {
+	let handle;
+	try {
+		handle = await fs.promises.open(filePath, "r");
+		const stat = await handle.stat();
+		const { size } = stat;
+
+		if (size === 0) {
+			return { lines: [], size: 0, truncated: false };
+		}
+
+		let position = size;
+		let scanned = 0;
+		let newlineCount = 0;
+		const chunks = [];
+
+		while (position > 0 && newlineCount <= maxLines && scanned < MAX_SCAN_BYTES) {
+			const readSize = Math.min(CHUNK_SIZE, position);
+			position -= readSize;
+			const buffer = Buffer.alloc(readSize);
+			await handle.read(buffer, 0, readSize, position);
+			scanned += readSize;
+			for (let i = buffer.length - 1; i >= 0; i--) {
+				if (buffer[i] === 0x0a) newlineCount++;
+			}
+			chunks.unshift(buffer);
+		}
+
+		const truncated = position > 0 && scanned >= MAX_SCAN_BYTES;
+
+		// If we didn't start reading from byte 0, the first line in our buffer is only
+		// partial *unless* it happens that `position` landed exactly on a line boundary
+		// (the byte right before it is a newline) - check that one byte to avoid
+		// silently dropping a perfectly valid line.
+		let startsOnLineBoundary = position === 0;
+		if (position > 0) {
+			const boundaryByte = Buffer.alloc(1);
+			await handle.read(boundaryByte, 0, 1, position - 1);
+			startsOnLineBoundary = boundaryByte[0] === 0x0a;
+		}
+
+		const text = Buffer.concat(chunks).toString("utf8");
+		const allLines = text.split("\n");
+
+		if (!startsOnLineBoundary && allLines.length > 0) {
+			allLines.shift();
+		}
+		// Drop the trailing empty element caused by a final trailing newline.
+		if (allLines.length > 0 && allLines[allLines.length - 1] === "") {
+			allLines.pop();
+		}
+
+		return { lines: allLines.slice(-maxLines), size, truncated };
+	} finally {
+		if (handle) {
+			await handle.close();
+		}
+	}
+};
+
+/**
+ * Resolves a validated {type, host_type, host_id, channel} selection to the
+ * fixed, absolute path of the log file on disk. Throws if the combination
+ * isn't a recognised source.
+ *
+ * `channel` ("access" | "error") picks which of the two log files nginx writes
+ * per host - it's deliberately not named "stream" to avoid confusion with the
+ * "stream" host_type (TCP/UDP stream hosts).
+ *
+ * @param   {Object} data
+ * @returns {String}
+ */
+const resolveFilePath = (data) => {
+	switch (data.type) {
+		case "system":
+			return SYSTEM_LOG_FILE;
+		case "letsencrypt":
+			return LETSENCRYPT_LOG_FILE;
+		case "host": {
+			const prefix = HOST_FILE_PREFIX[data.host_type];
+			if (!prefix || !data.host_id || !["access", "error"].includes(data.channel)) {
+				throw new errs.ValidationError("Invalid host log source");
+			}
+			return `/data/logs/${prefix}-${data.host_id}_${data.channel}.log`;
+		}
+		default:
+			throw new errs.ItemNotFoundError(data.type);
+	}
+};
+
+/**
+ * @param   {Array} rows
+ * @returns {Array}
+ */
+const toHostOptions = (rows) =>
+	rows.map((row) => ({
+		id: row.id,
+		label: Array.isArray(row.domain_names) ? row.domain_names.join(", ") : `Host #${row.id}`,
+	}));
+
+const internalLogViewer = {
+	/**
+	 * Lists the log sources available for the log viewer: the system (backend)
+	 * log, the Let's Encrypt (certbot) log, and one entry per host the caller
+	 * can see, for each host type.
+	 *
+	 * @param   {Access} access
+	 * @returns {Promise}
+	 */
+	listSources: async (access) => {
+		await access.can("logs:list");
+
+		const [proxyHosts, redirectionHosts, deadHosts, streams] = await Promise.all([
+			internalProxyHost.getAll(access),
+			internalRedirectionHost.getAll(access),
+			internalDeadHost.getAll(access),
+			internalStream.getAll(access),
+		]);
+
+		return {
+			system: { label: "System" },
+			letsencrypt: { label: "Let's Encrypt" },
+			hosts: {
+				proxy: toHostOptions(proxyHosts),
+				redirection: toHostOptions(redirectionHosts),
+				dead: toHostOptions(deadHosts),
+				stream: streams.map((row) => ({
+					id: row.id,
+					label: `Port ${row.incoming_port} → ${row.forwarding_host}:${row.forwarding_port}`,
+				})),
+			},
+		};
+	},
+
+	/**
+	 * Returns the last N lines of the requested log source, optionally
+	 * filtered by level and/or a plain-text search term.
+	 *
+	 * @param   {Access} access
+	 * @param   {Object} data
+	 * @param   {String} data.type        "system" | "letsencrypt" | "host"
+	 * @param   {String} [data.host_type] "proxy" | "redirection" | "dead" | "stream"
+	 * @param   {Number} [data.host_id]
+	 * @param   {String} [data.channel]   "access" | "error"
+	 * @param   {Number} [data.lines]
+	 * @param   {String} [data.level]
+	 * @param   {String} [data.search]
+	 * @returns {Promise}
+	 */
+	tail: async (access, data) => {
+		await access.can("logs:list");
+
+		const filePath = resolveFilePath(data);
+		const lines = Math.min(Math.max(data.lines || DEFAULT_LINES, 1), MAX_LINES);
+
+		let result;
+		try {
+			result = await readLastLines(filePath, lines);
+		} catch (err) {
+			if (err.code === "ENOENT") {
+				return { lines: [], size: 0, truncated: false, exists: false };
+			}
+			throw err;
+		}
+
+		let outputLines = result.lines;
+
+		// Only the system log is written in our own "LEVEL   [scope]" format - level
+		// filtering on nginx/certbot lines would just match nothing and look like an
+		// empty log, so the filter is a no-op for any other source.
+		if (data.type === "system" && data.level) {
+			const needle = ` ${data.level.toUpperCase().padEnd(7)} `;
+			outputLines = outputLines.filter((line) => line.includes(needle));
+		}
+
+		if (data.search) {
+			const needle = data.search.toLowerCase();
+			outputLines = outputLines.filter((line) => line.toLowerCase().includes(needle));
+		}
+
+		return {
+			lines: outputLines,
+			size: result.size,
+			truncated: result.truncated,
+			exists: true,
+		};
+	},
+};
+
+export default internalLogViewer;