chore: Extract the sqlserver monitor to its own monitor-type. Enable support conditions for a single result value.

server/monitor-types/mssql.js

@@ -0,0 +1,118 @@
+const { MonitorType } = require("./monitor-type");
+const { log, UP } = require("../../src/util");
+const dayjs = require("dayjs");
+const mssql = require("mssql");
+const { ConditionVariable } = require("../monitor-conditions/variables");
+const { defaultStringOperators } = require("../monitor-conditions/operators");
+const {
+    ConditionExpressionGroup,
+} = require("../monitor-conditions/expression");
+const { evaluateExpressionGroup } = require("../monitor-conditions/evaluator");
+
+class MssqlMonitorType extends MonitorType {
+    name = "sqlserver";
+
+    supportsConditions = true;
+    conditionVariables = [
+        new ConditionVariable("result", defaultStringOperators),
+    ];
+
+    /**
+     * @inheritdoc
+     */
+    async check(monitor, heartbeat, _server) {
+        let startTime = dayjs().valueOf();
+
+        let query = monitor.databaseQuery;
+        // No query provided by user, use SELECT 1
+        if (!query || (typeof query === "string" && query.trim() === "")) {
+            query = "SELECT 1";
+        }
+
+        let result;
+        try {
+            result = await this.mssqlQuery(
+                monitor.databaseConnectionString,
+                query
+            );
+        } catch (error) {
+            log.error("sqlserver", "Database query failed:", error.message);
+            throw new Error(
+                `Database connection/query failed: ${error.message}`
+            );
+        } finally {
+            heartbeat.ping = dayjs().valueOf() - startTime;
+        }
+
+        const conditions = ConditionExpressionGroup.fromMonitor(monitor);
+        const handleConditions = (data) =>
+            conditions ? evaluateExpressionGroup(conditions, data) : true;
+
+        // Since result is now a single value, pass it directly to conditions
+        const conditionsResult = handleConditions({ result: String(result) });
+
+        if (!conditionsResult) {
+            throw new Error(
+                `Query result did not meet the specified conditions (${result})`
+            );
+        }
+
+        heartbeat.msg = "";
+        heartbeat.status = UP;
+    }
+
+    /**
+     * Run a query on MSSQL server
+     * @param {string} connectionString The database connection string
+     * @param {string} query The query to validate the database with
+     * @returns {Promise<any>} Single value from the first column of the first row
+     */
+    async mssqlQuery(connectionString, query) {
+        let pool;
+        try {
+            pool = new mssql.ConnectionPool(connectionString);
+            await pool.connect();
+            const result = await pool.request().query(query);
+
+            // Check if we have results
+            if (!result.recordset || result.recordset.length === 0) {
+                throw new Error("Query returned no results");
+            }
+
+            // Check if we have multiple rows
+            if (result.recordset.length > 1) {
+                throw new Error(
+                    "Multiple values were found, expected only one value"
+                );
+            }
+
+            const firstRow = result.recordset[0];
+            const columnNames = Object.keys(firstRow);
+
+            // Check if we have multiple columns
+            if (columnNames.length > 1) {
+                throw new Error(
+                    "Multiple columns were found, expected only one value"
+                );
+            }
+
+            // Return the single value from the first (and only) column
+            return firstRow[columnNames[0]];
+        } catch (err) {
+            log.debug(
+                "sqlserver",
+                "Error caught in the query execution.",
+                err.message
+            );
+            throw err;
+        } finally {
+            if (pool) {
+                await pool.close();
+            }
+        }
+    }
+}
+
+module.exports = {
+    MssqlMonitorType,
+};