Convert MongoDB from standalone to replica set

.gitignore

@@ -34,7 +34,7 @@ Session.vim
 scripts/*.js
 !scripts/frontendScripts.js
 !scripts/jestTest.js
-!scripts/setupMongo.js
+!scripts/startDatabase.js
 database/*.js
 *.log
 *-debug.log*

.vscode/tasks.json

@@ -28,9 +28,9 @@
     },
     {
       "label": "run-mongo",
-      "command": "mongod",
+      "command": "npm",
       "type": "process",
-      "args": ["--dbpath", "${workspaceFolder}/mongo_database"],
+      "args": ["run", "database"],
       "problemMatcher": "$tsc"
     }
   ]

Backend/appsettings.json

@@ -1,7 +1,7 @@
 {
   "MongoDB": {
-    "ConnectionString": "mongodb://localhost:27017",
-    "ContainerConnectionString": "mongodb://database:27017",
+    "ConnectionString": "mongodb://localhost:27017/?replicaSet=rs0",
+    "ContainerConnectionString": "mongodb://database:27017/?replicaSet=rs0",
     "CombineDatabase": "CombineDatabase"
   },
   "Logging": {

README.md

@@ -473,7 +473,7 @@ npm run license-report-frontend
 
 To browse the database locally during development, open [MongoDB Compass](https://www.mongodb.com/try/download/compass).
 
-1. Under New Connection, enter `mongodb://localhost:27017`
+1. Under New Connection, enter `mongodb://localhost:27017/?replicaSet=rs0`
 2. Under Databases, select CombineDatabase
 
 ### Add or Update Dictionary Files

database/init/00-replica-set.js

@@ -0,0 +1,31 @@
+// Initialize the replica set on first startup.
+// See: https://www.mongodb.com/docs/manual/tutorial/convert-standalone-to-replica-set/
+//
+// MONGO_INITDB_REPLICA_HOST can be set to the resolvable hostname:port
+// used to advertise this member (e.g. the Kubernetes Service name "database:27017").
+// It defaults to "localhost:27017" for local development.
+try {
+  rs.status();
+} catch (e) {
+  print(`Replica set not yet initialized (${e}), initializing now...`);
+  const host = process.env.MONGO_INITDB_REPLICA_HOST || "localhost:27017";
+  rs.initiate({ _id: "rs0", members: [{ _id: 0, host: host }] });
+  // Wait for replica set to reach PRIMARY state before other init scripts run.
+  const maxWaitMs = 30000;
+  const intervalMs = 500;
+  let waited = 0;
+  let isPrimary = false;
+  while (!isPrimary && waited < maxWaitMs) {
+    sleep(intervalMs);
+    waited += intervalMs;
+    const status = rs.status();
+    isPrimary =
+      status.members !== undefined &&
+      status.members.some((m) => m.stateStr === "PRIMARY");
+  }
+  if (!isPrimary) {
+    throw new Error(
+      `Replica set did not reach PRIMARY state after ${maxWaitMs}ms`
+    );
+  }
+}

deploy/helm/thecombine/charts/database/templates/database.yaml

@@ -46,6 +46,35 @@ spec:
         - image: {{ include "database.containerImage" . }}
           imagePullPolicy: {{ .Values.global.imagePullPolicy }}
           name: database
+          args:
+            - "--replSet"
+            - "rs0"
+          lifecycle:
+            postStart:
+              exec:
+                command:
+                  - /bin/sh
+                  - -c
+                  - |
+                    set -e
+                    max_attempts=60
+                    attempt=1
+                    while [ "$attempt" -le "$max_attempts" ]; do
+                      if mongosh --quiet --host 127.0.0.1 --eval "const host = '${MONGO_INITDB_REPLICA_HOST}'; try { rs.status(); const conf = rs.conf(); if (conf.members[0].host !== host) { print('Updating replica set member host to ' + host); conf.members[0].host = host; conf.version++; rs.reconfig(conf); } else { print('Replica set already initialized with correct host'); } } catch (e) { print('Initializing replica set (' + e + ')'); rs.initiate({_id: 'rs0', members: [{_id: 0, host: host}]}); }" ; then
+                        exit 0
+                      fi
+                      sleep 1
+                      attempt=$((attempt + 1))
+                    done
+                    echo "Failed to ensure replica set initialization after ${max_attempts} attempts"
+                    exit 1
+          env:
+            - name: POD_IP
+              valueFrom:
+                fieldRef:
+                  fieldPath: status.podIP
+            - name: MONGO_INITDB_REPLICA_HOST
+              value: "$(POD_IP):27017"
           ports:
             - containerPort: 27017
           resources:

package.json

@@ -8,8 +8,7 @@
     "backend": "dotnet watch --project Backend/BackendFramework.csproj",
     "build": "parcel build",
     "build:analyze": "npm run build -- --reporter @parcel/reporter-bundle-analyzer",
-    "predatabase": "node scripts/setupMongo.js",
-    "database": "mongod --dbpath=./mongo_database",
+    "database": "node scripts/startDatabase.js",
     "drop-database": "tsc scripts/dropDB.ts && node scripts/dropDB.js",
     "find-circular-deps": "npx --ignore-scripts -y madge -c src/index.tsx --ts-config tsconfig.json",
     "fmt-backend": "      dotnet format                     && dotnet format                     Backend.Tests",

scripts/startDatabase.js

@@ -0,0 +1,89 @@
+"use strict";
+
+const { spawn, spawnSync } = require("child_process");
+const { ensureDir } = require("fs-extra");
+
+const dbPath = "./mongo_database";
+const replSetName = "rs0";
+const maxAttempts = 30;
+const retryInterval = 1000; // ms
+
+async function waitForMongo() {
+  for (let i = 0; i < maxAttempts; i++) {
+    const result = spawnSync("mongosh", [
+      "--eval",
+      "db.adminCommand('ping')",
+      "--quiet",
+    ]);
+    if (result.status === 0) {
+      return true;
+    }
+    await new Promise((resolve) => setTimeout(resolve, retryInterval));
+  }
+  return false;
+}
+
+async function initReplicaSet() {
+  const result = spawnSync(
+    "mongosh",
+    [
+      "--eval",
+      "try { rs.status() } catch(e) { rs.initiate({ _id: 'rs0', members: [{ _id: 0, host: 'localhost:27017' }] }) }",
+      "--quiet",
+    ],
+    { stdio: "inherit" }
+  );
+  return result.status === 0;
+}
+
+async function waitForMongoToCloseThenExit(mongod) {
+  const exitCode = await new Promise((resolve) =>
+    mongod.on("close", (code) => resolve(code))
+  );
+  process.exit(exitCode ?? 1);
+}
+
+async function main() {
+  await ensureDir(dbPath);
+
+  const mongod = spawn(
+    "mongod",
+    [`--dbpath=${dbPath}`, "--replSet", replSetName],
+    {
+      stdio: "inherit",
+    }
+  );
+
+  mongod.on("error", (err) => {
+    console.error(`mongod error: ${err.message}`);
+    process.exit(1);
+  });
+
+  process.on("SIGINT", () => {
+    mongod.kill("SIGINT");
+  });
+  process.on("SIGTERM", () => {
+    mongod.kill("SIGTERM");
+  });
+
+  const ready = await waitForMongo();
+  if (!ready) {
+    console.error("MongoDB did not start in time");
+    mongod.kill("SIGTERM");
+    await waitForMongoToCloseThenExit(mongod);
+  }
+
+  const initialized = await initReplicaSet();
+  if (!initialized) {
+    console.error("Replica set initialization failed");
+    mongod.kill("SIGTERM");
+    await waitForMongoToCloseThenExit(mongod);
+  }
+
+  await waitForMongoToCloseThenExit(mongod);
+}
+
+main().catch((err) => {
+  console.error(err);
+  process.exit(1);
+});