enable mongodb oplog

necessary for query.observerChanges to work probably with changes to mongodb via a different client.
Otherwise some events are missing due to a fallback via polling, which leads to lost state updates in the meantime.

took me now 3 days to debug....  :'D

docker-compose.tmpl.yml

@@ -103,6 +103,13 @@ services:
   mongodb:
     image: mongo:4.4
     restart: unless-stopped
+    volumes:
+      - ./mod/mongo/mongod.conf:/etc/mongod.conf
+      - ./mod/mongo/init-replica.sh:/docker-entrypoint-initdb.d/init-replica.sh
+    tmpfs:
+      - /data/configdb
+      - /data/db
+    command: mongod --config /etc/mongod.conf --oplogSize 8 --replSet rs0 --noauth
     healthcheck:
       test: bash -c "if mongo --eval 'quit(db.runCommand({ ping':' 1 }).ok ? 0 ':' 2)'; then exit 0; fi; exit 1;"
     networks:

mod/html5/entrypoint.sh

@@ -2,7 +2,7 @@
 set -e
 
 cd /app
-# export MONGO_OPLOG_URL=mongodb://10.7.7.6/local
+export MONGO_OPLOG_URL=mongodb://10.7.7.6/local
 export MONGO_URL=mongodb://10.7.7.6/meteor
 export NODE_ENV=production
 export SERVER_WEBSOCKET_COMPRESSION=0

mod/mongo/init-replica.sh

@@ -0,0 +1,16 @@
+#!/bin/sh
+set -e
+
+
+host=${HOSTNAME:-$(hostname -f)}
+
+# init replset with defaults
+mongo local --eval "rs.initiate({
+   _id: 'rs0',
+   members: [ { _id: 0, host: '127.0.0.1:27017' } ]
+})"
+
+echo "Waiting to become a master"
+echo 'while (!db.isMaster().ismaster) { sleep(100); }' | mongo
+
+echo "I'm the master!"

mod/mongo/mongod.conf

@@ -0,0 +1,28 @@
+# mongod.conf
+
+# for documentation of all options, see:
+#   http://docs.mongodb.org/manual/reference/configuration-options/
+
+storage:
+  dbPath: /data/db
+  journal:
+   enabled: true
+  wiredTiger:
+    engineConfig:
+         cacheSizeGB: 0
+         journalCompressor: none
+         directoryForIndexes: true
+    collectionConfig:
+         blockCompressor: none
+    indexConfig:
+         prefixCompression: false
+
+
+net:
+  port: 27017
+  bindIp: 0.0.0.0
+
+
+replication:
+  replSetName: rs0
+