Update dependancies

It seems like there is now a non-beta version of the zeromq package that is compatible with the EDDN output (or maybe the EDDN service has been updated, I'm not sure).

Either way tested this and it seems to work without having to use an older beta release now.

I've also explicitly specific the version of Node.js used in production (and consequently have tested against).

README.md

@@ -13,6 +13,23 @@ generates reports from the data (e.g. summaries of commodity supply and demand
 and trade reports for different regions) and provides access to the data via 
 the [Ardent API](https://github.com/iaincollins/ardent-api) and raw data dumps.
 
+## Notes
+
+This software assumes an internet connection as it attempts to connect to the 
+the EDDN (Elite Dangerous Data Network) ZeroMQ instance at 
+tcp://eddn.edcd.io:9500 at startup to receive a data stream.
+
+Because of this, and other dependancies, it is build against Node.js v18.x,
+an older LTS release that is end-of-life 2025-04-30 and may not work with 
+other versions of Node.js.
+
+After doing `npm install` you can run the service with `npm start`.
+
+You may need to run additional commands like `npm run commodity-stats` and 
+`npm run database-stats` to generate at least once to avoid errors, but the 
+process will run these automatically if left running for long enough (they 
+are scheduled tasks that run periodically).
+
 ## Credits
 
 _This software would not be possible without work from dozens of enthusiasts 

index.js

@@ -127,9 +127,10 @@ if (SAVE_PAYLOAD_EXAMPLES === true &&
     })
   })
 
-  // Generate high level db stats like total star systems, trade orders, etc.
-  // Takes about 30 seconds to run.
-  // @TODO Replace with triggers on tables?
+  // Generate high level stats like total star systems, trade orders, etc.
+  // Takes about 20s to run in test but 1m 30s in production due to load.
+  // @TODO Could maybe be real time if replaced with triggers on tables,
+  // or a best-effort internal counter that tracks changes between updates.
   cron.schedule('0 0 * * * *', () => {
     exec('npm run database-stats', (error, stdout, stderr) => {
       if (error) console.error(error)
@@ -218,7 +219,7 @@ function printStats () {
           `* Trade updates in last 7 days: ${stats.trade.updatedInLast7Days.toLocaleString()}\n` +
           `* Trade updates in last 30 days: ${stats.trade.updatedInLast30Days.toLocaleString()}\n` +
           `* Unique commodities: ${stats.trade.uniqueCommodities.toLocaleString()}\n` +
-          `Stats last updated: ${stats.timestamp} (updated every 15 minutes)`
+          `Stats last updated: ${stats.timestamp}`
         : 'Stats not generated yet')
   } catch (e) {
     return 'Error: Could not load stats'