feat(server): add multi-core support via the cluster module

cmd/server.js

@@ -1,19 +1,42 @@
+/**
+  The http server improves performance on multicore machines by using the
+  node core 'cluster' module to fork worker processes.
+
+  The default setting is to use all available CPUs, this will spawn 32 child
+  processes on a 32 core machine.
+
+  If you would like to disable this feature (maybe because you are running
+  inside a container) then you can do so by setting the env var CPUS=1
+
+  You may also specify exactly how many child processes you would like to
+  spawn by setting the env var to a numeric value >1, eg CPUS=4
+
+  If the CPUS env var is set less than 1 or greater than os.cpus().length
+  then the default setting will be used (using all available cores).
+**/
+
+const os = require('os');
 const express = require('express');
+const cluster = require('cluster');
 const polyline = require('@mapbox/polyline');
 const search = require('../api/search');
 const extract = require('../api/extract');
 const street = require('../api/street');
 const near = require('../api/near');
 const pretty = require('../lib/pretty');
-const analyze = require('../lib/analyze');
 
 const morgan = require( 'morgan' );
 const logger = require('pelias-logger').get('interpolation');
 const through = require( 'through2' );
 const _ = require('lodash');
 
-// optionally override port using env var
+// select the amount of cpus we will use
+const envCpus = parseInt(process.env.CPUS, 10);
+const cpus = Math.min(Math.max(envCpus || Infinity, 1), os.cpus().length);
+
+// optionally override port/host using env var
 const PORT = process.env.PORT || 3000;
+const HOST = process.env.HOST || undefined;
 
 // help text
 if( process.argv.length !== 4 ){
@@ -217,10 +240,38 @@ app.use('/demo', express.static('demo'));
 // app.use('/builds', express.static('/data/builds'));
 // app.use('/builds', directory('/data/builds', { hidden: false, icons: false, view: 'details' }));
 
-app.listen( PORT, async function() {
+// start multi-threaded server
+if (cpus > 1) {
+  if (cluster.isMaster) {
+    logger.info('[master] using %d cpus', cpus);
 
-  // force loading of libpostal
-  await analyze.street( 'test street' );
+    // worker exit event
+    cluster.on('exit', (worker, code, signal) => {
+      logger.error('[master] worker died', worker.process.pid);
+    });
 
-  console.log( 'server listening on port', PORT );
-});
+    // worker fork event
+    cluster.on('fork', (worker, code, signal) => {
+      logger.info('[master] worker forked', worker.process.pid);
+    });
+
+    // fork workers
+    for (var c = 0; c < cpus; c++) {
+      cluster.fork();
+    }
+
+  } else {
+    app.listen(PORT, HOST, () => {
+      logger.info('[worker %d] listening on %s:%s', process.pid, HOST || '0.0.0.0', PORT);
+    });
+  }
+}
+
+// start single-threaded server
+else {
+  logger.info('[master] using %d cpus', cpus);
+
+  app.listen(PORT, HOST, async () => {
+    logger.info('[master] listening on %s:%s', HOST || '0.0.0.0', PORT);
+  });
+}