Improve readStream to support more records

Previously, the WOF importer loaded all records into memory in one
stream, and then processed and indexed the records in Elasticsearch in a
second stream after the first stream was done.

This has several problems:
* It requires that all data can fit into memory. While this is not
  _so_ bad for WOF admin data, where a reasonably new machine can handle
  things just fine, it's horrible for venue data, where there are already
  10s of millions of records.
* Its slower: by separating the disk and network I/O sections, they
  can't be interleaved to speed things up.
* It doesn't give good feedback when running the importer that something
  is happening: the importer sits for several minutes loading records
  before the dbclient progress logs start displaying

This change fixes all those issues, by processing all records in a
single stream, starting at the highest hierarchy level, and finishing at
the lowest, so that all records always have the admin data they need to
be processed.

Fixes #101
Connects #7
Connects #94

import.js

@@ -1,9 +1,8 @@
 var peliasConfig = require( 'pelias-config' ).generate();
-var readStream = require('./src/readStream');
+var readStreamModule = require('./src/readStream');
 var importStream = require('./src/importStream');
 var peliasDbclient = require( 'pelias-dbclient' );
 var peliasDocGenerators = require('./src/peliasDocGenerators');
-var wofRecordStream = require('./src/wofRecordStream');
 var hierarchyFinder = require('./src/hierarchyFinder');
 var checker = require('node-version-checker').default;
 
@@ -43,24 +42,20 @@ var types = [
   'neighbourhood'
 ];
 
-var wofRecords = {};
+// a cache of only admin records, to be used to fill the hierarchy
+// of other, lower admin records as well as venues
+var wofAdminRecords = {};
 
-readStream(directory, types, wofRecords, function() {
-  console.log(Object.keys(wofRecords).length + ' records loaded');
+var readStream = readStreamModule.create(directory, types, wofAdminRecords);
 
-  // a stream of WOF records
-  var recordStream = wofRecordStream.createWofRecordsStream(wofRecords);
+// how to convert WOF records to Pelias Documents
+var documentGenerator = peliasDocGenerators.create(
+  hierarchyFinder.hierarchies_walker(wofAdminRecords));
 
-  // how to convert WOF records to Pelias Documents
-  var documentGenerator = peliasDocGenerators.create(
-    hierarchyFinder.hierarchies_walker(wofRecords));
-
-  // the final destination of Pelias Documents
-  var dbClientStream = peliasDbclient();
-
-  // import WOF records into ES
-  importStream(recordStream, documentGenerator, dbClientStream, function() {
-    console.log('import finished');
-  });
+// the final destination of Pelias Documents
+var dbClientStream = peliasDbclient();
 
+// import WOF records into ES
+importStream(readStream, documentGenerator, dbClientStream, function() {
+  console.log('import finished');
 });

package.json

@@ -28,6 +28,7 @@
   "dependencies": {
     "batchflow": "^0.4.0",
     "clone": "^1.0.2",
+    "combined-stream": "^1.0.5",
     "csv-parse": "^1.0.0",
     "fs-extra": "^0.30.0",
     "iso3166-1": "^0.2.5",

src/readStream.js

@@ -1,7 +1,9 @@
+var combinedStream = require('combined-stream');
 var parse = require('csv-parse');
 var fs = require('fs');
-var batch = require('batchflow');
-var sink = require('through2-sink');
+var through2 = require('through2');
+
+var logger = require( 'pelias-logger' ).get( 'whosonfirst' );
 
 var isValidId = require('./components/isValidId');
 var fileIsReadable = require('./components/fileIsReadable');
@@ -12,31 +14,67 @@ var extractFields = require('./components/extractFields');
 var recordHasName = require('./components/recordHasName');
 
 /*
-  This function finds all the `latest` files in `meta/`, CSV parses them,
-  extracts the required fields, and assigns to a big collection
-*/
-function readData(directory, types, wofRecords, callback) {
-  batch(types).parallel(2).each(function(idx, type, done) {
-    fs.createReadStream(directory + 'meta/wof-' + type + '-latest.csv')
-      .pipe(parse({ delimiter: ',', columns: true }))
-      .pipe(isValidId.create())
-      .pipe(fileIsReadable.create(directory + 'data/'))
-      .pipe(loadJSON.create(directory + 'data/'))
-      .pipe(recordHasIdAndProperties.create())
-      .pipe(isActiveRecord.create())
-      .pipe(extractFields.create())
-      .pipe(recordHasName.create())
-      .pipe(sink.obj(function(wofRecord) {
-        wofRecords[wofRecord.id] = wofRecord;
-      }))
-      .on('finish', done);
-
-  }).error(function(err) {
-    console.error(err);
-  }).end(function() {
-    callback();
+ * Convert a base directory and list of types into a list of meta file paths
+ */
+function getMetaFilePaths(directory, types) {
+  return types.map(function(type) {
+    return directory + 'meta/wof-' + type + '-latest.csv';
+  });
+}
+
+/*
+ * Given the path to a meta CSV file, return a stream of the individual records
+ * within that CSV file.
+ */
+function createOneMetaRecordStream(metaFilePath) {
+  return fs.createReadStream(metaFilePath)
+    .pipe(parse({ delimiter: ',', columns: true }));
+}
+
+/*
+ * given a list of meta file paths, create a combined stream that reads all the
+ * records via the csv parser
+ */
+function createMetaRecordStream(metaFilePaths, types) {
+  var metaRecordStream = combinedStream.create();
+
+  metaFilePaths.forEach(function appendToCombinedStream(metaFilePath, idx) {
+    var type = types[idx];
+    metaRecordStream.append( function ( next ){
+      logger.info( 'Loading ' + type + ' records from ' + metaFilePath );
+      next(createOneMetaRecordStream(metaFilePath));
+    });
   });
 
+  return metaRecordStream;
+}
+
+/*
+  This function creates a steram that finds all the `latest` files in `meta/`,
+  CSV parses them, extracts the required fields, stores only admin records for
+  later, and passes all records on for further processing
+*/
+function createReadStream(directory, types, wofAdminRecords) {
+  var metaFilePaths = getMetaFilePaths(directory, types);
+
+  return createMetaRecordStream(metaFilePaths, types)
+  .pipe(isValidId.create())
+  .pipe(fileIsReadable.create(directory + 'data/'))
+  .pipe(loadJSON.create(directory + 'data/'))
+  .pipe(recordHasIdAndProperties.create())
+  .pipe(isActiveRecord.create())
+  .pipe(extractFields.create())
+  .pipe(recordHasName.create())
+  .pipe(through2.obj(function(wofRecord, enc, callback) {
+    // store admin records in memory to traverse the heirarchy
+    if (wofRecord.place_type !== 'venue') {
+      wofAdminRecords[wofRecord.id] = wofRecord;
+    }
+
+    callback(null, wofRecord);
+  }));
 }
 
-module.exports = readData;
+module.exports = {
+  create: createReadStream
+};

test/readStreamTest.js

@@ -1,5 +1,6 @@
 var tape = require('tape');
 var fs = require('fs-extra');
+var sink = require('through2-sink');
 
 var readStream = require('../src/readStream');
 
@@ -8,7 +9,7 @@ tape('readStream', function(test) {
     this test is not terribly attractive, i'm not happy with it but setup wasn't
     all that painful.
   */
-  test.test('readStream should return from all requested types and populate wofRecords', function(t) {
+  test.test('readStream should return from all requested types and populate wofAdminRecords', function(t) {
     function setupTestEnvironment() {
       // remove tmp directory if for some reason it's been hanging around from a previous run
       fs.removeSync('tmp');
@@ -75,12 +76,13 @@ tape('readStream', function(test) {
 
     setupTestEnvironment();
 
-    var wofRecords = {};
+    var wofAdminRecords = {};
+    var stream = readStream.create('./tmp/', ['type1', 'type2'], wofAdminRecords);
 
-    readStream('./tmp/', ['type1', 'type2'], wofRecords, function() {
-      t.equals(Object.keys(wofRecords).length, 2, 'there should be 2 records loaded');
+    stream.pipe(sink.obj(function() {})).on('finish', function() {
+      t.equals(Object.keys(wofAdminRecords).length, 2, 'there should be 2 records loaded');
 
-      t.deepEqual(wofRecords[1234567], {
+      t.deepEqual(wofAdminRecords[1234567], {
         id: 1234567,
         name: 'name 1',
         place_type: 'place type 1',
@@ -94,7 +96,7 @@ tape('readStream', function(test) {
         popularity: 87654
       }, 'id 1234567 should have been loaded');
 
-      t.deepEqual(wofRecords[12345678], {
+      t.deepEqual(wofAdminRecords[12345678], {
         id: 12345678,
         name: 'name 2',
         place_type: 'place type 2',