https://codereview.stackexchange.com/questions/198343/crawl-and-gather-all-the-urls-recursively-in-a-domain
http://lucene.472066.n3.nabble.com/Using-nutch-just-for-the-crawler-fetcher-td611918.html

https://www.quora.com/What-are-some-Web-crawler-tips-to-avoid-crawler-traps

https://cwiki.apache.org/confluence/display/nutch/
https://cwiki.apache.org/confluence/display/NUTCH/Nutch2Crawling
https://cwiki.apache.org/confluence/display/nutch/ReaddbOptions

https://moz.com/top500
-----------
NUTCH
-----------
https://stackoverflow.com/questions/35449673/nutch-and-solr-indexing-blacklist-domain
	https://nutch.apache.org/apidocs/apidocs-1.6/org/apache/nutch/urlfilter/domainblacklist/DomainBlacklistURLFilter.html
	
https://lucene.472066.n3.nabble.com/blacklist-for-crawling-td618343.html
https://lucene.472066.n3.nabble.com/Content-of-size-X-was-truncated-to-Y-td4003517.html


Google: nutch mirror web site
https://stackoverflow.com/questions/33354460/nutch-clone-website
[https://stackoverflow.com/questions/35714897/nutch-not-crawling-entire-website
fetch -all seems to be a nutch v2 thing?]

Google (30 Sep): site mirroring with nutch
https://grokbase.com/t/nutch/user/125sfbg0pt/using-nutch-for-web-site-mirroring
https://lucene.472066.n3.nabble.com/Using-nutch-just-for-the-crawler-fetcher-td611918.html
http://www.cs.ucy.ac.cy/courses/EPL660/lectures/lab6.pdf
	slide p.5 onwards

crawler softw options: https://repositorio.iscte-iul.pt/bitstream/10071/2871/1/Building%20a%20Scalable%20Index%20and%20Web%20Search%20Engine%20for%20Music%20on.pdf
See also p.20. HTTrack


Google: nutch performance tuning
* https://stackoverflow.com/questions/24383212/apache-nutch-performance-tuning-for-whole-web-crawling
* https://stackoverflow.com/questions/4871972/how-to-speed-up-crawling-in-nutch
* https://cwiki.apache.org/confluence/display/nutch/OptimizingCrawls

NUTCH INSTALLATION:
* Nutch v1: https://cwiki.apache.org/confluence/display/nutch/NutchTutorial#NutchTutorial-SetupSolrforsearch

Nutch v2 installation and set up:
* https://cwiki.apache.org/confluence/display/NUTCH/Nutch2Tutorial
* https://subscription.packtpub.com/book/big_data_and_business_intelligence/9781783286850/1/ch01lvl1sec09/installing-and-configuring-apache-nutch


Nutch doesn't work with spark (yet):
https://stackoverflow.com/questions/29950299/distributed-web-crawling-using-apache-spark-is-it-possible

SOLR:
* Query syntax: http://www.solrtutorial.com/solr-query-syntax.html
* Deleting a core: https://factorpad.com/tech/solr/reference/solr-delete.html


* If you change a nutch 2 configuration, https://stackoverflow.com/questions/16401667/java-lang-classnotfoundexception-org-apache-gora-hbase-store-hbasestore
explains you can rebuild nutch with:
	 cd <apache-nutch>
	 ant clean
	 ant runtime
----------------------------------
Apache Nutch 2 with newer HBase

hbase-common-1.4.8.jar

1. hbase jar files need to go into runtime/local/lib

But not slf4j-log4j12-1.7.10.jar (there's already a slf4j-log4j12-1.7.5.jar) - so remove that from runtime/local/lib after copying it over.

2. https://stackoverflow.com/questions/46340416/how-to-compile-nutch-2-3-1-with-hbase-1-2-6
	https://stackoverflow.com/questions/39834423/apache-nutch-fetcherjob-throws-nosuchelementexception-deep-in-gora/39837926#39837926

Unfortunately, the page https://paste.apache.org/jjqz referred to above that contains patches for using Gora 0.7 is no longer available.

http://mail-archives.apache.org/mod_mbox/nutch-user/201602.mbox/%3C56B2EA23.8080801@cisinlabs.com%3E

https://www.mail-archive.com/user@nutch.apache.org/msg14245.html

------------------------------------------------------------------------------
Other way: Nutch on its own vagrant with specified hbase or nutch with mongodb
------------------------------------------------------------------------------
* https://lobster1234.github.io/2017/08/14/search-with-nutch-mongodb-solr/
* https://waue0920.wordpress.com/2016/08/25/nutch-2-3-1-hbase-0-98-hadoop-2-5-solr-4-10-3/

The older but recommended hbase 0.98.21 for hadoop 2 can be downloaded from https://archive.apache.org/dist/hbase/0.98.21/

-----
HBASE commands
/usr/local/hbase/bin/hbase shell
https://learnhbase.net/2013/03/02/hbase-shell-commands/
http://dwgeek.com/read-hbase-table-using-hbase-shell-get-command.html/
dropping tables: https://www.tutorialspoint.com/hbase/hbase_drop_table.htm

> list

davidbHomePage_webpage is a table

> get 'davidbHomePage_webpage', '1'

Solution to get a working nutch2:
get http://trac.greenstone.org/browser/gs3-extensions/maori-lang-detection/hdfs-cc-work/vagrant-for-nutch2.tar.gz
And follow the instructions in my README file in there.

---------------------------------------------------------------------
ALTERNATIVES TO NUTCH - looking for site mirroring capabilities
---------------------------------------------------------------------
=> https://anarc.at/services/archive/web/ 
	Autistici's crawl [https://git.autistici.org/ale/crawl] needs Go:
	https://medium.com/better-programming/install-go-1-11-on-ubuntu-18-04-16-04-lts-8c098c503c5f	
	https://guide.freecodecamp.org/go/installing-go/ubuntu-apt-get/
		To uninstall: https://medium.com/@firebitsbr/how-to-uninstall-from-the-apt-manager-uninstall-just-golang-go-from-universe-debian-ubuntu-82d6a3692cbd
	https://tecadmin.net/install-go-on-ubuntu/ [our vagrant VMs are Ubuntu 16.04 LTS, as discovered by running the cmd "lsb_release -a"]
https://alternativeto.net/software/apache-nutch/
https://alternativeto.net/software/wget/
https://github.com/ArchiveTeam/grab-site/blob/master/README.md#inspecting-warc-files-in-the-terminal
https://github.com/ArchiveTeam/wpull

-------------------

Running nutch 2.x

-------------------

LINKS

https://lucene.472066.n3.nabble.com/Nutch-2-x-readdb-command-dump-td4033937.html
https://cwiki.apache.org/confluence/display/nutch/ReaddbOptions


https://lobster1234.github.io/2017/08/14/search-with-nutch-mongodb-solr/ ## most useful for running nutch 2.x crawls

https://www.mobomo.com/2017/06/the-basics-working-with-nutch-2-x/
	"Fetch

	This is where the magic happens.  During the fetch step, Nutch crawls the urls selected in the generate step.  The most important argument you need is -threads: this sets the number of fetcher threads per task.  Increasing this will make crawling faster, but setting it too high can overwhelm a site and it might shut out your crawler, as well as take up too much memory from your machine.  Run it like this:
	$ nutch fetch -threads 50"


https://examples.javacodegeeks.com/enterprise-java/apache-hadoop/apache-hadoop-nutch-tutorial/
https://www.yegor256.com/2019/04/17/nutch-from-java.html

http://nutch.sourceforge.net/docs/en/tutorial.html

Intranet: Configuration
To configure things for intranet crawling you must:

    Create a flat file of root urls. For example, to crawl the nutch.org site you might start with a file named urls containing just the Nutch home page. All other Nutch pages should be reachable from this page. The urls file would thus look like:

    http://www.nutch.org/

    Edit the file conf/crawl-urlfilter.txt and replace MY.DOMAIN.NAME with the name of the domain you wish to crawl. For example, if you wished to limit the crawl to the nutch.org domain, the line should read:

    +^http://([a-z0-9]*\.)*nutch.org/

    This will include any url in the domain nutch.org.

Intranet: Running the Crawl
Once things are configured, running the crawl is easy. Just use the crawl command. Its options include:

    -dir dir names the directory to put the crawl in.
    -depth depth indicates the link depth from the root page that should be crawled.
    -delay delay determines the number of seconds between accesses to each host.
    -threads threads determines the number of threads that will fetch in parallel.

For example, a typical call might be:

bin/nutch crawl urls -dir crawl.test -depth 3 >& crawl.log

Typically one starts testing one's configuration by crawling at low depths, and watching the output to check that desired pages are found. Once one is more confident of the configuration, then an appropriate depth for a full crawl is around 10. <===========

Once crawling has completed, one can skip to the Searching section below.


-----------------------------------
Actually running nutch 2.x - steps
-----------------------------------
MANUALLY GOING THROUGH THE CYCLE 3 TIMES:

cd ~/apache-nutch-2.3.1/runtime/local

./bin/nutch inject urls

./bin/nutch generate -topN 50
./bin/nutch fetch -all
./bin/nutch parse -all
./bin/nutch updatedb -all

./bin/nutch generate -topN 50
./bin/nutch fetch -all
./bin/nutch parse -all
./bin/nutch updatedb -all

./bin/nutch generate -topN 50
./bin/nutch fetch -all
./bin/nutch parse -all
./bin/nutch updatedb -all

Dump output on local filesystem:
	rm -rf /tmp/bla
	./bin/nutch readdb -dump /tmp/bla [-crawlId ID -text]
	less /tmp/bla/part-r-00000

To dump output on local filesystem:
   Need hdfs host name if sending/dumping nutch crawl output to a location on hdfs
   Host is defined in /usr/local/hadoop/etc/hadoop/core-site.xml for property fs.defaultFS, (https://stackoverflow.com/questions/27956973/java-io-ioexception-incomplete-hdfs-uri-no-host)
   host is hdfs://node2/ in this case.
   So:

	hdfs dfs -rmdir /user/vagrant/dump
	XXX ./bin/nutch readdb -dump user/vagrant/dump -text ### won't work
	XXX ./bin/nutch readdb -dump hdfs:///user/vagrant/dump -text ### won't work
	./bin/nutch readdb -dump hdfs://node2/user/vagrant/dump -text


USING THE SCRIPT TO ATTEMPT TO CRAWL A SITE
* Choosing to repeat the cycle 10 times because, as per http://nutch.sourceforge.net/docs/en/tutorial.html

"Typically one starts testing one's configuration by crawling at low depths, and watching the output to check that desired pages are found. Once one is more confident of the configuration, then an appropriate depth for a full crawl is around 10." 

* Use the ./bin/crawl script, provide the seed urls dir, the crawlId and number of times to repeat = 10 
vagrant@node2:~/apache-nutch-2.3.1/runtime/local$ ./bin/crawl urls davidbHomePage 10


* View the downloaded crawls.
This time need to provide crawlId to readdb, in order to get a dump of its text contents:
   hdfs dfs -rm -r hdfs://node2/user/vagrant/dump2
   ./bin/nutch readdb -dump hdfs://node2/user/vagrant/dump2 -text -crawlId davidbHomePage

* View the contents:
hdfs dfs -cat hdfs://node2/user/vagrant/dump2/part-r-*


* FIND OUT NUMBER OF URLS DOWNLOADED FOR THE SITE:
vagrant@node2:~/apache-nutch-2.3.1/runtime/local$ ./bin/nutch readdb -stats -crawlId davidbHomePage
WebTable statistics start
Statistics for WebTable: 
retry 0:	44
status 5 (status_redir_perm):	4
status 3 (status_gone):	1
status 2 (status_fetched):	39
jobs:	{[davidbHomePage]db_stats-job_local647846559_0001={jobName=[davidbHomePage]db_stats, jobID=job_local647846559_0001, counters={Map-Reduce Framework={MAP_OUTPUT_MATERIALIZED_BYTES=135, REDUCE_INPUT_RECORDS=8, SPILLED_RECORDS=16, MERGED_MAP_OUTPUTS=1, VIRTUAL_MEMORY_BYTES=0, MAP_INPUT_RECORDS=44, SPLIT_RAW_BYTES=935, FAILED_SHUFFLE=0, MAP_OUTPUT_BYTES=2332, REDUCE_SHUFFLE_BYTES=135, PHYSICAL_MEMORY_BYTES=0, GC_TIME_MILLIS=0, REDUCE_INPUT_GROUPS=8, COMBINE_OUTPUT_RECORDS=8, SHUFFLED_MAPS=1, REDUCE_OUTPUT_RECORDS=8, MAP_OUTPUT_RECORDS=176, COMBINE_INPUT_RECORDS=176, CPU_MILLISECONDS=0, COMMITTED_HEAP_BYTES=595591168}, File Input Format Counters ={BYTES_READ=0}, File System Counters={FILE_LARGE_READ_OPS=0, FILE_WRITE_OPS=0, FILE_READ_OPS=0, FILE_BYTES_WRITTEN=1788140, FILE_BYTES_READ=1223290}, File Output Format Counters ={BYTES_WRITTEN=275}, Shuffle Errors={CONNECTION=0, WRONG_LENGTH=0, BAD_ID=0, WRONG_MAP=0, WRONG_REDUCE=0, IO_ERROR=0}}}}
TOTAL urls:	44
max score:	1.0
avg score:	0.022727273
min score:	0.0
WebTable statistics: done

------------------------------------
STOPPING CONDITION
Seems inbuilt
* When I tell it to cycle 15 times, it stops after 6 cycles saying no more URLs to fetch:

vagrant@node2:~/apache-nutch-2.3.1/runtime/local$ ./bin/crawl urls davidbHomePage2 15
---
No SOLRURL specified. Skipping indexing.
Injecting seed URLs

...

Thu Oct 3 09:22:23 UTC 2019 : Iteration 6 of 15
Generating batchId
Generating a new fetchlist
...
Generating batchId
Generating a new fetchlist
/home/vagrant/apache-nutch-2.3.1/runtime/local/bin/nutch generate -D mapred.reduce.tasks=2 -D mapred.child.java.opts=-Xmx1000m -D mapred.reduce.tasks.speculative.execution=false -D mapred.map.tasks.speculative.execution=false -D mapred.compress.map.output=true -topN 50000 -noNorm -noFilter -adddays 0 -crawlId davidbHomePage2 -batchId 1570094569-27637
GeneratorJob: starting at 2019-10-03 09:22:49
GeneratorJob: Selecting best-scoring urls due for fetch.
GeneratorJob: starting
GeneratorJob: filtering: false
GeneratorJob: normalizing: false
GeneratorJob: topN: 50000
GeneratorJob: finished at 2019-10-03 09:22:52, time elapsed: 00:00:02
GeneratorJob: generated batch id: 1570094569-27637 containing 0 URLs
Generate returned 1 (no new segments created)
Escaping loop: no more URLs to fetch now
vagrant@node2:~/apache-nutch-2.3.1/runtime/local$ 
---

* running readdb -stats show 44 URLs fetched, just as first time (when crawlId had been "davidbHomePage"):

vagrant@node2:~/apache-nutch-2.3.1/runtime/local$ ./bin/nutch readdb -stats -crawlId davidbHomePage2
---
WebTable statistics start
Statistics for WebTable: 
retry 0:	44
status 5 (status_redir_perm):	4
status 3 (status_gone):	1
status 2 (status_fetched):	39
jobs:	{[davidbHomePage2]db_stats-job_local985519583_0001={jobName=[davidbHomePage2]db_stats, jobID=job_local985519583_0001, counters={Map-Reduce Framework={MAP_OUTPUT_MATERIALIZED_BYTES=135, REDUCE_INPUT_RECORDS=8, SPILLED_RECORDS=16, MERGED_MAP_OUTPUTS=1, VIRTUAL_MEMORY_BYTES=0, MAP_INPUT_RECORDS=44, SPLIT_RAW_BYTES=935, FAILED_SHUFFLE=0, MAP_OUTPUT_BYTES=2332, REDUCE_SHUFFLE_BYTES=135, PHYSICAL_MEMORY_BYTES=0, GC_TIME_MILLIS=4, REDUCE_INPUT_GROUPS=8, COMBINE_OUTPUT_RECORDS=8, SHUFFLED_MAPS=1, REDUCE_OUTPUT_RECORDS=8, MAP_OUTPUT_RECORDS=176, COMBINE_INPUT_RECORDS=176, CPU_MILLISECONDS=0, COMMITTED_HEAP_BYTES=552599552}, File Input Format Counters ={BYTES_READ=0}, File System Counters={FILE_LARGE_READ_OPS=0, FILE_WRITE_OPS=0, FILE_READ_OPS=0, FILE_BYTES_WRITTEN=1788152, FILE_BYTES_READ=1223290}, File Output Format Counters ={BYTES_WRITTEN=275}, Shuffle Errors={CONNECTION=0, WRONG_LENGTH=0, BAD_ID=0, WRONG_MAP=0, WRONG_REDUCE=0, IO_ERROR=0}}}}
TOTAL urls:	44
---

----------------------------------------------------------------------
	Testing URLFilters: testing a URL to see if it's accepted
----------------------------------------------------------------------
Use the command
	./bin/nutch org.apache.nutch.net.URLFilterChecker -allCombined 
(mentioned at https://lucene.472066.n3.nabble.com/Correct-syntax-for-regex-urlfilter-txt-trying-to-exclude-single-path-results-td3600376.html)

Use as follows:

	cd apache-nutch-2.3.1/runtime/local

	./bin/nutch org.apache.nutch.net.URLFilterChecker -allCombined 

Then paste the URL you want to test, press Enter.
	A + in front of response means accepted
	A - in front of response means rejected.
Can continue pasting URLs to test against filters until you send Ctrl-D to terminate input.




-------------------
Dr Nichols's suggestion: can store listing of potential product sites to inspect by checking url for /mi in combination with whether the domain's IP geolocates to OUTSIDE New Zealand (tld nz).
* https://stackoverflow.com/questions/1415851/best-way-to-get-geo-location-in-java
  - https://mvnrepository.com/artifact/com.maxmind.geoip/geoip-api/1.2.10
  - older .dat.gz file is archived at https://web.archive.org/web/20180917084618/http://geolite.maxmind.com/download/geoip/database/GeoLiteCity.dat.gz
  - and newer geo country data at https://dev.maxmind.com/geoip/geoip2/geolite2/
* https://dev.maxmind.com/geoip/geoip2/geolite2/
* older GeoIp API (has LookupService): https://github.com/maxmind/geoip-api-java
* Newer GeoIp2 API: https://dev.maxmind.com/geoip/geoip2/downloadable/#MaxMind_APIs
	and https://maxmind.github.io/GeoIP2-java/doc/v2.12.0/
* https://maxmind.github.io/GeoIP2-java/
* https://github.com/AtlasOfLivingAustralia/ala-hub/issues/11


---
https://check-host.net/ip-info
https://ipinfo.info/html/ip_checker.php



----------
MongoDB
Installation:
	https://docs.mongodb.com/manual/tutorial/install-mongodb-on-ubuntu/
		https://docs.mongodb.com/manual/administration/install-on-linux/
	https://hevodata.com/blog/install-mongodb-on-ubuntu/
	https://www.digitalocean.com/community/tutorials/how-to-install-mongodb-on-ubuntu-16-04
	CENTOS (Analytics): https://tecadmin.net/install-mongodb-on-centos/
	FROM SOURCE: https://github.com/mongodb/mongo/wiki/Build-Mongodb-From-Source
GUI:
	https://robomongo.org/
	Robomongo is Robo 3T now

https://www.tutorialspoint.com/mongodb/mongodb_java.htm
JAR FILE:
	http://central.maven.org/maven2/org/mongodb/mongo-java-driver/
	https://mongodb.github.io/mongo-java-driver/


INSTALLING THE MONGODB SERVER AND MONGO CLIENT ON LINUX
Need to have sudo and root powers.

https://docs.mongodb.com/manual/tutorial/install-mongodb-on-ubuntu/
http://www.programmersought.com/article/6500308940/

   52  sudo apt-get install mongodb-clients
   53  mongo 'mongodb://mongodb.cms.waikato.ac.nz:27017' -u anupama -p

Failed with
	Error: HostAndPort: host is empty at src/mongo/shell/mongo.js:148
	exception: connect failed

This is due to a version incompatibility between Client and mongodb Server.
The solution is to follow instructions at http://www.programmersought.com/article/6500308940/
and then https://docs.mongodb.com/manual/tutorial/install-mongodb-on-ubuntu/
as below:

   54  sudo apt-get purge mongodb-clients
   55  sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv 9DA31620334BD75D9DCB49F368818C72E52529D4
   56  echo "deb [ arch=amd64,arm64 ] https://repo.mongodb.org/apt/ubuntu xenial/mongodb-org/4.0 multiverse" | sudo tee /etc/apt/sources.list.d/mongodb-org-4.0.list
   57  sudo apt-get update
   58  sudo apt-get install mongodb-clients
   59  mongo 'mongodb://mongodb.cms.waikato.ac.nz:27017' -u anupama -p
(still doesn't work)
   60  sudo apt-get install -y mongodb-org
The above ensures an up to date mongo client but installs the mongodb server too. Maybe this is the only step that is needed to install up-to-date mongo client and mongodb server?
   72  sudo service mongod status

  103  sudo service mongod start
"mongod" stands for mongo-daemon. This runs the mongo db server listening for client connections
  104  sudo service mongod status
   88  sudo service mongod stop


RUNNING AND USING THE MONGO CLIENT SHELL:
Among the many things you can do with the Mongo client shell, one can use it to find the mongo client version (which is the version of the shell) and the mongo db version.

To run the mongo client shell WITHOUT loading a db:


	wharariki:[880]/Scratch/ak19/gs3-extensions/maori-lang-detection>mongo --shell -nodb
	MongoDB shell version: 2.6.10 <<<<<<<<<-------------------<<<< MONGO CLIENT VERSION

	type "help" for help
	> help
		db.help()                    help on db methods
		db.mycoll.help()             help on collection methods
		sh.help()                    sharding helpers
		rs.help()                    replica set helpers
		help admin                   administrative help
		help connect                 connecting to a db help
		help keys                    key shortcuts
		help misc                    misc things to know
		help mr                      mapreduce

		show dbs                     show database names
		show collections             show collections in current database
		show users                   show users in current database
		show profile                 show most recent system.profile entries with time >= 1ms
		show logs                    show the accessible logger names
		show log [name]              prints out the last segment of log in memory, 'global' is default
		use <db_name>                set current database
		db.foo.find()                list objects in collection foo
		db.foo.find( { a : 1 } )     list objects in foo where a == 1
		it                           result of the last line evaluated; use to further iterate
		DBQuery.shellBatchSize = x   set default number of items to display on shell
		exit                         quit the mongo shell

	> help connect

	Normally one specifies the server on the mongo shell command line.  Run mongo --help to see those options.
	Additional connections may be opened:

	    var x = new Mongo('host[:port]');
	    var mydb = x.getDB('mydb');
	  or
	    var mydb = connect('host[:port]/mydb');

	Note: the REPL prompt only auto-reports getLastError() for the shell command line connection.

	Getting help on connect options: 

	> var x = new Mongo('mongodb.cms.waikato.ac.nz:27017');
	> var mydb = x.getDB('anupama');

	> mydb.connect.help()
	DBCollection help
		db.connect.find().help() - show DBCursor help
		db.connect.count()
		db.connect.copyTo(newColl) - duplicates collection by copying all documents to newColl; no indexes are copied.
		db.connect.convertToCapped(maxBytes) - calls {convertToCapped:'connect', size:maxBytes}} command
		db.connect.dataSize()
		db.connect.distinct( key ) - e.g. db.connect.distinct( 'x' )
		db.connect.drop() drop the collection
		db.connect.dropIndex(index) - e.g. db.connect.dropIndex( "indexName" ) or db.connect.dropIndex( { "indexKey" : 1 } )
		db.connect.dropIndexes()
		db.connect.ensureIndex(keypattern[,options]) - options is an object with these possible fields: name, unique, dropDups
		db.connect.reIndex()
		db.connect.find([query],[fields]) - query is an optional query filter. fields is optional set of fields to return.
			                                      e.g. db.connect.find( {x:77} , {name:1, x:1} )
		db.connect.find(...).count()
		db.connect.find(...).limit(n)
		db.connect.find(...).skip(n)
		db.connect.find(...).sort(...)
		db.connect.findOne([query])
		db.connect.findAndModify( { update : ... , remove : bool [, query: {}, sort: {}, 'new': false] } )
		db.connect.getDB() get DB object associated with collection
		db.connect.getPlanCache() get query plan cache associated with collection
		db.connect.getIndexes()
		db.connect.group( { key : ..., initial: ..., reduce : ...[, cond: ...] } )
		db.connect.insert(obj)
		db.connect.mapReduce( mapFunction , reduceFunction , <optional params> )
		db.connect.aggregate( [pipeline], <optional params> ) - performs an aggregation on a collection; returns a cursor
		db.connect.remove(query)
		db.connect.renameCollection( newName , <dropTarget> ) renames the collection.
		db.connect.runCommand( name , <options> ) runs a db command with the given name where the first param is the collection name
		db.connect.save(obj)
		db.connect.stats()
		db.connect.storageSize() - includes free space allocated to this collection
		db.connect.totalIndexSize() - size in bytes of all the indexes
		db.connect.totalSize() - storage allocated for all data and indexes
		db.connect.update(query, object[, upsert_bool, multi_bool]) - instead of two flags, you can pass an object with fields: upsert, multi
		db.connect.validate( <full> ) - SLOW
		db.connect.getShardVersion() - only for use with sharding
		db.connect.getShardDistribution() - prints statistics about data distribution in the cluster
		db.connect.getSplitKeysForChunks( <maxChunkSize> ) - calculates split points over all chunks and returns splitter function
		db.connect.getWriteConcern() - returns the write concern used for any operations on this collection, inherited from server/db if set
		db.connect.setWriteConcern( <write concern doc> ) - sets the write concern for writes to the collection
		db.connect.unsetWriteConcern( <write concern doc> ) - unsets the write concern for writes to the collection
	> mydb.version()
	4.0.13 <<<<<<<<<-------------------<<<< MONGODB SERVER VERSION

(Check Mongo server version: https://stackoverflow.com/questions/38160412/how-to-find-the-exact-version-of-installed-mongodb)

Finally we now know the mongodb server version: 4.0.13
This version didn't work with our mongo client (shell) version of 2.6.10. And that's we had to upgrade the client.


INSTALLATION MONGO-DB AND CLIENT
FROM: https://docs.mongodb.com/manual/tutorial/install-mongodb-on-ubuntu/
	wget -qO - https://www.mongodb.org/static/pgp/server-4.2.asc | sudo apt-key add -
	echo "deb [ arch=amd64 ] https://repo.mongodb.org/apt/ubuntu xenial/mongodb-org/4.2 multiverse" | sudo tee /etc/apt/sources.list.d/mongodb-org-4.2.list
	sudo apt-get update
	sudo apt-get install -y mongodb-org

UNINSTALLING
	https://www.anintegratedworld.com/uninstall-mongodb-in-ubuntu-via-command-line-in-3-easy-steps/


MONGO DB ROBO 3T
1. Download "Double Pack" from https://robomongo.org/
2. Untar its contents. Then untar the tarball in that.
3. Run:
	wharariki:[110]~/Downloads/robo3t-1.3.1-linux-x86_64-7419c406>./bin/robo3t