1. Solr 4
The NoSQL Search Server
Yonik Seeley
May 30, 2013

2. 2 2
NoSQL Databases
• Wikipedia says:
A NoSQL database provides a mechanism for storage and retrieval of data that
use looser consistency models than traditional relational databases in order to
achieve horizontal scaling and higher availability. Some authors refer to them as
"Not only SQL" to emphasize that some NoSQL systems do allow SQL-like query
language to be used.
• Non-traditional data stores
• Doesn’t use / isn’t designed around SQL
• May not give full ACID guarantees
• Offers other advantages such as greater scalability as a
tradeoff
• Distributed, fault-tolerant architecture

3. 3 3
Solr Cloud Design Goals
• Automatic Distributed Indexing
• HA for Writes
• Durable Writes
• Near Real-time Search
• Real-time get
• Optimistic Concurrency

4. 4 4
Solr Cloud
• Distributed Indexing designed from the ground up to
accommodate desired features
• CAP Theorem
• Consistency, Availability, Partition Tolerance (saying goes “choose 2”)
• Reality: Must handle P – the real choice is tradeoffs between C and A
• Ended up with a CP system (roughly)
• Value Consistency over Availability
• Eventual consistency is incompatible with optimistic concurrency
• Closest to MongoDB in architecture
• We still do well with Availability
• All N replicas of a shard must go down before we lose writability for that
shard
• For a network partition, the “big” partition remains active (i.e. Availability
isn’t “on” or “off”)

5. 5 5
Solr 4

6. 6 6
Solr 4 at a glance
• Document Oriented NoSQL Search Server
• Data-format agnostic (JSON, XML, CSV, binary)
• Schema-less options (more coming soon)
• Distributed
• Multi-tenanted
• Fault Tolerant
• HA + No single points of failure
• Atomic Updates
• Optimistic Concurrency
• Near Real-time Search
• Full-Text search + Hit Highlighting
• Tons of specialized queries: Faceted search, grouping,
pseudo-join, spatial search, functions
The desire for these
features drove some
of the “SolrCloud”
architecture

7. 7 7
Quick Start
1. Unzip the binary distribution (.ZIP file)
Note: no “installation” required
3. Start Solr
4. Go!
Browse to http://localhost:8983/solr for the new admin
interface
$
cd
example
$
java
–jar
start.jar

8. 8 8
New admin UI

9. 9 9
Add and Retrieve document
$ curl http://localhost:8983/solr/update -H 'Content-type:application/json' -d '
[
{ "id" : "book1",
"title" : "American Gods",
"author" : "Neil Gaiman"
}
]'
$ curl http://localhost:8983/solr/get?id=book1
{
"doc":
{
"id"
:
"book1",
"author":
"Neil
Gaiman",
"title"
:
"American
Gods",
"_version_":
1410390803582287872
}
}
Note: no type of “commit”
is necessary to retrieve
documents via /get
(real-time get)

10. 10 10
Simplified JSON Delete Syntax
• Singe delete-by-id
{"delete":”book1"}
• Multiple delete-by-id
{"delete":[”book1”,”book2”,”book3”]}
• Delete with optimistic concurrency
{"delete":{"id":”book1",
"_version_":123456789}}
• Delete by Query
{"delete":{”query":”tag:category1”}}

11. 11 11
Atomic Updates
$
curl
http://localhost:8983/solr/update
-­‐H
'Content-­‐type:application/json'
-­‐d
'
[
{"id"
:
"book1",
"pubyear_i"
:
{
"add"
:
2001
},
"ISBN_s"
:
{
"add"
:
"0-­‐380-­‐97365-­‐1"}
}
]'
$
curl
http://localhost:8983/solr/update
-­‐H
'Content-­‐type:application/json'
-­‐d
'
[
{"id"
:
"book1",
"copies_i"
:
{
"inc"
:
1},
"cat"
:
{
"add"
:
"fantasy"},
"ISBN_s"
:
{
"set"
:
"0-­‐380-­‐97365-­‐0"}
"remove_s"
:
{
"set"
:
null
}
}
]'

12. 12 12
Optimistic Concurrency
• Conditional update based on document version
Solr
1. /get document
2. Modify
document,
retaining
_version_
3. /update resulting
document
4. Go back to
step #1 if fail
code=409
client

13. 13 13
Version semantics
_version_ Update Semantics
> 1 Document version must exactly match supplied
_version_
1 Document must exist
< 0 Document must not exist
0 Don’t care (normal overwrite if exists)
• Specifying _version_ on any update
invokes optimistic concurrency

14. 14 14
Optimistic Concurrency Example
$
curl
http://localhost:8983/solr/update
-­‐H
'Content-­‐type:application/json'
-­‐d
'
[
{
"id":"book2",
"title":["Neuromancer"],
"author":"William
Gibson",
"copiesIn_i":6,
"copiesOut_i":4,
"_version_":123456789
}
]'
$
curl
http://localhost:8983/solr/get?id=book2
{
"doc”
:
{
"id":"book2",
"title":["Neuromancer"],
"author":"William
Gibson",
"copiesIn_i":7,
"copiesOut_i":3,
"_version_":123456789
}}
curl http://localhost:8983/solr/update?_version_=123456789 -H 'Content-type:application/json'
-d […]
Get the document
Modify and resubmit, using
the same _version_
Alternately, specify
the _version_ as a
request parameter

15. 15 15
Optimistic Concurrency Errors
• HTTP Code 409 (Conflict) returned on version mismatch
$ curl -i http://localhost:8983/solr/update -H 'Content-type:application/json' -d '
[{"id":"book1", "author":"Mr Bean", "_version_":54321}]'
HTTP/1.1
409
Conflict
Content-­‐Type:
text/plain;charset=UTF-­‐8
Transfer-­‐Encoding:
chunked
{
"responseHeader":{
"status":409,
"QTime":1},
"error":{
"msg":"version
conflict
for
book1
expected=12345
actual=1408814192853516288",
"code":409}}

16. 16 16
Schema

17. 17 17
Schema REST API
• Restlet is now integrated with Solr
• Get a specific field
curl
http://localhost:8983/solr/schema/fields/price
{"field":{
"name":"price",
"type":"float",
"indexed":true,
"stored":true
}}
• Get all fields
curl
http://localhost:8983/solr/schema/fields
• Get Entire Schema!
curl
http://localhost:8983/solr/schema

18. 18 18
Dynamic Schema
• Add a new field (Solr 4.4)
curl
-­‐XPUT
http://localhost:8983/solr/schema/fields/strength
-­‐d
‘
{"type":”float",
"indexed":"true”}
‘
• Works in distributed (cloud) mode too!
• Schema must be managed & mutable (not currently the default)
<schemaFactory
class="ManagedIndexSchemaFactory">
<bool
name="mutable">true</bool>
<str
name="managedSchemaResourceName">managed-­‐schema</str>
</schemaFactory>

19. 19 19
Schemaless
• “Schemaless” really normally means that the client(s) have an implicit
schema
• “No Schema” impossible for anything based on Lucene
• A field must be indexed the same way across documents
• Dynamic fields: convention over configuration
• Only pre-define types of fields, not fields themselves
• No guessing. Any field name ending in _i is an integer
• “Guessed Schema” or “Type Guessing”
• For previously unknown fields, guess using JSON type as a hint
• Coming soon (4.4?) based on the Dynamic Schema work
• Many disadvantages to guessing
• Lose ability to catch field naming errors
• Can’t optimize based on types
• Guessing incorrectly means having to start over

20. 20 20
Solr Cloud

21. 21 21
Solr Cloud
shard1
replica2
replica3
replica2
replica3
ZooKeeper
quorum
ZK
node
ZK
node
ZK
node
ZK
node
ZK
node
/configs
/myconf
solrconfig.xml
schema.xml
/clusterstate.json
/aliases.json
/livenodes
server1:8983/solr
server2:8983/solr/collections
/collection1
configName=myconf
/shards
/shard1
server1:8983/solr
server2:8983/solr
/shard2
server3:8983/solr
server4:8983/solr
http://.../solr/collection1/query?q=awesome
Load-balanced
sub-request
replica1
shard2
replica1
ZooKeeper holds cluster state
• Nodes in the cluster
• Collections in the cluster
• Schema & config for each collection
• Shards in each collection
• Replicas in each shard
• Collection aliases

22. 22 22
Distributed Indexing
shard1
http://.../solr/collection1/update
shard2
• Update sent to any node
• Solr determines what shard the document is on, and forwards to shard leader
• Shard Leader versions document and forwards to all other shard replicas
• HA for updates (if one leader fails, another takes it’s place)

23. 23 23
Collections API
l Create a new document collection
http://localhost:8983/solr/admin/collections?
action=CREATE
&name=mycollection
&numShards=4
&replicationFactor=3
l Delete a collection
http://localhost:8983/solr/admin/collections?
action=DELETE
&name=mycollection
l Create an alias to a collection (or a group of collections)
http://localhost:8983/solr/admin/collections?
action=CREATEALIAS
&name=tri_state
&collections=NY,NJ,CT

24. 24 24
http://localhost:8983/solr/#/~cloud

25. 25 25
Distributed Query Requests
l Distributed query across all shards in the collection
http://localhost:8983/solr/collection1/query?q=foo
l Explicitly specify node addresses to load-balance across
shards=localhost:8983/solr|localhost:8900/solr,
localhost:7574/solr|localhost:7500/solr
l A list of equivalent nodes are separated by “|”
l Different phases of the same distributed request use the same node
l Specify logical shards to search across
shards=NY,NJ,CT
l Specify multiple collections to search across
collection=collection1,collection2
l public
CloudSolrServer(String
zkHost)
l ZK aware SolrJ Java client that load-balances across all nodes in cluster
l Calculate where document belongs and directly send to shard leader (new)

26. 26 26
Durable Writes
• Lucene flushes writes to disk on a “commit”
• Uncommitted docs are lost on a crash (at lucene level)
• Solr 4 maintains it’s own transaction log
• Contains uncommitted documents
• Services real-time get requests
• Recovery (log replay on restart)
• Supports distributed “peer sync”
• Writes forwarded to multiple shard replicas
• A replica can go away forever w/o collection data loss
• A replica can do a fast “peer sync” if it’s only slightly out of date
• A replica can do a full index replication (copy) from a peer

27. 27 27
Near Real Time (NRT) softCommit
• softCommit opens a new view of the index without
flushing + fsyncing files to disk
• Decouples update visibility from update durability
• commitWithin now implies a soft commit
• Current autoCommit defaults from solrconfig.xml:
<autoCommit>
<maxTime>15000</maxTime>
<openSearcher>false</openSearcher>
</autoCommit>
<!-­‐-­‐
<autoSoftCommit>
<maxTime>5000</maxTime>
</autoSoftCommit>
-­‐-­‐>

28. 28 28
Document Routing
80000000-bfffffff
00000000-3fffffff
40000000-7ffffff
f
c0000000-ffffffff
shard1shard4
shard3 shard2
id
=
BigCo!doc5
9f27 3c71
(MurmurHash3)
q=my_query
shard.keys=BigCo!
9f27 0000 9f27 ffffto
(hash)
shard1
numShards=4
router=compositeId
hash
ring

29. 29 29
Seamless Online Shard Splitting
Shard2_0
Shard1
replica
leader
Shard2
replica
leader
Shard3
replica
leader
Shard2_1
1. http://localhost:8983/solr/admin/collections?
action=SPLITSHARD&collection=mycollection&shard=Shard2
2. New sub-shards created in “construction” state
3. Leader starts forwarding applicable updates, which are buffered by the sub-shards
4. Leader index is split and installed on the sub-shards
5. Sub-shards apply buffered updates then become “active” leaders and old shard
becomes “inactive”
update

30. 30 30
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