View Source

This document describes the REST API exposed to access Couchbase

{note:title=Open Questions}
* Expose documents and views APIs through the same HTTP socket.
** Let people operate on two endpoints separately and optionally map them to the endpoints they want. It will be the most natural way with nginx, where everything built around {{location}} entity.
** Develop some standard schema prefixes like {{_doc/}} and {{_design}}, to allow to reference them, but here is another question "do we need to inject prefix in all places, like view results?"
* Represent document keys so that they could be passed in URI. Urlencoding is quite common, but in views the server is using base64
* Unlike memcache protocol, it should also encode bodies of the documents somehow, therefore MIME support. How we should do it?
* _low priority_ Evaluate what we need to support CouchApp-like deployment:
** authentication and authorization!
** proxy to syncgateway instead to raw couchbase?
** new API to store attachments somewhere
** additional useful APIs, like lists (can be done with multi-get)
{note}

There are several terms we are using while describing this API.

|| Term || Definition||
| mount point | The part of URI which where couchbase nginx module connected |
| document | Arbitrary JSON or BLOB value. It could be referenced by its ID |

h2. Configuration and URIs

The Couchbase API could be mount to any endpoint in your application, and during configuration the bucket name and credentials should be specified like this:

{code:none}
server {
location /wonderland/ {
couchbase_pass example.com:8091,example.org bucket=wonderland;
}
...
}
{code}

The config section above tell nginx to use {{/wonderland/}} mount point to expose Couchbase API.

By default only Document API will be mounted, i.e. only CRUD operations can be executed there. Because in Couchbase itself both Document and Views APIs lives in completely different namespaces, the nginx module also keeps them separate. The example below will mount views and the documents into the common root.

{code:none}
server {
location /wonderland/docs/ {
couchbase_pass example.com:8091,example.org bucket=wonderland;
}
location /wonderland/views/ {
couchbase_pass example.com:8091,example.org bucket=wonderland views=true;
}
...
}
{code}

The connection configuration could be shared amound the locations using upstream

{code:none}
upstream couchbase {
couchbase_server example.com:8091;
couchbase_server example.org;
couchbase_bucket wonderland;
}

server {
location /wonderland/docs/ {
couchbase_pass couchbase;
}
location /wonderland/views/ {
couchbase_pass couchbase views=true;
}
...
}
{code}

h2. Document CRUD

The module maps basic data operations to HTTP methods. The table below assumes that the bucket mount to {{/storage}} location:

|| Couchbase operation || HTTP method || Comments ||
| get "foo" | GET /storage/foo | |
| add "foo" "bar" | POST /storage/foo | document goes in request's body, fails if ID exists already |
| | POST /storage | the same as above, but will generate ID |
| set "foo" "bar" | PUT /storage/foo | document goes in request's body |
| delete "foo" | DELETE /storage/foo | |

Apart from HTTP methods, it is possible to use arguments in query string, to specify the command. To do so, the name of the parameter must be specified in the config:

{code:none}
server {
location /wonderland/ {
couchbase_pass example.com:8091,example.org bucket=wonderland;
set $couchbase_cmd $arg_cmd
set $couchbase_exptime $arg_exptime;
}
...
}
{code}

The snippet above will translate this URI {{/storage/foo?cmd=replace&exptime=40}} to the {{replace "foo" ...}} command with expiration of 40 seconds. In the same way can be controller ID, value, flags and expiration time.

The rest of the section demonstrates various example of usage the API, including optimistic locking with CAS. It assumes the following config:

{code:none}
server {
location /wonderland/ {
couchbase_pass example.com:8091,example.org bucket=wonderland;
add_header ETag $couchbase_cas;
}
...
}
{code}

Create document in the bucket
{code:none}
POST /wonderland
> Content-Type: application/json
{"name":"Alice","species":"human"}
< 201
< ETag: 10952782243130507264
< Location: http://couchbasenginx.apiary.io/wonderland/0a4683e4b4b161f505d0c2ae0c3a1abf
{code}

You can also specify ID with POST request if you need to *create* the document with given ID.
{code:none}
POST /wonderland/alice
> Content-Type: application/json
{"name":"Alice","species":"human"}
< 201
< ETag: 10952782243130507265
< Location: http://couchbasenginx.apiary.io/wonderland/alice
{code}

Note that when you are using POST request, the server is always supposed to create the new document. This means that you will get an error if the document already exists.
{code:none}
POST /wonderland/foobar
> Content-Type: application/json
{"foo":"bar"}
< 409
< Content-Type: application/json
< Content-Length: 74
{"error":"key_eexists","reason":"Key exists (with a different ETag value)"}
{code}

Update the document
{code:none}
PUT /wonderland/white-rabbit
> Content-Type: application/json
{"name":"Write Rabbit","species":"rabbit"}
< 204
< ETag: 10952782243130507266
< Location: http://couchbasenginx.apiary.io/wonderland/white-rabbit
{code}

You can also specify *If-Match* header and the server will perform optimistic lock before updating. This operation might fail *412 Precondition Failed*
{code:none}
PUT /wonderland/duchess
> Content-Type: application/json
> If-Match: "wrong_etag"
{"name":"Duchess","species":"human"}
< 412
< Content-Type: application/json
< Content-Length: 74
{"error":"key_eexists","reason":"Key exists (with a different ETag value)"}
{code}

If the document being updated doesn't exist, you will get *404 Not Found* error
{code:none}
PUT /wonderland/sheep
{"name":"Sheep","species":"sheep"}
< 404
< Content-Type: application/json
< Content-Length: 45
{"error":"key_enoent","reason":"No such key"}
{code}

Removing document from the bucket
{code:none}
DELETE /wonderland/caterpillar
< 204
< ETag: 10952782243130507267
{code}

You can also specify *If-Match* header if you need to ensure you are removing know version of the document.
{code:none}
DELETE /wonderland/bill-the-lizard
> If-Match: "wrong_etag"
< 412
< Content-Type: application/json
< Content-Length: 74
{"error":"key_eexists","reason":"Key exists (with a different ETag value)"}
{code}


If the document being removed doesn't exist, you will get *404 Not Found* error
{code:none}
DELETE /wonderland/jabberwock
< 404
< Content-Type: application/json
< Content-Length: 45
{"error":"key_enoent","reason":"No such key"}
{code}

Getting the document by ID.
{code:none}
GET /wonderland/hatter
< 200
< Content-Type: application/json
< Content-Length: 36
< ETag: 10952782243130507268
{"name":"Hatter","species":"human"}
{code}

In case when the given document ID isn't exist in the bucket you will get *404 Not Found*
{code:none}
GET /wonderland/red-queen
< 404
< Content-Type: application/json
< Content-Length: 45
{"error":"key_enoent","reason":"No such key"}
{code}

Use *HEAD* request to skip the document body
{code:none}
HEAD /wonderland/gryphon
< 200
< Content-Type: application/json
< ETag: 10952782243130507269
{code}

Each operation is carry ETag, which internally is CAS value. The ETag value can be used in the conditional requests with *If-Match*, *If-None-Match*. See examples of *If-Match* above.

Check if the key has been modified (in this case the server responds that it wasn't modified):
{code:none}
HEAD /wonderland/dormouse
< If-None-Match: 10952782243130507269
< 304
{code}

h2. Couchbase Views

This section shows more advanced server feature: View indexes

One of the features of the Couchbase is ability to build efficient indexes leveraging Map/Reduce. They are called Views and you can define them on Admin Console UI.

The module allows you to query your views proxying them to Couchbase. All arguments will be transparently passed to Couchbase and the result will be streamed back.

As mentioned above, the view endpoint should be mount separately

{code:none}
server {
location /wonderland/views/ {
couchbase_pass example.com:8091,example.org bucket=wonderland views=true;
}
...
}
{code}

For example we have a view *all* defined in the design document *characters*. It is simple map which will just emit all known characters (without any reduce function):

{code:javascript}
function (doc, meta) {
emit(meta.id);
}
{code}

The result will look like
{code:none}
GET /wonderland/views/_design/characters/_view/all
< 200
< Transfer-Encoding: chunked
< Content-Type: application/json
{"total_rows":20,"rows":[
{"id":"alice","key":"alice","value":null},
{"id":"bill-the-lizard","key":"bill-the-lizard","value":null},
{"id":"caterpillar","key":"caterpillar","value":null},
{"id":"cheshire-cat","key":"cheshire-cat","value":null},
{"id":"dodo","key":"dodo","value":null},
{"id":"dormouse","key":"dormouse","value":null},
{"id":"duchess","key":"duchess","value":null},
{"id":"duck","key":"duck","value":null},
{"id":"eaglet","key":"eaglet","value":null},
{"id":"gryphon","key":"gryphon","value":null},
{"id":"hatter","key":"hatter","value":null},
{"id":"king-of-hearts","key":"king-of-hearts","value":null},
{"id":"knave-of-hearts","key":"knave-of-hearts","value":null},
{"id":"lory","key":"lory","value":null},
{"id":"march-hare","key":"march-hare","value":null},
{"id":"mock-turtle","key":"mock-turtle","value":null},
{"id":"mouse","key":"mouse","value":null},
{"id":"pat","key":"pat","value":null},
{"id":"queen-of-hearts","key":"queen-of-hearts","value":null},
{"id":"white-rabbit","key":"white-rabbit","value":null}
]
}
{code}

You can pass the any of supported query parameters, like *include_docs=true* for example (note that {{rev}} field replaced with {{etag}}:
{code:none}
GET /wonderland/views/_design/characters/_view/all?include_docs=true
< 200
< Transfer-Encoding: chunked
< Content-Type: application/json
{"total_rows":20,"rows":[
{"id":"alice","key":"alice","value":null,"doc":{"meta":{"id":"alice","expiration":0,"flags":0,"etag":88499348547108864},"json":{"name":"Alice","species":"human"}}},
{"id":"bill-the-lizard","key":"bill-the-lizard","value":null,"doc":{"meta":{"id":"bill-the-lizard","expiration":0,"flags":0,"etag":12227673967682453504},"json":{"name":"BilltheLizard","species":"lizard"}}},
{"id":"caterpillar","key":"caterpillar","value":null,"doc":{"meta":{"id":"caterpillar","expiration":0,"flags":0,"etag":7907600423173816320},"json":{"name":"Caterpillar","species":"caterpillar"}}},
{"id":"cheshire-cat","key":"cheshire-cat","value":null,"doc":{"meta":{"id":"cheshire-cat","expiration":0,"flags":0,"etag":15887700786432507904},"json":{"name":"CheshireCat","species":"cat"}}},
{"id":"dodo","key":"dodo","value":null,"doc":{"meta":{"id":"dodo","expiration":0,"flags":0,"etag":14764617828380246016},"json":{"name":"Dodo","species":"bird"}}},
{"id":"dormouse","key":"dormouse","value":null,"doc":{"meta":{"id":"dormouse","expiration":0,"flags":0,"etag":4027757040775528448},"json":{"name":"Dormouse","species":"dormouse"}}},
{"id":"duchess","key":"duchess","value":null,"doc":{"meta":{"id":"duchess","expiration":0,"flags":0,"etag":17543907245979402240},"json":{"name":"Duchess","species":"human"}}},
{"id":"duck","key":"duck","value":null,"doc":{"meta":{"id":"duck","expiration":0,"flags":0,"etag":13461959332744724480},"json":{"name":"Duck","species":"bird"}}},
{"id":"eaglet","key":"eaglet","value":null,"doc":{"meta":{"id":"eaglet","expiration":0,"flags":0,"etag":8572459711327174656},"json":{"name":"Eaglet","species":"bird"}}},
{"id":"gryphon","key":"gryphon","value":null,"doc":{"meta":{"id":"gryphon","expiration":0,"flags":0,"etag":14715372901595414528},"json":{"name":"Gryphon","species":"gryphon"}}},
{"id":"hatter","key":"hatter","value":null,"doc":{"meta":{"id":"hatter","expiration":0,"flags":0,"etag":3615690869010661376},"json":{"name":"Hatter","species":"human"}}},
{"id":"king-of-hearts","key":"king-of-hearts","value":null,"doc":{"meta":{"id":"king-of-hearts","expiration":0,"flags":0,"etag":6164167507172196352},"json":{"name":"KingofHearts","species":"card"}}},
{"id":"knave-of-hearts","key":"knave-of-hearts","value":null,"doc":{"meta":{"id":"knave-of-hearts","expiration":0,"flags":0,"etag":205344449230864384},"json":{"name":"KnaveofHearts","species":"card"}}},
{"id":"lory","key":"lory","value":null,"doc":{"meta":{"id":"lory","expiration":0,"flags":0,"etag":13830705845886844928},"json":{"name":"Lory","species":"bird"}}},
{"id":"march-hare","key":"march-hare","value":null,"doc":{"meta":{"id":"march-hare","expiration":0,"flags":0,"etag":14847959710254039040},"json":{"name":"MarchHare","species":"hare"}}},
{"id":"mock-turtle","key":"mock-turtle","value":null,"doc":{"meta":{"id":"mock-turtle","expiration":0,"flags":0,"etag":211262020811554816},"json":{"name":"MockTurtle","species":"turtle"}}},
{"id":"mouse","key":"mouse","value":null,"doc":{"meta":{"id":"mouse","expiration":0,"flags":0,"etag":7144275470706606080},"json":{"name":"Mouse","species":"mouse"}}},
{"id":"pat","key":"pat","value":null,"doc":{"meta":{"id":"pat","expiration":0,"flags":0,"etag":89110677012152320},"json":{"name":"Pat","species":"pig"}}},
{"id":"queen-of-hearts","key":"queen-of-hearts","value":null,"doc":{"meta":{"id":"queen-of-hearts","expiration":0,"flags":0,"etag":8409231712625688576},"json":{"name":"QueenofHearts","species":"card"}}},
{"id":"white-rabbit","key":"white-rabbit","value":null,"doc":{"meta":{"id":"white-rabbit","expiration":0,"flags":0,"etag":14777043409285742592},"json":{"name":"WhiteRabbit","species":"rabbit"}}}
]
}
{code}

h2. Misc

You can find executable spec here: http://docs.ngxcbm.apiary.io/