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# 10.2.1. `/`

`GET` `/`

  Accessing the root of a CouchDB instance returns meta information about the instance. The response is a JSON structure containing information about the server, including a welcome message and the version of the server.

  Request Headers:
  | Accept – application/json text/plain
  Response Headers:
  | Content-Type – application/json text/plain; charset=utf-8
  Status Codes: | 200 OK – Request completed successfully

  Request:

      GET / HTTP/1.1
      Accept: application/json
      Host: localhost:5984

  Response:

      HTTP/1.1 200 OK
      Cache-Control: must-revalidate
      Content-Length: 179
      Content-Type: application/json
      Date: Sat, 10 Aug 2013 06:33:33 GMT
      Server: CouchDB (Erlang/OTP)

      {
          "couchdb": "Welcome",
          "uuid": "85fb71bf700c17267fef77535820e371",
          "vendor": {
              "name": "The Apache Software Foundation",
              "version": "1.3.1"
          },
          "version": "1.3.1"
      }

# 10.2.2. `/_active_tasks`

`GET` `/_active_tasks`

  List of running tasks, including the task type, name, status and process ID. The result is a JSON array of the currently running tasks, with each task being described with a single object. Depending on operation type set of response object fields might be different.

  Request Headers:
  | Accept – application/json text/plain
  Response Headers:
  | Content-Type – application/json text/plain; charset=utf-8
  Response JSON Object:
  | changes_done (number) – Processed changes database (string) – Source database pid (string) – Process ID progress (number) – Current percentage progress started_on (number) – Task start time as unix timestamp status (string) – Task status message task (string) – Task name total_changes (number) – Total changes to process type (string) – Operation Type updated_on (number) – Unix timestamp of last operation update
  Status Codes: | 200 OK – Request completed successfully 401 Unauthorized – CouchDB Server Administrator privileges required

  Request:

      GET /_active_tasks HTTP/1.1
      Accept: application/json
      Host: localhost:5984

  Response:

      HTTP/1.1 200 OK
      Cache-Control: must-revalidate
      Content-Length: 1690
      Content-Type: application/json
      Date: Sat, 10 Aug 2013 06:37:31 GMT
      Server: CouchDB (Erlang/OTP)

      [
          {
              "changes_done": 64438,
              "database": "mailbox",
              "pid": "<0.12986.1>",
              "progress": 84,
              "started_on": 1376116576,
              "total_changes": 76215,
              "type": "database_compaction",
              "updated_on": 1376116619
          },
          {
              "changes_done": 14443,
              "database": "mailbox",
              "design_document": "c9753817b3ba7c674d92361f24f59b9f",
              "pid": "<0.10461.3>",
              "progress": 18,
              "started_on": 1376116621,
              "total_changes": 76215,
              "type": "indexer",
              "updated_on": 1376116650
          },
          {
              "changes_done": 5454,
              "database": "mailbox",
              "design_document": "_design/meta",
              "pid": "<0.6838.4>",
              "progress": 7,
              "started_on": 1376116632,
              "total_changes": 76215,
              "type": "indexer",
              "updated_on": 1376116651
          },
          {
              "checkpointed_source_seq": 68585,
              "continuous": false,
              "doc_id": null,
              "doc_write_failures": 0,
              "docs_read": 4524,
              "docs_written": 4524,
              "missing_revisions_found": 4524,
              "pid": "<0.1538.5>",
              "progress": 44,
              "replication_id": "9bc1727d74d49d9e157e260bb8bbd1d5",
              "revisions_checked": 4524,
              "source": "mailbox",
              "source_seq": 154419,
              "started_on": 1376116644,
              "target": "http://mailsrv:5984/mailbox",
              "type": "replication",
              "updated_on": 1376116651
          }
      ]

# 10.2.3. `/_all_dbs`

`GET` `/_all_dbs`

  Returns a list of all the databases in the CouchDB instance.

  Request Headers:
  | Accept – application/json text/plain
  Response Headers:
  | Content-Type – application/json text/plain; charset=utf-8
  Status Codes: | 200 OK – Request completed successfully

  Request:

      GET /_all_dbs HTTP/1.1
      Accept: application/json
      Host: localhost:5984

  Response:

      HTTP/1.1 200 OK
      Cache-Control: must-revalidate
      Content-Length: 52
      Content-Type: application/json
      Date: Sat, 10 Aug 2013 06:57:48 GMT
      Server: CouchDB (Erlang/OTP)

      [
         "_users",
         "contacts",
         "docs",
         "invoices",
         "locations"
      ]

# 10.2.4. `/_db_updates`

New in version 1.4.

`GET` `/_db_updates`

  Returns a list of all database events in the CouchDB instance.

  Request Headers:
  | Accept – application/json text/plain
  Query Parameters:
  | feed (string) – longpoll: Closes the connection after the first event. continuous: Send a line of JSON per event. Keeps the socket open until `timeout`. eventsource: Like, `continuous`, but sends the events in EventSource format. timeout (number) – Number of seconds until CouchDB closes the connection. Default is `60`. heartbeat (boolean) – Whether CouchDB will send a newline character (`\n`) on `timeout`. Default is `true`.
  Response Headers:
  | Content-Type – application/json text/plain; charset=utf-8 Transfer-Encoding – `chunked`
  Response JSON Object:
  | db_name (string) – Database name ok (boolean) – Event operation status type (string) – A database event is one of `created`, `updated`, `deleted`
  Status Codes: | 200 OK – Request completed successfully 401 Unauthorized – CouchDB Server Administrator privileges required

  Request:

      GET /_db_updates HTTP/1.1
      Accept: application/json
      Host: localhost:5984

  Response:

      HTTP/1.1 200 OK
      Cache-Control: must-revalidate
      Content-Type: application/json
      Date: Sat, 10 Aug 2013 07:02:41 GMT
      Server: CouchDB (Erlang/OTP)
      Transfer-Encoding: chunked

      {
          "db_name": "mailbox",
          "ok": true,
          "type": "created"
      }

# 10.2.5. `/_log`

`GET` `/_log`

  Gets the CouchDB log, equivalent to accessing the local log file of the corresponding CouchDB instance.

  Request Headers:
  | Accept – text/plain
  Query Parameters:
  | bytes (number) – Bytes to be returned. Default is `1000`. offset (number) – Offset in bytes where the log tail should be started. Default is `0`.
  Response Headers:
  | Content-Type – text/plain; charset=utf-8 Transfer-Encoding – `chunked`
  Status Codes: | 200 OK – Request completed successfully 401 Unauthorized – CouchDB Server Administrator privileges required

  Request:

      GET /_log HTTP/1.1
      Accept: application/json
      Host: localhost:5984

  Response:

      [Wed, 27 Oct 2010 10:49:42 GMT] [info] [<0.23338.2>] 192.168.0.2 - - 'PUT' /authdb 401
      [Wed, 27 Oct 2010 11:02:19 GMT] [info] [<0.23428.2>] 192.168.0.116 - - 'GET' /recipes/FishStew 200
      [Wed, 27 Oct 2010 11:02:19 GMT] [info] [<0.23428.2>] 192.168.0.116 - - 'GET' /_session 200
      [Wed, 27 Oct 2010 11:02:19 GMT] [info] [<0.24199.2>] 192.168.0.116 - - 'GET' / 200
      [Wed, 27 Oct 2010 13:03:38 GMT] [info] [<0.24207.2>] 192.168.0.116 - - 'GET' /_log?offset=5 200

If you want to pick out specific parts of the log information you can use the `bytes` argument, which specifies the number of bytes to be returned, and `offset`, which specifies where the reading of the log should start, counted back from the end. For example, if you use the following request:

    GET /_log?bytes=500&offset=2000

Reading of the log will start at 2000 bytes from the end of the log, and 500 bytes will be shown.

How bytes/offset works?

CouchDB reads specified amount of `bytes` from the end of log file, jumping to `offset` bytes towards the beginning of the file first:

     Log File    FilePos
     ----------
    |          |  10
    |          |  20
    |          |  30
    |          |  40
    |          |  50
    |          |  60
    |          |  70 -- Bytes = 20  --
    |          |  80                 | Chunk
    |          |  90 -- Offset = 10 --
    |__________| 100

# 10.2.6. `/_replicate`

`POST` `/_replicate`

  Request, configure, or stop, a replication operation.

  Request Headers:
  | Accept – application/json text/plain Content-Type – application/json
  Request JSON Object:
  | cancel (boolean) – Cancels the replication continuous (boolean) – Configure the replication to be continuous create_target (boolean) – Creates the target database. Required administrator’s privileges on target server. doc_ids (array) – Array of document IDs to be synchronized proxy (string) – Address of a proxy server through which replication should occur source (string) – Source database name or URL target (string) – Target database name or URL
  Response Headers:
  | Content-Type – application/json text/plain; charset=utf-8
  Response JSON Object:
  | history (array) – Replication history (see below) ok (boolean) – Replication status replication_id_version (number) – Replication protocol version session_id (string) – Unique session ID source_last_seq (number) – Last sequence number read from source database
  Status Codes: | 200 OK – Replication request successfully completed 202 Accepted – Continuous replication request has been accepted 400 Bad Request – Invalid JSON data 401 Unauthorized – CouchDB Server Administrator privileges required 404 Not Found – Either the source or target DB is not found or attempt to cancel unknown replication task 500 Internal Server Error – JSON specification was invalid

  The specification of the replication request is controlled through the JSON content of the request. The JSON should be an object with the fields defining the source, target and other options.

  The Replication history is an array of objects with following structure:

  JSON Object: | doc_write_failures (number) – Number of document write failures docs_read (number) – Number of documents read docs_written (number) – Number of documents written to target end_last_seq (number) – Last sequence number in changes stream end_time (string) – Date/Time replication operation completed in RFC 2822 format missing_checked (number) – Number of missing documents checked missing_found (number) – Number of missing documents found recorded_seq (number) – Last recorded sequence number session_id (string) – Session ID for this replication operation start_last_seq (number) – First sequence number in changes stream start_time (string) – Date/Time replication operation started in RFC 2822 format

  Request

      POST /_replicate HTTP/1.1
      Accept: application/json
      Content-Length: 36
      Content-Type: application/json
      Host: localhost:5984

      {
          "source": "db_a",
          "target": "db_b"
      }

  Response

      HTTP/1.1 200 OK
      Cache-Control: must-revalidate
      Content-Length: 692
      Content-Type: application/json
      Date: Sun, 11 Aug 2013 20:38:50 GMT
      Server: CouchDB (Erlang/OTP)

      {
          "history": [
              {
                  "doc_write_failures": 0,
                  "docs_read": 10,
                  "docs_written": 10,
                  "end_last_seq": 28,
                  "end_time": "Sun, 11 Aug 2013 20:38:50 GMT",
                  "missing_checked": 10,
                  "missing_found": 10,
                  "recorded_seq": 28,
                  "session_id": "142a35854a08e205c47174d91b1f9628",
                  "start_last_seq": 1,
                  "start_time": "Sun, 11 Aug 2013 20:38:50 GMT"
              },
              {
                  "doc_write_failures": 0,
                  "docs_read": 1,
                  "docs_written": 1,
                  "end_last_seq": 1,
                  "end_time": "Sat, 10 Aug 2013 15:41:54 GMT",
                  "missing_checked": 1,
                  "missing_found": 1,
                  "recorded_seq": 1,
                  "session_id": "6314f35c51de3ac408af79d6ee0c1a09",
                  "start_last_seq": 0,
                  "start_time": "Sat, 10 Aug 2013 15:41:54 GMT"
              }
          ],
          "ok": true,
          "replication_id_version": 3,
          "session_id": "142a35854a08e205c47174d91b1f9628",
          "source_last_seq": 28
      }

## Replication Operation

The aim of the replication is that at the end of the process, all active documents on the source database are also in the destination database and all documents that were deleted in the source databases are also deleted (if they exist) on the destination database.

Replication can be described as either push or pull replication:

- Pull replication is where the `source` is the remote CouchDB instance, and the `target` is the local database.

  Pull replication is the most useful solution to use if your source database has a permanent IP address, and your destination (local) database may have a dynamically assigned IP address (for example, through DHCP). This is particularly important if you are replicating to a mobile or other device from a central server.

- Push replication is where the `source` is a local database, and `target` is a remote database.

## Specifying the Source and Target Database

You must use the URL specification of the CouchDB database if you want to perform replication in either of the following two situations:

- Replication with a remote database (i.e. another instance of CouchDB on the same host, or a different host)
- Replication with a database that requires authentication

For example, to request replication between a database local to the CouchDB instance to which you send the request, and a remote database you might use the following request:

    POST http://couchdb:5984/_replicate
    Content-Type: application/json
    Accept: application/json

    {
       "source" : "recipes",
       "target" : "http://coucdb-remote:5984/recipes",
    }

In all cases, the requested databases in the `source` and `target` specification must exist. If they do not, an error will be returned within the JSON object:

    {
       "error" : "db_not_found"
       "reason" : "could not open http://couchdb-remote:5984/ol1ka/",
    }

You can create the target database (providing your user credentials allow it) by adding the `create_target` field to the request object:

    POST http://couchdb:5984/_replicate
    Content-Type: application/json
    Accept: application/json

    {
       "create_target" : true
       "source" : "recipes",
       "target" : "http://couchdb-remote:5984/recipes",
    }

The `create_target` field is not destructive. If the database already exists, the replication proceeds as normal.

## Single Replication

You can request replication of a database so that the two databases can be synchronized. By default, the replication process occurs one time and synchronizes the two databases together. For example, you can request a single synchronization between two databases by supplying the `source` and `target` fields within the request JSON content.

    POST http://couchdb:5984/_replicate
    Accept: application/json
    Content-Type: application/json

    {
       "source" : "recipes",
       "target" : "recipes-snapshot",
    }

In the above example, the databases `recipes` and `recipes-snapshot` will be synchronized. These databases are local to the CouchDB instance where the request was made. The response will be a JSON structure containing the success (or failure) of the synchronization process, and statistics about the process:

    {
       "ok" : true,
       "history" : [
          {
             "docs_read" : 1000,
             "session_id" : "52c2370f5027043d286daca4de247db0",
             "recorded_seq" : 1000,
             "end_last_seq" : 1000,
             "doc_write_failures" : 0,
             "start_time" : "Thu, 28 Oct 2010 10:24:13 GMT",
             "start_last_seq" : 0,
             "end_time" : "Thu, 28 Oct 2010 10:24:14 GMT",
             "missing_checked" : 0,
             "docs_written" : 1000,
             "missing_found" : 1000
          }
       ],
       "session_id" : "52c2370f5027043d286daca4de247db0",
       "source_last_seq" : 1000
    }

## Continuous Replication

Synchronization of a database with the previously noted methods happens only once, at the time the replicate request is made. To have the target database permanently replicated from the source, you must set the `continuous` field of the JSON object within the request to true.

With continuous replication changes in the source database are replicated to the target database in perpetuity until you specifically request that replication ceases.

    POST http://couchdb:5984/_replicate
    Accept: application/json
    Content-Type: application/json

    {
       "continuous" : true
       "source" : "recipes",
       "target" : "http://couchdb-remote:5984/recipes",
    }

Changes will be replicated between the two databases as long as a network connection is available between the two instances.

Note

Two keep two databases synchronized with each other, you need to set replication in both directions; that is, you must replicate from `source` to `target`, and separately from `target` to `source`.

## Canceling Continuous Replication

You can cancel continuous replication by adding the `cancel` field to the JSON request object and setting the value to true. Note that the structure of the request must be identical to the original for the cancellation request to be honoured. For example, if you requested continuous replication, the cancellation request must also contain the `continuous` field.

For example, the replication request:

    POST http://couchdb:5984/_replicate
    Content-Type: application/json
    Accept: application/json

    {
       "source" : "recipes",
       "target" : "http://couchdb-remote:5984/recipes",
       "create_target" : true,
       "continuous" : true
    }

Must be canceled using the request:

    POST http://couchdb:5984/_replicate
    Accept: application/json
    Content-Type: application/json

    {
        "cancel" : true,
        "continuous" : true
        "create_target" : true,
        "source" : "recipes",
        "target" : "http://couchdb-remote:5984/recipes",
    }

Requesting cancellation of a replication that does not exist results in a 404 error.

# 10.2.7. `/_restart`

`POST` `/_restart`

  Restarts the CouchDB instance. You must be authenticated as a user with administration privileges for this to work.

  Request Headers:
  | Accept – application/json text/plain Content-Type – application/json
  Response Headers:
  | Content-Type – application/json text/plain; charset=utf-8
  Status Codes: | 202 Accepted – Server goes to restart (there is no guarantee that it will be alive after) 401 Unauthorized – CouchDB Server Administrator privileges required 415 Unsupported Media Type – Bad request`s Content-Type

  Request:

      POST /_restart HTTP/1.1
      Accept: application/json
      Host: localhost:5984

  Response:

      HTTP/1.1 202 Accepted
      Cache-Control: must-revalidate
      Content-Length: 12
      Content-Type: application/json
      Date: Sat, 10 Aug 2013 11:33:50 GMT
      Server: CouchDB (Erlang/OTP)

      {
          "ok": true
      }

# 10.2.8. `/_stats`

`GET` `/_stats`

  The `_stats` resource returns a JSON object containing the statistics for the running server. The object is structured with top-level sections collating the statistics for a range of entries, with each individual statistic being easily identified, and the content of each statistic is self-describing

  Request Headers:
  | Accept – application/json text/plain
  Response Headers:
  | Content-Type – application/json text/plain; charset=utf-8
  Status Codes: | 200 OK – Request completed successfully

  Request:

      GET /_stats/couchdb/request_time HTTP/1.1
      Accept: application/json
      Host: localhost:5984

  Response:

      HTTP/1.1 200 OK
      Cache-Control: must-revalidate
      Content-Length: 187
      Content-Type: application/json
      Date: Sat, 10 Aug 2013 11:41:11 GMT
      Server: CouchDB (Erlang/OTP)

      {
          "couchdb": {
              "request_time": {
                  "current": 21.0,
                  "description": "length of a request inside CouchDB without MochiWeb",
                  "max": 19.0,
                  "mean": 7.0,
                  "min": 1.0,
                  "stddev": 10.392,
                  "sum": 21.0
              }
          }
      }

The fields provide the current, minimum and maximum, and a collection of statistical means and quantities. The quantity in each case is not defined, but the descriptions below provide

The statistics are divided into the following top-level sections:

## `couchdb`

Describes statistics specific to the internals of CouchDB

Statistic ID | Description | Unit
--- | --- | ---
`auth_cache_hits` | Number of authentication cache hits | number
`auth_cache_misses` | Number of authentication cache misses | number
`database_reads` | Number of times a document was read from a database | number
`database_writes` | Number of times a database was changed | number
`open_databases` | Number of open databases | number
`open_os_files` | Number of file descriptors CouchDB has open | number
`request_time` | Length of a request inside CouchDB without MochiWeb | milliseconds

## `httpd_request_methods`

Statistic ID | Description | Unit
--- | --- | ---
`COPY` | Number of HTTP COPY requests | number
`DELETE` | Number of HTTP DELETE requests | number
`GET` | Number of HTTP GET requests | number
`HEAD` | Number of HTTP HEAD requests | number
`POST` | Number of HTTP POST requests | number
`PUT` | Number of HTTP PUT requests | number

## `httpd_status_codes`

Statistic ID | Description | Unit
--- | --- | ---
`200` | Number of HTTP 200 OK responses | number
`201` | Number of HTTP 201 Created responses | number
`202` | Number of HTTP 202 Accepted responses | number
`301` | Number of HTTP 301 Moved Permanently responses | number
`304` | Number of HTTP 304 Not Modified responses | number
`400` | Number of HTTP 400 Bad Request responses | number
`401` | Number of HTTP 401 Unauthorized responses | number
`403` | Number of HTTP 403 Forbidden responses | number
`404` | Number of HTTP 404 Not Found responses | number
`405` | Number of HTTP 405 Method Not Allowed responses | number
`409` | Number of HTTP 409 Conflict responses | number
`412` | Number of HTTP 412 Precondition Failed responses | number
`500` | Number of HTTP 500 Internal Server Error responses | number

## `httpd`

Statistic ID | Description | Unit
--- | --- | ---
`bulk_requests` | Number of bulk requests | number
`clients_requesting_changes` | Number of clients for continuous _changes | number
`requests` | Number of HTTP requests | number
`temporary_view_reads` | Number of temporary view reads | number
`view_reads` | Number of view reads | number

You can also access individual statistics by quoting the statistics sections and statistic ID as part of the URL path. For example, to get the `request_time` statistics, you can use:

    GET /_stats/couchdb/request_time

This returns an entire statistics object, as with the full request, but containing only the request individual statistic. Hence, the returned structure is as follows:

    {
       "couchdb" : {
          "request_time" : {
             "stddev" : 7454.305,
             "min" : 1,
             "max" : 34185,
             "current" : 34697.803,
             "mean" : 1652.276,
             "sum" : 34697.803,
             "description" : "length of a request inside CouchDB without MochiWeb"
          }
       }
    }

# 10.2.9. `/_utils`

`GET` `/_utils`

  Accesses the built-in Futon administration interface for CouchDB.

  Response Headers:
  | Location – New URI location
  Status Codes: | 301 Moved Permanently – Redirects to `GET /_utils/`

`GET` `/_utils/`

  Response Headers:
  | Content-Type – text/html Last-Modified – Static files modification timestamp
  Status Codes: | 200 OK – Request completed successfully

# 10.2.10. `/_uuids`

`GET` `/_uuids`

  Requests one or more Universally Unique Identifiers (UUIDs) from the CouchDB instance. The response is a JSON object providing a list of UUIDs.

  Request Headers:
  | Accept – application/json text/plain
  Query Parameters:
  | count (number) – Number of UUIDs to return. Default is `1`.
  Response Headers:
  | Content-Type – application/json text/plain; charset=utf-8 ETag – Response hash
  Status Codes: | 200 OK – Request completed successfully

  Request:

      GET /_uuids?count=10 HTTP/1.1
      Accept: application/json
      Host: localhost:5984

  Response:

      HTTP/1.1 200 OK
      Content-Length: 362
      Content-Type: application/json
      Date: Sat, 10 Aug 2013 11:46:25 GMT
      ETag: "DGRWWQFLUDWN5MRKSLKQ425XV"
      Expires: Fri, 01 Jan 1990 00:00:00 GMT
      Pragma: no-cache
      Server: CouchDB (Erlang/OTP)

      {
          "uuids": [
              "75480ca477454894678e22eec6002413",
              "75480ca477454894678e22eec600250b",
              "75480ca477454894678e22eec6002c41",
              "75480ca477454894678e22eec6003b90",
              "75480ca477454894678e22eec6003fca",
              "75480ca477454894678e22eec6004bef",
              "75480ca477454894678e22eec600528f",
              "75480ca477454894678e22eec6005e0b",
              "75480ca477454894678e22eec6006158",
              "75480ca477454894678e22eec6006161"
          ]
      }

The UUID type is determined by the `UUID algorithm` setting in the CouchDB configuration.

The UUID type may be changed at any time through the Configuration API. For example, the UUID type could be changed to `random` by sending this HTTP request:

    PUT http://couchdb:5984/_config/uuids/algorithm
    Content-Type: application/json
    Accept: */*

    "random"

You can verify the change by obtaining a list of UUIDs:

    {
       "uuids" : [
          "031aad7b469956cf2826fcb2a9260492",
          "6ec875e15e6b385120938df18ee8e496",
          "cff9e881516483911aa2f0e98949092d",
          "b89d37509d39dd712546f9510d4a9271",
          "2e0dbf7f6c4ad716f21938a016e4e59f"
       ]
    }

# 10.2.11. `/favicon.ico`

`GET` `/favicon.ico`

  Binary content for the favicon.ico site icon.

  Response Headers:
  | Content-Type – image/x-icon
  Status Codes: | 200 OK – Request completed successfully 404 Not Found – The requested content could not be found

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