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Posted to commits@couchdb.apache.org by dc...@apache.org on 2012/09/14 12:17:00 UTC
[37/49] export DocBook XML to RST files
http://git-wip-us.apache.org/repos/asf/couchdb/blob/5cb488bf/share/docs/rst/release.rst
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+=================================
+CouchDB Release 1.1 Feature Guide
+=================================
+
+Upgrading to CouchDB 1.1
+========================
+
+You can upgrade your existing CouchDB 1.0.x installation to CouchDB 1.1
+without any specific steps or migration. When you run CouchDB 1.1 the
+existing data and index files will be opened and used as normal.
+
+The first time you run a compaction routine on your database within
+CouchDB 1.1, the data structure and indexes will be updated to the new
+version of the CouchDB database format that can only be read by CouchDB
+1.1 and later. This step is not reversable. Once the data files have
+been updated and migrated to the new version the data files will no
+longer work with a CouchDB 1.0.x release.
+
+ **Warning**
+
+ If you want to retain support for openein gthe data files in CouchDB
+ 1.0.x you must back up your data files before performing the upgrade
+ and compaction process.
+
+Replicator Database
+===================
+
+A database where you ``PUT``/``POST`` documents to trigger replications
+and you ``DELETE`` to cancel ongoing replications. These documents have
+exactly the same content as the JSON objects we used to ``POST`` to
+``_replicate`` (fields ``source``, ``target``, ``create_target``,
+``continuous``, ``doc_ids``, ``filter``, ``query_params``.
+
+Replication documents can have a user defined ``_id``. Design documents
+(and ``_local`` documents) added to the replicator database are ignored.
+
+The default name of this database is ``_replicator``. The name can be
+changed in the ``local.ini`` configuration, section ``[replicator]``,
+parameter ``db``.
+
+Basics
+------
+
+Let's say you PUT the following document into \_replicator:
+
+::
+
+ {
+ "_id": "my_rep",
+ "source": "http://myserver.com:5984/foo",
+ "target": "bar",
+ "create_target": true
+ }
+
+In the couch log you'll see 2 entries like these:
+
+::
+
+ [Thu, 17 Feb 2011 19:43:59 GMT] [info] [<0.291.0>] Document `my_rep` triggered replication `c0ebe9256695ff083347cbf95f93e280+create_target`
+ [Thu, 17 Feb 2011 19:44:37 GMT] [info] [<0.124.0>] Replication `c0ebe9256695ff083347cbf95f93e280+create_target` finished (triggered by document `my_rep`)
+
+As soon as the replication is triggered, the document will be updated by
+CouchDB with 3 new fields:
+
+::
+
+ {
+ "_id": "my_rep",
+ "source": "http://myserver.com:5984/foo",
+ "target": "bar",
+ "create_target": true,
+ "_replication_id": "c0ebe9256695ff083347cbf95f93e280",
+ "_replication_state": "triggered",
+ "_replication_state_time": 1297974122
+ }
+
+Special fields set by the replicator start with the prefix
+``_replication_``.
+
+- ``_replication_id``
+
+ The ID internally assigned to the replication. This is also the ID
+ exposed by ``/_active_tasks``.
+
+- ``_replication_state``
+
+ The current state of the replication.
+
+- ``_replication_state_time``
+
+ A Unix timestamp (number of seconds since 1 Jan 1970) that tells us
+ when the current replication state (marked in ``_replication_state``)
+ was set.
+
+When the replication finishes, it will update the ``_replication_state``
+field (and ``_replication_state_time``) with the value ``completed``, so
+the document will look like:
+
+::
+
+ {
+ "_id": "my_rep",
+ "source": "http://myserver.com:5984/foo",
+ "target": "bar",
+ "create_target": true,
+ "_replication_id": "c0ebe9256695ff083347cbf95f93e280",
+ "_replication_state": "completed",
+ "_replication_state_time": 1297974122
+ }
+
+When an error happens during replication, the ``_replication_state``
+field is set to ``error`` (and ``_replication_state`` gets updated of
+course).
+
+When you PUT/POST a document to the ``_replicator`` database, CouchDB
+will attempt to start the replication up to 10 times (configurable under
+``[replicator]``, parameter ``max_replication_retry_count``). If it
+fails on the first attempt, it waits 5 seconds before doing a second
+attempt. If the second attempt fails, it waits 10 seconds before doing a
+third attempt. If the third attempt fails, it waits 20 seconds before
+doing a fourth attempt (each attempt doubles the previous wait period).
+When an attempt fails, the Couch log will show you something like:
+
+::
+
+ [error] [<0.149.0>] Error starting replication `67c1bb92010e7abe35d7d629635f18b6+create_target` (document `my_rep_2`): {db_not_found,<<"could not open http://myserver:5986/foo/">>
+
+ **Note**
+
+ The ``_replication_state`` field is only set to ``error`` when all
+ the attempts were unsuccessful.
+
+There are only 3 possible values for the ``_replication_state`` field:
+``triggered``, ``completed`` and ``error``. Continuous replications
+never get their state set to ``completed``.
+
+Documents describing the same replication
+-----------------------------------------
+
+Lets suppose 2 documents are added to the ``_replicator`` database in
+the following order:
+
+::
+
+ {
+ "_id": "doc_A",
+ "source": "http://myserver.com:5984/foo",
+ "target": "bar"
+ }
+
+and
+
+::
+
+ {
+ "_id": "doc_B",
+ "source": "http://myserver.com:5984/foo",
+ "target": "bar"
+ }
+
+Both describe exactly the same replication (only their ``_ids`` differ).
+In this case document ``doc_A`` triggers the replication, getting
+updated by CouchDB with the fields ``_replication_state``,
+``_replication_state_time`` and ``_replication_id``, just like it was
+described before. Document ``doc_B`` however, is only updated with one
+field, the ``_replication_id`` so it will look like this:
+
+::
+
+ {
+ "_id": "doc_B",
+ "source": "http://myserver.com:5984/foo",
+ "target": "bar",
+ "_replication_id": "c0ebe9256695ff083347cbf95f93e280"
+ }
+
+While document ``doc_A`` will look like this:
+
+::
+
+ {
+ "_id": "doc_A",
+ "source": "http://myserver.com:5984/foo",
+ "target": "bar",
+ "_replication_id": "c0ebe9256695ff083347cbf95f93e280",
+ "_replication_state": "triggered",
+ "_replication_state_time": 1297974122
+ }
+
+Note that both document get exactly the same value for the
+``_replication_id`` field. This way you can identify which documents
+refer to the same replication - you can for example define a view which
+maps replication IDs to document IDs.
+
+Canceling replications
+----------------------
+
+To cancel a replication simply ``DELETE`` the document which triggered
+the replication. The Couch log will show you an entry like the
+following:
+
+::
+
+ [Thu, 17 Feb 2011 20:16:29 GMT] [info] [<0.125.0>] Stopped replication `c0ebe9256695ff083347cbf95f93e280+continuous+create_target` because replication document `doc_A` was deleted
+
+ **Note**
+
+ You need to ``DELETE`` the document that triggered the replication.
+ ``DELETE``\ ing another document that describes the same replication
+ but did not trigger it, will not cancel the replication.
+
+Server restart
+--------------
+
+When CouchDB is restarted, it checks its ``_replicator`` database and
+restarts any replication that is described by a document that either has
+its ``_replication_state`` field set to ``triggered`` or it doesn't have
+yet the ``_replication_state`` field set.
+
+ **Note**
+
+ Continuous replications always have a ``_replication_state`` field
+ with the value ``triggered``, therefore they're always restarted
+ when CouchDB is restarted.
+
+Changing the Replicator Database
+--------------------------------
+
+Imagine your replicator database (default name is \_replicator) has the
+two following documents that represent pull replications from servers A
+and B:
+
+::
+
+ {
+ "_id": "rep_from_A",
+ "source": "http://aserver.com:5984/foo",
+ "target": "foo_a",
+ "continuous": true,
+ "_replication_id": "c0ebe9256695ff083347cbf95f93e280",
+ "_replication_state": "triggered",
+ "_replication_state_time": 1297971311
+ }
+ {
+ "_id": "rep_from_B",
+ "source": "http://bserver.com:5984/foo",
+ "target": "foo_b",
+ "continuous": true,
+ "_replication_id": "231bb3cf9d48314eaa8d48a9170570d1",
+ "_replication_state": "triggered",
+ "_replication_state_time": 1297974122
+ }
+
+Now without stopping and restarting CouchDB, you change the name of the
+replicator database to ``another_replicator_db``:
+
+::
+
+ $ curl -X PUT http://localhost:5984/_config/replicator/db -d '"another_replicator_db"'
+ "_replicator"
+
+As soon as this is done, both pull replications defined before, are
+stopped. This is explicitly mentioned in CouchDB's log:
+
+::
+
+ [Fri, 11 Mar 2011 07:44:20 GMT] [info] [<0.104.0>] Stopping all ongoing replications because the replicator database was deleted or changed
+ [Fri, 11 Mar 2011 07:44:20 GMT] [info] [<0.127.0>] 127.0.0.1 - - PUT /_config/replicator/db 200
+
+Imagine now you add a replication document to the new replicator
+database named ``another_replicator_db``:
+
+::
+
+ {
+ "_id": "rep_from_X",
+ "source": "http://xserver.com:5984/foo",
+ "target": "foo_x",
+ "continuous": true
+ }
+
+From now own you have a single replication going on in your system: a
+pull replication pulling from server X. Now you change back the
+replicator database to the original one ``_replicator``:
+
+::
+
+ $ curl -X PUT http://localhost:5984/_config/replicator/db -d '"_replicator"'
+ "another_replicator_db"
+
+Immediately after this operation, the replication pulling from server X
+will be stopped and the replications defined in the \_replicator
+database (pulling from servers A and B) will be resumed.
+
+Changing again the replicator database to ``another_replicator_db`` will
+stop the pull replications pulling from servers A and B, and resume the
+pull replication pulling from server X.
+
+Replicating the replicator database
+-----------------------------------
+
+Imagine you have in server C a replicator database with the two
+following pull replication documents in it:
+
+::
+
+ {
+ "_id": "rep_from_A",
+ "source": "http://aserver.com:5984/foo",
+ "target": "foo_a",
+ "continuous": true,
+ "_replication_id": "c0ebe9256695ff083347cbf95f93e280",
+ "_replication_state": "triggered",
+ "_replication_state_time": 1297971311
+ }
+ {
+ "_id": "rep_from_B",
+ "source": "http://bserver.com:5984/foo",
+ "target": "foo_b",
+ "continuous": true,
+ "_replication_id": "231bb3cf9d48314eaa8d48a9170570d1",
+ "_replication_state": "triggered",
+ "_replication_state_time": 1297974122
+ }
+
+Now you would like to have the same pull replications going on in server
+D, that is, you would like to have server D pull replicating from
+servers A and B. You have two options:
+
+- Explicitly add two documents to server's D replicator database
+
+- Replicate server's C replicator database into server's D replicator
+ database
+
+Both alternatives accomplish exactly the same goal.
+
+Delegations
+-----------
+
+Replication documents can have a custom ``user_ctx`` property. This
+property defines the user context under which a replication runs. For
+the old way of triggering replications (POSTing to ``/_replicate/``),
+this property was not needed (it didn't exist in fact) - this is because
+at the moment of triggering the replication it has information about the
+authenticated user. With the replicator database, since it's a regular
+database, the information about the authenticated user is only present
+at the moment the replication document is written to the database - the
+replicator database implementation is like a \_changes feed consumer
+(with ``?include_docs=true``) that reacts to what was written to the
+replicator database - in fact this feature could be implemented with an
+external script/program. This implementation detail implies that for non
+admin users, a ``user_ctx`` property, containing the user's name and a
+subset of his/her roles, must be defined in the replication document.
+This is ensured by the document update validation function present in
+the default design document of the replicator database. This validation
+function also ensure that a non admin user can set a user name property
+in the ``user_ctx`` property that doesn't match his/her own name (same
+principle applies for the roles).
+
+For admins, the ``user_ctx`` property is optional, and if it's missing
+it defaults to a user context with name null and an empty list of roles
+- this mean design documents will not be written to local targets. If
+writing design documents to local targets is desired, the a user context
+with the roles ``_admin`` must be set explicitly.
+
+Also, for admins the ``user_ctx`` property can be used to trigger a
+replication on behalf of another user. This is the user context that
+will be passed to local target database document validation functions.
+
+ **Note**
+
+ The ``user_ctx`` property only has effect for local endpoints.
+
+Example delegated replication document:
+
+::
+
+ {
+ "_id": "my_rep",
+ "source": "http://bserver.com:5984/foo",
+ "target": "bar",
+ "continuous": true,
+ "user_ctx": {
+ "name": "joe",
+ "roles": ["erlanger", "researcher"]
+ }
+ }
+
+As stated before, for admins the user\_ctx property is optional, while
+for regular (non admin) users it's mandatory. When the roles property of
+``user_ctx`` is missing, it defaults to the empty list ``[ ]``.
+
+Native SSL Support
+==================
+
+CouchDB 1.1 supports SSL natively. All your secure connection needs can
+now be served without the need set and maintain a separate proxy server
+that handles SSL.
+
+SSL setup can be tricky, but the configuration in CouchDB was designed
+to be as easy as possible. All you need is two files; a certificate and
+a private key. If you bought an official SSL certificate from a
+certificate authority, both should be in your possession already.
+
+If you just want to try this out and don't want to pay anything upfront,
+you can create a self-signed certificate. Everything will work the same,
+but clients will get a warning about an insecure certificate.
+
+You will need the OpenSSL command line tool installed. It probably
+already is.
+
+::
+
+ shell>
+ shell>
+ shell>
+ shell>
+ mycert.pem privkey.pem
+
+Now, you need to edit CouchDB's configuration, either by editing your
+``local.ini`` file or using the ``/_config`` API calls or the
+configuration screen in Futon. Here is what you need to do in
+``local.ini``, you can infer what needs doing in the other places.
+
+Be sure to make these edits. Under ``[daemons]`` you should see:
+
+::
+
+ ; enable SSL support by uncommenting the following line and supply the PEM's below.
+ ; the default ssl port CouchDB listens on is 6984
+ ;httpsd = {couch_httpd, start_link, [https]}
+
+Here uncomment the last line:
+
+::
+
+ httpsd = {couch_httpd, start_link, [https]}
+
+Next, under ``[ssl]`` you will see:
+
+::
+
+ ;cert_file = /full/path/to/server_cert.pem
+ ;key_file = /full/path/to/server_key.pem
+
+Uncomment and adjust the paths so it matches your system's paths:
+
+::
+
+ cert_file = /home/jan/cert/mycert.pem
+ key_file = /home/jan/cert/privkey.pem
+
+For more information please read
+`http://www.openssl.org/docs/HOWTO/certificates.txt`_.
+
+Now start (or restart) CouchDB. You should be able to connect to it
+using HTTPS on port 6984:
+
+::
+
+ shell>
+ curl: (60) SSL certificate problem, verify that the CA cert is OK. Details:
+ error:14090086:SSL routines:SSL3_GET_SERVER_CERTIFICATE:certificate verify failed
+ More details here: http://curl.haxx.se/docs/sslcerts.html
+
+ curl performs SSL certificate verification by default, using a "bundle"
+ of Certificate Authority (CA) public keys (CA certs). If the default
+ bundle file isn't adequate, you can specify an alternate file
+ using the --cacert option.
+ If this HTTPS server uses a certificate signed by a CA represented in
+ the bundle, the certificate verification probably failed due to a
+ problem with the certificate (it might be expired, or the name might
+ not match the domain name in the URL).
+ If you'd like to turn off curl's verification of the certificate, use
+ the -k (or --insecure) option.
+
+Oh no what happened?! — Remember, clients will notify their users that
+your certificate is self signed. ``curl`` is the client in this case and
+it notifies you. Luckily you trust yourself (don't you?) and you can
+specify the ``-k`` option as the message reads:
+
+::
+
+ shell>
+ {"couchdb":"Welcome","version":"1.1.0"}
+
+All done.
+
+HTTP Range Requests
+===================
+
+HTTP allows you to specify byte ranges for requests. This allows the
+implementation of resumable downloads and skippable audio and video
+streams alike. Now this is available for all attachments inside CouchDB.
+
+This is just a real quick run through how this looks under the hood.
+Usually, you will have larger binary files to serve from CouchDB, like
+MP3s and videos, but to make things a little more obvious, I use a text
+file here (Note that I use the ``application/octet-stream`` Content-Type
+instead of ``text/plain``).
+
+::
+
+ shell>
+ My hovercraft is full of eels!
+
+Now lets store this text file as an attachment in CouchDB. First, we
+create a database:
+
+::
+
+ shell>
+ {"ok":true}
+
+Then we create a new document and the file attachment in one go:
+
+::
+
+ shell>
+ {"ok":true,"id":"doc","rev":"1-287a28fa680ae0c7fb4729bf0c6e0cf2"}
+
+Now we can request the whole file easily:
+
+::
+
+ shell>
+ My hovercraft is full of eels!
+
+But say we only want the first 13 bytes:
+
+::
+
+ shell>
+ My hovercraft
+
+HTTP supports many ways to specify single and even multiple byte
+rangers. Read all about it in `RFC 2616`_.
+
+ **Note**
+
+ Databases that have been created with CouchDB 1.0.2 or earlier will
+ support range requests in 1.1.0, but they are using a less-optimal
+ algorithm. If you plan to make heavy use of this feature, make sure
+ to compact your database with CouchDB 1.1.0 to take advantage of a
+ better algorithm to find byte ranges.
+
+HTTP Proxying
+=============
+
+The HTTP proxy feature makes it easy to map and redirect different
+content through your CouchDB URL. The proxy works by mapping a pathname
+and passing all content after that prefix through to the configured
+proxy address.
+
+Configuration of the proxy redirect is handled through the
+``[httpd_global_handlers]`` section of the CouchDB configuration file
+(typically ``local.ini``). The format is:
+
+::
+
+ [httpd_global_handlers]
+ PREFIX = {couch_httpd_proxy, handle_proxy_req, <<"DESTINATION">>}
+
+Where:
+
+- ``PREFIX``
+
+ Is the string that will be matched. The string can be any valid
+ qualifier, although to ensure that existing database names are not
+ overridden by a proxy configuration, you can use an underscore
+ prefix.
+
+- ``DESTINATION``
+
+ The fully-qualified URL to which the request should be sent. The
+ destination must include the ``http`` prefix. The content is used
+ verbatim in the original request, so you can also forward to servers
+ on different ports and to specific paths on the target host.
+
+The proxy process then translates requests of the form:
+
+::
+
+ http://couchdb:5984/PREFIX/path
+
+To:
+
+::
+
+ DESTINATION/path
+
+ **Note**
+
+ Everything after ``PREFIX`` including the required forward slash
+ will be appended to the ``DESTINATION``.
+
+The response is then communicated back to the original client.
+
+For example, the following configuration:
+
+::
+
+ _google = {couch_httpd_proxy, handle_proxy_req, <<"http://www.google.com">>}
+
+Would forward all requests for ``http://couchdb:5984/_google`` to the
+Google website.
+
+The service can also be used to forward to related CouchDB services,
+such as Lucene:
+
+::
+
+ [httpd_global_handlers]
+ _fti = {couch_httpd_proxy, handle_proxy_req, <<"http://127.0.0.1:5985">>}
+
+ **Note**
+
+ The proxy service is basic. If the request is not identified by the
+ ``DESTINATION``, or the remainder of the ``PATH`` specification is
+ incomplete, the original request URL is interpreted as if the
+ ``PREFIX`` component of that URL does not exist.
+
+ For example, requesting ``http://couchdb:5984/_intranet/media`` when
+ ``/media`` on the proxy destination does not exist, will cause the
+ request URL to be interpreted as ``http://couchdb:5984/media``. Care
+ should be taken to ensure that both requested URLs and destination
+ URLs are able to cope
+
+Added CommonJS support to map functions
+=======================================
+
+We didn't have CommonJS require in map functions because the current
+CommonJS implementation is scoped to the whole design doc, and giving
+views access to load code from anywhere in the design doc would mean
+we'd have to blow away your view index any time you changed anything.
+Having to rebuild views from scratch just because you changed some CSS
+or a show function isn't fun, so we avoided the issue by keeping
+CommonJS require out of map and reduce altogether.
+
+The solution we came up with is to allow CommonJS inside map and reduce
+funs, but only of libraries that are stored inside the views part of the
+design doc.
+
+So you could continue to access CommonJS code in design\_doc.foo, from
+your list functions etc, but we'd add the ability to require CommonJS
+modules within map and reduce, but only from design\_doc.views.lib
+
+There's no worry here about namespace collisions, as Couch just plucks
+``views.*.map`` and ``views.*.reduce`` out of the design doc. So you
+could have a view called ``lib`` if you wanted, and still have CommonJS
+stored in ``views.lib.sha1`` and ``views.lib.stemmer`` if you wanted.
+
+We simplified the implementation by enforcing that CommonJS modules to
+be used in map functions be stored in views.lib.
+
+A sample design doc (taken from the test suite in Futon) is below:
+
+::
+
+ {
+ "views" : {
+ "lib" : {
+ "baz" : "exports.baz = 'bam';",
+ "foo" : {
+ "zoom" : "exports.zoom = 'yeah';",
+ "boom" : "exports.boom = 'ok';",
+ "foo" : "exports.foo = 'bar';"
+ }
+ },
+ "commonjs" : {
+ "map" : "function(doc) { emit(null, require('views/lib/foo/boom').boom)}"
+ }
+ },
+ "_id" : "_design/test"
+ }
+
+The ``require()`` statement is relative to the design document, but
+anything loaded form outside of ``views/lib`` will fail.
+
+More granular ETag support for views
+====================================
+
+ETags have been assigned to a map/reduce group (the collection of views
+in a single design document). Any change to any of the indexes for those
+views would generate a new ETag for all view URL's in a single design
+doc, even if that specific view's results had not changed.
+
+In CouchDB 1.1 each ``_view`` URL has it's own ETag which only gets
+updated when changes are made to the database that effect that index. If
+the index for that specific view does not change, that view keeps the
+original ETag head (therefore sending back 304 Not Modified more often).
+
+Added built-in filters for ``_changes``: ``_doc_ids`` and ``_design``.
+======================================================================
+
+The ``_changes`` feed can now be used to watch changes to specific
+document ID's or the list of ``_design`` documents in a database. If the
+``filters`` parameter is set to ``_doc_ids`` a list of doc IDs can be
+passed in the "doc\_ids" as a JSON array.
+
+Allow wildcards in vhosts definitions
+=====================================
+
+Similar to the rewrites section of a ``_design`` document, the new
+``vhosts`` system uses variables in the form of :varname or wildcards in
+the form of asterisks. The variable results can be output into the
+resulting path as they are in the rewriter.
+
+OS Daemons
+==========
+
+CouchDB now supports starting external processes. The support is simple
+and enables CouchDB to start each configured OS daemon. If the daemon
+stops at any point, CouchDB will restart it (with protection to ensure
+regularly failing daemons are not repeatedly restarted).
+
+The daemon starting process is one-to-one; for each each configured
+daemon in the configuration file, CouchDB will start exactly one
+instance. If you need to run multiple instances, then you must create
+separate individual configurations. Daemons are configured within the
+``[os_daemons]`` section of your configuration file (``local.ini``). The
+format of each configured daemon is:
+
+::
+
+ NAME = PATH ARGS
+
+Where ``NAME`` is an arbitrary (and unique) name to identify the daemon;
+``PATH`` is the full path to the daemon to be executed; ``ARGS`` are any
+required arguments to the daemon.
+
+For example:
+
+::
+
+ [os_daemons]
+ basic_responder = /usr/local/bin/responsder.js
+
+There is no interactivity between CouchDB and the running process, but
+you can use the OS Daemons service to create new HTTP servers and
+responders and then use the new proxy service to redirect requests and
+output to the CouchDB managed service. For more information on proxying,
+see ?. For further background on the OS Daemon service, see `CouchDB
+Externals API`_
+
+Stale views and ``update_after``
+================================
+
+Currently a view request can include the ``stale=ok`` query argument,
+which allows the contents of a stale view index to be used to produce
+the view output. In order to trigger a build of the outdated view index,
+a second view request must be made.
+
+To simplify this process, the ``update_after`` value can be supplied to
+the ``stale`` query argument. This triggers a rebuild of the view index
+after the results of the view have been retrieved.
+
+Socket Options Configuration Setting
+====================================
+
+The socket options for the listening socket in CouchDB can now be set
+within the CouchDB configuration file. The setting should be added to
+the ``[httpd]`` section of the file using the option name
+``socket_options``. The specification is as a list of tuples. For
+example:
+
+::
+
+ [httpd]
+ socket_options = [{recbuf, 262144}, {sndbuf, 262144}, {nodelay, true}]
+
+The options supported are a subset of full options supported by the
+TCP/IP stack. A list of the supported options are provided in the
+`Erlang inet`_ documentation.
+
+Server Options Configuration Setting
+====================================
+
+Server options for the MochiWeb component of CouchDB can now be added to
+the configuration file. Settings should be added to the
+``server_options`` option of the ``[httpd]`` section of ``local.ini``.
+For example:
+
+::
+
+ [httpd]
+ server_options = [{backlog, 128}, {acceptor_pool_size, 16}]
+
+Improved Error Messages
+=======================
+
+The errors reported when CouchDB is unable to read a required file have
+been updated so that explicit information about the files and problem
+can now be identified from the error message. The errors report file
+permission access either when reading or writing to configuration and
+database files.
+
+The error is raised both through the log file and the error message
+returned through the API call as a JSON error message. For example, when
+setting configuration values:
+
+::
+
+ shell>
+ {"error":"file_permission_error","reason":"/etc/couchdb/local.ini"}
+
+Errors will always be reported using the ``file_permission_error`` error
+type.
+
+During startup permissions errors on key files are also reported in the
+log with a descriptive error message and file location so that
+permissions can be fixed before restart.
+
+Multiple micro-optimizations when reading data.
+===============================================
+
+We found a number of places where CouchDB wouldn't do the absolute
+optimal thing when reading data and got rid of quite a few
+inefficiencies. The problem with small optimizations all over the place
+is that you may not notice them with every use-case, but we sure hope
+you can see an improvement overall.
+
+Upgrading to CouchDB 1.1
+========================
+
+You can upgrade your existing CouchDB 1.0.x installation to CouchDB 1.1
+without any specific steps or migration. When you run CouchDB 1.1 the
+existing data and index files will be opened and used as normal.
+
+The first time you run a compaction routine on your database within
+CouchDB 1.1, the data structure and indexes will be updated to the new
+version of the CouchDB database format that can only be read by CouchDB
+1.1 and later. This step is not reversable. Once the data files have
+been updated and migrated to the new version the data files will no
+longer work with a CouchDB 1.0.x release.
+
+ **Warning**
+
+ If you want to retain support for openein gthe data files in CouchDB
+ 1.0.x you must back up your data files before performing the upgrade
+ and compaction process.
+
+Replicator Database
+===================
+
+A database where you ``PUT``/``POST`` documents to trigger replications
+and you ``DELETE`` to cancel ongoing replications. These documents have
+exactly the same content as the JSON objects we used to ``POST`` to
+``_replicate`` (fields ``source``, ``target``, ``create_target``,
+``continuous``, ``doc_ids``, ``filter``, ``query_params``.
+
+Replication documents can have a user defined ``_id``. Design documents
+(and ``_local`` documents) added to the replicator database are ignored.
+
+The default name of this database is ``_replicator``. The name can be
+changed in the ``local.ini`` configuration, section ``[replicator]``,
+parameter ``db``.
+
+Basics
+------
+
+Let's say you PUT the following document into \_replicator:
+
+::
+
+ {
+ "_id": "my_rep",
+ "source": "http://myserver.com:5984/foo",
+ "target": "bar",
+ "create_target": true
+ }
+
+In the couch log you'll see 2 entries like these:
+
+::
+
+ [Thu, 17 Feb 2011 19:43:59 GMT] [info] [<0.291.0>] Document `my_rep` triggered replication `c0ebe9256695ff083347cbf95f93e280+create_target`
+ [Thu, 17 Feb 2011 19:44:37 GMT] [info] [<0.124.0>] Replication `c0ebe9256695ff083347cbf95f93e280+create_target` finished (triggered by document `my_rep`)
+
+As soon as the replication is triggered, the document will be updated by
+CouchDB with 3 new fields:
+
+::
+
+ {
+ "_id": "my_rep",
+ "source": "http://myserver.com:5984/foo",
+ "target": "bar",
+ "create_target": true,
+ "_replication_id": "c0ebe9256695ff083347cbf95f93e280",
+ "_replication_state": "triggered",
+ "_replication_state_time": 1297974122
+ }
+
+Special fields set by the replicator start with the prefix
+``_replication_``.
+
+- ``_replication_id``
+
+ The ID internally assigned to the replication. This is also the ID
+ exposed by ``/_active_tasks``.
+
+- ``_replication_state``
+
+ The current state of the replication.
+
+- ``_replication_state_time``
+
+ A Unix timestamp (number of seconds since 1 Jan 1970) that tells us
+ when the current replication state (marked in ``_replication_state``)
+ was set.
+
+When the replication finishes, it will update the ``_replication_state``
+field (and ``_replication_state_time``) with the value ``completed``, so
+the document will look like:
+
+::
+
+ {
+ "_id": "my_rep",
+ "source": "http://myserver.com:5984/foo",
+ "target": "bar",
+ "create_target": true,
+ "_replication_id": "c0ebe9256695ff083347cbf95f93e280",
+ "_replication_state": "completed",
+ "_replication_state_time": 1297974122
+ }
+
+When an error happens during replication, the ``_replication_state``
+field is set to ``error`` (and ``_replication_state`` gets updated of
+course).
+
+When you PUT/POST a document to the ``_replicator`` database, CouchDB
+will attempt to start the replication up to 10 times (configurable under
+``[replicator]``, parameter ``max_replication_retry_count``). If it
+fails on the first attempt, it waits 5 seconds before doing a second
+attempt. If the second attempt fails, it waits 10 seconds before doing a
+third attempt. If the third attempt fails, it waits 20 seconds before
+doing a fourth attempt (each attempt doubles the previous wait period).
+When an attempt fails, the Couch log will show you something like:
+
+::
+
+ [error] [<0.149.0>] Error starting replication `67c1bb92010e7abe35d7d629635f18b6+create_target` (document `my_rep_2`): {db_not_found,<<"could not open http://myserver:5986/foo/">>
+
+ **Note**
+
+ The ``_replication_state`` field is only set to ``error`` when all
+ the attempts were unsuccessful.
+
+There are only 3 possible values for the ``_replication_state`` field:
+``triggered``, ``completed`` and ``error``. Continuous replications
+never get their state set to ``completed``.
+
+Documents describing the same replication
+-----------------------------------------
+
+Lets suppose 2 documents are added to the ``_replicator`` database in
+the following order:
+
+::
+
+ {
+ "_id": "doc_A",
+ "source": "http://myserver.com:5984/foo",
+ "target": "bar"
+ }
+
+and
+
+::
+
+ {
+ "_id": "doc_B",
+ "source": "http://myserver.com:5984/foo",
+ "target": "bar"
+ }
+
+Both describe exactly the same replication (only their ``_ids`` differ).
+In this case document ``doc_A`` triggers the replication, getting
+updated by CouchDB with the fields ``_replication_state``,
+``_replication_state_time`` and ``_replication_id``, just like it was
+described before. Document ``doc_B`` however, is only updated with one
+field, the ``_replication_id`` so it will look like this:
+
+::
+
+ {
+ "_id": "doc_B",
+ "source": "http://myserver.com:5984/foo",
+ "target": "bar",
+ "_replication_id": "c0ebe9256695ff083347cbf95f93e280"
+ }
+
+While document ``doc_A`` will look like this:
+
+::
+
+ {
+ "_id": "doc_A",
+ "source": "http://myserver.com:5984/foo",
+ "target": "bar",
+ "_replication_id": "c0ebe9256695ff083347cbf95f93e280",
+ "_replication_state": "triggered",
+ "_replication_state_time": 1297974122
+ }
+
+Note that both document get exactly the same value for the
+``_replication_id`` field. This way you can identify which documents
+refer to the same replication - you can for example define a view which
+maps replication IDs to document IDs.
+
+Canceling replications
+----------------------
+
+To cancel a replication simply ``DELETE`` the document which triggered
+the replication. The Couch log will show you an entry like the
+following:
+
+::
+
+ [Thu, 17 Feb 2011 20:16:29 GMT] [info] [<0.125.0>] Stopped replication `c0ebe9256695ff083347cbf95f93e280+continuous+create_target` because replication document `doc_A` was deleted
+
+ **Note**
+
+ You need to ``DELETE`` the document that triggered the replication.
+ ``DELETE``\ ing another document that describes the same replication
+ but did not trigger it, will not cancel the replication.
+
+Server restart
+--------------
+
+When CouchDB is restarted, it checks its ``_replicator`` database and
+restarts any replication that is described by a document that either has
+its ``_replication_state`` field set to ``triggered`` or it doesn't have
+yet the ``_replication_state`` field set.
+
+ **Note**
+
+ Continuous replications always have a ``_replication_state`` field
+ with the value ``triggered``, therefore they're always restarted
+ when CouchDB is restarted.
+
+Changing the Replicator Database
+--------------------------------
+
+Imagine your replicator database (default name is \_replicator) has the
+two following documents that represent pull replications from servers A
+and B:
+
+::
+
+ {
+ "_id": "rep_from_A",
+ "source": "http://aserver.com:5984/foo",
+ "target": "foo_a",
+ "continuous": true,
+ "_replication_id": "c0ebe9256695ff083347cbf95f93e280",
+ "_replication_state": "triggered",
+ "_replication_state_time": 1297971311
+ }
+ {
+ "_id": "rep_from_B",
+ "source": "http://bserver.com:5984/foo",
+ "target": "foo_b",
+ "continuous": true,
+ "_replication_id": "231bb3cf9d48314eaa8d48a9170570d1",
+ "_replication_state": "triggered",
+ "_replication_state_time": 1297974122
+ }
+
+Now without stopping and restarting CouchDB, you change the name of the
+replicator database to ``another_replicator_db``:
+
+::
+
+ $ curl -X PUT http://localhost:5984/_config/replicator/db -d '"another_replicator_db"'
+ "_replicator"
+
+As soon as this is done, both pull replications defined before, are
+stopped. This is explicitly mentioned in CouchDB's log:
+
+::
+
+ [Fri, 11 Mar 2011 07:44:20 GMT] [info] [<0.104.0>] Stopping all ongoing replications because the replicator database was deleted or changed
+ [Fri, 11 Mar 2011 07:44:20 GMT] [info] [<0.127.0>] 127.0.0.1 - - PUT /_config/replicator/db 200
+
+Imagine now you add a replication document to the new replicator
+database named ``another_replicator_db``:
+
+::
+
+ {
+ "_id": "rep_from_X",
+ "source": "http://xserver.com:5984/foo",
+ "target": "foo_x",
+ "continuous": true
+ }
+
+From now own you have a single replication going on in your system: a
+pull replication pulling from server X. Now you change back the
+replicator database to the original one ``_replicator``:
+
+::
+
+ $ curl -X PUT http://localhost:5984/_config/replicator/db -d '"_replicator"'
+ "another_replicator_db"
+
+Immediately after this operation, the replication pulling from server X
+will be stopped and the replications defined in the \_replicator
+database (pulling from servers A and B) will be resumed.
+
+Changing again the replicator database to ``another_replicator_db`` will
+stop the pull replications pulling from servers A and B, and resume the
+pull replication pulling from server X.
+
+Replicating the replicator database
+-----------------------------------
+
+Imagine you have in server C a replicator database with the two
+following pull replication documents in it:
+
+::
+
+ {
+ "_id": "rep_from_A",
+ "source": "http://aserver.com:5984/foo",
+ "target": "foo_a",
+ "continuous": true,
+ "_replication_id": "c0ebe9256695ff083347cbf95f93e280",
+ "_replication_state": "triggered",
+ "_replication_state_time": 1297971311
+ }
+ {
+ "_id": "rep_from_B",
+ "source": "http://bserver.com:5984/foo",
+ "target": "foo_b",
+ "continuous": true,
+ "_replication_id": "231bb3cf9d48314eaa8d48a9170570d1",
+ "_replication_state": "triggered",
+ "_replication_state_time": 1297974122
+ }
+
+Now you would like to have the same pull replications going on in server
+D, that is, you would like to have server D pull replicating from
+servers A and B. You have two options:
+
+- Explicitly add two documents to server's D replicator database
+
+- Replicate server's C replicator database into server's D replicator
+ database
+
+Both alternatives accomplish exactly the same goal.
+
+Delegations
+-----------
+
+Replication documents can have a custom ``user_ctx`` property. This
+property defines the user context under which a replication runs. For
+the old way of triggering replications (POSTing to ``/_replicate/``),
+this property was not needed (it didn't exist in fact) - this is because
+at the moment of triggering the replication it has information about the
+authenticated user. With the replicator database, since it's a regular
+database, the information about the authenticated user is only present
+at the moment the replication document is written to the database - the
+replicator database implementation is like a \_changes feed consumer
+(with ``?include_docs=true``) that reacts to what was written to the
+replicator database - in fact this feature could be implemented with an
+external script/program. This implementation detail implies that for non
+admin users, a ``user_ctx`` property, containing the user's name and a
+subset of his/her roles, must be defined in the replication document.
+This is ensured by the document update validation function present in
+the default design document of the replicator database. This validation
+function also ensure that a non admin user can set a user name property
+in the ``user_ctx`` property that doesn't match his/her own name (same
+principle applies for the roles).
+
+For admins, the ``user_ctx`` property is optional, and if it's missing
+it defaults to a user context with name null and an empty list of roles
+- this mean design documents will not be written to local targets. If
+writing design documents to local targets is desired, the a user context
+with the roles ``_admin`` must be set explicitly.
+
+Also, for admins the ``user_ctx`` property can be used to trigger a
+replication on behalf of another user. This is the user context that
+will be passed to local target database document validation functions.
+
+ **Note**
+
+ The ``user_ctx`` property only has effect for local endpoints.
+
+Example delegated replication document:
+
+::
+
+ {
+ "_id": "my_rep",
+ "source": "http://bserver.com:5984/foo",
+ "target": "bar",
+ "continuous": true,
+ "user_ctx": {
+ "name": "joe",
+ "roles": ["erlanger", "researcher"]
+ }
+ }
+
+As stated before, for admins the user\_ctx property is optional, while
+for regular (non admin) users it's mandatory. When the roles property of
+``user_ctx`` is missing, it defaults to the empty list ``[ ]``.
+
+Native SSL Support
+==================
+
+CouchDB 1.1 supports SSL natively. All your secure connection needs can
+now be served without the need set and maintain a separate proxy server
+that handles SSL.
+
+SSL setup can be tricky, but the configuration in CouchDB was designed
+to be as easy as possible. All you need is two files; a certificate and
+a private key. If you bought an official SSL certificate from a
+certificate authority, both should be in your possession already.
+
+If you just want to try this out and don't want to pay anything upfront,
+you can create a self-signed certificate. Everything will work the same,
+but clients will get a warning about an insecure certificate.
+
+You will need the OpenSSL command line tool installed. It probably
+already is.
+
+::
+
+ shell>
+ shell>
+ shell>
+ shell>
+ mycert.pem privkey.pem
+
+Now, you need to edit CouchDB's configuration, either by editing your
+``local.ini`` file or using the ``/_config`` API calls or the
+configuration screen in Futon. Here is what you need to do in
+``local.ini``, you can infer what needs doing in the other places.
+
+Be sure to make these edits. Under ``[daemons]`` you should see:
+
+::
+
+ ; enable SSL support by uncommenting the following line and supply the PEM's below.
+ ; the default ssl port CouchDB listens on is 6984
+ ;httpsd = {couch_httpd, start_link, [https]}
+
+Here uncomment the last line:
+
+::
+
+ httpsd = {couch_httpd, start_link, [https]}
+
+Next, under ``[ssl]`` you will see:
+
+::
+
+ ;cert_file = /full/path/to/server_cert.pem
+ ;key_file = /full/path/to/server_key.pem
+
+Uncomment and adjust the paths so it matches your system's paths:
+
+::
+
+ cert_file = /home/jan/cert/mycert.pem
+ key_file = /home/jan/cert/privkey.pem
+
+For more information please read
+`http://www.openssl.org/docs/HOWTO/certificates.txt`_.
+
+Now start (or restart) CouchDB. You should be able to connect to it
+using HTTPS on port 6984:
+
+::
+
+ shell>
+ curl: (60) SSL certificate problem, verify that the CA cert is OK. Details:
+ error:14090086:SSL routines:SSL3_GET_SERVER_CERTIFICATE:certificate verify failed
+ More details here: http://curl.haxx.se/docs/sslcerts.html
+
+ curl performs SSL certificate verification by default, using a "bundle"
+ of Certificate Authority (CA) public keys (CA certs). If the default
+ bundle file isn't adequate, you can specify an alternate file
+ using the --cacert option.
+ If this HTTPS server uses a certificate signed by a CA represented in
+ the bundle, the certificate verification probably failed due to a
+ problem with the certificate (it might be expired, or the name might
+ not match the domain name in the URL).
+ If you'd like to turn off curl's verification of the certificate, use
+ the -k (or --insecure) option.
+
+Oh no what happened?! — Remember, clients will notify their users that
+your certificate is self signed. ``curl`` is the client in this case and
+it notifies you. Luckily you trust yourself (don't you?) and you can
+specify the ``-k`` option as the message reads:
+
+::
+
+ shell>
+ {"couchdb":"Welcome","version":"1.1.0"}
+
+All done.
+
+HTTP Range Requests
+===================
+
+HTTP allows you to specify byte ranges for requests. This allows the
+implementation of resumable downloads and skippable audio and video
+streams alike. Now this is available for all attachments inside CouchDB.
+
+This is just a real quick run through how this looks under the hood.
+Usually, you will have larger binary files to serve from CouchDB, like
+MP3s and videos, but to make things a little more obvious, I use a text
+file here (Note that I use the ``application/octet-stream`` Content-Type
+instead of ``text/plain``).
+
+::
+
+ shell>
+ My hovercraft is full of eels!
+
+Now lets store this text file as an attachment in CouchDB. First, we
+create a database:
+
+::
+
+ shell>
+ {"ok":true}
+
+Then we create a new document and the file attachment in one go:
+
+::
+
+ shell>
+ {"ok":true,"id":"doc","rev":"1-287a28fa680ae0c7fb4729bf0c6e0cf2"}
+
+Now we can request the whole file easily:
+
+::
+
+ shell>
+ My hovercraft is full of eels!
+
+But say we only want the first 13 bytes:
+
+::
+
+ shell>
+ My hovercraft
+
+HTTP supports many ways to specify single and even multiple byte
+rangers. Read all about it in `RFC 2616`_.
+
+ **Note**
+
+ Databases that have been created with CouchDB 1.0.2 or earlier will
+ support range requests in 1.1.0, but they are using a less-optimal
+ algorithm. If you plan to make heavy use of this feature, make sure
+ to compact your database with CouchDB 1.1.0 to take advantage of a
+ better algorithm to find byte ranges.
+
+HTTP Proxying
+=============
+
+The HTTP proxy feature makes it easy to map and redirect different
+content through your CouchDB URL. The proxy works by mapping a pathname
+and passing all content after that prefix through to the configured
+proxy address.
+
+Configuration of the proxy redirect is handled through the
+``[httpd_global_handlers]`` section of the CouchDB configuration file
+(typically ``local.ini``). The format is:
+
+::
+
+ [httpd_global_handlers]
+ PREFIX = {couch_httpd_proxy, handle_proxy_req, <<"DESTINATION">>}
+
+
+Where:
+
+- ``PREFIX``
+
+ Is the string that will be matched. The string can be any valid
+ qualifier, although to ensure that existing database names are not
+ overridden by a proxy configuration, you can use an underscore
+ prefix.
+
+- ``DESTINATION``
+
+ The fully-qualified URL to which the request should be sent. The
+ destination must include the ``http`` prefix. The content is used
+ verbatim in the original request, so you can also forward to servers
+ on different ports and to specific paths on the target host.
+
+The proxy process then translates requests of the form:
+
+::
+
+ http://couchdb:5984/PREFIX/path
+
+To:
+
+::
+
+ DESTINATION/path
+
+ **Note**
+
+ Everything after ``PREFIX`` including the required forward slash
+ will be appended to the ``DESTINATION``.
+
+The response is then communicated back to the original client.
+
+For example, the following configuration:
+
+::
+
+
+ _google = {couch_httpd_proxy, handle_proxy_req, <<"http://www.google.com">>}
+
+Would forward all requests for ``http://couchdb:5984/_google`` to the
+Google website.
+
+The service can also be used to forward to related CouchDB services,
+such as Lucene:
+
+::
+
+
+ [httpd_global_handlers]
+ _fti = {couch_httpd_proxy, handle_proxy_req, <<"http://127.0.0.1:5985">>}
+
+ **Note**
+
+ The proxy service is basic. If the request is not identified by the
+ ``DESTINATION``, or the remainder of the ``PATH`` specification is
+ incomplete, the original request URL is interpreted as if the
+ ``PREFIX`` component of that URL does not exist.
+
+ For example, requesting ``http://couchdb:5984/_intranet/media`` when
+ ``/media`` on the proxy destination does not exist, will cause the
+ request URL to be interpreted as ``http://couchdb:5984/media``. Care
+ should be taken to ensure that both requested URLs and destination
+ URLs are able to cope
+
+Added CommonJS support to map functions
+=======================================
+
+We didn't have CommonJS require in map functions because the current
+CommonJS implementation is scoped to the whole design doc, and giving
+views access to load code from anywhere in the design doc would mean
+we'd have to blow away your view index any time you changed anything.
+Having to rebuild views from scratch just because you changed some CSS
+or a show function isn't fun, so we avoided the issue by keeping
+CommonJS require out of map and reduce altogether.
+
+The solution we came up with is to allow CommonJS inside map and reduce
+funs, but only of libraries that are stored inside the views part of the
+design doc.
+
+So you could continue to access CommonJS code in design\_doc.foo, from
+your list functions etc, but we'd add the ability to require CommonJS
+modules within map and reduce, but only from design\_doc.views.lib
+
+There's no worry here about namespace collisions, as Couch just plucks
+``views.*.map`` and ``views.*.reduce`` out of the design doc. So you
+could have a view called ``lib`` if you wanted, and still have CommonJS
+stored in ``views.lib.sha1`` and ``views.lib.stemmer`` if you wanted.
+
+We simplified the implementation by enforcing that CommonJS modules to
+be used in map functions be stored in views.lib.
+
+A sample design doc (taken from the test suite in Futon) is below:
+
+::
+
+ {
+ "views" : {
+ "lib" : {
+ "baz" : "exports.baz = 'bam';",
+ "foo" : {
+ "zoom" : "exports.zoom = 'yeah';",
+ "boom" : "exports.boom = 'ok';",
+ "foo" : "exports.foo = 'bar';"
+ }
+ },
+ "commonjs" : {
+ "map" : "function(doc) { emit(null, require('views/lib/foo/boom').boom)}"
+ }
+ },
+ "_id" : "_design/test"
+ }
+
+The ``require()`` statement is relative to the design document, but
+anything loaded form outside of ``views/lib`` will fail.
+
+More granular ETag support for views
+====================================
+
+ETags have been assigned to a map/reduce group (the collection of views
+in a single design document). Any change to any of the indexes for those
+views would generate a new ETag for all view URL's in a single design
+doc, even if that specific view's results had not changed.
+
+In CouchDB 1.1 each ``_view`` URL has it's own ETag which only gets
+updated when changes are made to the database that effect that index. If
+the index for that specific view does not change, that view keeps the
+original ETag head (therefore sending back 304 Not Modified more often).
+
+Added built-in filters for ``_changes``: ``_doc_ids`` and ``_design``.
+======================================================================
+
+The ``_changes`` feed can now be used to watch changes to specific
+document ID's or the list of ``_design`` documents in a database. If the
+``filters`` parameter is set to ``_doc_ids`` a list of doc IDs can be
+passed in the "doc\_ids" as a JSON array.
+
+Allow wildcards in vhosts definitions
+=====================================
+
+Similar to the rewrites section of a ``_design`` document, the new
+``vhosts`` system uses variables in the form of :varname or wildcards in
+the form of asterisks. The variable results can be output into the
+resulting path as they are in the rewriter.
+
+OS Daemons
+==========
+
+CouchDB now supports starting external processes. The support is simple
+and enables CouchDB to start each configured OS daemon. If the daemon
+stops at any point, CouchDB will restart it (with protection to ensure
+regularly failing daemons are not repeatedly restarted).
+
+The daemon starting process is one-to-one; for each each configured
+daemon in the configuration file, CouchDB will start exactly one
+instance. If you need to run multiple instances, then you must create
+separate individual configurations. Daemons are configured within the
+``[os_daemons]`` section of your configuration file (``local.ini``). The
+format of each configured daemon is:
+
+::
+
+ NAME = PATH ARGS
+
+
+Where ``NAME`` is an arbitrary (and unique) name to identify the daemon;
+``PATH`` is the full path to the daemon to be executed; ``ARGS`` are any
+required arguments to the daemon.
+
+For example:
+
+::
+
+ [os_daemons]
+ basic_responder = /usr/local/bin/responsder.js
+
+There is no interactivity between CouchDB and the running process, but
+you can use the OS Daemons service to create new HTTP servers and
+responders and then use the new proxy service to redirect requests and
+output to the CouchDB managed service. For more information on proxying,
+see ?. For further background on the OS Daemon service, see `CouchDB
+Externals API`_
+
+Stale views and ``update_after``
+================================
+
+Currently a view request can include the ``stale=ok`` query argument,
+which allows the contents of a stale view index to be used to produce
+the view output. In order to trigger a build of the outdated view index,
+a second view request must be made.
+
+To simplify this process, the ``update_after`` value can be supplied to
+the ``stale`` query argument. This triggers a rebuild of the view index
+after the results of the view have been retrieved.
+
+Socket Options Configuration Setting
+====================================
+
+The socket options for the listening socket in CouchDB can now be set
+within the CouchDB configuration file. The setting should be added to
+the ``[httpd]`` section of the file using the option name
+``socket_options``. The specification is as a list of tuples. For
+example:
+
+::
+
+ [httpd]
+ socket_options = [{recbuf, 262144}, {sndbuf, 262144}, {nodelay, true}]
+
+The options supported are a subset of full options supported by the
+TCP/IP stack. A list of the supported options are provided in the
+`Erlang inet`_ documentation.
+
+Server Options Configuration Setting
+====================================
+
+Server options for the MochiWeb component of CouchDB can now be added to
+the configuration file. Settings should be added to the
+``server_options`` option of the ``[httpd]`` section of ``local.ini``.
+For example:
+
+::
+
+ [httpd]
+ server_options = [{backlog, 128}, {acceptor_pool_size, 16}]
+
+
+Improved Error Messages
+=======================
+
+The errors reported when CouchDB is unable to read a required file have
+been updated so that explicit information about the files and problem
+can now be identified from the error message. The errors report file
+permission access either when reading or writing to configuration and
+database files.
+
+The error is raised both through the log file and the error message
+returned through the API call as a JSON error message. For example, when
+setting configuration values:
+
+::
+
+ shell>
+ {"error":"file_permission_error","reason":"/etc/couchdb/local.ini"}
+
+
+Errors will always be reported using the ``file_permission_error`` error
+type.
+
+During startup permissions errors on key files are also reported in the
+log with a descriptive error message and file location so that
+permissions can be fixed before restart.
+
+Multiple micro-optimizations when reading data.
+===============================================
+
+We found a number of places where CouchDB wouldn't do the absolute
+optimal thing when reading data and got rid of quite a few
+inefficiencies. The problem with small optimizations all over the place
+is that you may not notice them with every use-case, but we sure hope
+you can see an improvement overall.
+
+.. _`http://www.openssl.org/docs/HOWTO/certificates.txt`: http://www.openssl.org/docs/HOWTO/certificates.txt
+.. _RFC 2616: http://tools.ietf.org/html/rfc2616#section-14.27
+.. _CouchDB Externals API: http://davispj.com/2010/09/26/new-couchdb-externals-api.html
+.. _Erlang inet: http://www.erlang.org/doc/man/inet.html#setopts-2