[doc] add blobs api doc

12 files changed, 170 insertions, 89 deletions

diff --git a/docs/api.rst b/docs/api.rst
index 362c632c..a184c9f7 100644
--- a/docs/api.rst
+++ b/docs/api.rst
@@ -5,5 +5,6 @@ API Reference
    :maxdepth: 1
 
    api/client
-   api/blobs
    api/attachments
+   api/blobs-client
+   api/blobs-server
diff --git a/docs/api/attachments.rst b/docs/api/attachments.rst
index 80b81d67..434a7526 100644
--- a/docs/api/attachments.rst
+++ b/docs/api/attachments.rst
@@ -1,5 +1,5 @@
-Client-side Attachments API
-===========================
+Document Attachments API
+========================
 
 Soledad Documents implement the ``IDocumentWithAttachment`` API that associates
 :ref:`blobs` with documents.
diff --git a/docs/api/blobs-client.rst b/docs/api/blobs-client.rst
new file mode 100644
index 00000000..b5811cc6
--- /dev/null
+++ b/docs/api/blobs-client.rst
@@ -0,0 +1,13 @@
+Blobs Client-side Python API
+============================
+
+Each Soledad Client has a property called ``blobmanager`` which is an instance
+of the ``BlobManager`` class and handles Blobs creation, retrieval, deletion
+and synchronization.
+
+.. toctree::
+   :maxdepth: 1
+
+   blobs/blobmanager
+   blobs/sync
+   blobs/errors
diff --git a/docs/api/blobs-server.rst b/docs/api/blobs-server.rst
new file mode 100644
index 00000000..3efe86bd
--- /dev/null
+++ b/docs/api/blobs-server.rst
@@ -0,0 +1,63 @@
+Blobs Server-side HTTP API
+==========================
+
+Soledad Server provides two different REST APIs for interacting with blobs:
+
+* A *public* :ref:`blobs-http-api`, providing the *Blobs* service for Soledad
+  Client (i.e. actual users of the infrastructure).
+
+* A *local* :ref:`incoming-http-api`, providing the delivery part of the
+  :ref:`incoming-box` service, currently used for the MX mail delivery.
+
+Authentication is handled differently for each of the endpoints, see
+:ref:`authentication` for more details.
+
+.. _blobs-http-api:
+
+Public Blobs HTTP API
+---------------------
+
+The *public endpoint* provides the following REST API for interacting with the
+*Blobs* service:
+
+=========================== ========== ================================= ============================================
+path                        method     action                            accepted query string fields
+=========================== ========== ================================= ============================================
+``/blobs/{uuid}``           ``GET``    Get a list of blobs. filtered by  ``namespace``, ``filter_flag``, ``order_by``
+                                       a flag.
+``/blobs/{uuid}/{blob_id}`` ``GET``    Get the contents of a blob.       ``namespace``
+``/blobs/{uuid}/{blob_id}`` ``PUT``    Create a blob. The content of the ``namespace``
+                                       blob should be sent in the body
+                                       of the request.
+``/blobs/{uuid}/{blob_id}`` ``POST``   Set the flags for a blob. A list  ``namespace``
+                                       of flags should be sent in the
+                                       body of the request.
+``/blobs/{uuid}/{blob_id}`` ``DELETE`` Delete a blob.                    ``namespace``
+=========================== ========== ================================= ============================================
+
+The Blobs service supports *namespaces*. All requests can be modified by the
+``namespace`` query string parameter, and the results will be restricted to
+a certain namespace. When no namespace explicitelly given, the ``default``
+namespace is used.
+
+When listing blobs, the results can be filtered by flag and/or ordered by date
+using the ``filter_flag`` and ``order_by`` query string parameters. The
+possible values for ``order_by`` are ``date`` or ``+date`` for increasing
+order, or ``-date`` for decreasing order.
+
+.. _incoming-http-api:
+
+Local Incoming Box HTTP API
+---------------------------
+
+The *local endpoint* provides the following REST API for interacting with the
+:ref:`incoming-box` service.
+
+============================== ========== =================================
+path                           method     action
+============================== ========== =================================
+``/incoming/{uuid}/{blob_id}`` ``PUT``    Create an incoming blob. The content of the blob should be sent in the body of the request.
+============================== ========== =================================
+
+All blobs created using this API are inserted under the namespace ``MX`` and
+flagged as ``PENDING``.
diff --git a/docs/api/blobs.rst b/docs/api/blobs.rst
deleted file mode 100644
index fbf31e1c..00000000
--- a/docs/api/blobs.rst
+++ /dev/null
@@ -1,11 +0,0 @@
-Client-side Blobs API
-=====================
-
-The Soledad Client object has a ``blobmanager`` property which is responsible
-for handling blobs.
-
-.. autoclass:: leap.soledad.client._db.blobs.BlobManager
-   :members:
-   :special-members: __init__
-   :undoc-members:
-   :show-inheritance:
diff --git a/docs/api/blobs/blobmanager.rst b/docs/api/blobs/blobmanager.rst
new file mode 100644
index 00000000..04165a57
--- /dev/null
+++ b/docs/api/blobs/blobmanager.rst
@@ -0,0 +1,15 @@
+.. _blobmanager-api:
+
+Blobs creation, retrieval, deletion and flagging
+================================================
+
+The ``BlobManager`` class is responsible for blobs creation, retrieval,
+deletion, flagging and synchronizing. For better code organization, the methods
+related to synchronization are implemented separatelly in a superclass (see
+:ref:`blobs-sync-api`).
+
+.. autoclass:: leap.soledad.client._db.blobs.BlobManager
+   :members:
+   :special-members: __init__
+   :undoc-members:
+   :show-inheritance:
diff --git a/docs/api/blobs/errors.rst b/docs/api/blobs/errors.rst
new file mode 100644
index 00000000..66454631
--- /dev/null
+++ b/docs/api/blobs/errors.rst
@@ -0,0 +1,6 @@
+Blobs Errors
+============
+
+.. automodule:: leap.soledad.client._db.blobs.errors
+   :members:
+   :undoc-members:
diff --git a/docs/api/blobs/sync.rst b/docs/api/blobs/sync.rst
new file mode 100644
index 00000000..53740d64
--- /dev/null
+++ b/docs/api/blobs/sync.rst
@@ -0,0 +1,12 @@
+.. _blobs-sync-api:
+
+Blobs Synchronization
+=====================
+
+The synchronization part of the ``BlobManager`` class is implemented in the
+``BlobsSynchronizer`` class, whose API can be seen below.
+
+.. autoclass:: leap.soledad.client._db.blobs.sync.BlobsSynchronizer
+   :members:
+   :special-members: __init__
+   :undoc-members:
diff --git a/docs/reference/attachments.rst b/docs/reference/attachments.rst
index 29387b36..4f3740f1 100644
--- a/docs/reference/attachments.rst
+++ b/docs/reference/attachments.rst
@@ -26,7 +26,7 @@ Server-side
 -----------
 
 In the server, attachments are stored as :ref:`blobs`. See
-:ref:`http-blobs-api` for more information on how to interact with the server
+:ref:`blobs-http-api` for more information on how to interact with the server
 using HTTP.
 
 The :ref:`IBlobsBackend <i-blobs-backend>` interface is provided, so in the
diff --git a/docs/reference/blobs/client.rst b/docs/reference/blobs/client.rst
index 75c3d997..734866fe 100644
--- a/docs/reference/blobs/client.rst
+++ b/docs/reference/blobs/client.rst
@@ -1,20 +1,47 @@
 Client-side blobs
 =================
 
-On the client-side, blobs can be managed using the BlobManager API.  The
-BlobManager is responsible for managing storage of blobs both in local and
-remote storages
+Data storage
+------------
+
+On the client-side, blobs can be managed using the ``BlobManager`` API, which
+is responsible for managing storage of blobs both in local and remote storages.
+See :ref:`blobmanager-api` and :ref:`blobs-sync-api` for information on the
+client-side API.
 
 All data is stored locally in the ``blobs`` table of a SQLCipher database
 called ``{uuid}_blobs.db`` that lies in the same directory as the Soledad
-Client's JSON documents database. Both databases are encrypted with the same
-symmetric secret. All actions performed locally are mirrored remotelly using
-the :ref:`http-blobs-api`.
-
-The BlobManager supports *namespaces* and *flags* and can list local and remote
-blobs, possibly filtering by flags and ordering by date (increasingly or
-decreasingly). It has helper methods to send or fetch all missing blobs, thus
-aiding in synchronization of local and remote data.
+Client's JSON documents database (see :ref:`client-databases`). All actions
+performed locally are mirrored remotelly using the :ref:`blobs-http-api`.
+
+Namespaces
+----------
+
+The Blobs API supports **namespaces** so that applications can store and fetch
+blobs without interfering in each another. Namespaces are also used to
+implement the server-side :ref:`incoming-http-api`, used for mail delivery. All
+methods that deal with blobs storage, transfer and flagging provide
+a `namespace` parameter. If no namespace is given, the value `default` is used.
+
+Remote flags
+------------
+
+In order to allow clients to control the processing of blobs that are delivered
+by external applications, the Blobs API has the concept of **remote flags**.
+The client can get and set the following flags for Blobs that reside in the
+server: ``PENDING``, ``PROCESSING``, ``PROCESSED``, and ``FAILED``.
+
+Remote listing
+--------------
+
+The client can obtain a list of blobs in the server side so it can compare with
+its own local list and queue up blobs for download and upload. The remote
+listing can be ordered by *upload date* and filtered by *namespace* and *flag*.
+The listing can also only return the number of matches instead of the whole
+content.
+
+Client-side encryption
+----------------------
 
 When uploading, the content of the blob is encrypted with a symmetric secret
 prior to being sent to the server. When downloading, the content of the blob is
diff --git a/docs/reference/blobs/server.rst b/docs/reference/blobs/server.rst
index 532fccd7..cda0b95c 100644
--- a/docs/reference/blobs/server.rst
+++ b/docs/reference/blobs/server.rst
@@ -1,68 +1,23 @@
 Server-side blobs
 =================
 
+The server-side implementation of blobs provides HTTP APIs for data storage
+using a filesystem backend.
+
+HTTP APIs
+---------
+
 Soledad Server provides two different REST APIs for interacting with blobs:
 
-* A public **HTTP Blobs API**, providing the *Blobs* service for Soledad Client
-  (i.e. actual users of the infrastructure).
+* A *public* :ref:`blobs-http-api`, providing the *Blobs* service for Soledad
+  Client (i.e. actual users of the infrastructure).
 
-* A local **HTTP Incoming Box API**, providing the delivery part of the
+* A *local* :ref:`incoming-http-api`, providing the delivery part of the
   :ref:`incoming-box` service, currently used for the MX mail delivery.
 
 Authentication is handled differently for each of the endpoints, see
 :ref:`authentication` for more details.
 
-
-.. _http-blobs-api:
-
-HTTP Blobs API
---------------
-
-The *public endpoint* provides the following REST API for interacting with the
-*Blobs* service:
-
-=========================== ========== ================================= ============================================
-path                        method     action                            accepted query string fields
-=========================== ========== ================================= ============================================
-``/blobs/{uuid}``           ``GET``    Get a list of blobs. filtered by  ``namespace``, ``filter_flag``, ``order_by``
-                                       a flag.
-``/blobs/{uuid}/{blob_id}`` ``GET``    Get the contents of a blob.       ``namespace``
-``/blobs/{uuid}/{blob_id}`` ``PUT``    Create a blob. The content of the ``namespace``
-                                       blob should be sent in the body
-                                       of the request.
-``/blobs/{uuid}/{blob_id}`` ``POST``   Set the flags for a blob. A list  ``namespace``
-                                       of flags should be sent in the
-                                       body of the request.
-``/blobs/{uuid}/{blob_id}`` ``DELETE`` Delete a blob.                    ``namespace``
-=========================== ========== ================================= ============================================
-
-The Blobs service supports *namespaces*. All requests can be modified by the
-``namespace`` query string parameter, and the results will be restricted to
-a certain namespace. When no namespace explicitelly given, the ``default``
-namespace is used.
-
-When listing blobs, the results can be filtered by flag and/or ordered by date
-using the ``filter_flag`` and ``order_by`` query string parameters. The
-possible values for ``order_by`` are ``date`` or ``+date`` for increasing
-order, or ``-date`` for decreasing order.
-
-
-HTTP Incoming Box API
----------------------
-
-The *local endpoint* provides the following REST API for interacting with the
-:ref:`incoming-box` service.
-
-============================== ========== =================================
-path                           method     action
-============================== ========== =================================
-``/incoming/{uuid}/{blob_id}`` ``PUT``    Create an incoming blob. The content of the blob should be sent in the body of the request.
-============================== ========== =================================
-
-All blobs created using this API are inserted under the namespace ``MX`` and
-flagged as ``PENDING``.
-
-
 .. _filesystem-backend:
 
 Filesystem backend
diff --git a/docs/reference/blobs/sync.rst b/docs/reference/blobs/sync.rst
index 729bb0ab..bdfad0cf 100644
--- a/docs/reference/blobs/sync.rst
+++ b/docs/reference/blobs/sync.rst
@@ -19,10 +19,10 @@ Synchronization status
 In the client-side, each has an associated synchronization status, which can be
 one of:
 
-- `SYNCED`: The blob exists both in this client and in the server.
-- `PENDING_UPLOAD`: The blob was inserted locally, but has not yet been uploaded.
-- `PENDING_DOWNLOAD`: The blob exists in the server, but has not yet been downloaded.
-- `FAILED_DOWNLOAD`: A download attempt has been made but the content is corrupted for some reason.
+- ``SYNCED``: The blob exists both in this client and in the server.
+- ``PENDING_UPLOAD``: The blob was inserted locally, but has not yet been uploaded.
+- ``PENDING_DOWNLOAD``: The blob exists in the server, but has not yet been downloaded.
+- ``FAILED_DOWNLOAD``: A download attempt has been made but the content is corrupted for some reason.
 
 Concurrency limits
 ------------------
@@ -41,8 +41,8 @@ the transfer has been successful or until there has been an unrecoverable
 transfer error. Currently, the only unrecoverable transfer error is a failed
 verification of the blob tag (i.e. a failed MAC verification).
 
-Successive transfer attempts have an increasing delay between them, to minimize
-competition for resources used by other concurrent transfer attempts. The delay
-starts with 10 seconds and increases to 20, 30, 40, 50, and finally 60 seconds
-on each new failed attempt. The delay for a new retry then stays at 60 seconds
-for new attempts.
+Successive failed transfer attempts of the same blob are separated by an
+increasing time interval to minimize competition for resources used by other
+concurrent transfer attempts. The interaval starts at 10 seconds and increases
+to 20, 30, 40, 50, and finally 60 seconds. All further retries will be
+separated by a 60 seconds time interval.