Building .NET Apps using Couchbase Lite

Building .NET Apps using Couchbase Lite
Zack Gramana

About Me
Zack Gramana
Senior Software Engineer
Mobile
@zgramana

And, about me…
Wayne Carter
Architect
Mobile
@waynecarter

4
Couchbase Lite
On-device, lightweight, native
embedded JSON database
Sync Gateway
Synchronize on-device
Couchbase Lite with Couchbase
Server in the cloud
Couchbase Server
High performance, scalable,
always-on JSON database in
the cloud
Couchbase Mobile

5
Couchbase Lite
Couchbase Lite
Full Featured
JSON
Native
Lightweight
Secure
Beta

6
Sync Gateway
Sync Gateway
Replication
Authentication
Data Partitioning
Data Access Control

Authentication, Partitioning, Access Control
7
Pluggable Authentication
JavaScript sync function runs on all mutations.
Data Partitioning
– channel(…): Routes the document to the named channel
Data Access Control
– Read
– access(…): Grants access to a channel to a specified user, list of users, or a role
– role(…): Grants a user a role
– Write
– throw(…): Prevents a document mutation from persisting
– requireUser/Role/Access(…): Validates the user, their role assignments, or their
access privileges.

8
Couchbase Server
Couchbase Server
JSON
Highly Scalable
High Performance
Always On

Highlights
• Document Database
• Map Reduce Queries
• Sync
• Small: Assembly is < 500KB

Document Database Overview
• Semi-structured
• Key-value pairs
• Schemaless
• JSON-backed
• Very low-friction

Map Reduce Queries Overview
• Functional queries, instead of set-theoretic
• Write query logic in pure C#, not SQL
• Can be one-off, or auto-updating as data changes
• You probably already know how to use it:
– Map is like LINQ’s Select method
– Reduce is like LINQ’s Aggregate method

Sync Overview
• Master-master replication
• Uses HTTP + REST
• Offline mode for free
• Manual or continuous modes
• Automatic retry on failure
• Responds to network changes

Programming Model
• You: make your changes to docs
• Queries: will reflect those changes
• Replicators: sync changes for you

Getting Started with Documents

Opening a Database
var db = Manager.SharedInstance.GetDatabase("foo");
Debug.Assert(db != null);
var db = Manager.SharedInstance.GetExistingDatabase("foo");
Debug.Assert(db == null);

Getting a Document
var doc = db.GetDocument("foo-doc");
Debug.Assert(doc != null);
var doc = db.GetExistingDocument("foo-doc");
Debug.Assert(doc == null);

Creating a Document
var doc = db.CreateDocument();
Debug.Assert(doc.Id != null);

Deleting a Document
doc.Delete();
Debug.Assert(doc.Deleted);

Updating a New Document
var rev = doc.CreateRevision();
var props = new Dictionary<string, object>
{
{ "foo", "bar"},
{ "fizz", "buzz"}
};
rev.SetUserProperties(props);
rev.Save();

Updating an Existing Document
var props = doc.Properties;
var newProps = new Dictionary<string, object>(props)
{
{ "foo", "bar"}
};
doc.PutProperties(newProps); // Saves a new revision

Dealing with Changes
doc.Change += (sender, e) =>
{
// e.g. if we get a conflict...
if (e.Change.IsConflict)
{
// we can resolve it!
}
};

DocumentChange Members
String
Boolean
Boolean
String
Uri
RevisionInternal
DocumentId
IsConflict
IsCurrentRevision
RevisionId
SourceUrl
WinningRevision

Handling Conflicts
var current = doc.CurrentRevision;
foreach(var rev in doc.ConflictingRevisions)
{
var newRev = rev.CreateRevision();
if (rev.Equals(current)) {
newRev.SetProperties(mergedProps);
} else {
newRev.IsDeletion = true;
}
newRev.Save();
}

Auto-merging Properties using LINQ
Dictionary<string, object> mergedProps;
try
{
mergedProps = doc.ConflictingRevisions
.SelectMany(rev => rev.UserProperties)
.Distinct()
.ToDictionary(
kvp => kvp.Key,
kvp => kvp.Value
);
} catch (ArgumentException ex) {
// Merge conflict requires manual resolution.
}

Create a View
var view = db.GetView("foo");
Debug.Assert(view != null);
var view = db.GetExistingView("foo");
Debug.Assert(view == null);

Add a Map Function
view.SetMap((doc, emit) =>
{
var foo = (String)doc["foo"];
if (foo.Equals("bar")) {
emit ("text", doc["text"]);
}
}, "1");

Using a Reduce Function
ReduceDelegate reducer = (keys, values, rereduce) =>
{
var i = 0; var wordCount = 0;
foreach(var key in keys) {
if (key == "text") {
var str = (String)values[i];
wordCount += str.Split(' ').Length;
}
}
return wordCount;
};
view.SetMapReduce(mapper, reducer, "1");

Create a Query
var query = view.CreateQuery();
// Options, like...
query.Completed += (sender, e) => {
Log("Results: {0}", e.Rows);
};
query.Descending = true;
// Get records...
var rows = await query.RunAsync();
rows.Where(row => ...);

Create a LiveQuery
var liveQuery = query.ToLiveQuery();
// Respond to changes in the view.
liveQuery.Changed += (sender, e) =>
{
Log("Updates: {0}", e.Rows.Count);
};

Getting Started with Replication

Pull Replicator
var uri = new Uri(syncGatewayUrl);
var pull = db.CreatePullReplication(uri);
pull.Continuous = true;
pull.Changed += ReplicationChanged;
pull.Start();

Push Replicator
var uri = new Uri(syncGatewayUrl);
var push = db.CreatePushReplication(uri);
push.Continuous = true;
push.Changed += ReplicationChanged;
push.Start();

Couchbase Developer Portal
developer.couchbase.com/mobile

Xamarin Component Store
components.xamarin.com/view/couchbase-lite-net

Mailing List
groups.google.com/d/forum/mobile-couchbase

Contact Me
zack@couchbase.com (email)
@zgramana (twitter)

Building .NET Apps using Couchbase Lite

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