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2015, Tuesday March 31

ORM Master/Slave Replication

As stated during TSQLRecord fields definition, the ORM is able to maintain a revision number for any TSQLRecord table, so that it the table may be easily synchronized remotely by another TSQLRestServer instance.
If you define a TRecordVersion published property, the ORM core will fill this field just before any write with a monotonically increasing revision number, and will take care of any deletion, so that those modifications may be replayed later on any other database.

This synchronization will work as a strict master/slave replication scheme, as a one-way on demand refresh of a replicated table.
Each write operation on the master database on a given table may be easily reflected on one or several slave databases, with almost no speed nor storage size penalty.

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2014, Wednesday December 31

2015: the future of mORMot is BigData

How would be 2015 like for our little rodents?
Due to popular request of several users of mORMot, we identified and designed some feature requests dedicated to BigData process.

In fact, your data is the new value, especially if you propose SaaS (Software As A Service) hosting to your customers, with a farm of mORMot servers.
Recent Linux support for mORMot servers, together with the high performance and installation ease of our executable, open the gate to cheap cloud-based hosting.
As a consequence, a lot of information would certainly be gathered by your mORMot servers, and a single monolithic database is not an option any more.

For mORMot solutions hosted in cloud, a lot of data may be generated. The default SQLite3 storage engine may be less convenient, once it reaches some GB of file content. Backup becomes to be slow and inefficient, and hosting this oldest data in the main DB, probably stored on an expensive SSD, may be a lost of resource. Vertical scaling is limited by hardware and price factors.

This is were data sharding comes into scene.
Note that sharding is not replication/backup, nor clustering, nor just spreading. We are speaking about application-level data splitting, to ease maintenance and horizontal scalability of mORMot servers.

Data sharding could already be implemented with mORMot servers, thanks to TSQLRestStorage:

  • Using TSQLRestStorageExternal: any table may have its own external SQL database engine, may be in its separated DB server;
  • Using TSQLRestStorageMongoDB: any table may be stored on a MongoDB cluster, with its own sharding abilities;
  • Using TSQLRestStorageRemote: each table may have its own remote ORM/REST server.

But when data stored in a single table tends to grow without limit, this feature is not enough.
Let's see how the close future of mORMot looks like.

Continue reading...

2014, Wednesday May 7

MongoDB + mORMot benchmark

Here are some benchmark charts about MongoDB integration in mORMot's ORM.

MongoDB appears as a serious competitor to SQL databases, with the potential benefit of horizontal scaling and installation/administration ease - performance is very high, and its document-based storage fits perfectly with mORMot's advanced ORM features like Shared nothing architecture (or sharding).

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MongoDB + mORMot ORM = ODM

MongoDB (from "humongous") is a cross-platform document-oriented database system, and certainly the best known NoSQL database.
According to http://db-engines.com in April 2014, MongoDB is in 5th place of the most popular types of database management systems, and first place for NoSQL database management systems.
Our mORMot gives premium access to this database, featuring full NoSQL and Object-Document Mapping (ODM) abilities to the framework.

Integration is made at two levels:

  • Direct low-level access to the MongoDB server, in the SynMongoDB.pas unit;
  • Close integration with our ORM (which becomes defacto an ODM), in the mORMotMongoDB.pas unit.

MongoDB eschews the traditional table-based relational database structure in favor of JSON-like documents with dynamic schemas (MongoDB calls the format BSON), which matches perfectly mORMot's RESTful approach.

This second article will focus on integration of MongoDB with our ORM.

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Direct MongoDB database access

MongoDB (from "humongous") is a cross-platform document-oriented database system, and certainly the best known NoSQL database.
According to http://db-engines.com in April 2014, MongoDB is in 5th place of the most popular types of database management systems, and first place for NoSQL database management systems.
Our mORMot framework gives premium access to this database, featuring full NoSQL and Object-Document Mapping (ODM) abilities to the framework.

Integration is made at two levels:

  • Direct low-level access to the MongoDB server, in the SynMongoDB.pas unit;
  • Close integration with our ORM (which becomes defacto an ODM), in the mORMotMongoDB.pas unit.

MongoDB eschews the traditional table-based relational database structure in favor of JSON-like documents with dynamic schemas (MongoDB calls the format BSON), which matches perfectly mORMot's RESTful approach.

In this first article, we will detail direct low-level access to the MongoDB server, via the SynMongoDB.pas unit.

Continue reading...

2014, Friday April 18

Introducing mORMot's architecture and design principles

We have just released a set of slides introducing 

  • ORM, SOA, REST, JSON, MVC, MVVM, SOLID, Mocks/Stubs, Domain-Driven Design concepts with Delphi, 
  • and showing some sample code using our Open Source mORMot framework.

You can follow the public link on Google Drive!

This is a great opportunity to discovers some patterns you may not be familiar with, and find out how mORMot try to implement them.
This set of slides may be less intimidating than our huge documentation - do not be terrified by our Online Documentation!
The first set of pages (presenting architecture and design principles) is worth reading.

Feedback is welcome on our forum, as usual.

2014, Tuesday February 25

TDocVariant custom variant type

With revision 1.18 of the framework, we just introduced two new custom types of variants:

  • TDocVariant kind of variant;
  • TBSONVariant kind of variant.

The second custom type (which handles MongoDB-specific extensions - like ObjectID or other specific types like dates or binary) will be presented later, when dealing with MongoDB support in mORMot, together with the BSON kind of content. BSON / MongoDB support is implemented in the SynMongoDB.pas unit.

We will now focus on TDocVariant itself, which is a generic container of JSON-like objects or arrays.
This custom variant type is implemented in SynCommons.pas unit, so is ready to be used everywhere in your code, even without any link to the mORMot ORM kernel, or MongoDB.

TDocVariant documents

TDocVariant implements a custom variant type which can be used to store any JSON/BSON document-based content, i.e. either:

  • Name/value pairs, for object-oriented documents;
  • An array of values (including nested documents), for array-oriented documents;
  • Any combination of the two, by nesting TDocVariant instances.

Here are the main features of this custom variant type:

  • DOM approach of any object or array documents;
  • Perfect storage for dynamic value-objects content, with a schema-less approach (as you may be used to in scripting languages like Python or JavaScript);
  • Allow nested documents, with no depth limitation but the available memory;
  • Assignment can be either per-value (default, safest but slower when containing a lot of nested data), or per-reference (immediate reference-counted assignment);
  • Very fast JSON serialization / un-serialization with support of MongoDB-like extended syntax;
  • Access to properties in code, via late-binding (including almost no speed penalty due to our VCL hack as already detailed);
  • Direct access to the internal variant names and values arrays from code, by trans-typing into a TDocVariantData record;
  • Instance life-time is managed by the compiler (like any other variant type), without the need to use interfaces or explicit try..finally blocks;
  • Optimized to use as little memory and CPU resource as possible (in contrast to most other libraries, it does not allocate one class instance per node, but rely on pre-allocated arrays);
  • Opened to extension of any content storage - for instance, it will perfectly integrate with BSON serialization and custom MongoDB types (ObjectID, RegEx...), to be used in conjunction with MongoDB servers;
  • Perfectly integrated with our Dynamic array wrapper and its JSON serialization as with the record serialization;
  • Designed to work with our mORMot ORM: any TSQLRecord instance containing such variant custom types as published properties will be recognized by the ORM core, and work as expected with any database back-end (storing the content as JSON in a TEXT column);
  • Designed to work with our mORMot SOA: any interface-based service is able to consume or publish such kind of content, as variant kind of parameters;
  • Fully integrated with the Delphi IDE: any variant instance will be displayed as JSON in the IDE debugger, making it very convenient to work with.

To create instances of such variant, you can use some easy-to-remember functions:

  • _Obj() _ObjFast() global functions to create a variant object document;
  • _Arr() _ArrFast() global functions to create a variant array document;
  • _Json() _JsonFast() _JsonFmt() _JsonFastFmt() global functions to create any variant object or array document from JSON, supplied either with standard or MongoDB-extended syntax.

Continue reading...

2013, Saturday January 5

Domain-Driven-Design and mORMot

Implementing Domain-Driven-Design (DDD) is one goal of our mORMot framework.

We already presented this particular n-Tier architecture.

It is now time to enter deeper into the material, provide some definition and reference.
You can also search the web for reference, or look at the official web site.
A general presentation of the corresponding concepts, in the .NET world, was used as reference of this blog entry.

Stay tuned, and ride the mORMot!

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2012, Friday April 13

Custom JSON serialization of any class

By default, our mORMot framework is able to serialize any class into a true JSON object.

All published properties will be written as JSON object members.

In some cases, it may be handy to have a custom serialization, for instance if you want to manage some third-party classes, or to adapt the serialization scheme to a particular purpose, at runtime.

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2012, Thursday April 12

Custom JSON serialization of any dynamic array content

One nice feature of the TDynArray wrapper and its associated methods, as defined and used in our framework, is the ability to serialize any dynamic array as JSON content.

By default, only "standard" dynamic arrays (like TIntegerDynArray) are serialized as true JSON array: other not known kind of arrays are serialized as binary content, within a Base64 encoding.

This is a very efficient solution for a pure Delphi application, since it will be fast and always works, but won't be easy to deal with from an AJAX client.

Applications can now supply a custom JSON serialization for any other dynamic array, via the TTextWriter.RegisterCustomJSONSerializer() class method.
Two callbacks are to be supplied for a dynamic array type information, in order to handle proper serialization and un-serialization of the JSON array.

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2011, Sunday July 3

"Sharding" or "Share nothing" architecture

Here is what wikipedia states at http://en.wikipedia.org/wiki/Shared_nothing_architecture:

A shared nothing architecture (SN) is a distributed computing architecture in which each node is independent and self-sufficient, and there is no single point of contention across the system. People typically contrast SN with systems that keep a large amount of centrally-stored state information, whether in a database, an application server, or any other similar single point of contention.

This is just one approach of "sharding". Sharding is indeed related to a shared nothing architecture - once sharded, each shard can live in a totally separate logical schema instance.
"I sharded, therefore it scales"...

You can do this in Delphi... and opens a new world of scaling opportunities... Just as Google, Facebook, or eBay do... 

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