Strange encrypted store behavior
by Tadeas Kriz
Hi there,
in December, I’ve reported [1] and today Passos asked me if I could rather send it here to discuss it, as this behavior is the same in other platform’s implementations (which I wasn’t aware of before). So please read the description on that JIRA issue. Basically I have nothing more to say about it, what’s not in the description already. So, what do you think?
1 - https://issues.jboss.org/browse/AGDROID-173
—
Tadeas Kriz
tkriz(a)redhat.com
12 years, 1 month
DataManager API draft
by Tadeas Kriz
Hey,
It’s me again with more changes to the DataManager API. I’ve tried many different approaches and this one is basically the only one I got to work as intended (these are only interfaces, no real implementation, but that’s not a problem as it won’t make it much difficult to change current implementations to match those interfaces). Basically, it’s not the best and I had better APIs, but they unfortunately weren’t possible because of restrictions in Java.
You can find the draft here: https://gist.github.com/TadeasKriz/e0f5583e2a24c32dc253
What can I say about this API is, that in this approach the user shouldn’t need to cast the Store<T> (which is real pain in current API) unless he really needs to (like some methods that’ll be available only for the store he wants). In other cases, when the cast is not needed, users will be able to just work with the Store<T> and change the underlying store as they like. So let’s say they’ll be working with MemoryStore in development, because it’s easier to debug. Then the release will be closing in, they’ll just switch to SQLStore very easily.
So, what do you think guys?
—
Tadeas Kriz
tkriz(a)redhat.com
12 years, 2 months
Unified Push Server integration capabilities
by Wolfgang
Hello dear aerogear dev team,
a couple of weeks ago we had to integrate a PushServer for iOS and Android
into our solution. We used the UPS out-of-the-box for a first prototype to
figure out better the capabilities and to be able to better define the
requirements in regards to push. So far we are very excited about the
product!
The drawback is that some piece of information like devices, users, apps as
are represented in another system (i.e. MongoDB) or capabilities like
authorization/authentication are already present. Thus there is some
redundancy and overhead and the UPS is a little bit alien in regards to the
rest of the existing architecture/infrastructure. This has pre and cons -- I
know ...
I thought that maybe a "simple"/exchangable mechanisms (e.g. persistence
layer) of defined integration interfaces and mechanisms would be great in
order to be able to better integrate the UPS in existing or already
constrained system environments. This might also help in regards to
scalability and flexibility of the existing design/architecture.
Wondered if that would make sense in your opinion ... ?
~Wolfgang
--
View this message in context: http://aerogear-dev.1069024.n5.nabble.com/Unified-Push-Server-integration...
Sent from the aerogear-dev mailing list archive at Nabble.com.
12 years, 2 months
sync
by Erik Jan de Wit
So we already agreed that CouchDB has some nice features, but why wouldn’t we just use pouchdb for javascript and touchdb? I’ve just tested the javascript and it syncs with the server perfectly, even if there are some things missing we could add them because these projects are open source.
Cheers,
Erik Jan
12 years, 2 months
[aerogear-android] DataManager API inconsistency + solution
by Tadeas Kriz
Hey everyone,
I’ve been recently going through the DataManager API in aerogear-android. In this email, I’d like to suggest addiction of two method (or possibly three) into the `Store<T>` interface. These would be:
```java
/**
* If store is open, it can be read or written to.
*/
boolean isOpen();
/**
* Opens store in current thread (blocking).
*/
Store<T> open();
/**
* Opens store in background thread and then callback#onSuccess is called.
*/
void open(Callback<Store<T>> callback);
```
>From my point of view, this makes sense to be in the `Store<T>` so I can switch between stores easily during development with no need to change other code. Also, if `read` or `write` operations are done with closed store, there are two possible workflows. First one is, that I’d fail and throw an exception. Second (and for me a preferred one) is, that all those methods would internally check if the store is open and if not, they’d call the `open` method. This also leads me to another API change for `Store<T>`.
```java
/**
* Reads all the data from the underlying storage system asynchronously.
*/
void readAll(Callback<Collection<T>> callback);
/**
* Reads a specific object/record from the underlying storage system asynchronously.
*/
void read(Serializable id, Callback<T> callback);
/**
* Search for objects/records from the underlying storage system asynchronously.
*/
void readWithFilter(ReadFilter filter, Callback<List<T>> callback);
/**
* Saves the given object in the underlying storage system asynchronously.
*/
void save(T item, Callback<Void> callback);
/**
* Resets the entire storage system asynchronously.
*/
void reset(Callback<Void> callback);
/**
* Removes a specific object/record from the underlying storage system asynchronously.
*/
void remove(Serializable id, Callback<Void> callback);
/**
* Checks if the storage system contains no stored elements asynchronously.
*/
void isEmpty(Callback<Boolean> callback);
```
That’s right, async methods for easy access to the storage from background thread, without the pain of writing it myself (for example, it makes no sense if I want to just call `store.save(..)` and I’d have to write all the `AsyncTask` boilerplate).
So, what do you think?
PS: You can find the whole text with highlighted syntax here:
—
Tadeas Kriz
tkriz(a)redhat.com
12 years, 2 months
sync spec strawman
by Summers Pittman
I've updated the sync spec on the data-sync branch on aerogear.org with
what qmx posted yesterday and some ideas I had as well. If I don't get
any tomatoes I will try to see what a POC on Android looks like this
afternoon.
Sync doc follows.
# Status: Experimental
# AeroGear Data Sync
## basics?
Since we've been catering the enterprise market, this essentially means
we need to get the __boring__ stuff right first, then move over to the
__shiny__ stuff, like realtime data sync, update policies & friends.
### data model
For starters, I think that the most important thing that needs to be
agreed upon is the data model and the atomic operations around it. As
previous discussed, I really like CouchDB's datamodel -- and hate erlang ;)
`{_id:<guid>, content:<arbitrary json>, rev:<last revision>}`
#### JS
Well, it's JSON, it _Just Works_™
#### Java
I didn't want to pick on Java, but since its fame forces me to it. First
stab (a courtesy of our friend Dan Bevenius):
public interface Document {
public String id;
public String content;
public String rev;
}
We naturally want to kick this a notch, and use objects instead of plain
strings:
public interface Document<T, ID> {
public ID id;
public T content;
public String rev;
}
In this case, we can use the convention requiring that `T` is any
**object serializable to JSON**. `ID` is a convenience shorthand since
it's a **GUID/UUID**. I think this key isn't necessarily a natural key
(a surrogate key instead).
#### Objective-C
volunteers needed ;)
### Transactions
These are the most basic parts of sync I can think of that our system
should be able to do/manage. Our internal representation of the client
documents and collections should make implementing this automatically
and without user intervention as simple as possible
* Detect Change
When a user changes her local data, the system should note the
change and generate a sync message to send to the server. This can be
done automatically or manually but SHOULD be done automatically.
* Send update
When a sync message is ready to be sent, and the system allows for
it to be sent (network available, not in blackout window from
exponential backoff, etc) then sync message should be sent. This being
done automatically should be the default, but the developer can override
this behavior.
* Receive Update
When a client updates it data and successfully syncs to the remote
server, the remote server will notify all of the relevant clients. The
client must automatically and without user intervention receive this
update and either act on it or store it for later processing.
* Apply Update
Once a client application has an update message from the server, it
can apply the message correctly to the data on it. This should be done
automatically as part of receiving the update, but it may be done
manually or may be delayed and automatically executed later.
* Detect Conflict
When applying an update fails, the system must detect this. The
system will provide state to the application and/or the user to handle
the conflict. The user MUST NOT have to check for conflicts on her own.
* Resolve Conflict
There must be a mechanism for resolving a conflict. The CAN be
done automatically using default resolvers provided by AeroGear, by
using a resolver provided by the developer/user, or by the app user
selecting the correct merge. This will possibly generate a new sync
message.
### API levels
As soon as we have a rough data-model defined, we can start dabbling
around different API levels to be served:
(parts **I think** are potentially deliverable for a 1.0)
- level 0: explodes when there's a conflict
- level 1: semi-automatic conflict resolution via something like
google's diff-match-patch
- level 2: business rules determine who wins a conflicting update
(supervisor wins over normal user)
(parts **I think** are potentially deliverable for a 2.0)
- level 3: real-time updates via diff-match-patch
- level 4: real-time updates via OT/EC
All those proposed API operations should be serializable, meaning I can
potentially keep doing changes offline then just replying them to the
server when online.
### transport
Since we know about the future-looking ideas on v2.0, it would be really
nice for us to specify a very simple/dumb JSON-based protocol for those
change messages. Something that could accomodate both the full document
updates and the OT/EC incremental bits too. I have no ideas on this, tbh.
#### Strawman - Summers
{id : Object, data : String, checksum: long}
**id** :
This is the global identifier for the object. This field is optional.
**data** :
This is the sync data for the application. It may be a diff, a whole
object, etc. This field is required.
**checksum** :
This is the client's idea of what a known good sync will look like.
If, post merge, the server's checksum and client's check sum do not
match then the client is out of sync and must resync and handle the
conflict.
## Appendix Use Cases:
Here are a few contrived use cases that we may want to keep in mind.
1. Legacy Bug Trackers From Hell
a. It is a webapp written in COBOL, no one will ever EVER update or
change the code
b. It has TONS of legacy but important data
c. It has TONS of users
d. It only has a few transactions per day, all creating and
updating
bug reports
e. Multiple users can edit the same report
2. Slacker Gallery
a. Each User has a multiple galleries, each gallery has multiple
photos
b. A Gallery has only one user, but the user may be on multiple
devices
c. Galleries may be renamed, created, and deleted
d. Photos may only be created or deleted. Photos also have meta
data
which may be updated, but its creation and deletion is tied to the Photo
object.
3. Dropbox clone
a. A folder of files may be shared among users
b. There is a size limit to files and how much storage may be used
per folder
c. Files are not updated. If there is a new file, there is an
atomic
delete and create operation
4. Email client
a. This is an AG-controller which accesses a mail account.
b. There are mobile offline and sync enabled clients which connect
to this controller.
5. Google Docs clone
a. Operational Transform out the wazzoo
b. What would the server need?
c. What would the client need?
6. Building Inspector app
Building inspector system - we have mobile apps that store relevant info
and are bound to be accessed on places where we won't have any kind of
connection, or very poor signal.
You can have several inspectors screening the same building simultaneously.
Let's say we have Agnes and Joe are doing the fire extinguisher
inspection in a new hospital building. Technically each fire
extinguisher has its own identifier and can be an independent document.
In this case we would have no conflict happening.
Now they start finding expired fire extinguishers and start to add them
to the report. This report could potentially have two divergent lists of
fire extinguishers to be replenished/revalidated, as the building's
compliance status.
7. Census App
Census system - we have mobile apps focused on offline data collection.
We have the previous year's info that needs to be updated on the server.
The interviewee needs to take a call, then asks the interviewer to come
back later. This results in two sets of changes for the same document,
stacked together, which should work flawlessly.
# Appendix Reference (Open Source) Products:
- Wave-in-a-box
- CouchDB
- Google Drive RealtimeAPI
- [diff-merge-patch
algorithm](http://code.google.com/p/google-diff-match-patch/)
- [Summers' Realtime Sync Demo](http://www.youtube.com/watch?v=WEkZGbVk4Lc)
- [Summers' Devnexus Sync
Demo](https://plus.google.com/103442292643366117394/posts/HGVHwtPArPW)
- Google Android Sync Architecture
12 years, 2 months
Android and JDK 1.6
by Summers Pittman
Karel brought up the fact that the Android project relies on classes
from Java 7. I would like for the Android project to compile using JDK
6, but I was wondering what the rest of the project thought.
For a little back story, until recently the dexer (Android Java byte
code to Dex byte code compiler) could only consume Java 6 byte code.
That was very recently fixed and almost all Java 7 features are
supported on Android version greater than Gingerbread. The exception is
try with resources which is only supported on KitKat.
I havn't looked at the project yet to even get an idea for how much work
it would be, but I suspect it will be rather minimal.
12 years, 2 months
