Is there any way to know data which is not uploaded on firebase and is persisting on disk? I have enabled offline capability by using-
FirebaseDatabase.getInstance().setPersistenceEnabled(true);
By doing this my all data remains cached. I want to know which data is uploaded and which isnt.
There is no method in the API that returns an indication of which write operations have not yet been committed to the Firebase server. If you need that status, you can manage it yourself. The setValue() and updateChildren() methods provide two options for getting a callback when the value is committed to the Firebase server. One option is to provide a CompletionListener parameter:
FirebaseDatabase.getInstance().getReference("test")
.setValue("SomeValue", new DatabaseReference.CompletionListener() {
#Override
public void onComplete(DatabaseError databaseError, DatabaseReference databaseReference) {
if (databaseError == null) {
// the data was successfully committed to the server
} else {
// the operation failed, for example permission failure
}
}
});
The other option is to add a listener to the returned Task:
FirebaseDatabase.getInstance().getReference("test")
.setValue("SomeValue").addOnCompleteListener(new OnCompleteListener<Void>() {
#Override
public void onComplete(#NonNull Task<Void> task) {
if (task.isSuccessful()) {
// the data was successfully committed to the server
} else {
// the operation failed, for example permission failure
}
}
});
For both cases, the update is in the local cache immediately after the call to setValue() or updateChildren(), but is not in the server database until the callback fires.
Related
I have implemented the Firebase Real-Time Database presence system as shown in the official Firebase documentation. I would like to make the database secure so that logged-in users can only write to their own presence entries in the DB. So, on login, the user writes to the reference path /auth/{authId}/connections and at the same time sets up the onDisconnect to remove the value.
Here is the code from the Android app that is setting presence in rtdb:
getFirebaseDatabase().goOnline();
DatabaseReference.goOnline();
// Since I can connect from multiple devices, we store each connection instance separately
// any time that connectionsRef's value is null (i.e. has no children) I am offline
final FirebaseDatabase database = getFirebaseDatabase();
final DatabaseReference myConnectionsRef = database.getReference("/auth/" + getFirebaseAuth().getUid() + "/connections");
// Stores the timestamp of my last disconnect (the last time I was seen online)
final DatabaseReference lastOnlineRef = database.getReference("/auth/" + getFirebaseAuth().getUid() + "/lastOnline");
connectedRef = database.getReference(".info/connected");
presenceChangeListener = connectedRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot snapshot) {
boolean connected = snapshot.getValue(Boolean.class);
if (connected) {
DatabaseReference con = myConnectionsRef.push();
// When this device disconnects, remove it
con.onDisconnect().removeValue()
.addOnSuccessListener(new OnSuccessListener<Void>() {
#Override
public void onSuccess(Void aVoid) {
// Add this device to my connections list
// this value could contain info about the device or a timestamp too
con.setValue("ANDROID");
}
})
.addOnFailureListener(new OnFailureListener() {
#Override
public void onFailure(#NonNull Exception e) {
Log.d(TAG, "### Failed to set onDisconnect ###");
e.printStackTrace();
}
});
// When I disconnect, update the last time I was seen online
lastOnlineRef.onDisconnect().setValue(ServerValue.TIMESTAMP);
}
}
#Override
public void onCancelled(DatabaseError error) {
Log.w(TAG, "Listener was cancelled at .info/connected");
}
});
The problem that I am having is that if the user logs out, the onDisconnect doesn't execute unless I first manually disconnect from rtdb. I'm assuming that the code running on the Real-Time DB gets a permission denied since the auth is no longer valid.
//If I don't go offline first the record in rtdb will not be removed.
DatabaseReference.goOffline();
AuthUI.getInstance().signOut(this)
.addOnCompleteListener(new OnCompleteListener<Void>() {
public void onComplete(#NonNull Task<Void> task) {
// user is now signed out
Log.d(TAG, "Logged out");
application.clearData();
DatabaseReference.goOffline(); //This doesn't cause a presence update here
finish();
}
});
Above is the work-around I'm using, first telling the database to goOffline then to logout. If the user ever gets logged out by another means (the web app is seeing if multiple tabs are using the app and one logs out) the user will be left with a connection not removed.
If I don't call the goOffline() prior to logout, the connection in rtdb will not be removed, even if I force close the application.
I have also verified that I can get everything working fine if I change my rtdb rules to be ".write": "true" <-which is no good. This tells me that there is a permission denied with the onDisconnect running when a user logs out of the auth.
I would like my real-time rules to be something like this.
{
"rules": {
"auth": {
"$uid": {
".read": "auth != null && auth.uid == $uid",
".write": "auth != null && auth.uid == $uid"
}
}
}
}
I would have hoped that the onDisconnect would still be able to execute with the auth of the user when the onDisconnect was setup.
When you attach a onDisconnect() handler, you're registering a delayed write on the Firebase servers. Whether that write is allowed is checked both when you attach the handler, and when the handler is triggered. And since your user is signed out when the write is triggered, it get rejected by your rules. There is no configuration option to change this behavior, so you'll have to come up with a different approach.
So, because 1.) the onDisconnect() execution is evaluated against the rules of the RTDB, 2.) the user who setup the onDisconnect() may lose authentication, and 3.) I would like to make the presence system secure for my auth'ed users... I came up with the following solution:
First, write the presence entries to the RTDB under a path that contains both the user's authId and a UUID to make the location "unguessable".
"/presence/" + {auth-uid} + "/connections/" + {UUID}
and setup a .onDisconnect() to remove this value stored at the unguessable location.
Then, setup the RTDB rules to do the following:
do not allow any reading of the presence data
allow users to add/modify data only under their auth directory
allow any user to delete records (they would need to know the unguessable path)
"presence": {
".read": "false",
".write": "false",
"$auth_id": {
"connections": {
"$uuid": {
".write": "(newData.exists() && $auth_id === auth.uid) || !newData.exists()"
}
}
}
}
Finally, setup a trigger function on the RTDB to read the .ref('/presence/{authid}') location and push the user's presence to another user accessible location (I'm pushing it to my Firestore DB). Also, if the user is changing from "online" to "offline" update a lastOnline timestamp to the current time.
This seems like the best solution given my requirements of having reliable and secure presence system. I hope this helps others.
It is an old question but it made me think about a possible solution and came with the following...
use onDisconnect.setValue/removeValue as long as you have control/awareness over the application
use onDisconnect.cancel and delete to data before logging out
I took #FrankvanPuffelen code and modified it but didn't tested it so....
//getFirebaseDatabase().goOnline();
//DatabaseReference.goOnline();
// Since I can connect from multiple devices, we store each connection instance separately
// any time that connectionsRef's value is null (i.e. has no children) I am offline
final FirebaseDatabase database = getFirebaseDatabase();
final DatabaseReference myConnectionsRef = database.getReference("/auth/" + getFirebaseAuth().getUid() + "/connections");
// Stores the timestamp of my last disconnect (the last time I was seen online)
final DatabaseReference lastOnlineRef = database.getReference("/auth/" + getFirebaseAuth().getUid() + "/lastOnline");
connectedRef = database.getReference(".info/connected");
presenceChangeListener = connectedRef.addValueEventListener(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot snapshot) {
boolean connected = snapshot.getValue(Boolean.class);
if (connected) {
// simple solution to reuse the old unique key-name otherwise current solution is like performing new registration of a new client over and over on the same client. we should use the old unique key-name until logout is performed
String keyName = SharedPrefUtil.INSTANCE.getFirebaseConnectionKeyName(context);
DatabaseReference con;
if (TextUtils.isEmpty(keyName)) {
con = myConnectionsRef.push();
SharedPrefUtil.INSTANCE.setFirebaseConnectionKeyName(context.getApplicationContext(), con.getKey());
}else{
con = myConnectionsRef.child(keyName);
}
// When this device disconnects, remove it
con.onDisconnect().removeValue()
.addOnSuccessListener(new OnSuccessListener<Void>() {
#Override
public void onSuccess(Void aVoid) {
// Add this device to my connections list
// this value could contain info about the device or a timestamp too
con.setValue("ANDROID");
}
})
.addOnFailureListener(new OnFailureListener() {
#Override
public void onFailure(#NonNull Exception e) {
Log.d(TAG, "### Failed to set onDisconnect ###");
e.printStackTrace();
}
});
// When I disconnect, update the last time I was seen online
lastOnlineRef.onDisconnect().setValue(ServerValue.TIMESTAMP);
}
}
#Override
public void onCancelled(DatabaseError error) {
Log.w(TAG, "Listener was cancelled at .info/connected");
}
});
in the logout method we need to cancel the disconnect
String keyName = SharedPrefUtil.INSTANCE.getFirebaseConnectionKeyName(context);
if (!TextUtils.isEmpty(keyName)) {
final FirebaseDatabase database = getFirebaseDatabase();
final DatabaseReference myConnectionsRef = database.getReference("/auth/" + getFirebaseAuth().getUid() + "/connections/" + keyName);
// Stores the timestamp of my last disconnect (the last time I was seen online)
final DatabaseReference lastOnlineRef = database.getReference("/auth/" + getFirebaseAuth().getUid() + "/lastOnline");
// This client/user doesn't need the disconnect functionality
myConnectionsRef.onDisconnect().cancel();
// now we are on our own so we need to remove the key-name from the rmdb
myConnectionsRef.setValue(null);
// remove the key-name from the preferences so we will create a new one in the next login session
SharedPrefUtil.INSTANCE.removeFirebaseConnectionKeyName(context);
// we will not forget to disconnect last time updates
lastOnlineRef.onDisconnect().cancel()
}
AuthUI.getInstance().signOut(this)
I didn't tested it and it will not run as it is missing the SharedPrefUtil implementation
Its a very weird issue with Firebase. I am calling setValue() on a Firebase node and then expecting OnComplete callback function to be called, which is never being called on a particular internet connection. Other firebase queries are also not working on that particular WiFi,
individualUserNode.setValue(user, new DatabaseReference.CompletionListener() {
#Override
public void onComplete(DatabaseError databaseError, DatabaseReference databaseReference) {
if (databaseError == null) {
EventBus.getDefault().post(new MyEvents.UserSaved(true));
} else {
EventBus.getDefault().post(new MyEvents.UserSaved(false));
}
}
});
That's expected. The listener only fires once the server acknowledges the request:
This interface is used as a method of being notified when an operation
has been acknowledged by the Database servers and can be considered
complete
I'm totally new to Firebase and need to know how to check if my writing task was successful because if I don't, the MainActivity starts and messes up my Register progress.
This checks if Username is already taken and registers the user if it isn't:
Query usernamequery = myRef.orderByChild("Username").equalTo(Username);
usernamequery.addListenerForSingleValueEvent(new ValueEventListener() {
#Override
public void onDataChange(DataSnapshot snapshot) {
if (snapshot.exists()) {
// TODO: handle the case where the data already exists
editText.setError("Username taken!");
return;
}
else {
// TODO: handle the case where the data does not yet exist
myRef.child("Users").child(Username).child("Userid").setValue(user.getUid());
myRef.child("Users").child(Username).child("Username").setValue(Username);
startActivity(maps);
finish();
}
}
#Override
public void onCancelled(DatabaseError databaseError) {
Toast.makeText(Username.this, "Error", Toast.LENGTH_LONG).show();
}
});
But I want the Intent to Main Activity (maps) only be fired when
myRef.child("Users").child(Username).child("Userid").setValue(user.getUid());
and the other one is finished with its task and is successful.
What can I do?
To know when a write operation has completed on the server, add a completion listener:
myRef.child("Users").child(Username).child("Userid").setValue(user.getUid(), new DatabaseReference.CompletionListener() {
void onComplete(DatabaseError error, DatabaseReference ref) {
System.err.println("Value was set. Error = "+error);
// Or: throw error.toException();
}
});
If there was an error, details will be in the error operation. If the write operation was completed without problems, the error will be null.
If you want to write to multiple locations with a single operation, you'll want to look at the update() method
The correct overload for setValue() is documented here.
mFirebaseRemoteConfig.fetch(0)
.addOnCompleteListener(new OnCompleteListener<Void>() {
#Override
public void onComplete(#NonNull Task<Void> task) {
if (task.isSuccessful()) {
System.out.println("Fetch Succeeded");
// Once the config is successfully fetched it must be
// values are returned.
mFirebaseRemoteConfig.activateFetched();
} else {
System.out.println("Fetch failed");
}
}
});
I added this to get the remote config from the server. I was able to get the values a couple of times. I updated the remote config conditions after that and now fetch doesnt return anything. Tried a lot of approaches including moving the call after on onResume and calling it from a separate thread. Updating to 9.2.1 also didnt worked for me
What else can be done to get the config?
I am using the new Firebase console. I am trying to save an object to the database but its not getting saved. Following is the code.
DatabaseReference mFirebaseRef = FirebaseDatabase.getInstance().getReference();
mFirebaseRef.push().setValue(object, new DatabaseReference.CompletionListener() {
#Override
public void onComplete(DatabaseError databaseError, DatabaseReference reference) {
if (databaseError != null) {
Log.e(TAG, "Failed to write message", databaseError.toException());
}
}
});
the 'object' is created properly. There is no error I am getting and I have checked in debugging that the onComplete method is not getting triggered.
Security Rule is also true for write.
Note that DatabaseReference.CompletionListener fires "when an operation has been acknowledged by the Database servers". Is it possible you did not have a network connection at the time you ran your test? I copied your code and ran it successfully on a phone with object defined like this:
Object object = new String("Test");
I then enabled airplane mode, re-ran the code and observed the behavior you describe. The completion listener did not fire until I disabled airplane mode and a network connection was established.
Example code for checking the status of your network connection is provided in this documentation.
use the below code:
mFirebaseRef.push().setValue(object).addOnCompleteListener(new OnCompleteListener<Void>()
{
#Override
public void onComplete(#NonNull Task<Void> task) {
if(task.isSuccessful()){
// write code for successfull operation
}
}
});
}
.push will generate a random key on which your data will stored if you do not use .push it will overwrite on previous stored data.