The documentation of the Jaeger API is very superficial and I am reaching out to understand better the purpose of these methods.
I wrote some simple code:
def MyMethod(name: String): Unit = {
val span = tracer.buildSpan("MyMethod").start()
val str = create_string("hugo", span)
print_string(str, span)
span.finish()
}
def create_string(name: String, parentSpan: Span): String = {
val span = tracer.buildSpan("create string method").asChildOf(parentSpan).start()
val string: String = s"Hello, ${helloTo}!"
span.finish()
string
}
def print_string(name: String, parentSpan: Span): Unit = {
val span = tracer.buildSpan("printHello").asChildOf(parentSpan).start()
println(name)
span.finish()
}
I noticed the variable span has a span context with WithFlag and BaggageItems methods, but I have no clue what is this for.
val spanContext: JaegerSpanContext = span.context().withBaggageItem("item1", "item2")
Anyone with experience using these methods? Could you give a small example?
I have API that post and get dates:
this is the data class:
data class PlannerGet(
val date: String,
val endTime: String,
val id: Int,
val location: String,
val note: String,
val startTime: String,
val title: String
)
and i am using this library for the calendar:
https://github.com/VarunBarad/Highlightable-Calendar-View
now in the fragment i was able to highlight certain days like this:
HighlightableCalendarView.dayDecorators = listOf(
DayDecorator(
Calendar.getInstance().apply {
set(Calendar.DAY_OF_MONTH, 4)
},
Color.parseColor("#ffffff"),
Color.parseColor("#ff0000")
),
)
but i want to highlight the days from API
i tried to make it like this:
HighlightableCalendarView.dayDecorators = listOf(
DayDecorator(
Calendar.getInstance().apply {
set(PlannerGet.date)
},
Color.parseColor("#ffffff"),
Color.parseColor("#ff0000")
),
)
but i am having a problem with "set" it show "None of the following functions can be called with the arguments supplied."
i tried to add "toInt()" and still the same problem.
what is the correct way to achieve this?
This is because the params which you are passing do not match the required params.
Calendar.getInstance().apply {
set(Calendar.DAY_OF_MONTH, 4)
}
The set functions accept the int field, int value but you are passing the params as the string
PlannerGet.date
The function set
public void set(int field, int value) {
throw new RuntimeException("Stub!");
}
If you want the date to be passed from the API dates please convert the string dates to java Date object.
SOLUTION:
if (response?.body().toString() == "[]") {
}
else if (response.isSuccessful) {
response.body()?.forEach {
getplanner.add(it)
Log.e("gggg gggg",getplanner.toString())
Log.e("gggg ddddd",getplanner[0].date)
}
val list = arrayListOf<DayDecorator>()
for (dsds in getplanner) {
list.add( DayDecorator(
Calendar.getInstance().apply {
// getplanner[0].date
val input_date = dsds.date
val format1 = SimpleDateFormat("yyyy-MM-dd")
var dt1: Date? = null
dt1 = format1.parse(input_date)
val format2: DateFormat = SimpleDateFormat("dd")
val strMonth: String = format2.format(dt1)
val month = strMonth.toInt()
Log.e("dateinplanner", "" + month)
set(Calendar.DAY_OF_MONTH, month)
},
Color.parseColor("#ffffff"),
Color.parseColor("#1AB7B8")
))
}
HighlightableCalendarView.dayDecorators = list
I am following this tutorial by Raywenderlich on paging-library-for-android-with-kotlin on how to use android paging library. This is one of the easiest tutorials on the net and I have followed it thoroughly. However, I would like to make some changes so that I can intelligently switch between online data and offline data.
That is, I have old some posts in my database. Initially I have internet connection. So I load latest data from internet, then insert it into my database. Finally, I show this latest data in my recyclerView / PagedListAdapter.
If for some reason, there is no internet connection after sometime, I should show the old posts from database.
How can I do this?
My attempts:
This is my code on github repository.
Here, I tried to create a factory pattern. It checks if initially I have internet, the factory returns pagedList from online dataSource. ELse, the factory returns pagedList from offline dataSource.
But this doesnot intelligently switch between the 2 states.
I tried some random codes such as creating a boundary callback. But I am not sure how to make the necessary changes.
I am not adding codes here (at least for now) to keep it short and precise.
Can anyone help me?
Edit:
To be specific, I am loading paged data primarily from network. If there is a network error, I don't want to show the user an error. Instead I load paged data from cache / database and continuously show it to my user as long as possible. If the network is back,switch back to network paged data. (that's what instagram / facebook does I think). What is the appropriate way to implement this? See my code / attemp in the answer.
Okay, so after trying out some codes for 2 days, this is what I came up with. However, I really don't know if this is a good pratice or not. So I am open to any acceptable answers.
Explanation:
Since I have multiple data sources(network and database), I created ProfilePostDataSource: PageKeyedDataSource<Pair<Long, Long>, ProfilePost> here the key is a pair, the 1st one for network pagination, the 2nd one is for database pagination.
I used kotlin's Coroutine to write some asynchronous codes in a simple if-else like manner. So we can write it in a psudo-code like this:
Database db;
Retrofit retrofit;
inside loadInitial/loadBefore / loadAfter:
currNetworkKey = params.key.first;
currDBKey = params.key.second;
ArrayList<Model> pagedList;
coroutine{
ArrayList<Model> onlineList = retrofit.getNetworkData(currNetworkKey); // <-- we primarily load data from network
if(onlineList != null) {
pagedList = onlineList;
db.insertAll(onlineList); // <-- update our cache
}else{
ArrayList<Model> offlineList = db.getOfflineData(currDBKey); // <-- incase the network fails, we load cache from database
if(offlineList !=null){
pagedList = offlineList;
}
}
if(pagedList != null or empty) {
nextNetworkKey = // update it accordingly
nextDBKey = // update it accordingly
Pair<int, int> nextKey = new Pair(nextNetworkKey, nextDBKey);
pagingLibraryCallBack.onResult(pagedList, nextKey); // <-- submit the data to paging library via callback. this updates your adapter, recyclerview etc...
}
}
So in apps like facebook, instagram etc, we see them primarily loading data from network. But if the network is down, they show you a cashed data. We can intelligently make this switch like this code.
Here is a relevant code snippet, the PageKeyedDataSource written in kotlin:
ProfilePostDataSource.kt
/** #brief: <Key, Value> = <Integer, ProfilePost>. The key = pageKey used in api. Value = single item data type in the recyclerView
*
* We have a situation. We need a 2nd id to fetch profilePosts from database.
* Change of plan: <Key, Value> = < Pair<Int, Int>, ProfilePost>. here the
*
* key.first = pageKey used in api. <-- Warning: Dont switch these 2!
* Key.second = db last items id
* used as out db page key
*
* Value = single item data type in the recyclerView
*
* */
class ProfilePostDataSource: PageKeyedDataSource<Pair<Long, Long>, ProfilePost> {
companion object{
val TAG: String = ProfilePostDataSource::class.java.simpleName;
val INVALID_KEY: Long = -1;
}
private val context: Context;
private val userId: Int;
private val liveLoaderState: MutableLiveData<NetworkState>;
private val profilePostLocalData: ProfilePostLocalDataProvider;
public constructor(context: Context, userId: Int, profilePostLocalData: ProfilePostLocalDataProvider, liveLoaderState: MutableLiveData<NetworkState>) {
this.context = context;
this.userId = userId;
this.profilePostLocalData = profilePostLocalData;
this.liveLoaderState = liveLoaderState;
}
override fun loadInitial(params: LoadInitialParams<Pair<Long, Long>>, pagingLibraryCallBack: LoadInitialCallback<Pair<Long, Long>, ProfilePost>) {
val initialNetworkKey: Long = 1L; // suffix = networkKey cz later we'll add dbKey
var nextNetworkKey = initialNetworkKey + 1;
val prevNetworkKey = null; // cz we wont be using it in this case
val initialDbKey: Long = Long.MAX_VALUE; // dont think I need it
var nextDBKey: Long = 0L;
GlobalScope.launch(Dispatchers.IO) {
val pagedProfilePosts: ArrayList<ProfilePost> = ArrayList(); // cz kotlin emptyList() sometimes gives a weird error. So use arraylist and be happy
val authorization : String = AuthManager.getInstance(context).authenticationToken;
try{
setLoading();
val res: Response<ProfileServerResponse> = getAPIService().getFeedProfile(
sessionToken = authorization, id = userId, withProfile = false, withPosts = true, page = initialNetworkKey.toInt()
);
if(res.isSuccessful && res.body()!=null) {
pagedProfilePosts.addAll(res.body()!!.posts);
}
}catch (x: Exception) {
Log.e(TAG, "Exception -> "+x.message);
}
if(pagedProfilePosts.isNotEmpty()) {
// this means network call is successfull
Log.e(TAG, "key -> "+initialNetworkKey+" size -> "+pagedProfilePosts.size+" "+pagedProfilePosts.toString());
nextDBKey = pagedProfilePosts.last().id;
val nextKey: Pair<Long, Long> = Pair(nextNetworkKey, nextDBKey);
pagingLibraryCallBack.onResult(pagedProfilePosts, prevNetworkKey, nextKey);
// <-- this is paging library's callback to a pipeline that updates data which inturn updates the recyclerView. There is a line: adapter.submitPost(list) in FeedProfileFragment. this callback is related to that line...
profilePostLocalData.insertProfilePosts(pagedProfilePosts, userId); // insert the latest data in db
}else{
// fetch data from cache
val cachedList: List<ProfilePost> = profilePostLocalData.getProfilePosts(userId);
pagedProfilePosts.addAll(cachedList);
if(pagedProfilePosts.size>0) {
nextDBKey = cachedList.last().id;
}else{
nextDBKey = INVALID_KEY;
}
nextNetworkKey = INVALID_KEY; // <-- probably there is a network error / sth like that. So no need to execute further network call. thus pass invalid key
val nextKey: Pair<Long, Long> = Pair(nextNetworkKey, nextDBKey);
pagingLibraryCallBack.onResult(pagedProfilePosts, prevNetworkKey, nextKey);
}
setLoaded();
}
}
override fun loadBefore(params: LoadParams<Pair<Long, Long>>, pagingLibraryCallBack: LoadCallback<Pair<Long, Long>, ProfilePost>) {} // we dont need it in feedProflie
override fun loadAfter(params: LoadParams<Pair<Long, Long>>, pagingLibraryCallBack: LoadCallback<Pair<Long, Long>, ProfilePost>) {
val currentNetworkKey: Long = params.key.first;
var nextNetworkKey = currentNetworkKey; // assuming invalid key
if(nextNetworkKey!= INVALID_KEY) {
nextNetworkKey = currentNetworkKey + 1;
}
val currentDBKey: Long = params.key.second;
var nextDBKey: Long = 0;
if(currentDBKey!= INVALID_KEY || currentNetworkKey!= INVALID_KEY) {
GlobalScope.launch(Dispatchers.IO) {
val pagedProfilePosts: ArrayList<ProfilePost> = ArrayList(); // cz kotlin emptyList() sometimes gives a weird error. So use arraylist and be happy
val authorization : String = AuthManager.getInstance(context).authenticationToken;
try{
setLoading();
if(currentNetworkKey!= INVALID_KEY) {
val res: Response<ProfileServerResponse> = getAPIService().getFeedProfile(
sessionToken = authorization, id = userId, withProfile = false, withPosts = true, page = currentNetworkKey.toInt()
);
if(res.isSuccessful && res.body()!=null) {
pagedProfilePosts.addAll(res.body()!!.posts);
}
}
}catch (x: Exception) {
Log.e(TAG, "Exception -> "+x.message);
}
if(pagedProfilePosts.isNotEmpty()) {
// this means network call is successfull
Log.e(TAG, "key -> "+currentNetworkKey+" size -> "+pagedProfilePosts.size+" "+pagedProfilePosts.toString());
nextDBKey = pagedProfilePosts.last().id;
val nextKey: Pair<Long, Long> = Pair(nextNetworkKey, nextDBKey);
pagingLibraryCallBack.onResult(pagedProfilePosts, nextKey);
setLoaded();
// <-- this is paging library's callback to a pipeline that updates data which inturn updates the recyclerView. There is a line: adapter.submitPost(list) in FeedProfileFragment. this callback is related to that line...
profilePostLocalData.insertProfilePosts(pagedProfilePosts, userId); // insert the latest data in db
}else{
// fetch data from cache
// val cachedList: List<ProfilePost> = profilePostLocalData.getProfilePosts(userId);
val cachedList: List<ProfilePost> = profilePostLocalData.getPagedProfilePosts(userId, nextDBKey, 20);
pagedProfilePosts.addAll(cachedList);
if(pagedProfilePosts.size>0) {
nextDBKey = cachedList.last().id;
}else{
nextDBKey = INVALID_KEY;
}
nextNetworkKey = INVALID_KEY; // <-- probably there is a network error / sth like that. So no need to execute further network call. thus pass invalid key
val nextKey: Pair<Long, Long> = Pair(nextNetworkKey, nextDBKey);
pagingLibraryCallBack.onResult(pagedProfilePosts, nextKey);
setLoaded();
}
}
}
}
private suspend fun setLoading() {
withContext(Dispatchers.Main) {
liveLoaderState.value = NetworkState.LOADING;
}
}
private suspend fun setLoaded() {
withContext(Dispatchers.Main) {
liveLoaderState.value = NetworkState.LOADED;
}
}
}
Thank you for reading this far. If you have a better solution, feel free to let me know. I'm open to any working solutions.
How can I aggregate by Hour in the mongodb-async-driver (http://www.allanbank.com/mongodb-async-driver/usage.html)
I have an ISODate-Field in my Collection.
[
{ name = "a", date = ISODate(...)},
{ name = "b", date = ISODate(...)},
...
]
I want to display a graph of how may documents occur per hour.
in the MongoDB-Console. I would do something like this:
db.mycollection.aggregate([{$group : {_id : {day:{ $hour : "$date"}}, count: { $sum: 1 }}}])
but I get stuck at the driver-api:
import static com.allanbank.mongodb.builder.AggregationGroupField.set;
import static com.allanbank.mongodb.builder.AggregationGroupId.id;
Aggregate.Builder builder = new Aggregate.Builder();
builder.group(id().add(???), set("pop").sum("pop"))
You need to make use of the Expressions class. Make use of the group method that takes a Builder and the AggregationGroupField array as input.
public Aggregate.Builder group(AggregationGroupId.Builder id,
AggregationGroupField... aggregations)
Build the hour Expression and pass it as the id.
Builder hour = new Builder();
hour.add(Expressions.set("day",Expressions.hour(Expressions.field("date"))));
Aggregate.Builder builder = Aggregate.builder();
builder.group(
hour,
AggregationGroupField.set("pop").sum("pop")
);
MongoIterator<Document> result = col.aggregate(builder);
while(result.hasNext())
{
System.out.println(result.next());
};
I have tested three variation of the same code and I got it to work just fine. I want to know why the different behavior.
So I have this working code, which converts a long time stamp to a string of the ECMA date standard format :
lazy val dateFormat = new java.text.SimpleDateFormat("yyyy-MM-DD'T'HH:mm:ss.sssZ")
implicit def dateToECMAFormat(time: Long) = new {
def asECMADateString: String = {
dateFormat.format(new java.util.Date(time))
}
}
Other variation that works :
implicit def dateToECMAFormat(time: Long) = new {
val dateFormat = new java.text.SimpleDateFormat("yyyy-MM-DD'T'HH:mm:ss.sssZ")
def asECMADateString: String = {
dateFormat.format(new java.util.Date(time))
}
}
But I do not want the SimpleDateFormat to be re instanciated all the time . So I prefere the first one. But now the real mystery :
val dateFormat = new java.text.SimpleDateFormat("yyyy-MM-DD'T'HH:mm:ss.sssZ")
implicit def dateToECMAFormat(time: Long) = new {
def asECMADateString: String = {
dateFormat.format(new java.util.Date(time))
}
}
This last piece of code compiles but throws an exception at run-time; I did not manage to get the stack trace from play framework. I just know my controller in play framework 2.1 return with a 500 (Internal Server Error) without any more information (the other controllers work though and the main services are still up).
In each case the call looks like this: 100000L.asECMADateString
Can someone explain to me the different behaviors and why does the last one does not work? I though I had a good grasp of the difference between val, lazy val and def, but now I feel like I am missing something.
UPDATE
The code is called in object like this :
object MyController extends Controller{
implicit val myExecutionContext = getMyExecutionContext
lazy val dateFormat = new java.text.SimpleDateFormat("yyyy-MM-DD'T'HH:mm:ss.sssZ")
implicit def dateToECMAFormat(time: Long) = new {
def asECMADateString: String = {
dateFormat.format(new java.util.Date(time))
}
}
def myAction = Action {
Async {
future {
blocking{
//here get some result from a db
val result = getStuffFromDb
result.someLong.asECMADateString
}
} map { result => Ok(result) } recover { /* return some error code */ }
}
}
}
It is your basic playframework Async action call.
Since the difference between the 1st and 3rd examples are the lazy val, I'd be looking at exactly where your call (100000L.asECMADateString) is being made. lazy val helps correct some "order of initialization" issues with mix-ins, for example: see this recent issue to see if it's similar to yours.