Greatly improve performance with remote HTTP tiles.

Leverage back-pressure, simplified the core. Update Readme
p-lr · Nov 12, 2019 · c423e02 · c423e02
1 parent f69f6d6
commit c423e02
Show file tree

Hide file tree

Showing 8 changed files with 60 additions and 58 deletions.
diff --git a/Readme.md b/Readme.md
@@ -1,4 +1,4 @@
-[ ![Download](https://api.bintray.com/packages/peterlaurence/maven/mapview/images/download.svg?version=1.0.3) ](https://bintray.com/peterlaurence/maven/mapview/1.0.3/link)
+[ ![Download](https://api.bintray.com/packages/peterlaurence/maven/mapview/images/download.svg?version=1.0.4) ](https://bintray.com/peterlaurence/maven/mapview/1.0.4/link)
 
 # MapView
 
@@ -29,7 +29,7 @@ This project holds the source code of this library, but also a demo app (which i
 
 Add this to your module's build.gradle
 ```groovy
-implementation 'com.peterlaurence:mapview:1.0.3'
+implementation 'com.peterlaurence:mapview:1.0.4'
 ```
 
 ## Origin and motivation

diff --git a/build.gradle b/build.gradle
@@ -8,7 +8,7 @@ buildscript {
 
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.5.1'
+        classpath 'com.android.tools.build:gradle:3.5.2'
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
         classpath "org.jetbrains.kotlin:kotlin-serialization:$kotlin_version"
         // NOTE: Do not place your application dependencies here; they belong

diff --git a/doc/technical/mapview/MapView.drawio b/doc/technical/mapview/MapView.drawio
@@ -1 +1 @@
-<mxfile modified="2019-06-23T07:06:38.443Z" host="www.draw.io" agent="Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/75.0.3770.90 Safari/537.36" etag="iE7Z7vuxXtPxiJQQoQrZ" version="10.8.0" type="device"><diagram name="Page-1" id="b33cb84f-bf7a-9ccf-f142-242d16432e5d">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</diagram></mxfile>
+<mxfile modified="2019-11-12T12:32:01.670Z" host="www.draw.io" agent="Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.87 Safari/537.36" etag="y3SiWZxfgyiBVglI6z8O" version="12.2.4" type="device" pages="1"><diagram name="Page-1" id="b33cb84f-bf7a-9ccf-f142-242d16432e5d">7V1bc5u6Fv41fqwHXRGPufbsPbvndKY9u6eP2GCbKTHemCROf/2RMMIgybYggEnTdKYJwgizvnXX0mKCbh52H1N/s/qUBGE8gU6wm6DbCYSAEsR/iZGX/YiHyX5gmUZB8aHDwJfoZ1gMOsXoYxSE29oHsySJs2hTH5wn63U4z2pjfpomz/WPLZK4fteNvwy1gS9zP5ajU3IY/xYF2aoYB9Q7nPhXGC1Xxc0ZpPsTM3/+Y5kmj+vijhOIFvnP/vSDL+cqHnW78oPkuTKE7iboJk2SbP/Xw+4mjAV1JeHkddmL/LYTdL3KHmJ+APif+en7IxcDm4v5w6XhOqve7th8j982zz8hu/f/ePnvP+vvX+E1W3yA+1me/PhR3gTSmM93vUj4tNXb038eE3niwzbngyv+AUA2u8NJ/tdS/P7kb/6Owmc5Gf9W+/n2Z7Uny0EIg+LJnldRFn7Z+HNx9pmzbf3BF1Ec3yRxkubXosAP2WLOx7dZmvwIK2fonIWzhZFUBXGfwjQLd5WhgnQfw+QhzNIX/pHirMsKMAsxAfL4ucJyEvBVhdtoMeYXfL4spz5gxf8o4GoAHeoJuq9RHN746yd/W0Vwlh7A6wHTDhBiCkLIITpCeEiEsAEhhUjhOrgSSpAfzWN/u43mdbpwcqQv/+MHDldzxeH36rlb8fROefQij3ZRVrmMH32vnDlcJA7kNapckZAF2CRXDM4QpeUZqXRhPuKnmXyidbIO5dh9JGhXfNOgODqJ/DZ5TOfhCfKywtr46TLMzgtKGNQMic5HFT4hBjaRY2kY+1n0VDdKJt4p7vA5iXJxlEwMFEVSahI5x/7Bi8uqCl2diaozIWWmPWm0mXJmLh+8PX+TRvxdcIOZud3euXv+mD6V2qi5CdFZvT3jIkvGheNm3HLipozruvWZqDrREb7lnOS/VD62ER/YHv/GHqzfR2r6gxjsZ+xUKFhPZlkY48J7P2J/dUN91CI7w1hkr05/4lzaZ/I0cIS3s9UoxR8wq5PDj6PlWlhpTo6QK4drQYaIhyFXxYmHKAjE5Ua61n0hAVsRSAHcyvB2AI6nWA+MdHBM3hLsCxuou0vXUfbgbz7zcNKCu3XM0pALlT/LPyA4vtAX/NPkekJuBaqPWbItkKiAHIeLzABxlggstxzaaL38Kg5uP2ADnl2goyhbF+roeIOiQxsZe6Mzq9tQlXJt3d3m9ryNC1Fzbg9PWPVvX+fRAmzpGbBReQaeas9BW48WUWcKKOCsjfi3YzKCkxEd8qYMMdfxqOti4CFk5TZ0Zdmhe14EGplYlfsDf7sqjUQHSgQAouh4gwEmRjXCYF96RPeP8oRDEsfhPONi+rrUUPeaGCBcJyKyzfwg0hMNgcnHVMh2hlB1Pi0Tm46mpQ3REs1/6tSGuGI+0z0NFO1bxH9dGEcG6vqGuDoiBkBUtdQdIDaZnjiONttjDmK/jjdFBgKZWFZNRbShEPSJ74AggCEGaDHj1IHvnF0l9Ut2hRdmV4vEzS8NCBkbIBaexS8NiLRoEhD30oDoiYL3BYg7MkCksXq3gKg25OKAgHcOiGpDLg7Iby+rDohnCNMGBcS0QP+eAFEl5NKAYIsoTZQDbewfvixrKrLMk2phkDGb4DA8rWe1iJyqShdUljUNkt3FFtq8WWqrgxqd0yBa8yHVqWsKfXujLbLI1lgnB04vJGnUde+u6J3TC3Wr9ARDsqqFWn2D5NyVrDk1lC0NSmBTdqC2gj0vKXJYpEae5zgivayuW1cyu+oS3o8wXYfGpT27CjNrmP3tZl96uoh2Am0V97qyWrB5OJ/b8MOMEUzM/NA8zwyV+jXs6YzAesrZmct7LIzCBewlpgZPe2B7KRNG47eXpDEjXtpekjek4BtQ91LqnHS5NjEeco7HXhLziuYXbnKEvlv569zIKSTvr8LIUZAxWbj9Lgd0vUz9IOL3M53rwqYBx1GjHazD5XlDwmVK7TYs0AOb3d5NMZTOVzG3c2PGwQqdwA1UuDHWg36TE9Mb3LTryPa4kmsjZCo6nZeAEKU2Bxvk74h97w0S3SJdnSn9aIMLoshDgRkXxgy074LcqhNPPGTF/wj2RWw9mvuWpDzyEo+aF1a+faITpdwBO+zCRLcoluw9csKyKqWsvvZ0yXcG1cWdF9D1FTWVAFozIY9SKXSRSzEkjBDpyVa9HDDl3o9LICPA5ZYSDkn5N5SDbED7qnxPESUO8Lhzhh3KZOZtGOpaVAu8QeqWxRlTirDHHI8xbs6Anh+4JO2lezMuVWvweodVte6bWdApAfxFVK2sA3gLyqAB7cci7m8oOdics0euai0yibVdts32A5kwOOwHmlR2A1U2B53dIOzlUUe5v2eKXDhpsAm+XAs6vvYjLv8cphEnssjV3J5cDxrJjh2AiDd1OL9Bmv8N6+aLs5kLGSAEIc6MMsHZeDcPBmzqAEwoAg51PVKvKSSAfwU+TAHgLI2Zsluioz3AAKmbUIvazl43Abt61P07J3zEWcJMj9YHzQi7erT+G6wDWGoCnxr8rUHhssgidGyGmm/QLg1XuXPVznAdxezsllCZ1x2LhcmVvwMIBIzreG5H6lxEnCmknosBQC7X/4ryb7BhFE9dl1LP21uz+sYwgri/BB3EGPeqCMC9mRjFfhblAf2aGJukw6nuK6fZXunP4jhEYWQIz/lg4kh1jKRjBmpOmdyC3V1fIquN2odGRK8TPToy5444wrPyXOpiLoXUUZITXPQciPhvxjmXqLtUrUWPcNGjhDtv0PXE3RQBx95U3oFbeFmcPdBWbWaR/nilcLQIFFrahDKYqQcylJ2UGlNY0q1cnG1nMDq5oO700FuAYkUuuMEiuNJfoK1cAC5f8hZExvDVoKdyEgwrFnoEXy4G6u0mG+2819geehTe3+uCAoFH75FJoJL+3NhyGfZEDaFryqW4x5nsVU4sO7EseypT+8shQaR1uhgSevRXIvHvd4WEYX/OsEiYAruGlVnM1DptOp22r8Uybo+q4lcM9Rn9dwE3VTpKCTdQLwUatOMXs1mVflVPqVoU80GEMajue1F4ttfkqTBGNq4svDIZ1fTSgbK9H2bbKFWqwrH4aw6qs6zbuq+Uo5RlUbXDYFepAKB8ZQaGaDmppwL2nfP42H3MZaeplquy3TFGHbu+A17dvXcdvQfOoJWo0rwazFsQPRmtm8DpQ0FoYd7yvoSaebPZnRVS8e/4tduNv5ZjdzuR816KSmbJRtR/EKitZ9tN5SJOhup1prlmYfYchvzQefAj8StbpaEfCPquxf/P0tWaJ5wlsoibUniTg5St+LFQRrtNHM2j3Py/rOerNFlHP7laSdZnvsaR/qh8OCd3SwdA1DjmP7polOO9LgTUPcLynkVXyr/yzpW3HfUIBUBJqLrI1FPdsPOKdtD7bDNb/yf86P1JvCsQvfiQRVc/O+6pjomS1iwXnVt5A7UEDTyd1TzlDVgkk9p7A9Q2rSl3Do3FHYBKKTtRK9TtVw2UxtC4pwbUoGy4WOYdunUHjCLSrC27WUTM3VH34tEo5Xgs6QnPZT2bi0RNotrLB7Ftzz6uJqzAwVqA19ZbPta3u2vxUL8yZgOIRweNjI+1KRYG5TUGpN9VsfYiYf2mjbGLhNeZSGA7keiKaS1qHmx1+oWYbCw8AbU9igS1XerRdnupM/XMFX29a+KTL6Kyv/yXPAR7Ky+AosobDQZ9AZQRn9eWaFTsDBz89U9t3onT3AU7xddv7AU56mttUNt0JTvy3pqu/S+Xmu/T0v3ih4d3Ie4/fnjlJLr7Pw==</diagram></mxfile>
diff --git a/doc/technical/mapview/MapView.jpg b/doc/technical/mapview/MapView.jpg
diff --git a/mapview/build.gradle b/mapview/build.gradle
@@ -4,7 +4,7 @@ apply plugin: 'kotlin-android'
 apply plugin: 'kotlin-android-extensions'
 apply plugin: 'kotlinx-serialization'
 
-def version = "1.0.3"
+def version = "1.0.4"
 
 androidExtensions {
     experimental = true
@@ -56,9 +56,9 @@ dependencies {
     testImplementation 'junit:junit:4.12'
     testImplementation 'org.robolectric:robolectric:4.3'
     implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
-    implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-core:1.3.1'
-    implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-android:1.3.1'
-    implementation "org.jetbrains.kotlinx:kotlinx-serialization-runtime:0.11.0"
+    implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-core:1.3.2'
+    implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-android:1.3.2'
+    implementation "org.jetbrains.kotlinx:kotlinx-serialization-runtime:0.13.0"
 }
 repositories {
     mavenCentral()

diff --git a/mapview/src/main/java/com/peterlaurence/mapview/core/TileCollector.kt b/mapview/src/main/java/com/peterlaurence/mapview/core/TileCollector.kt
@@ -2,12 +2,14 @@ package com.peterlaurence.mapview.core
 
 import android.graphics.Bitmap
 import android.graphics.BitmapFactory
-import kotlinx.coroutines.*
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.channels.Channel
 import kotlinx.coroutines.channels.ReceiveChannel
 import kotlinx.coroutines.channels.SendChannel
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.single
+import kotlinx.coroutines.launch
 import kotlinx.coroutines.selects.select
 
 
@@ -24,16 +26,17 @@ import kotlinx.coroutines.selects.select
  *              ---------------- [*********] <----------------------------------------------------- | | worker | |   |
  *             |                               |                                                    |  --------  |   |
  *             ↓                               |                                                    |  ________  |   |
- *  _____________________                      |                                  tileStatus        | | worker | |   |
+ *  _____________________                      |                                  tileSpecs         | | worker | |   |
  * | TileCanvasViewModel |                     |    _____________________  <---- [**********] <---- |  --------  |   |
  *  ---------------------  ----> [*********] ----> | tileCollectorKernel |                          |  ________  |   |
  *                                tileSpecs    |    ---------------------  ----> [**********] ----> | | worker | |   |
- *                                             |                                  tileStatus        |  --------  |   |
+ *                                             |                                  tileSpecs         |  --------  |   |
  *                                             |                                                    |____________|   |
  *                                             |                                                      worker pool    |
  *                                             |                                                                     |
  *                                              ---------------------------------------------------------------------
  * ```
+ * This architecture is an example of Communicating Sequential Processes (CSP).
  *
  * @author peterLaurence on 22/06/19
  */
@@ -42,38 +45,34 @@ class TileCollector(private val workerCount: Int) {
     /**
      * Sets up the tile collector machinery. The architecture is inspired from
      * [Kotlin Conf 2018](https://www.youtube.com/watch?v=a3agLJQ6vt8).
-     * @param [tileSpecs] channel of [TileSpec], which capacity should be [Channel.CONFLATED].
+     * It support back-pressure, and avoids deadlock in CSP taking into account recommendations of
+     * this [article](https://medium.com/@elizarov/deadlocks-in-non-hierarchical-csp-e5910d137cc),
+     * which is from the same author.
+     *
+     * @param [tileSpecs] channel of [TileSpec], which capacity should be [Channel.RENDEZVOUS].
      * @param [tilesOutput] channel of [Tile], which should be set as [Channel.RENDEZVOUS].
      */
-    fun CoroutineScope.collectTiles(tileSpecs: ReceiveChannel<List<TileSpec>>,
+    fun CoroutineScope.collectTiles(tileSpecs: ReceiveChannel<TileSpec>,
                                     tilesOutput: SendChannel<Tile>,
                                     tileStreamProvider: TileStreamProvider,
                                     bitmapFlow: Flow<Bitmap>) {
-        val tilesToDownload = Channel<TileStatus>(capacity = Channel.RENDEZVOUS)
-        val tilesDownloadedFromWorker = Channel<TileStatus>(capacity = Channel.UNLIMITED)
+        val tilesToDownload = Channel<TileSpec>(capacity = Channel.RENDEZVOUS)
+        val tilesDownloadedFromWorker = Channel<TileSpec>(capacity = 1)
 
         repeat(workerCount) { worker(tilesToDownload, tilesDownloadedFromWorker, tilesOutput, tileStreamProvider, bitmapFlow) }
         tileCollectorKernel(tileSpecs, tilesToDownload, tilesDownloadedFromWorker)
     }
 
-    private fun CoroutineScope.worker(tilesToDownload: ReceiveChannel<TileStatus>,
-                                      tilesDownloaded: SendChannel<TileStatus>,
+    private fun CoroutineScope.worker(tilesToDownload: ReceiveChannel<TileSpec>,
+                                      tilesDownloaded: SendChannel<TileSpec>,
                                       tilesOutput: SendChannel<Tile>,
                                       tileStreamProvider: TileStreamProvider,
                                       bitmapFlow: Flow<Bitmap>) = launch(Dispatchers.IO) {
 
         val bitmapLoadingOptions = BitmapFactory.Options()
         bitmapLoadingOptions.inPreferredConfig = Bitmap.Config.RGB_565
 
-        for (tileStatus in tilesToDownload) {
-            /* If it was cancelled, do nothing and send back the TileSpec as is */
-            if (tileStatus.cancelled) {
-                tilesDownloaded.send(tileStatus)
-                continue
-            }
-
-            val spec = tileStatus.spec
-
+        for (spec in tilesToDownload) {
             val i = tileStreamProvider.getTileStream(spec.row, spec.col, spec.zoom)
 
             if (spec.subSample > 0) {
@@ -97,44 +96,33 @@ class TileCollector(private val workerCount: Int) {
             } catch (e: Exception) {
                 // maybe retry
             } finally {
-                tilesDownloaded.send(tileStatus)
+                tilesDownloaded.send(spec)
                 i?.close()
             }
         }
     }
 
-    private fun CoroutineScope.tileCollectorKernel(tileSpecs: ReceiveChannel<List<TileSpec>>,
-                                                   tilesToDownload: SendChannel<TileStatus>,
-                                                   tilesDownloadedFromWorker: ReceiveChannel<TileStatus>) = launch(Dispatchers.Default) {
+    private fun CoroutineScope.tileCollectorKernel(tileSpecs: ReceiveChannel<TileSpec>,
+                                                   tilesToDownload: SendChannel<TileSpec>,
+                                                   tilesDownloadedFromWorker: ReceiveChannel<TileSpec>) = launch(Dispatchers.Default) {
 
-        val tilesBeingProcessed = mutableListOf<TileStatus>()
+        val tilesBeingProcessed = mutableListOf<TileSpec>()
 
         while (true) {
             select<Unit> {
+                tilesDownloadedFromWorker.onReceive {
+                    tilesBeingProcessed.remove(it)
+                }
                 tileSpecs.onReceive {
-                    for (loc in it) {
-                        if (!tilesBeingProcessed.any { status -> status.spec == loc }) {
-                            /* Add it to the list of locations being processed */
-                            val status = TileStatus(loc)
-                            tilesBeingProcessed.add(status)
+                    if (!tilesBeingProcessed.any { spec -> spec == it }) {
+                        /* Add it to the list of locations being processed */
+                        tilesBeingProcessed.add(it)
 
-                            /* Now download the tile */
-                            tilesToDownload.send(status)
-                        }
+                        /* Now download the tile */
+                        tilesToDownload.send(it)
                     }
-                    for (status in tilesBeingProcessed) {
-                        if (!it.contains(status.spec)) {
-                            status.cancelled = true
-                        }
-                    }
-                }
-
-                tilesDownloadedFromWorker.onReceive {
-                    tilesBeingProcessed.remove(it)
                 }
             }
         }
     }
-
-    data class TileStatus(val spec: TileSpec, @Volatile var cancelled: Boolean = false)
 }
Original file line number	Diff line number	Diff line change
		@@ -1 +1 @@
		<mxfile modified="2019-06-23T07:06:38.443Z" host="www.draw.io" agent="Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/75.0.3770.90 Safari/537.36" etag="iE7Z7vuxXtPxiJQQoQrZ" version="10.8.0" type="device"><diagram name="Page-1" id="b33cb84f-bf7a-9ccf-f142-242d16432e5d">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</diagram></mxfile>
		<mxfile modified="2019-11-12T12:32:01.670Z" host="www.draw.io" agent="Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/78.0.3904.87 Safari/537.36" etag="y3SiWZxfgyiBVglI6z8O" version="12.2.4" type="device" pages="1"><diagram name="Page-1" id="b33cb84f-bf7a-9ccf-f142-242d16432e5d">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</diagram></mxfile>