ApiUtil: Add cache with per request timeout and per class histogram

1 files changed, 138 insertions, 0 deletions

diff --git a/src/main/kotlin/io/github/moulberry/notenoughupdates/util/ApiCache.kt b/src/main/kotlin/io/github/moulberry/notenoughupdates/util/ApiCache.kt
new file mode 100644
index 00000000..49a79ae9
--- /dev/null
+++ b/src/main/kotlin/io/github/moulberry/notenoughupdates/util/ApiCache.kt
@@ -0,0 +1,138 @@
+/*
+ * Copyright (C) 2023 NotEnoughUpdates contributors
+ *
+ * This file is part of NotEnoughUpdates.
+ *
+ * NotEnoughUpdates is free software: you can redistribute it
+ * and/or modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation, either
+ * version 3 of the License, or (at your option) any later version.
+ *
+ * NotEnoughUpdates is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with NotEnoughUpdates. If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package io.github.moulberry.notenoughupdates.util
+
+import io.github.moulberry.notenoughupdates.NotEnoughUpdates
+import io.github.moulberry.notenoughupdates.options.customtypes.NEUDebugFlag
+import io.github.moulberry.notenoughupdates.util.ApiUtil.Request
+import org.apache.http.NameValuePair
+import java.time.Duration
+import java.util.*
+import java.util.concurrent.CompletableFuture
+import java.util.function.Supplier
+import kotlin.time.Duration.Companion.hours
+import kotlin.time.Duration.Companion.seconds
+import kotlin.time.ExperimentalTime
+import kotlin.time.TimeSource
+import kotlin.time.toKotlinDuration
+
+@OptIn(ExperimentalTime::class)
+
+object ApiCache {
+    data class CacheKey(
+        val baseUrl: String,
+        val requestParameters: List<NameValuePair>,
+        val shouldGunzip: Boolean,
+    )
+
+    data class CacheResult(
+        val future: CompletableFuture<String>,
+        val firedAt: TimeSource.Monotonic.ValueTimeMark,
+    )
+
+    val cachedRequests = mutableMapOf<CacheKey, CacheResult>()
+    val histogramTotalRequests: MutableMap<String, Int> = mutableMapOf()
+    val histogramNonCachedRequests: MutableMap<String, Int> = mutableMapOf()
+    val timeout = 10.seconds
+    val maxCacheAge = 1.hours
+
+    fun log(message: String) {
+        NEUDebugFlag.API_CACHE.log(message)
+    }
+
+    fun traceApiRequest(
+        request: Request,
+        failReason: String?,
+    ) {
+        if (!NotEnoughUpdates.INSTANCE.config.hidden.dev) return
+        val callingClass = Thread.currentThread().stackTrace
+            .find {
+                !it.className.startsWith("java.") &&
+                        !it.className.startsWith("kotlin.") &&
+                        it.className != ApiCache::class.java.name &&
+                        it.className != ApiUtil::class.java.name &&
+                        it.className != Request::class.java.name
+            }
+        val callingClassText = callingClass?.let {
+            "${it.className}.${it.methodName} (${it.fileName}:${it.lineNumber})"
+        } ?: "no calling class found"
+        callingClass?.className?.let {
+            histogramTotalRequests[it] = (histogramTotalRequests[it] ?: 0) + 1
+            if (failReason != null)
+                histogramNonCachedRequests[it] = (histogramNonCachedRequests[it] ?: 0) + 1
+        }
+        if (failReason != null) {
+            log("Executing api request for url ${request.baseUrl} by $callingClassText: $failReason")
+        } else {
+            log("Cache hit for api request for url ${request.baseUrl} by $callingClassText.")
+        }
+
+    }
+
+    fun evictCache() {
+        synchronized(this) {
+            val it = cachedRequests.iterator()
+            while (it.hasNext()) {
+                if (it.next().value.firedAt.elapsedNow() >= maxCacheAge)
+                    it.remove()
+            }
+        }
+    }
+
+    fun cacheRequest(
+        request: Request,
+        cacheKey: CacheKey?,
+        futureSupplier: Supplier<CompletableFuture<String>>,
+        maxAge: Duration?
+    ): CompletableFuture<String> {
+        evictCache()
+        if (cacheKey == null) {
+            traceApiRequest(request, "uncacheable request (probably POST)")
+            return futureSupplier.get()
+        }
+        if (maxAge == null) {
+            traceApiRequest(request, "manually specified as uncacheable")
+            return futureSupplier.get()
+        }
+        fun recache(): CompletableFuture<String> {
+            return futureSupplier.get().also {
+                cachedRequests[cacheKey] = CacheResult(it, TimeSource.Monotonic.markNow())
+            }
+        }
+        synchronized(this) {
+            val cachedRequest = cachedRequests[cacheKey]
+            if (cachedRequest == null) {
+                traceApiRequest(request, "no cache found")
+                return recache()
+            }
+            if (cachedRequest.future.isDone && cachedRequest.firedAt.elapsedNow() > maxAge.toKotlinDuration()) {
+                traceApiRequest(request, "outdated cache")
+                return recache()
+            }
+            if (!cachedRequest.future.isDone && cachedRequest.firedAt.elapsedNow() > timeout) {
+                traceApiRequest(request, "suspiciously slow api response")
+                return recache()
+            }
+            traceApiRequest(request, null)
+            return cachedRequest.future
+        }
+    }
+
+}