1/* 2 * Copyright (C) 2009 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17package com.android.common; 18 19import android.content.SharedPreferences; 20import android.net.http.AndroidHttpClient; 21import android.text.format.Time; 22 23import java.util.Map; 24import java.util.TreeSet; 25 26/** 27 * Tracks the success/failure history of a particular network operation in 28 * persistent storage and computes retry strategy accordingly. Handles 29 * exponential backoff, periodic rescheduling, event-driven triggering, 30 * retry-after moratorium intervals, etc. based on caller-specified parameters. 31 * 32 * <p>This class does not directly perform or invoke any operations, 33 * it only keeps track of the schedule. Somebody else needs to call 34 * {@link #getNextTimeMillis()} as appropriate and do the actual work. 35 */ 36public class OperationScheduler { 37 /** Tunable parameter options for {@link #getNextTimeMillis}. */ 38 public static class Options { 39 /** Wait this long after every error before retrying. */ 40 public long backoffFixedMillis = 0; 41 42 /** Wait this long times the number of consecutive errors so far before retrying. */ 43 public long backoffIncrementalMillis = 5000; 44 45 /** Maximum duration of moratorium to honor. Mostly an issue for clock rollbacks. */ 46 public long maxMoratoriumMillis = 24 * 3600 * 1000; 47 48 /** Minimum duration after success to wait before allowing another trigger. */ 49 public long minTriggerMillis = 0; 50 51 /** Automatically trigger this long after the last success. */ 52 public long periodicIntervalMillis = 0; 53 54 @Override 55 public String toString() { 56 return String.format( 57 "OperationScheduler.Options[backoff=%.1f+%.1f max=%.1f min=%.1f period=%.1f]", 58 backoffFixedMillis / 1000.0, backoffIncrementalMillis / 1000.0, 59 maxMoratoriumMillis / 1000.0, minTriggerMillis / 1000.0, 60 periodicIntervalMillis / 1000.0); 61 } 62 } 63 64 private static final String PREFIX = "OperationScheduler_"; 65 private final SharedPreferences mStorage; 66 67 /** 68 * Initialize the scheduler state. 69 * @param storage to use for recording the state of operations across restarts/reboots 70 */ 71 public OperationScheduler(SharedPreferences storage) { 72 mStorage = storage; 73 } 74 75 /** 76 * Parse scheduler options supplied in this string form: 77 * 78 * <pre> 79 * backoff=(fixed)+(incremental) max=(maxmoratorium) min=(mintrigger) [period=](interval) 80 * </pre> 81 * 82 * All values are times in (possibly fractional) <em>seconds</em> (not milliseconds). 83 * Omitted settings are left at whatever existing default value was passed in. 84 * 85 * <p> 86 * The default options: <code>backoff=0+5 max=86400 min=0 period=0</code><br> 87 * Fractions are OK: <code>backoff=+2.5 period=10.0</code><br> 88 * The "period=" can be omitted: <code>3600</code><br> 89 * 90 * @param spec describing some or all scheduler options. 91 * @param options to update with parsed values. 92 * @return the options passed in (for convenience) 93 * @throws IllegalArgumentException if the syntax is invalid 94 */ 95 public static Options parseOptions(String spec, Options options) 96 throws IllegalArgumentException { 97 for (String param : spec.split(" +")) { 98 if (param.length() == 0) continue; 99 if (param.startsWith("backoff=")) { 100 int plus = param.indexOf('+', 8); 101 if (plus < 0) { 102 options.backoffFixedMillis = parseSeconds(param.substring(8)); 103 } else { 104 if (plus > 8) { 105 options.backoffFixedMillis = parseSeconds(param.substring(8, plus)); 106 } 107 options.backoffIncrementalMillis = parseSeconds(param.substring(plus + 1)); 108 } 109 } else if (param.startsWith("max=")) { 110 options.maxMoratoriumMillis = parseSeconds(param.substring(4)); 111 } else if (param.startsWith("min=")) { 112 options.minTriggerMillis = parseSeconds(param.substring(4)); 113 } else if (param.startsWith("period=")) { 114 options.periodicIntervalMillis = parseSeconds(param.substring(7)); 115 } else { 116 options.periodicIntervalMillis = parseSeconds(param); 117 } 118 } 119 return options; 120 } 121 122 private static long parseSeconds(String param) throws NumberFormatException { 123 return (long) (Float.parseFloat(param) * 1000); 124 } 125 126 /** 127 * Compute the time of the next operation. Does not modify any state 128 * (unless the clock rolls backwards, in which case timers are reset). 129 * 130 * @param options to use for this computation. 131 * @return the wall clock time ({@link System#currentTimeMillis()}) when the 132 * next operation should be attempted -- immediately, if the return value is 133 * before the current time. 134 */ 135 public long getNextTimeMillis(Options options) { 136 boolean enabledState = mStorage.getBoolean(PREFIX + "enabledState", true); 137 if (!enabledState) return Long.MAX_VALUE; 138 139 boolean permanentError = mStorage.getBoolean(PREFIX + "permanentError", false); 140 if (permanentError) return Long.MAX_VALUE; 141 142 // We do quite a bit of limiting to prevent a clock rollback from totally 143 // hosing the scheduler. Times which are supposed to be in the past are 144 // clipped to the current time so we don't languish forever. 145 146 int errorCount = mStorage.getInt(PREFIX + "errorCount", 0); 147 long now = currentTimeMillis(); 148 long lastSuccessTimeMillis = getTimeBefore(PREFIX + "lastSuccessTimeMillis", now); 149 long lastErrorTimeMillis = getTimeBefore(PREFIX + "lastErrorTimeMillis", now); 150 long triggerTimeMillis = mStorage.getLong(PREFIX + "triggerTimeMillis", Long.MAX_VALUE); 151 long moratoriumSetMillis = getTimeBefore(PREFIX + "moratoriumSetTimeMillis", now); 152 long moratoriumTimeMillis = getTimeBefore(PREFIX + "moratoriumTimeMillis", 153 moratoriumSetMillis + options.maxMoratoriumMillis); 154 155 long time = triggerTimeMillis; 156 if (options.periodicIntervalMillis > 0) { 157 time = Math.min(time, lastSuccessTimeMillis + options.periodicIntervalMillis); 158 } 159 160 time = Math.max(time, moratoriumTimeMillis); 161 time = Math.max(time, lastSuccessTimeMillis + options.minTriggerMillis); 162 if (errorCount > 0) { 163 time = Math.max(time, lastErrorTimeMillis + options.backoffFixedMillis + 164 options.backoffIncrementalMillis * errorCount); 165 } 166 return time; 167 } 168 169 /** 170 * Return the last time the operation completed. Does not modify any state. 171 * 172 * @return the wall clock time when {@link #onSuccess()} was last called. 173 */ 174 public long getLastSuccessTimeMillis() { 175 return mStorage.getLong(PREFIX + "lastSuccessTimeMillis", 0); 176 } 177 178 /** 179 * Return the last time the operation was attempted. Does not modify any state. 180 * 181 * @return the wall clock time when {@link #onSuccess()} or {@link 182 * #onTransientError()} was last called. 183 */ 184 public long getLastAttemptTimeMillis() { 185 return Math.max( 186 mStorage.getLong(PREFIX + "lastSuccessTimeMillis", 0), 187 mStorage.getLong(PREFIX + "lastErrorTimeMillis", 0)); 188 } 189 190 /** 191 * Fetch a {@link SharedPreferences} property, but force it to be before 192 * a certain time, updating the value if necessary. This is to recover 193 * gracefully from clock rollbacks which could otherwise strand our timers. 194 * 195 * @param name of SharedPreferences key 196 * @param max time to allow in result 197 * @return current value attached to key (default 0), limited by max 198 */ 199 private long getTimeBefore(String name, long max) { 200 long time = mStorage.getLong(name, 0); 201 if (time > max) mStorage.edit().putLong(name, (time = max)).commit(); 202 return time; 203 } 204 205 /** 206 * Request an operation to be performed at a certain time. The actual 207 * scheduled time may be affected by error backoff logic and defined 208 * minimum intervals. Use {@link Long#MAX_VALUE} to disable triggering. 209 * 210 * @param millis wall clock time ({@link System#currentTimeMillis()}) to 211 * trigger another operation; 0 to trigger immediately 212 */ 213 public void setTriggerTimeMillis(long millis) { 214 mStorage.edit().putLong(PREFIX + "triggerTimeMillis", millis).commit(); 215 } 216 217 /** 218 * Forbid any operations until after a certain (absolute) time. 219 * Limited by {@link #Options.maxMoratoriumMillis}. 220 * 221 * @param millis wall clock time ({@link System#currentTimeMillis()}) 222 * when operations should be allowed again; 0 to remove moratorium 223 */ 224 public void setMoratoriumTimeMillis(long millis) { 225 mStorage.edit() 226 .putLong(PREFIX + "moratoriumTimeMillis", millis) 227 .putLong(PREFIX + "moratoriumSetTimeMillis", currentTimeMillis()) 228 .commit(); 229 } 230 231 /** 232 * Forbid any operations until after a certain time, as specified in 233 * the format used by the HTTP "Retry-After" header. 234 * Limited by {@link #Options.maxMoratoriumMillis}. 235 * 236 * @param retryAfter moratorium time in HTTP format 237 * @return true if a time was successfully parsed 238 */ 239 public boolean setMoratoriumTimeHttp(String retryAfter) { 240 try { 241 long ms = Long.valueOf(retryAfter) * 1000; 242 setMoratoriumTimeMillis(ms + currentTimeMillis()); 243 return true; 244 } catch (NumberFormatException nfe) { 245 try { 246 setMoratoriumTimeMillis(AndroidHttpClient.parseDate(retryAfter)); 247 return true; 248 } catch (IllegalArgumentException iae) { 249 return false; 250 } 251 } 252 } 253 254 /** 255 * Enable or disable all operations. When disabled, all calls to 256 * {@link #getNextTimeMillis()} return {@link Long#MAX_VALUE}. 257 * Commonly used when data network availability goes up and down. 258 * 259 * @param enabled if operations can be performed 260 */ 261 public void setEnabledState(boolean enabled) { 262 mStorage.edit().putBoolean(PREFIX + "enabledState", enabled).commit(); 263 } 264 265 /** 266 * Report successful completion of an operation. Resets all error 267 * counters, clears any trigger directives, and records the success. 268 */ 269 public void onSuccess() { 270 resetTransientError(); 271 resetPermanentError(); 272 mStorage.edit() 273 .remove(PREFIX + "errorCount") 274 .remove(PREFIX + "lastErrorTimeMillis") 275 .remove(PREFIX + "permanentError") 276 .remove(PREFIX + "triggerTimeMillis") 277 .putLong(PREFIX + "lastSuccessTimeMillis", currentTimeMillis()).commit(); 278 } 279 280 /** 281 * Report a transient error (usually a network failure). Increments 282 * the error count and records the time of the latest error for backoff 283 * purposes. 284 */ 285 public void onTransientError() { 286 mStorage.edit().putLong(PREFIX + "lastErrorTimeMillis", currentTimeMillis()).commit(); 287 mStorage.edit().putInt(PREFIX + "errorCount", 288 mStorage.getInt(PREFIX + "errorCount", 0) + 1).commit(); 289 } 290 291 /** 292 * Reset all transient error counts, allowing the next operation to proceed 293 * immediately without backoff. Commonly used on network state changes, when 294 * partial progress occurs (some data received), and in other circumstances 295 * where there is reason to hope things might start working better. 296 */ 297 public void resetTransientError() { 298 mStorage.edit().remove(PREFIX + "errorCount").commit(); 299 } 300 301 /** 302 * Report a permanent error that will not go away until further notice. 303 * No operation will be scheduled until {@link #resetPermanentError()} 304 * is called. Commonly used for authentication failures (which are reset 305 * when the accounts database is updated). 306 */ 307 public void onPermanentError() { 308 mStorage.edit().putBoolean(PREFIX + "permanentError", true).commit(); 309 } 310 311 /** 312 * Reset any permanent error status set by {@link #onPermanentError}, 313 * allowing operations to be scheduled as normal. 314 */ 315 public void resetPermanentError() { 316 mStorage.edit().remove(PREFIX + "permanentError").commit(); 317 } 318 319 /** 320 * Return a string description of the scheduler state for debugging. 321 */ 322 public String toString() { 323 StringBuilder out = new StringBuilder("[OperationScheduler:"); 324 for (String key : new TreeSet<String>(mStorage.getAll().keySet())) { // Sort keys 325 if (key.startsWith(PREFIX)) { 326 if (key.endsWith("TimeMillis")) { 327 Time time = new Time(); 328 time.set(mStorage.getLong(key, 0)); 329 out.append(" ").append(key.substring(PREFIX.length(), key.length() - 10)); 330 out.append("=").append(time.format("%Y-%m-%d/%H:%M:%S")); 331 } else { 332 out.append(" ").append(key.substring(PREFIX.length())); 333 out.append("=").append(mStorage.getAll().get(key).toString()); 334 } 335 } 336 } 337 return out.append("]").toString(); 338 } 339 340 /** 341 * Gets the current time. Can be overridden for unit testing. 342 * 343 * @return {@link System#currentTimeMillis()} 344 */ 345 protected long currentTimeMillis() { 346 return System.currentTimeMillis(); 347 } 348} 349