001 /*
002 * Copyright (C) 2012 eXo Platform SAS.
003 *
004 * This is free software; you can redistribute it and/or modify it
005 * under the terms of the GNU Lesser General Public License as
006 * published by the Free Software Foundation; either version 2.1 of
007 * the License, or (at your option) any later version.
008 *
009 * This software is distributed in the hope that it will be useful,
010 * but WITHOUT ANY WARRANTY; without even the implied warranty of
011 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
012 * Lesser General Public License for more details.
013 *
014 * You should have received a copy of the GNU Lesser General Public
015 * License along with this software; if not, write to the Free
016 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
017 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
018 */
019
020 package org.crsh.shell.impl.async;
021
022 import org.crsh.shell.ShellProcess;
023 import org.crsh.shell.ShellProcessContext;
024 import org.crsh.shell.ShellResponse;
025 import org.crsh.text.Chunk;
026
027 import java.io.IOException;
028 import java.util.concurrent.Callable;
029
030 public class AsyncProcess implements ShellProcess {
031
032
033 /** . */
034 private final String request;
035
036 /** . */
037 private ShellProcessContext caller;
038
039 /** . */
040 private ShellProcess callee;
041
042 /** . */
043 private AsyncShell shell;
044
045 /** . */
046 private Status status;
047
048 /** . */
049 private final Object lock;
050
051 AsyncProcess(AsyncShell shell, String request) {
052 this.shell = shell;
053 this.request = request;
054 this.callee = null;
055 this.status = Status.CONSTRUCTED;
056 this.lock = new Object();
057 }
058
059 public Status getStatus() {
060 return status;
061 }
062
063 /** . */
064 private final ShellProcessContext context = new ShellProcessContext() {
065 public int getWidth() {
066 return caller.getWidth();
067 }
068
069 public int getHeight() {
070 return caller.getHeight();
071 }
072
073 public String getProperty(String name) {
074 return caller.getProperty(name);
075 }
076
077 public String readLine(String msg, boolean echo) {
078 return caller.readLine(msg, echo);
079 }
080
081 public void provide(Chunk element) throws IOException {
082 caller.provide(element);
083 }
084
085 public void flush() throws IOException {
086 caller.flush();
087 }
088
089 public void end(ShellResponse response) {
090 // Always leave the status in terminated status if the method succeeds
091 // Cancelled -> Terminated
092 // Evaluating -> Terminated
093 // Terminated -> Terminated
094 synchronized (lock) {
095 switch (status) {
096 case CONSTRUCTED:
097 case QUEUED:
098 throw new AssertionError("Should not happen");
099 case CANCELED:
100 // We substitute the response
101 response = ShellResponse.cancelled();
102 status = Status.TERMINATED;
103 break;
104 case EVALUATING:
105 status = Status.TERMINATED;
106 break;
107 case TERMINATED:
108 throw new IllegalStateException("Cannot end a process already terminated");
109 }
110 }
111
112 //
113 caller.end(response);
114 }
115 };
116
117 public void execute(ShellProcessContext processContext) {
118
119 // Constructed -> Queued
120 synchronized (lock) {
121 if (status != Status.CONSTRUCTED) {
122 throw new IllegalStateException("State was " + status);
123 }
124
125 // Update state
126 status = Status.QUEUED;
127 callee = shell.shell.createProcess(request);
128 caller = processContext;
129 }
130
131 // Create the task
132 Callable<AsyncProcess> task = new Callable<AsyncProcess>() {
133 public AsyncProcess call() throws Exception {
134 try {
135 // Cancelled -> Cancelled
136 // Queued -> Evaluating
137 ShellResponse response;
138 synchronized (lock) {
139 switch (status) {
140 case CANCELED:
141 // Do nothing it was canceled in the mean time
142 response = ShellResponse.cancelled();
143 break;
144 case QUEUED:
145 // Ok we are going to run it
146 status = Status.EVALUATING;
147 response = null;
148 break;
149 default:
150 // Just in case but this can only be called by the queue
151 throw new AssertionError();
152 }
153 }
154
155 // Execute the process if we are in evalating state
156 if (response == null) {
157 // Here the status could already be in status cancelled
158 // it is a race condition, execution still happens
159 // but the callback of the callee to the end method will make the process
160 // terminate and use a cancel response
161 try {
162 callee.execute(context);
163 response = ShellResponse.ok();
164 }
165 catch (Throwable t) {
166 response = ShellResponse.internalError("Unexpected throwable when executing process", t);
167 }
168 }
169
170 // Make the callback
171 // Calling terminated twice will have no effect
172 try {
173 context.end(response);
174 }
175 catch (Throwable t) {
176 // Log it
177 }
178
179 // We return this but we don't really care for now
180 return AsyncProcess.this;
181 }
182 finally {
183 synchronized (shell.lock) {
184 shell.processes.remove(AsyncProcess.this);
185 }
186 }
187 }
188 };
189
190 //
191 synchronized (shell.lock) {
192 if (!shell.closed) {
193 shell.executor.submit(task);
194 shell.processes.add(this);
195 } else {
196 boolean invokeEnd;
197 synchronized (lock) {
198 invokeEnd = status != Status.TERMINATED;
199 status = Status.TERMINATED;
200 }
201 if (invokeEnd) {
202 caller.end(ShellResponse.cancelled());
203 }
204 }
205 }
206 }
207
208 public void cancel() {
209 // Construcuted -> ISE
210 // Evaluating -> Canceled
211 // Queued -> Canceled
212 // Cancelled -> Cancelled
213 // Terminated -> Terminated
214 boolean cancel;
215 synchronized (lock) {
216 switch (status) {
217 case CONSTRUCTED:
218 throw new IllegalStateException("Cannot call cancel on process that was not scheduled for execution yet");
219 case QUEUED:
220 status = Status.CANCELED;
221 cancel = false;
222 break;
223 case EVALUATING:
224 status = Status.CANCELED;
225 cancel = true;
226 break;
227 default:
228 cancel = false;
229 break;
230 }
231 }
232
233 //
234 if (cancel) {
235 callee.cancel();
236 }
237 }
238 }