• Skip to main content
  • Select language
  • Skip to search
MDN Web Docs
  • Technologies
    • HTML
    • CSS
    • JavaScript
    • Graphics
    • HTTP
    • APIs / DOM
    • WebExtensions
    • MathML
  • References & Guides
    • Learn web development
    • Tutorials
    • References
    • Developer Guides
    • Accessibility
    • Game development
    • ...more docs
Archive of obsolete content
  1. MDN
  2. Archive of obsolete content
  3. Archived Mozilla and build documentation
  4. Monitoring downloads

Monitoring downloads

In This Article
    1. Setting up
    2. Handling download state changes
    3. Displaying the download log
    4. Exercises for the reader
    5. See also

Obsolete
This feature is obsolete. Although it may still work in some browsers, its use is discouraged since it could be removed at any time. Try to avoid using it.

Warning: This interface is deprecated as of Firefox 26. Please use Downloads.jsm instead.

Firefox 3 makes it easier than ever to monitor the status of downloads. Although it was possible to do so in previous versions of Firefox, it was previously only possible for one observer to do so at a time. Firefox 3 introduces new API that allows any number of listeners to observe downloads.

This article demonstrates how to monitor downloads in Firefox 3, using the Download Manager. As a nice bonus, it also demonstrates how to use the Storage API to issue sqlite commands on a database. The result is a window you can open by choosing "Download log" in the Tools menu, which lists all downloads that have been started since you installed the extension. In the list is the name of the file, the start and end times of the download, the download speed, and the status of the download. A tooltip is included that displays the full source URL of the file.

Download the full sample.

Setting up

When the extension loads, it will do some housekeeping chores. In particular, it needs to get an instance of the Download Manager's nsIDownloadManager interface and create the database into which its data will be stored.

 onLoad: function() {
   // initialization code
   this.initialized = true;
   this.strings = document.getElementById("downloadlogger-strings");
   this.dlMgr = Components.classes["@mozilla.org/download-manager;1"]
                          .getService(Components.interfaces.nsIDownloadManager);
   this.dlMgr.addListener(downloadlogger);
   // Open the database, placing its file in the profile directory
   this.dbFile = Components.classes["@mozilla.org/file/directory_service;1"]
                    .getService(Components.interfaces.nsIProperties)
                    .get("ProfD", Components.interfaces.nsIFile);
   this.dbFile.append("downloadlogger.sqlite");
   // Get access to the storage service and open the database
   this.storageService = Components.classes["@mozilla.org/storage/service;1"]
                       .getService(Components.interfaces.mozIStorageService);
   var dbConn = this.storageService.openDatabase(this.dbFile);
   // Now create the table; if it already exists, this fails, but we don't care!
   dbConn.executeSimpleSQL("CREATE TABLE items (source TEXT, size INTEGER," +
                           " startTime INTEGER, endTime INTEGER," +
                           " speed REAL, status INTEGER)");
   dbConn.close();
 },

This is fairly simple stuff. The Download Manager instance is cached into a member variable in the downloadlogger object for reuse later, and its addListener() method is called to start listening for download status updates. The database file is opened, and an sqlite CREATE TABLE command is executed to create the table.

Finally, the database is closed.

Note: The mozIStorageConnection method close() is being added to Firefox 3 alpha 8; in prior versions of Firefox, there is no way to explicitly close the database. Instead, it is closed when the garbage collector disposes of the connection object.

Handling download state changes

Once the code above is run, our onDownloadStateChange() method is called whenever a download's state changes. This is part of the nsIDownloadProgressListener interface.

That code looks like this:

 onDownloadStateChange: function(aState, aDownload) {
   var statement;
   switch(aDownload.state) {
     case Components.interfaces.nsIDownloadManager.DOWNLOAD_DOWNLOADING:
       // Add a new row for the download being started; each row includes the
       // source URI, size, and start time.  The end time and download speed
       // are both set to 0 at first, since we don't know those yet.
       // status is the same status value that came from the download manager.
       var dbConn = this.storageService.openDatabase(this.dbFile);
       statement = dbConn.createStatement("REPLACE INTO items VALUES " +
                                          "(?1, ?2, ?3, 0, 0.0, 0)");
       statement.bindStringParameter(0, aDownload.source.spec);
       statement.bindInt64Parameter(1, aDownload.size);
       statement.bindInt64Parameter(2, aDownload.startTime);
       statement.execute();
       statement.reset();
       dbConn.close();
       break;
     // Record the completion (whether failed or successful) of the download
     case Components.interfaces.nsIDownloadManager.DOWNLOAD_FINISHED:
     case Components.interfaces.nsIDownloadManager.DOWNLOAD_FAILED:
     case Components.interfaces.nsIDownloadManager.DOWNLOAD_CANCELED:
       this.logTransferCompleted(aDownload);
       break;
   }
 },

We're interested in four states. If the download's state, indicated by the aDownload.state field, is Components.interfaces.nsIDownloadManager.DOWNLOAD_DOWNLOADING, the file has begun to download. The aDownload object is an nsIDownload object.

In that case, we create a new row in our database for the new file by opening the database and building a REPLACE INTO sqlite command. The first three rows are set to the values of the source URI, file size, and start time fields from the download object. The remaining rows are set to zeroes since that's not information we have at the moment.

If the download's state indicates that the download is finished, canceled, or failed, we call our logTransferCompleted routine to update the log to indicate that state change. That code looks like this:

 logTransferCompleted: function(aDownload) {
     var endTime = new Date();                // Current time is the end time
     // Issue the REPLACE sqlite command to update the record.  We find a
     // record for the same source URI and start time, then update the end
     // time, size, and speed entries in the record.  By matching on both
     // source URI and start time, we support logging multiple downloads of
     // the same file.
     var dbConn = this.storageService.openDatabase(this.dbFile);
     var statement = dbConn.createStatement("UPDATE items SET size=?1, " + 
         "endTime=?2, speed=?3, status=?4 WHERE source=?5 and startTime=?6");
     statement.bindInt64Parameter(0, aDownload.size);
     statement.bindInt64Parameter(1, endTime.getTime());
     statement.bindDoubleParameter(2, aDownload.speed);
     statement.bindInt32Parameter(3, aDownload.state);
     statement.bindStringParameter(4, aDownload.source.spec);
     statement.bindInt64Parameter(5, aDownload.startTime);
     statement.execute();
     statement.reset();
     dbConn.close();
 },

This simply opens the database and builds and executes a UPDATE sqlite command that finds the download item whose source URI and start time match the download that has completed and updates its information. By looking for a record with both the same URI and start time, we properly support the case where the user downloads the same file multiple times.

Displaying the download log

The download log window's code is encapsulated in an object called downloadlogger_dlwindow. Since this is a simple example, it's a one-shot log window; it doesn't monitor for further changes to the log. It simply displays the state of downloads at the moment the window was opened.

That means all its work can be done in its load event handler, which looks like this:

 onLoad: function() {    
   // Open the database
   this.dbFile = Components.classes["@mozilla.org/file/directory_service;1"]
                    .getService(Components.interfaces.nsIProperties)
                    .get("ProfD", Components.interfaces.nsIFile);
   this.dbFile.append("downloadlogger.sqlite");
   // Get access to the storage service and open the database
   this.storageService = Components.classes["@mozilla.org/storage/service;1"]
                       .getService(Components.interfaces.mozIStorageService);
   var dbConn = this.storageService.openDatabase(this.dbFile);
   var loglist = document.getElementById("loglist");
   var statement = dbConn.createStatement("SELECT * FROM items");   // Get all items in table
   try {
     while (statement.executeStep()) {
       var row = document.createElement('listitem');
       // Add the cells to the row
       var cell = document.createElement('listcell');
       var sourceStr = statement.getString(0);
       row.setAttribute("tooltiptext", sourceStr);
       sourceStr = sourceStr.slice(sourceStr.lastIndexOf("/")+1);
       cell.setAttribute("label", sourceStr);   // Source
       row.appendChild(cell);
       cell = document.createElement('listcell');
       cell.setAttribute("label", (statement.getInt64(1) / 1024).toFixed(1) + "KB");    // Size
       cell.setAttribute("style", "text-align:right");
       row.appendChild(cell);
       var theDate = new Date(statement.getInt64(2) / 1000);        // Start time
       cell = document.createElement('listcell');
       var dateStr = theDate.toLocaleString();
       cell.setAttribute("label", dateStr);
       row.appendChild(cell);
       theDate = new Date(statement.getInt64(3));            // End time
       cell = document.createElement('listcell');
       dateStr = theDate.toLocaleString();
       cell.setAttribute("label", dateStr);
       row.appendChild(cell);
       var speed = statement.getDouble(4) / 1024.0;
       cell = document.createElement('listcell');
       cell.setAttribute("label", speed.toFixed(1) + "KB/sec");
       cell.setAttribute("style", "text-align:right");
       row.appendChild(cell);
       var status = statement.getInt32(5);
       var style = "color:black";
       cell = document.createElement('listcell');
       var statusStr;
       switch(status) {
         case 0:
           statusStr = "Downloading";
           break;
         case 1:
           statusStr = "Complete";
           style = "color:green";
           break;
         case 2:
           statusStr = "Failed";
           style = "color:red";
           break;
         case 3:
           statusStr = "Canceled";
           style = "color:purple";
           break;
         case 4:
           statusStr = "Paused";
           style = "color:blue";
           break;
         case 5:
           statusStr = "Queued";
           style = "color:teal";
           break;
         case 6:
           statusStr = "Blocked";
           style = "color:white background-color:red";
           break;
         case 7:
           statusStr = "Scanning";
           style = "color:silver";
           break;
         default:
           statusStr = "Unknown";
           break;
       }
       cell.setAttribute("label", statusStr);
       cell.setAttribute("style", style);
       row.appendChild(cell);
       loglist.appendChild(row);
     }
   } finally {
     statement.reset();
     dbConn = null;
   }
 }

This code is fairly simple. It starts by opening the sqlite database containing the log information, then creates a SELECT SQL statement to pull all entries from the database.

To iterate over the results, we use a while loop that calls the mozIStorageStatement object's executeStep() method. Each time that method is called, one row of the results is fetched.

After that, the list row object is created, and each entry in the search result is fetched and inserted into the appropriate list cell.

The interesting bits to take away from this:

  • mozIStorageStatement has several data getter routines for fetching search results, including getString(), getDouble(), and getInt64(). These methods take as a parameter the zero-based index number of the column whose value you wish to retrieve.
  • Note that the start time is being divided by 1000 before we create a JavaScript Date object from it. That's to adjust the value from the granularity stored in the database to that expected by JavaScript.
  • To right-justify the numeric columns, we set the appropriate cells' style attribute to text-align:right.

Exercises for the reader

There are some obvious things that could be done to improve this extension. If you're learning to use the Download Manager or Storage APIs, they're things you might look into doing for practice:

  • Add code to update the download log window on the fly, instead of generating a static list when it's first opened.
  • Add additional statistics. What's the average download speed across all downloads? What times of day do you get the best download performance?
  • Add buttons to delete items from the log, or to delete all items that have finished downloading.
  • Add searching.

See also

Storage, nsIDownloadManager, nsIDownload, nsIDownloadProgressListener

Document Tags and Contributors

Tags: 
  • Download Manager
  • Firefox 3
 Contributors to this page: teoli, kmaglione, newacct, Mgjbot, Kohei, Nickolay, Sheppy
 Last updated by: kmaglione, Aug 6, 2013, 1:14:13 PM

  1. .htaccess ( hypertext access )
  2. <input> archive
  3. Add-ons
    1. Add-ons
    2. Firefox addons developer guide
    3. Interaction between privileged and non-privileged pages
    4. Tabbed browser
    5. bookmarks.export()
    6. bookmarks.import()
  4. Adding preferences to an extension
  5. An Interview With Douglas Bowman of Wired News
  6. Apps
    1. Apps
    2. App Development API Reference
    3. Designing Open Web Apps
    4. Graphics and UX
    5. Open web app architecture
    6. Tools and frameworks
    7. Validating web apps with the App Validator
  7. Archived Mozilla and build documentation
    1. Archived Mozilla and build documentation
    2. ActiveX Control for Hosting Netscape Plug-ins in IE
    3. Archived SpiderMonkey docs
    4. Autodial for Windows NT
    5. Automated testing tips and tricks
    6. Automatic Mozilla Configurator
    7. Automatically Handle Failed Asserts in Debug Builds
    8. BlackConnect
    9. Blackwood
    10. Bonsai
    11. Bookmark Keywords
    12. Building TransforMiiX standalone
    13. Chromeless
    14. Creating a Firefox sidebar extension
    15. Creating a Microsummary
    16. Creating a Mozilla Extension
    17. Creating a Release Tag
    18. Creating a Skin for Firefox/Getting Started
    19. Creating a Skin for Mozilla
    20. Creating a Skin for SeaMonkey 2.x
    21. Creating a hybrid CD
    22. Creating regular expressions for a microsummary generator
    23. DTrace
    24. Dehydra
    25. Developing New Mozilla Features
    26. Devmo 1.0 Launch Roadmap
    27. Download Manager improvements in Firefox 3
    28. Download Manager preferences
    29. Drag and Drop
    30. Embedding FAQ
    31. Embedding Mozilla in a Java Application using JavaXPCOM
    32. Error Console
    33. Exception logging in JavaScript
    34. Existing Content
    35. Extension Frequently Asked Questions
    36. Fighting Junk Mail with Netscape 7.1
    37. Firefox Sync
    38. Force RTL
    39. GRE
    40. Gecko Coding Help Wanted
    41. HTTP Class Overview
    42. Hacking wiki
    43. Help Viewer
    44. Helper Apps (and a bit of Save As)
    45. Hidden prefs
    46. How to Write and Land Nanojit Patches
    47. Introducing the Audio API extension
    48. Java in Firefox Extensions
    49. JavaScript crypto
    50. Jetpack
    51. Litmus tests
    52. Makefile.mozextension.2
    53. Microsummary topics
    54. Migrate apps from Internet Explorer to Mozilla
    55. Monitoring downloads
    56. Mozilla Application Framework
    57. Mozilla Crypto FAQ
    58. Mozilla Modules and Module Ownership
    59. Mozprocess
    60. Mozprofile
    61. Mozrunner
    62. Nanojit
    63. New Skin Notes
    64. Persona
    65. Plug-n-Hack
    66. Plugin Architecture
    67. Porting NSPR to Unix Platforms
    68. Priority Content
    69. Prism
    70. Proxy UI
    71. Remote XUL
    72. SXSW 2007 presentations
    73. Space Manager Detailed Design
    74. Space Manager High Level Design
    75. Standalone XPCOM
    76. Stress testing
    77. Structure of an installable bundle
    78. Supporting private browsing mode
    79. Table Cellmap
    80. Table Cellmap - Border Collapse
    81. Table Layout Regression Tests
    82. Table Layout Strategy
    83. Tamarin
    84. The Download Manager schema
    85. The life of an HTML HTTP request
    86. The new nsString class implementation (1999)
    87. TraceVis
    88. Treehydra
    89. URIScheme
    90. URIs and URLs
    91. Using Monotone With Mozilla CVS
    92. Using SVK With Mozilla CVS
    93. Using addresses of stack variables with NSPR threads on win16
    94. Venkman
    95. Video presentations
    96. Why Embed Gecko
    97. XML in Mozilla
    98. XPInstall
    99. XPJS Components Proposal
    100. XRE
    101. XTech 2005 Presentations
    102. XTech 2006 Presentations
    103. XUL Explorer
    104. XULRunner
    105. ant script to assemble an extension
    106. calICalendarView
    107. calICalendarViewController
    108. calIFileType
    109. xbDesignMode.js
  8. Archived open Web documentation
    1. Archived open Web documentation
    2. Browser Detection and Cross Browser Support
    3. Browser Feature Detection
    4. Displaying notifications (deprecated)
    5. E4X
    6. E4X Tutorial
    7. LiveConnect
    8. MSX Emulator (jsMSX)
    9. Old Proxy API
    10. Properly Using CSS and JavaScript in XHTML Documents
    11. Reference
    12. Scope Cheatsheet
    13. Server-Side JavaScript
    14. Sharp variables in JavaScript
    15. Standards-Compliant Authoring Tools
    16. Using JavaScript Generators in Firefox
    17. Window.importDialog()
    18. Writing JavaScript for XHTML
    19. XForms
    20. background-size
    21. forEach
  9. B2G OS
    1. B2G OS
    2. Automated Testing of B2G OS
    3. B2G OS APIs
    4. B2G OS add-ons
    5. B2G OS architecture
    6. B2G OS build prerequisites
    7. B2G OS phone guide
    8. Building B2G OS
    9. Building and installing B2G OS
    10. Building the B2G OS Simulator
    11. Choosing how to run Gaia or B2G
    12. Customization with the .userconfig file
    13. Debugging on Firefox OS
    14. Developer Mode
    15. Developing Firefox OS
    16. Firefox OS Simulator
    17. Firefox OS apps
    18. Firefox OS board guide
    19. Firefox OS developer release notes
    20. Firefox OS security
    21. Firefox OS usage tips
    22. Gaia
    23. Installing B2G OS on a mobile device
    24. Introduction to Firefox OS
    25. Mulet
    26. Open web apps quickstart
    27. Pandaboard
    28. PasscodeHelper Internals
    29. Porting B2G OS
    30. Preparing for your first B2G build
    31. Resources
    32. Running tests on Firefox OS: A guide for developers
    33. The B2G OS platform
    34. Troubleshooting B2G OS
    35. Using the App Manager
    36. Using the B2G emulators
    37. Web Bluetooth API (Firefox OS)
    38. Web Telephony API
    39. Web applications
  10. Beginner tutorials
    1. Beginner tutorials
    2. Creating reusable content with CSS and XBL
    3. Underscores in class and ID Names
    4. XML data
    5. XUL user interfaces
  11. Case Sensitivity in class and id Names
  12. Creating a dynamic status bar extension
  13. Creating a status bar extension
  14. Gecko Compatibility Handbook
  15. Getting the page URL in NPAPI plugin
  16. Index
  17. Inner-browsing extending the browser navigation paradigm
  18. Install.js
  19. JXON
  20. List of Former Mozilla-Based Applications
  21. List of Mozilla-Based Applications
  22. Localizing an extension
  23. MDN
    1. MDN
    2. Content kits
  24. MDN "meta-documentation" archive
    1. MDN "meta-documentation" archive
    2. Article page layout guide
    3. Blog posts to integrate into documentation
    4. Current events
    5. Custom CSS classes for MDN
    6. Design Document
    7. DevEdge
    8. Developer documentation process
    9. Disambiguation
    10. Documentation Wishlist
    11. Documentation planning and tracking
    12. Editing MDN pages
    13. Examples
    14. Existing Content/DOM in Mozilla
    15. External Redirects
    16. Finding the right place to document bugs
    17. Getting started as a new MDN contributor
    18. Landing page layout guide
    19. MDN content on WebPlatform.org
    20. MDN page layout guide
    21. MDN subproject list
    22. Needs Redirect
    23. Page types
    24. RecRoom documentation plan
    25. Remove in-content iframes
    26. Team status board
    27. Trello
    28. Using the Mozilla Developer Center
    29. Welcome to the Mozilla Developer Network
    30. Writing chrome code documentation plan
    31. Writing content
  25. MMgc
  26. Makefile - .mk files
  27. Marketplace
    1. Marketplace
    2. API
    3. Monetization
    4. Options
    5. Publishing
  28. Mozilla release FAQ
  29. Newsgroup summaries
    1. Newsgroup summaries
    2. Format
    3. Mozilla.dev.apps.firefox-2006-09-29
    4. Mozilla.dev.apps.firefox-2006-10-06
    5. mozilla-dev-accessibility
    6. mozilla-dev-apps-calendar
    7. mozilla-dev-apps-firefox
    8. mozilla-dev-apps-thunderbird
    9. mozilla-dev-builds
    10. mozilla-dev-embedding
    11. mozilla-dev-extensions
    12. mozilla-dev-i18n
    13. mozilla-dev-l10n
    14. mozilla-dev-planning
    15. mozilla-dev-platform
    16. mozilla-dev-quality
    17. mozilla-dev-security
    18. mozilla-dev-tech-js-engine
    19. mozilla-dev-tech-layout
    20. mozilla-dev-tech-xpcom
    21. mozilla-dev-tech-xul
    22. mozilla.dev.apps.calendar
    23. mozilla.dev.tech.js-engine
  30. Obsolete: XPCOM-based scripting for NPAPI plugins
  31. Plugins
    1. Plugins
    2. Adobe Flash
    3. External resources for plugin creation
    4. Logging Multi-Process Plugins
    5. Monitoring plugins
    6. Multi-process plugin architecture
    7. NPAPI plugin developer guide
    8. NPAPI plugin reference
    9. Samples and Test Cases
    10. Shipping a plugin as a Toolkit bundle
    11. Supporting private browsing in plugins
    12. The First Install Problem
    13. Writing a plugin for Mac OS X
    14. XEmbed Extension for Mozilla Plugins
  32. SAX
  33. Security
    1. Security
    2. Digital Signatures
    3. Encryption and Decryption
    4. Introduction to Public-Key Cryptography
    5. Introduction to SSL
    6. NSPR Release Engineering Guide
    7. SSL and TLS
  34. Solaris 10 Build Prerequisites
  35. Sunbird Theme Tutorial
  36. Table Reflow Internals
  37. Tamarin Tracing Build Documentation
  38. The Basics of Web Services
  39. Themes
    1. Themes
    2. Building a Theme
    3. Common Firefox theme issues and solutions
    4. Creating a Skin for Firefox
    5. Making sure your theme works with RTL locales
    6. Theme changes in Firefox 2
    7. Theme changes in Firefox 3
    8. Theme changes in Firefox 3.5
    9. Theme changes in Firefox 4
  40. Updating an extension to support multiple Mozilla applications
  41. Using IO Timeout And Interrupt On NT
  42. Using SSH to connect to CVS
  43. Using workers in extensions
  44. WebVR
    1. WebVR
    2. WebVR environment setup
  45. XQuery
  46. XUL Booster
  47. XUL Parser in Python