Introduction

• What is location service?
• Introduction of Mozilla Location Service
• Help MLS by stumbling

1-1

What is location service?

• It is how your device knows where it is relative to the things around it, like WiFi access points and cell towers.
• It is crucial in two conditions
  • There is no GPS signal.
  • You don't have a GPS chip. (e.g. laptop)
• Right now, location services are not open services.

1-2

Mozilla Location Service

• Built by Mozilla.
• Give an open and trustworthy location service.
• The database relies on the community to collect data.
  • The process of gathering data is called "stumbling".

1-3

Help MLS by stumbling

• On Android, you can install "Mozilla Stumbler" app and start collecting data.
• On FxOS, we need today's work to do the stumbling.

1-4

Right Person for MLS :)

1-5

Team: Services Engineering TE (Toby Elliott)

Cost Center: 3210 - Services and Engineering Operations

Stumbling

• All data in the MLS database are contributed by user
  • The process of gathering data is called stumbling

> 15 KB

MLS Server

2-1

Upload

Stumbling

> 15 KB

MLS Server

2-2

Upload

Stumbling

Collect Data

> 15 KB

MLS Server

2-3

Upload

Stumbling

Write Stumble

> 15 KB

MLS Server

2-4

Upload

Stumbling

Upload Stumble

> 15 KB

MLS Server

3-1

Upload

Stumbling

Collect Data

Collect Data

• We hook our function[1] in the callback[2] which will be called when the device gets a new location from GPS.
• Ref :
  • [1] MozStumble
  • [2] GonkGPSGeolocationProvider::LocationCallback

3-2

3-3

Is there finished stumble?

Is the new location valid?

No

Yes

Exit

Try to upload finished stumble

Collect data

MozStumble

3-4

Yes

No

MozStumble

• Validate new location
  • New locations need to be 30 meters and 3 seconds apart.
• Collect data
  • Dispatch a runnable for scanning to main thread.

3-5

Runnable for scanning

• Purpose:
  • Trigger a cell-tower scan.
  • Trigger a WiFi access point scan.
• Implementation:
  • For cell-tower scan
    • Use "GetCellInfoList" with callback.
    • Set the number of expected Cell-Info responses.
  • For WiFi AP scan
    • Use "GetWifiScanResults" with callback.

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Cell-Tower scan result callback

WiFi AP scan result callback

Prepare the string. (Location Info/Cell Network/WiFi AP)

Trigger a runnable to write stumble

3-7

> 15 KB

MLS Server

4-1

Upload

Stumbling

Write Stumble

Is there finished stumble?

Does finished stumble ready to upload?

Yes

No

Exit

Write stumble

Upload stumble

Write Stumble

4-2

No

Yes

Write Stumble

• The status of finished stumble:
  • ExistsAndReadyToUpload:                                    Finished stumble exists and is older than 1 day.
  • Exists:                                                                       Finished stumble exists and is newer than 1 day.

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Write Stumble

• Write stumble
  • The maximum size of stumble is 15 KB.
  • Rename the file from stumbles.json.gz to stumbles.done.json.gz when it is bigger than 15KB.
• Only one file exists at the same time.
  • stumbles.json.gz is for writing.
  • stumbles.done.json.gz is for uploading.

4-4

> 15 KB

MLS Server

4-5

Upload

Stumbling

stumbles.json.gz

> 15 KB

MLS Server

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Upload

Stumbling

stumbles.done.json.gz

> 15 KB

MLS Server

4-7

Upload

Stumbling

stumbles.done.json.gz

> 15 KB

MLS Server

5-1

Upload

Stumbling

Upload Stumble

Is request successful?

Yes

Delete the finished stumble.

Do a XMLHttpRequest for uploading.

Upload Stumble

5-2

No

Keep the finished stumble. Retry to upload it next time.

Wait for the result

Upload Stumble

• How to upload stumble?
  • Do a "Geosubmit" request, which is using a POST request to the URL:

    https://location.services.mozilla.com/v2/geosubmit?key=<API_KEY>

  • https://mozilla.github.io/ichnaea/api/geosubmit2.html

5-3

> 15 KB

MLS Server

5-4

Upload

Stumbling

Stumble Format

6-1

{"items":[

]}

location Information

cell-tower Information

WiFi AP Information

},

{

{

},

{

},

location information

cell-tower information

WiFi AP information

In the end

• Main Bug : 1154435
  • Enabling stumbling on B2G.
  • A special thanks to Garvan Keeley, who involved to this feature deeply and gave me lots of help.
• Planning
  • https://etherpad.mozilla.org/W0PvfCsh3I
• Implementation
  • gecko/dom/system/gonk/mozstumbler
• related bugs : 1199395, 1200304, 1200310

7-1

Future Work

• A better event to trigger the upload. Ideally we would preferentially upload when connected to WiFi.

  • Currently we trigger the upload by a new location

    • Maximum upload currently: 15 KB per day.

    • Maximum attempt of upload is 20 times a day.

• Solve the problem on QCT BSP
  • QC replaces "GonkGPSGeolocationProvider.cpp" with their implementation. They collect the data by themselves.

• Show the contribution of stumbling to users

• Follow-up bug: 1199093

7-2

Thanks.

Stumbler on B2G: alchen@mozilla.com

MLS server: hschlichting@mozilla.com

Q & A

8-2

Privacy

8-3