Threaded collection download with model dependencies causes errors

[nkoenig]

Environment

• OS Version: Ubuntu 18.04
• Source and binary.

Description

There is a race condition with threaded collection download that can cause console errors. The condition occurs when a collection contains multiple models that all depend on the same upstream model. If the -j N command line option is used, where N > 1, with collection download then the downstream models can simultaneously download and unzip the same upstream model. The result are errors like:

[Err] [Zip.cc:161] Error opening: materials/textures/Chainlink_Albedo.jpg
[Err] [Zip.cc:161] Error opening: materials/textures/Chainlink_Transparency.jpg
[Err] [Zip.cc:161] Error opening: materials/textures/Door_Albedo.jpg
[Err] [Zip.cc:161] Error opening: materials/textures/Entrance.jpg
[Err] [Zip.cc:161] Error opening: materials/textures/GroundDirt_Albedo.jpg
[Err] [Zip.cc:161] Error opening: materials/textures/Light_Plastic_Albedo.jpg
[Err] [Zip.cc:161] Error opening: materials/textures/Light_Plastic_Emissive.jpg
[Err] [Zip.cc:161] Error opening: materials/textures/Pipes_Albedo.jpg
[Err] [Zip.cc:161] Error opening: materials/textures/Rails_Albedo.jpg
[Err] [Zip.cc:161] Error opening: materials/textures/RockWall_Albedo.jpg
[Err] [Zip.cc:161] Error opening: materials/textures/RustyMetal_Albedo.jpg
[Err] [Zip.cc:161] Error opening: materials/textures/Wood_Albedo.jpg
[Err] [Zip.cc:161] Error opening: materials/textures/YellowPlastic_Albedo.jpg
[Err] [Zip.cc:161] Error opening: meshes/
[Err] [Zip.cc:161] Error opening: meshes/Edgar_Section_01.DAE
[Err] [Zip.cc:161] Error opening: meshes/Edgar_Section_02.DAE
[Err] [Zip.cc:161] Error opening: meshes/Edgar_Section_03.DAE
[Err] [Zip.cc:161] Error opening: meshes/Edgar_Section_04.DAE
[Err] [Zip.cc:161] Error opening: meshes/Edgar_Section_05.DAE
[Err] [Zip.cc:161] Error opening: meshes/Edgar_Section_06.DAE
[Err] [Zip.cc:161] Error opening: meshes/Edgar_Section_07.DAE
[Err] [Zip.cc:161] Error opening: meshes/Edgar_Section_08.DAE
[Err] [Zip.cc:161] Error opening: meshes/Edgar_Section_09.DAE
[Err] [Zip.cc:161] Error opening: meshes/Edgar_Section_10.DAE
[Err] [Zip.cc:161] Error opening: meshes/Edgar_StartingArea.DAE
[Err] [Zip.cc:161] Error opening: model.config
[Err] [Zip.cc:161] Error opening: model.sdf
[Err] [Zip.cc:161] Error opening: thumbnails/
[Err] [Zip.cc:161] Error opening: thumbnails/1.jpg
[Err] [Zip.cc:161] Error opening: thumbnails/2.jpg
[Err] [Zip.cc:161] Error opening: thumbnails/3.jpg
[Err] [Zip.cc:161] Error opening: thumbnails/4.jpg
[Err] [Zip.cc:161] Error opening: thumbnails/5.jpg
[Err] [Zip.cc:118] Source archive does not exist: /home/maspence/.ignition/fuel/fuel.ignitionrobotics.org/openrobotics/models/edgar mine virtual stix/12/edgar mine virtual stix.zip
[Err] [LocalCache.cc:415] Unable to unzip [/home/maspence/.ignition/fuel/fuel.ignitionrobotics.org/openrobotics/models/edgar mine virtual stix/12/edgar mine virtual stix.zip]

Steps to reproduce

These errors can be seen using ign fuel download -v 4 -j 8 -u "https://fuel.ignitionrobotics.org/openrobotics/collections/SubT Tech Repo".

[mjcarroll]

Closed by #199