[tracker-miners/sam/ci-4-processes] ci: Run a maximum of 4 tests simultaneously

[Sam Thursfield <sthursfield src gnome org>]

commit 9cdf6ada3dbedc53fe8a362cafdac84a6495fd85
Author: Sam Thursfield <sam afuera me uk>
Date:   Sun Sep 15 17:59:53 2019 +0200

    ci: Run a maximum of 4 tests simultaneously
    
    This is an attempt to deal with the random test failures that sometimes
    appear.
    
    The CI runners on gitlab.gnome.org report 32 CPU cores, so Meson tries
    to run 32 tests at a time. I guess because our tests are mostly IO
    bound this actually makes things slower and causes random failures.

 .gitlab-ci.yml | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index b46da694b..b84742693 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -27,7 +27,10 @@ test-fedora-latest:
       # screenful of junk each time unless we strip these.
       unset $(env|grep -o '^CI_[^=]*')
 
-      su tracker -c 'cd build; dbus-run-session -- env LANG=en_US.UTF8 meson test --suite tracker-miners 
--print-errorlogs'
+      # We limit `meson test` to 4 parallel test processes. The default is to
+      # have one test process per CPU, but our tests are mostly IO bound
+      # and we get timeouts and failures if we try to run 32 of them at once.
+      su tracker -c 'cd build; dbus-run-session -- env LANG=en_US.UTF8 meson test --suite tracker-miners 
--num-processes=4 --print-errorlogs'
 
   artifacts:
     when: always