Travis: Reduce footprint of unit tests - so hopefully flakiness (#12350)

* ./tests: Remove legacy coverage collection code

The legacy tests/cover.test.bash script was not ./test script
compatible for a long time.

The following method of coverage collection works (also across
packages) and does not make all the test execution slower.

```
COVERDIR=coverage PASSES="build build_cov cov" ./test
go tool cover -html ./coverage/cover.out
```

* CI: Reduce duplicated coverage between different variants on Travis

We used to execute unit tests in 3 different jobs,
every time with --race detection and every time in 3 variants:1,2,4
CPUS.

The proposed change makes each of the jobs use different variant of
CPUS, and only 4-cpu variant is running with --race detection
(as the more-parallel variant is more likely to experience races),

.travis.yml

@@ -20,12 +20,12 @@ env:
     - TARGET=linux-amd64-integration-2-cpu
     - TARGET=linux-amd64-integration-4-cpu
     - TARGET=linux-amd64-functional
-    - TARGET=linux-amd64-unit
+    - TARGET=linux-amd64-unit-4-cpu-race
     - TARGET=all-build
     - TARGET=linux-amd64-grpcproxy
     - TARGET=linux-amd64-coverage
-    - TARGET=linux-amd64-fmt-unit-go-tip
-    - TARGET=linux-386-unit
+    - TARGET=linux-amd64-fmt-unit-go-tip-2-cpu
+    - TARGET=linux-386-unit-1-cpu
 
 matrix:
   fast_finish: true
@@ -35,9 +35,9 @@ matrix:
     - go: 1.14.3
       env: TARGET=linux-amd64-coverage
     - go: tip
-      env: TARGET=linux-amd64-fmt-unit-go-tip
+      env: TARGET=linux-amd64-fmt-unit-go-tip-2-cpu
     - go: 1.14.3
-      env: TARGET=linux-386-unit
+      env: TARGET=linux-386-unit-1-cpu
   exclude:
     - go: tip
       env: TARGET=linux-amd64-fmt
@@ -50,7 +50,7 @@ matrix:
     - go: tip
       env: TARGET=linux-amd64-functional
     - go: tip
-      env: TARGET=linux-amd64-unit
+      env: TARGET=linux-amd64-unit-4-cpu-race
     - go: tip
       env: TARGET=all-build
     - go: tip
@@ -58,9 +58,9 @@ matrix:
     - go: tip
       env: TARGET=linux-amd64-coverage
     - go: 1.14.3
-      env: TARGET=linux-amd64-fmt-unit-go-tip
+      env: TARGET=linux-amd64-fmt-unit-go-tip-2-cpu
     - go: tip
-      env: TARGET=linux-386-unit
+      env: TARGET=linux-386-unit-1-cpu
 
 before_install:
   - if [[ $TRAVIS_GO_VERSION == 1.* ]]; then docker pull gcr.io/etcd-development/etcd-test:go${TRAVIS_GO_VERSION}; fi
@@ -100,10 +100,10 @@ script:
           --volume=`pwd`:/go/src/go.etcd.io/etcd gcr.io/etcd-development/etcd-test:go${TRAVIS_GO_VERSION} \
           /bin/bash -c "GO_BUILD_FLAGS='-v -mod=readonly' ./build && GOARCH=amd64 PASSES='functional' ./test"
         ;;
-      linux-amd64-unit)
+      linux-amd64-unit-4-cpu-race)
         docker run --rm \
           --volume=`pwd`:/go/src/go.etcd.io/etcd gcr.io/etcd-development/etcd-test:go${TRAVIS_GO_VERSION} \
-          /bin/bash -c "GOARCH=amd64 PASSES='unit' ./test -p=2"
+          /bin/bash -c "GOARCH=amd64 PASSES='unit' RACE='true' CPU='4' ./test -p=2"
         ;;
       all-build)
         docker run --rm \
@@ -124,12 +124,12 @@ script:
       linux-amd64-coverage)
         sudo HOST_TMP_DIR=/tmp TEST_OPTS="VERBOSE='1'" make docker-test-coverage
         ;;
-      linux-amd64-fmt-unit-go-tip)
-        GOARCH=amd64 PASSES='fmt unit' ./test -p=2
+      linux-amd64-fmt-unit-go-tip-2-cpu)
+        GOARCH=amd64 PASSES='fmt unit' 'CPU=2' ./test -p=2
         ;;
-      linux-386-unit)
+      linux-386-unit-1-cpu)
         docker run --rm \
           --volume=`pwd`:/go/src/go.etcd.io/etcd gcr.io/etcd-development/etcd-test:go${TRAVIS_GO_VERSION} \
-          /bin/bash -c "GOARCH=386 PASSES='unit' ./test -p=2"
+          /bin/bash -c "GOARCH=386 PASSES='unit' RACE='false' CPU='1' ./test -p=4"
         ;;
     esac

test

@@ -29,7 +29,8 @@
 #
 # Run code coverage
 # COVERDIR must either be a absolute path or a relative path to the etcd root
-# $ COVERDIR=coverage PASSES="build_cov cov" ./test
+# $ COVERDIR=coverage PASSES="build build_cov cov" ./test
+# $ go tool cover -html ./coverage/cover.out
 set -e
 
 # The test script is not supposed to make any changes to the files
@@ -43,16 +44,12 @@ source ./scripts/test_lib.sh
 PASSES=${PASSES:-"fmt bom dep build unit"}
 PKG=${PKG:-}
 
-# Invoke ./tests/cover.test.bash for HTML output
-COVER="--cover=${COVER:-true}"
-
 if [ -z "$GOARCH" ]; then
   GOARCH=$(go env GOARCH);
 fi
 
 # determine the number of CPUs to use for Go tests
-CPU=${CPU:-"1,2,4"}
-echo "Running with CPU:" "${CPU}"
+CPU=${CPU:-"4"}
 
 # determine whether target supports race detection
 if [ -z "${RACE}" ] ; then
@@ -66,7 +63,8 @@ else
 fi
 
 # This options make sense for cases where SUT (System Under Test) is compiled by test.
-COMMON_TEST_FLAGS=("-cpu=${CPU}" "${RACE}" "${COVER}")
+COMMON_TEST_FLAGS=("-cpu=${CPU}" "${RACE}")
+log_callout "Running with ${COMMON_TEST_FLAGS[*]}"
 
 RUN_ARG=()
 if [ -n "${TESTCASE}" ]; then

tests/cover.test.bash

@@ -1,36 +0,0 @@
-#!/usr/bin/env bash
-#
-# Generate coverage HTML for a package
-# e.g. PKG=./unit ./tests/cover.test.bash
-#
-set -e
-
-if ! [[ "$0" =~ "tests/cover.test.bash" ]]; then
-  echo "must be run from repository root"
-  exit 255
-fi
-
-if [ -z "$PKG" ]; then
-  echo "cover only works with a single package, sorry"
-  exit 255
-fi
-
-COVEROUT="coverage"
-
-if ! [ -d "$COVEROUT" ]; then
-	mkdir "$COVEROUT"
-fi
-
-# strip leading dot/slash and trailing slash and sanitize other slashes
-# e.g. ./etcdserver/etcdhttp/ ==> etcdserver_etcdhttp
-COVERPKG=${PKG/#./}
-COVERPKG=${COVERPKG/#\//}
-COVERPKG=${COVERPKG/%\//}
-COVERPKG=${COVERPKG//\//_}
-
-# generate arg for "go test"
-export COVER="-coverprofile ${COVEROUT}/${COVERPKG}.out"
-
-source ./test
-
-go tool cover -html=${COVEROUT}/${COVERPKG}.out