* swarm/api: fix file descriptor leak in NewTestSwarmServer
Swarm storage (localstore) was not closed. That resulted a
"too many open files" error if `TestClientUploadDownloadRawEncrypted`
was run with `-count 1000`.
* cmd/swarm: speed up StartNewNodes() by parallelization
Reduce cluster startup time from 13s to 7s.
* swarm/api: disable flaky TestClientUploadDownloadRawEncrypted with -race
* swarm/storage: disable flaky TestLDBStoreCollectGarbage (-race)
With race detection turned on the disabled cases often fail with:
"ldbstore_test.go:535: expected surplus chunk 150 to be missing, but got no error"
* cmd/swarm: fix process leak in TestACT and TestSwarmUp
Each test run we start 3 nodes, but we did not terminate them. So
those 3 nodes continued eating up 1.2GB (3.4GB with -race) after test
completion.
6b6c4d1c2754f8dd70172ab58d7ee33cf9058c7d changed how we start clusters
to speed up tests. The changeset merged together test cases
and introduced a global cluster. But "forgot" about termination.
Let's get rid of "global cluster" so we have a clear owner of
termination (some time sacrifice), while leaving subtests to use the
same cluster.
- Replace "crypto/rand" to "math/rand" for files content generation
- Remove swarm/network_test.go.Shuffle and swarm/btm/btm_test.go.Shuffle - because go1.9 support dropped (see https://github.com/ethereum/go-ethereum/pull/17807 and comments to swarm/network_test.go.Shuffle)
