feat(provider-index): parallelize claim lookups

[frrist]

via 656fa67

• ProviderIndexService.getProviderResults now queries IPNI and legacy claims concurrently using channels. If IPNI returns a valid result, the legacy lookup is canceled.
• errors from both queries are joined to provide better context when neither returns data.
• tests have been updated to cover these new scenarios.
• closes Parallelize ProviderIndexService Find Method #120

via ae21e44

• adds a few more events to the span for the operation be modified allowing timing of various operations to be inferred. If we prefer this change be landed separately (or not at all!) happy to revert it.

[codecov]

Codecov Report

Attention: Patch coverage is 96.77419% with 2 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
pkg/service/providerindex/providerindex.go	96.77%	1 Missing and 1 partial ⚠️

Files with missing lines	Coverage Δ
pkg/service/providerindex/providerindex.go	62.85% <96.77%> (+7.24%)	⬆️

... and 1 file with indirect coverage changes

[hannahhoward]

LGTM

[volmedo]

LGTM. It may be valuable to add a couple more tests for the cases where IPNI and/or legacy return no results and no errors.

[frrist]

@volmedo great idea 😄

• I've added a couple new tests via 13931b0 that cover the case when IPNI/Legacy return a result and Legacy/IPNI return an empty result (but no error).
• Coverage for neither returning a result nor error is (thankfully) already well covered here:

  indexing-service/pkg/service/providerindex/providerindex_test.go

  Lines 127 to 145 in 9b1c5d6

  	t.Run("returns an empty slice when results are not found anywhere, nothing gets cached", func(t *testing.T) {
  	mockStore := types.NewMockProviderStore(t)
  	mockIpniFinder := extmocks.NewMockIpniFinder(t)
  	mockIpniPublisher := extmocks.NewMockIpniPublisher(t)
  	mockLegacyClaims := NewMockLegacyClaimsFinder(t)
  	providerIndex := New(mockStore, mockIpniFinder, mockIpniPublisher, mockLegacyClaims)
  	someHash := testutil.RandomMultihash()
  	mockStore.EXPECT().Members(testutil.AnyContext, someHash).Return(nil, types.ErrKeyNotFound)
  	mockIpniFinder.EXPECT().Find(testutil.AnyContext, someHash).Return(&model.FindResponse{}, nil)
  	mockLegacyClaims.EXPECT().Find(testutil.AnyContext, someHash, []multicodec.Code{0}).Return([]model.ProviderResult{}, nil)
  	results, err := providerIndex.getProviderResults(context.Background(), someHash, []multicodec.Code{0})
  	require.NoError(t, err)
  	require.Empty(t, results)
  	})

[volmedo]

thanks for adding the extra tests @frrist! 💯

A nitpick that we may want to implement at some point: I spotted a couple comments that I think should read different (in lines 321 and 371). They mention that an error is returned when it's in fact an empty result.