opendev/gerrit
Code Issues Proposed changes

Improve performance of ListBranches REST endpoint

Browse Source 
Branch listing was reading all the refs from the repo and then
filtering out any branches that were not refs/meta/config or starting
with refs/heads. This extra IO and processing is hard to notice on fast
file systems but it's not on slow ones, especially if repo has a lot of
refs that do not start with refs/heads (e.g. refs/changes).

Rework the branch listing to get only the refs that start with refs/heads
from the repo and then add the 2 other branches required: HEAD and
refs/meta/config.

In one of our repos with 10k branches and 250k changes, this change
reduced the branch listing to 10% of the time it took without this
change.

Change-Id: I0932d06229e6a8cbc9497abcc5b604d2f9a0113b
This commit is contained in:
Hugo Arès
2015-03-05 09:20:30 -05:00
parent 12dad02c89
commit 368d234ac6
1 changed files with 18 additions and 14 deletions
Download Patch File Download Diff File Expand all files Collapse all files

32
gerrit-server/src/main/java/com/google/gerrit/server/project/ListBranches.java
View File

@@ -32,10 +32,10 @@ import com.google.inject.util.Providers;
import org.eclipse.jgit.errors.RepositoryNotFoundException;
import org.eclipse.jgit.lib.Constants;
import org.eclipse.jgit.lib.Ref;
import org.eclipse.jgit.lib.RefDatabase;
import org.eclipse.jgit.lib.Repository;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
@@ -72,30 +72,34 @@ public class ListBranches implements RestReadView<ProjectResource> {
}
try {
final Map<String, Ref> all = db.getRefDatabase().getRefs(RefDatabase.ALL);
List<Ref> refs =
new ArrayList<>(db.getRefDatabase().getRefs(Constants.R_HEADS)
.values());
if (!all.containsKey(Constants.HEAD)) {
// The branch pointed to by HEAD doesn't exist yet, so getAllRefs
// filtered it out. If we ask for it individually we can find the
// underlying target and put it into the map anyway.
//
try {
Ref head = db.getRef(Constants.HEAD);
if (head != null) {
all.put(Constants.HEAD, head);
refs.add(head);
}
} catch (IOException e) {
// Ignore the failure reading HEAD.
}
}
try {
Ref config = db.getRef(RefNames.REFS_CONFIG);
if (config != null) {
refs.add(config);
}
} catch (IOException e) {
// Ignore the failure reading refs/meta/config.
}
for (final Ref ref : all.values()) {
for (Ref ref : refs) {
if (ref.isSymbolic()) {
targets.add(ref.getTarget().getName());
}
}
for (final Ref ref : all.values()) {
for (Ref ref : refs) {
if (ref.isSymbolic()) {
// A symbolic reference to another branch, instead of
// showing the resolved value, show the name it references.
@@ -122,10 +126,10 @@ public class ListBranches implements RestReadView<ProjectResource> {
final RefControl refControl = rsrc.getControl().controlForRef(ref.getName());
if (refControl.isVisible()) {
if (ref.getName().startsWith(Constants.R_HEADS)) {
branches.add(createBranchInfo(ref, refControl, targets));
} else if (RefNames.REFS_CONFIG.equals(ref.getName())) {
if (RefNames.REFS_CONFIG.equals(ref.getName())) {
configBranch = createBranchInfo(ref, refControl, targets);
} else {
branches.add(createBranchInfo(ref, refControl, targets));
}
}
}