treewide: introduce osbase package and move things around
All except localregistry moved from metropolis/pkg to osbase,
localregistry moved to metropolis/test as its only used there anyway.
Change-Id: If1a4bf377364bef0ac23169e1b90379c71b06d72
Reviewed-on: https://review.monogon.dev/c/monogon/+/3079
Tested-by: Jenkins CI
Reviewed-by: Serge Bazanski <serge@monogon.tech>
diff --git a/osbase/logtree/logtree.go b/osbase/logtree/logtree.go
new file mode 100644
index 0000000..c20681d
--- /dev/null
+++ b/osbase/logtree/logtree.go
@@ -0,0 +1,158 @@
+// Copyright 2020 The Monogon Project Authors.
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package logtree
+
+import (
+ "fmt"
+ "strings"
+ "sync"
+
+ "source.monogon.dev/osbase/logbuffer"
+)
+
+// LogTree is a tree-shaped logging system. For more information, see the package-
+// level documentation.
+type LogTree struct {
+ // journal is the tree's journal, storing all log data and managing subscribers.
+ journal *journal
+ // root is the root node of the actual tree of the log tree. The nodes contain per-
+ // DN configuration options, notably the current verbosity level of that DN.
+ root *node
+}
+
+func New() *LogTree {
+ lt := &LogTree{
+ journal: newJournal(),
+ }
+ lt.root = newNode(lt, "")
+ return lt
+}
+
+// node represents a given DN as a discrete 'logger'. It implements the
+// LeveledLogger interface for log publishing, entries from which it passes over to
+// the logtree's journal.
+type node struct {
+ // dn is the DN which this node represents (or "" if this is the root node).
+ dn DN
+ // tree is the LogTree to which this node belongs.
+ tree *LogTree
+ // verbosity is the current verbosity level of this DN/node, affecting .V(n)
+ // LeveledLogger calls
+ verbosity VerbosityLevel
+ rawLineBuffer *logbuffer.LineBuffer
+
+ // mu guards children.
+ mu sync.Mutex
+ // children is a map of DN-part to a children node in the logtree. A DN-part is a
+ // string representing a part of the DN between the deliming dots, as returned by
+ // DN.Path.
+ children map[string]*node
+}
+
+// newNode returns a node at a given DN in the LogTree - but doesn't set up the
+// LogTree to insert it accordingly.
+func newNode(tree *LogTree, dn DN) *node {
+ n := &node{
+ dn: dn,
+ tree: tree,
+ children: make(map[string]*node),
+ }
+ // TODO(q3k): make this limit configurable. If this happens, or the default (1024) gets changes, max chunk size
+ // calculations when serving the logs (eg. in NodeDebugService) must reflect this.
+ n.rawLineBuffer = logbuffer.NewLineBuffer(1024, n.logRaw)
+ return n
+}
+
+// nodeByDN returns the LogTree node corresponding to a given DN. If either the
+// node or some of its parents do not exist they will be created as needed.
+func (l *LogTree) nodeByDN(dn DN) (*node, error) {
+ traversal, err := newTraversal(dn)
+ if err != nil {
+ return nil, fmt.Errorf("traversal failed: %w", err)
+ }
+ return traversal.execute(l.root), nil
+}
+
+// nodeTraversal represents a request to traverse the LogTree in search of a given
+// node by DN.
+type nodeTraversal struct {
+ // want is the DN of the node's that requested to be found.
+ want DN
+ // current is the path already taken to find the node, in the form of DN parts. It
+ // starts out as want.Parts() and progresses to become empty as the traversal
+ // continues.
+ current []string
+ // left is the path that's still needed to be taken in order to find the node, in
+ // the form of DN parts. It starts out empty and progresses to become wants.Parts()
+ // as the traversal continues.
+ left []string
+}
+
+// next adjusts the traversal's current/left slices to the next element of the
+// traversal, returns the part that's now being looked for (or "" if the traveral
+// is done) and the full DN of the element that's being looked for.
+//
+// For example, a traversal of foo.bar.baz will cause .next() to return the
+// following on each invocation:
+// - part: foo, full: foo
+// - part: bar, full: foo.bar
+// - part: baz, full: foo.bar.baz
+// - part: "", full: foo.bar.baz
+func (t *nodeTraversal) next() (part string, full DN) {
+ if len(t.left) == 0 {
+ return "", t.want
+ }
+ part = t.left[0]
+ t.current = append(t.current, part)
+ t.left = t.left[1:]
+ full = DN(strings.Join(t.current, "."))
+ return
+}
+
+// newTraversal returns a nodeTraversal fora a given wanted DN.
+func newTraversal(dn DN) (*nodeTraversal, error) {
+ parts, err := dn.Path()
+ if err != nil {
+ return nil, err
+ }
+ return &nodeTraversal{
+ want: dn,
+ left: parts,
+ }, nil
+}
+
+// execute the traversal in order to find the node. This can only be called once
+// per traversal. Nodes will be created within the tree until the target node is
+// reached. Existing nodes will be reused. This is effectively an idempotent way of
+// accessing a node in the tree based on a traversal.
+func (t *nodeTraversal) execute(n *node) *node {
+ cur := n
+ for {
+ part, full := t.next()
+ if part == "" {
+ return cur
+ }
+
+ mu := &cur.mu
+ mu.Lock()
+ if _, ok := cur.children[part]; !ok {
+ cur.children[part] = newNode(n.tree, full)
+ }
+ cur = cur.children[part]
+ mu.Unlock()
+ }
+}