Merge pull request #55631 from mrunalp/parse_last_partial

Automatic merge from submit-queue (batch tested with PRs 55697, 55631, 51905, 55647, 55826). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

Parse the last partial line in CRI logs

@Random-Liu @yujuhong @runcom @feiskyer PTAL

Fixes part of https://github.com/kubernetes/kubernetes/issues/44976

This should work while we find a longer term format for CRI logs.

Signed-off-by: Mrunal Patel <mrunalp@gmail.com>

**What this PR does / why we need it**:
This PR attempts to parse the last line of  log even if it doesn't have a newline. Today for CRI based log formats such lines are ignored and empty output is returned.

**Which issue(s) this PR fixes** 
Fixes part of #44976

**Special notes for your reviewer**:
Use a CRI runtime like CRI-O and the output will be empty for these commands without this PR.
```
# kubectl create -f https://raw.githubusercontent.com/openshift-qe/v3-testfiles/master/configmap/configmap.yaml
# kubectl create -f https://raw.githubusercontent.com/openshift-qe/v3-testfiles/master/configmap/pod-configmap-volume1.yaml 
# kubectl logs dapi-test-pod-1 
very# 
```

**Release Note**:
```release-note
NONE
```

pkg/kubelet/kuberuntime/logs/logs.go

@@ -289,6 +289,27 @@ func ReadLogs(path, containerID string, opts *LogOptions, runtimeService interna
 				// Return directly when reading to the end if not follow.
 				if len(l) > 0 {
 					glog.Warningf("Incomplete line in log file %q: %q", path, l)
+					if parse == nil {
+						// Intialize the log parsing function.
+						parse, err = getParseFunc(l)
+						if err != nil {
+							return fmt.Errorf("failed to get parse function: %v", err)
+						}
+					}
+					// Log a warning and exit if we can't parse the partial line.
+					if err := parse(l, msg); err != nil {
+						glog.Warningf("Failed with err %v when parsing partial line for log file %q: %q", err, path, l)
+						return nil
+					}
+					// Write the log line into the stream.
+					if err := writer.write(msg); err != nil {
+						if err == errMaximumWrite {
+							glog.V(2).Infof("Finish parsing log file %q, hit bytes limit %d(bytes)", path, opts.bytes)
+							return nil
+						}
+						glog.Errorf("Failed with err %v when writing partial log for log file %q: %+v", err, path, msg)
+						return err
+					}
 				}
 				glog.V(2).Infof("Finish parsing log file %q", path)
 				return nil