Spring sleuth (#1378)

* Initial import of OpenCensus/Sleuth integration.

* Minor fixes for integration with master.

* Adds a README.

* Removes hardcoded dependencies in build file.

* Adds contrib to spring_sleuth file path.

* Updates package names appropriately based on file renames.

* Fixes build paths.

* Fixes for build checks.

* Mark as experimental.

* Minor fixes for build files (space vs tab).

* Minor fixes for build files (space vs tab).

* Update README to absolve Spring Sleuth team of any responsibility for this spring_sleuth plugin.

* Minor fixes for import control (space vs tab).

* Tag public classes @since 0.16

* Adds javadoc for public methods not already documented.

* Updates OpenCensusSleuthTracer to pass nullness checks.

* Fixes for formatting issues.

* Fixes for typos.

* Suppresses the check return value warning added by gRPC.

* Suppresses the check return value warning added by gRPC.

2 files changed, 28 insertions, 0 deletions

diff --git a/checker-framework/stubs/org-springframework-cloud-sleuth.astub b/checker-framework/stubs/org-springframework-cloud-sleuth.astub
new file mode 100644
index 00000000..61d2fa11
--- /dev/null
+++ b/checker-framework/stubs/org-springframework-cloud-sleuth.astub
@@ -0,0 +1,19 @@
+package org.springframework.cloud.sleuth;
+
+import org.checkerframework.checker.nullness.qual.Nullable;
+import org.springframework.cloud.sleuth.Sampler;
+import org.springframework.cloud.sleuth.Span;
+
+interface Tracer {
+  @Nullable Span close(@Nullable Span span);
+  @Nullable Span continueSpan(@Nullable Span span);
+  @Nullable Span createSpan(String name);
+  @Nullable Span createSpan(String name, @Nullable Sampler sampler);
+  @Nullable Span createSpan(String name, @Nullable Span parent);
+  @Nullable Span detach(@Nullable Span span);
+  @Nullable Span getCurrentSpan();
+}
+
+class Span {
+  Span (Span span, @Nullable Span parent);
+}
diff --git a/checker-framework/stubs/org-springframework-cloud-sleuth.log.astub b/checker-framework/stubs/org-springframework-cloud-sleuth.log.astub
new file mode 100644
index 00000000..9497f6f2
--- /dev/null
+++ b/checker-framework/stubs/org-springframework-cloud-sleuth.log.astub
@@ -0,0 +1,9 @@
+package org.springframework.cloud.sleuth.log;
+
+import org.checkerframework.checker.nullness.qual.Nullable;
+import org.springframework.cloud.sleuth.Span;
+
+interface SpanLogger {
+  void logStartedSpan(@Nullable Span parent, Span span);
+  void logStoppedSpan(@Nullable Span parent, Span span);
+}