Yen-Cheng Chou

- When CANCELED is returned, the operation was cancelled. Mark the error as recoverable and allows the Client to resend the samples. - When DEADLINE_EXCEEDED is returned, the operation might...

The Client should not drop the sample because the credential cannot be retrieved. Once the credential is set correctly, client should try to resend the samples.

Avoid retry on non-recoverable errors.

5

Rationale behind this change: in `retrieval.manager()`, retry with exponential backoff is used when [building Stackdriver sample](https://github.com/Stackdriver/stackdriver-prometheus-sidecar/pull/101/files#diff-9a6e1a2677ae9c077ad1ecd84a07c002L244). However, there are 2 types of errors which will always be thrown, and retrying...

Fix bug for TLSVersion.MarshalYAML

2

Signed-off-by: Yen-Cheng Chou

Add instrumentation and expose measurement in prometheus format

3

Add interface inside api_server, so we expose instrumentation metrics later on (currently working on it). Some thoughts: 1. I added a private function `MetadataApiServer::SerializeMetricsToPrometheusTextFormat()` so we can test the functionality...