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A set of refactorings to enable Kubernetes watch. #44

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igorpeshansky merged 8 commits into from
Dec 20, 2017
Merged

A set of refactorings to enable Kubernetes watch. #44

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4bec5c7
New DockerUpdater and KubernetesUpdater classes. Swap order of Pollin…
igorpeshansky Nov 9, 2017
157d9f4
Factor out the MetadataUpdater abstract class.
igorpeshansky Nov 9, 2017
00a9141
Split MetadataAgent::UpdateResource into UpdateResource and UpdateMet…
igorpeshansky Nov 9, 2017
6118758
Factor out metadata creation.
igorpeshansky Dec 15, 2017
6e91a2d
Factor out GetPodAndContainerMetadata; add a move constructor to Reso…
igorpeshansky Nov 16, 2017
a3258f5
Rename local variable.
igorpeshansky Dec 19, 2017
38d3db0
Address feedback.
igorpeshansky Dec 19, 2017
d623dcb
Rename variable.
igorpeshansky Dec 20, 2017
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14 changes: 9 additions & 5 deletions src/api_server.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -102,7 +102,7 @@ void MetadataApiServer::Handler::operator()(const HttpServer::request& request,
}
if (request.method == "GET" && request.destination.find(kPrefix) == 0) {
std::string id = request.destination.substr(kPrefix.size());
std::lock_guard<std::mutex> lock(agent_.mu_);
std::lock_guard<std::mutex> lock(agent_.resource_mu_);
const auto result = agent_.resource_map_.find(id);
if (result == agent_.resource_map_.end()) {
// TODO: This could be considered log spam.
Expand Down Expand Up @@ -286,9 +286,8 @@ MetadataAgent::MetadataAgent(const MetadataAgentConfiguration& config)
MetadataAgent::~MetadataAgent() {}

void MetadataAgent::UpdateResource(const std::vector<std::string>& resource_ids,
const MonitoredResource& resource,
Metadata&& entry) {
std::lock_guard<std::mutex> lock(mu_);
const MonitoredResource& resource) {
std::lock_guard<std::mutex> lock(resource_mu_);
// TODO: How do we handle deleted resources?
// TODO: Do we care if the value was already there?
for (const std::string& id : resource_ids) {
Expand All @@ -297,6 +296,11 @@ void MetadataAgent::UpdateResource(const std::vector<std::string>& resource_ids,
}
resource_map_.emplace(id, resource);
}
}

void MetadataAgent::UpdateMetadata(const MonitoredResource& resource,
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@qingling128 qingling128 Dec 19, 2017

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Just curious, why is this second map not keyed by resource_id as well?

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@igorpeshansky igorpeshansky Dec 19, 2017

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Because that map is sent to to the Resource Metadata API, which neither knows nor cares about the local resource ids.

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@qingling128 qingling128 Dec 20, 2017

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Ah, got it. Makes sense.

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@supriyagarg supriyagarg Dec 20, 2017

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Curious - how is the local resource_id different from the monitored resource ID?

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@igorpeshansky igorpeshansky Dec 20, 2017

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The local resource_id is an easily discoverable identifier for the resource that is unique within the current context (e.g., a Kubernetes node), but may not be globally unique, whereas the monitored resource (which actually is an id, so "monitored resource id" is redundant) is globally unique.

Metadata&& entry) {
std::lock_guard<std::mutex> lock(metadata_mu_);
if (config_.VerboseLogging()) {
LOG(INFO) << "Updating metadata map " << resource << "->{"
<< "version: " << entry.version << ", "
Expand All @@ -316,7 +320,7 @@ void MetadataAgent::UpdateResource(const std::vector<std::string>& resource_ids,

std::map<MonitoredResource, MetadataAgent::Metadata>
MetadataAgent::GetMetadataMap() const {
std::lock_guard<std::mutex> lock(mu_);
std::lock_guard<std::mutex> lock(metadata_mu_);

std::map<MonitoredResource, Metadata> result;
for (const auto& kv : metadata_map_) {
Expand Down
17 changes: 11 additions & 6 deletions src/api_server.h
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Expand Up @@ -81,12 +81,15 @@ class MetadataAgent {
MetadataAgent(const MetadataAgentConfiguration& config);
~MetadataAgent();

// Updates metadata for a given resource.
// Updates the local resource map entry for a given resource.
// Each local id in `resource_ids` is effectively an alias for `resource`.
// Adds a resource mapping from each of the `resource_ids` to the `resource`
// and a metadata mapping from the `resource` to the metadata `entry`.
// Adds a resource mapping from each of the `resource_ids` to the `resource`.
void UpdateResource(const std::vector<std::string>& resource_ids,
const MonitoredResource& resource,
const MonitoredResource& resource);

// Updates metadata for a given resource.
// Adds a metadata mapping from the `resource` to the metadata `entry`.
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@supriyagarg supriyagarg Dec 20, 2017

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What does "metadata mapping" mean. Is just "mapping" sufficient?

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@igorpeshansky igorpeshansky Dec 20, 2017

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The metadata agent maintains two mappings:

  • local resource map, from a locally unique id to the monitored resource (there may be multiple locally unique ids, all referring to the same monitored resource), which is exposed via a local endpoint to other agents so they don't have to discover all parts of the monitored resource themselves, and
  • metadata map, from the monitored resource to the metadata blob, which is sent to the Resource Metadata API.

void UpdateMetadata(const MonitoredResource& resource,
Metadata&& entry);

// Starts serving.
Expand All @@ -104,10 +107,12 @@ class MetadataAgent {

const MetadataAgentConfiguration& config_;

// A lock that guards access to the maps.
mutable std::mutex mu_;
// A lock that guards access to the local resource map.
mutable std::mutex resource_mu_;
// A map from a locally unique id to MonitoredResource.
std::map<std::string, MonitoredResource> resource_map_;
// A lock that guards access to the metadata map.
mutable std::mutex metadata_mu_;
// A map from MonitoredResource to (JSON) resource metadata.
std::map<MonitoredResource, Metadata> metadata_map_;

Expand Down
4 changes: 2 additions & 2 deletions src/docker.cc
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Expand Up @@ -43,7 +43,7 @@ constexpr const char resource_type_separator[] = ".";
DockerReader::DockerReader(const MetadataAgentConfiguration& config)
: config_(config), environment_(config) {}

std::vector<PollingMetadataUpdater::ResourceMetadata>
std::vector<MetadataUpdater::ResourceMetadata>
DockerReader::MetadataQuery() const {
if (config_.VerboseLogging()) {
LOG(INFO) << "Docker Query called";
Expand All @@ -58,7 +58,7 @@ std::vector<PollingMetadataUpdater::ResourceMetadata>
http::local_client client;
http::local_client::request list_request(
docker_endpoint + "/json?all=true" + container_filter);
std::vector<PollingMetadataUpdater::ResourceMetadata> result;
std::vector<MetadataUpdater::ResourceMetadata> result;
try {
http::local_client::response list_response = client.get(list_request);
Timestamp collected_at = std::chrono::system_clock::now();
Expand Down
12 changes: 11 additions & 1 deletion src/docker.h
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Expand Up @@ -30,13 +30,23 @@ class DockerReader {
public:
DockerReader(const MetadataAgentConfiguration& config);
// A Docker metadata query function.
std::vector<PollingMetadataUpdater::ResourceMetadata> MetadataQuery() const;
std::vector<MetadataUpdater::ResourceMetadata> MetadataQuery() const;

private:
const MetadataAgentConfiguration& config_;
Environment environment_;
};

class DockerUpdater : public PollingMetadataUpdater {
public:
DockerUpdater(MetadataAgent* server)
: reader_(server->config()), PollingMetadataUpdater(
server, server->config().DockerUpdaterIntervalSeconds(),
std::bind(&google::DockerReader::MetadataQuery, &reader_)) { }
private:
DockerReader reader_;
};

}

#endif // DOCKER_H_
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