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OpenCensus Service

IMPORTANT: This project is now archived: it is no longer accepting any PRs.

Development of new features and improvements will be done on its successor project: OpenTelemetry Service.

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The OpenCensus Service is an component that can collect traces and metrics from processes instrumented by OpenCensus or other monitoring/tracing libraries (Jaeger, Prometheus, etc.), do aggregation and smart sampling, and export traces and metrics to one or more monitoring/tracing backends.

Some frameworks and ecosystems are now providing out-of-the-box instrumentation by using OpenCensus, but the user is still expected to register an exporter in order to export data. This is a problem during an incident. Even though our users can benefit from having more diagnostics data coming out of services already instrumented with OpenCensus, they have to modify their code to register an exporter and redeploy. Asking our users recompile and redeploy is not an ideal at an incident time. In addition, currently users need to decide which service backend they want to export to, before they distribute their binary instrumented by OpenCensus.

The OpenCensus Service is trying to eliminate these requirements. With the OpenCensus Service, users do not need to redeploy or restart their applications as long as it has the OpenCensus exporter. All they need to do is just configure and deploy the OpenCensus Service separately. The OpenCensus Service will then automatically collect traces and metrics and export to any backend of users' choice.

Currently the OpenCensus Service consists of two components, OpenCensus Agent and OpenCensus Collector. For the detailed design specs, please see


The OpenCensus Service can be deployed in a variety of different ways. The OpenCensus Agent can be deployed with the application either as a separate process, as a sidecar, or via a Kubernetes daemonset. Typically, the OpenCensus Collector is deployed separately as either a Docker container, VM, or Kubernetes pod.


Getting Started


Instructions for setting up an end-to-end demo environment can be found here


Apply the sample YAML file:

$ kubectl apply -f example/k8s.yaml


Create an Agent configuration file based on the options described below. Please note the Agent requires the opencensus receiver be enabled. By default, the Agent has no exporters configured.

Build the Agent, see Usage, and start it:

$ ./bin/ocagent_$(go env GOOS)
$ 2018/10/08 21:38:00 Running OpenCensus receiver as a gRPC service at ""

Create an Collector configuration file based on the options described below. By default, the Collector has the opencensus receiver enabled, but no exporters.

Build the Collector and start it:

$ make collector
$ ./bin/occollector_$($GOOS)

Run the demo application:

$ go run "$(go env GOPATH)/src/"

You should be able to see the traces in your exporter(s) of choice. If you stop the ocagent, the example application will stop exporting. If you run it again, exporting will resume.


The OpenCensus Service (both the Agent and Collector) is configured via a YAML file. In general, you need to configure one or more receivers as well as one or more exporters. In addition, diagnostics can also be configured.


A receiver is how you get data into the OpenCensus Service. One or more receivers can be configured. By default, the opencensus receiver is enabled on the Collector and required as a defined receiver for the Agent.

A basic example of all available receivers is provided below. For detailed receiver configuration, please see the receiver

    address: ""

    address: ""

    jaeger-thrift-tchannel-port: 14267
    jaeger-thrift-http-port: 14268

        - job_name: 'caching_cluster'
          scrape_interval: 5s
            - targets: ['localhost:8889']


An exporter is how you send data to one or more backends/destinations. One or more exporters can be configured. By default, no exporters are configured on the OpenCensus Service (either the Agent or Collector).

A basic example of all available exporters is provided below. For detailed exporter configuration, please see the exporter

    headers: {"X-test-header": "test-header"}
    compression: "gzip"
    cert-pem-file: "server_ca_public.pem" # optional to enable TLS
    endpoint: ""
    reconnection-delay: 2s

    collector_endpoint: ""

    brokers: [""]
    topic: "opencensus-spans"

    project: "my-project-id" # optional, defaults to agent project if run on GCP
    enable_tracing: true

    endpoint: ""

    region: "us-west-2"
    default_service_name: "verifiability_agent"
    version: "latest"
    buffer_size: 200

    write_key: "739769d7-e61c-42ec-82b9-3ee88dfeff43"
    dataset_name: "dc8_9"


zPages is provided for monitoring running by default on port 55679. These routes below contain the various diagnostic resources:

Resource Route
RPC stats /debug/rpcz
Trace information /debug/tracez

The zPages configuration can be updated in the config.yaml file with fields:

  • disabled: if set to true, won't run zPages
  • port: by default is 55679, otherwise should be set to a value between 0 an 65535

For example:

    port: 8888 # To override the port from 55679 to 8888

To disable zPages, you can use disabled like this:

    disabled: true

OpenCensus Agent


It is recommended that you use the latest release.

The ocagent can be run directly from sources, binary, or a Docker image. If you are planning to run from sources or build on your machine start by cloning the repo using go get -d

The minimum Go version required for this project is Go 1.12.5. In addition, you must manually install Bazaar

  1. Run from sources:
$ GO111MODULE=on go run --help
  1. Run from binary (from the root of your repo):
$ make agent
  1. Build a Docker scratch image and use the appropriate Docker command for your scenario (note: additional ports may be required depending on your receiver configuration):

A Docker scratch image can be built with make by targeting docker-agent.

$ make docker-agent
$ docker run \
    --rm \
    --interactive \
    --tty \
    --publish 55678:55678 --publish 55679:55679 \
    --volume $(pwd)/ocagent-config.yaml:/conf/ocagent-config.yaml \
    ocagent \

OpenCensus Collector

The OpenCensus Collector is a component that runs “nearby” (e.g. in the same VPC, AZ, etc.) a user’s application components and receives trace spans and metrics emitted by the OpenCensus Agent or tasks instrumented with OpenCensus instrumentation (or other supported protocols/libraries). The received spans and metrics could be emitted directly by clients in instrumented tasks, or potentially routed via intermediate proxy sidecar/daemon agents (such as the OpenCensus Agent). The collector provides a central egress point for exporting traces and metrics to one or more tracing and metrics backends, with buffering and retries as well as advanced aggregation, filtering and annotation capabilities.

The collector is extensible enabling it to support a range of out-of-the-box (and custom) capabilities such as:

  • Retroactive (tail-based) sampling of traces
  • Cluster-wide z-pages
  • Filtering of traces and metrics
  • Aggregation of traces and metrics
  • Decoration with meta-data from infrastructure provider (e.g. k8s master)
  • much more ...

The collector also serves as a control plane for agents/clients by supplying them updated configuration (e.g. trace sampling policies), and reporting agent/client health information/inventory metadata to downstream exporters.

Receivers Configuration

For detailed information about configuring receivers for the collector refer to the receivers

Global Attributes

The collector also takes some global configurations that modify its behavior for all receivers / exporters.

  1. Add Attributes to all spans passing through this collector. These additional attributes can be configured to either overwrite existing keys if they already exist on the span, or respect the original values.
  2. The key of each attribute can also be mapped to different strings using the key-mapping configuration. The key matching is case sensitive.

An example using these configurations of this is provided below.

    overwrite: true
      # values are key value pairs where the value can be an int, float, bool, or string
      some_string: "hello world"
      some_int: 1234
      some_float: 3.14159
      some_bool: false
      # key-mapping is used to replace the attribute key with different keys
      - key: servertracer.http.responsecode
        replacement: http.status_code
      - key:  servertracer.http.responsephrase
        replacement: http.message
        overwrite: true # replace attribute key even if the replacement string is already a key on the span attributes
        keep: true # keep the attribute with the original key

Probabilistic Head-based Trace Sampling

In some scenarios it may be desirable to perform probabilistic head-based trace sampling on the collector. This can be done using by specifying probabilistic policy secion under the sampling section of the collector configuration file.

  # mode indicates if the sampling is head or tail based. For probabilistic the mode is head-based.
  mode: head
    # section below defines a probabilistic trace sampler based on hashing the trace ID associated to
    # each span and sampling the span according to the given spans.
        # sampling-percentage is the percentage of sampling to be applied to all spans, unless their service is specified
        # on sampling-percentage.
        sampling-percentage: 5
        # hash-seed allows choosing the seed for the hash function used in the trace sampling. This is important when
        # multiple layers of collectors are being used with head sampling, in such scenarios make sure to
        # choose different seeds for each layer.
        hash-seed: 1

Intelligent Sampling

  mode: tail
  # amount of time from seeing the first span in a trace until making the sampling decision
  decision-wait: 10s
  # maximum number of traces kept in the memory
  num-traces: 10000
    # user-defined policy name
      # exporters the policy applies to
        - jaeger
      policy: string-attribute-filter
        key: key1
          - value1
          - value2
        - zipkin
      policy: numeric-attribute-filter
        key: key1
        min-value: 0
        max-value: 100

Note that an exporter can only have a single sampling policy today.


It is recommended that you use the latest release.

The collector can be run directly from sources, binary, or a Docker image. If you are planning to run from sources or build on your machine start by cloning the repo using go get -d

The minimum Go version required for this project is Go 1.12.5.

  1. Run from sources:
$ GO111MODULE=on go run --help
  1. Run from binary (from the root of your repo):
$ make collector
$ ./bin/occollector_$($GOOS)
  1. Build a Docker scratch image and use the appropriate Docker command for your scenario (note: additional ports may be required depending on your receiver configuration):
$ make docker-collector
$ docker run \
    --rm \
    --interactive \
    -- tty \
    --publish 55678:55678 --publish 8888:8888 \
    --volume $(pwd)/occollector-config.yaml:/conf/occollector-config.yaml \
    occollector \

It can be configured via command-line or config file:

OpenCensus Collector

  occollector [flags]

      --config string                 Path to the config file
      --health-check-http-port uint   Port on which to run the healthcheck http server. (default 13133)
  -h, --help                          help for occollector
      --http-pprof-port uint          Port to be used by golang net/http/pprof (Performance Profiler), the profiler is disabled if no port or 0 is specified.
      --log-level string              Output level of logs (DEBUG, INFO, WARN, ERROR, FATAL) (default "INFO")
      --logging-exporter              Flag to add a logging exporter (combine with log level DEBUG to log incoming spans)
      --metrics-level string          Output level of telemetry metrics (NONE, BASIC, NORMAL, DETAILED) (default "BASIC")
      --metrics-port uint             Port exposing collector telemetry. (default 8888)
      --receive-jaeger                Flag to run the Jaeger receiver (i.e.: Jaeger Collector), default settings: {ThriftTChannelPort:14267 ThriftHTTPPort:14268}
      --receive-oc-trace              Flag to run the OpenCensus trace receiver, default settings: {Port:55678} (default true)
      --receive-zipkin                Flag to run the Zipkin receiver, default settings: {Port:9411}
      --receive-zipkin-scribe         Flag to run the Zipkin Scribe receiver, default settings: {Address: Port:9410 Category:zipkin}
      --tail-sampling-always-sample   Flag to use a tail-based sampling processor with an always sample policy, unless tail sampling setting is present on configuration file.

Sample configuration file:

log-level: DEBUG

  opencensus: {} # Runs OpenCensus receiver with default configuration (default behavior).

  jaeger-sender-test: # A friendly name for the exporter
    # num-workers is the number of queue workers that will be dequeuing batches and sending them out (default is 10)
    num-workers: 2

    # queue-size is the maximum number of batches allowed in the queue at a given time (default is 5000)
    queue-size: 100

    # retry-on-failure indicates whether queue processor should retry span batches in case of processing failure (default is true)
    retry-on-failure: true

    # backoff-delay is the amount of time a worker waits after a failed send before retrying (default is 5 seconds)
    backoff-delay: 3s

    # sender-type is the type of sender used by this processor, the default is an invalid sender so it forces one to be specified
    sender-type: jaeger-thrift-http

    # configuration of the selected sender-type, in this example Jaeger jaeger-thrift-http. Which supports 3 settings:
    # collector-endpoint: address of Jaeger collector jaeger-thrift-http endpoint
    # headers: a map of any additional headers to be sent with each batch (e.g.: api keys, etc)
    # timeout: the timeout for the sender to consider the operation as failed
      collector-endpoint: "http://svc-jaeger-collector:14268/api/traces"
      headers: { "x-header-key":"00000000-0000-0000-0000-000000000001" }
      timeout: 5s


OpenCensus service allows OpenCensus libraries to export to an exporter service rather than having to link vendor-specific exports.



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