❗ This sidecar is no longer recommend. Please the OpenTelemetry Collector Prometheus receiver instead, documentation on setting up and configuring the collector for Prometheus is available on the Lightstep Observability Learning Portal.
This repository contains a sidecar for the Prometheus Server that sends metrics data to an OpenTelemetry Metrics Protocol endpoint. This software is derived from the Stackdriver Prometheus Sidecar.
This repository is being maintained by Lightstep and will be donated to OpenTelemetry. We are moving this repository into the OpenTelemetry organization and will continue development on a public fork of the upstream Stackdriver Prometheus sidecar repository.
This code base is 100% OpenTelemetry and Prometheus, not a Lightstep-specific sidecar, functioning to read data collected and written by Prometheus, convert into the OpenTelemetry data model, and write to an OpenTelemetry endpoint.
This sidecar sends OpenTelemetry Protocol version 0.7 (or later versions) over gRPC.
The sidecar includes:
- Prometheus write-ahead log (WAL) reader
- Metadata cache that tracks active instruments
- Configured settings:
- Additional resource attributes to apply to all metric timeseries
- Renaming and prefixing to change the name of metric timeseries
- Filters to avoid reporting specific metric timeseries
- Specify whether to use use int64 (optional) vs. double (default) protocol encoding
Sidecar operates by continually:
- Reading the prometheus WAL log (package retrieval and tail);
- Refreshing its view of the instrument metadata (package metadata);
- Transforming WAL samples into OpenTelemetry Protocol(OTLP) metrics (package retrieval);
- Sending OTLP metrics to the destination endpoint (package otlp).
Resources to understand how the WAL log works can be found here and here.
Lightstep publishes Docker images of this binary named
lightstep/opentelemetry-prometheus-sidecar:${VERSION}, with the
latest release always tagged latest.
To build from source, please clone this repository. You will build a Docker image, push it to a private container registry, and then run the container as described below. To test and build a Docker image for the current operating system, simply:
export DOCKER_IMAGE_NAME=my.image.reposito.ry/opentelemetry/prometheus-sidecar
export DOCKER_IMAGE_TAG=$(cat ./VERSION)
make docker
docker push ${DOCKER_IMAGE_NAME}:${DOCKER_IMAGE_TAG}
The sidecar is deployed next to an already running Prometheus server.
An example command-line:
opentelemetry-prometheus-sidecar \
--destination.endpoint=${DESTINATION} \
--destination.header="lightstep-access-token=${VALUE}" \
--destination.attribute="service.name=${SERVICE}" \
--diagnostics.endpoint=${DIAGNOSTICS} \
--diagnostics.header="lightstep-access-token=${VALUE}" \
--diagnostics.attribute="service.name=${SERVICE}" \
--prometheus.wal=${WAL} \
--prometheus.endpoint=${PROMETHEUS} \
where:
DESTINATION: Destination address https://host:port for sending prometheus metricsDIAGNOSTICS: Diagnostics address https://host:port for sending sidecar telemetryVALUE: Value for theCustom-Headerrequest headerSERVICE: Value for theservice.nameresource attributeWAL: Prometheus' WAL directory, defaults todata/walPROMETHEUS: URL of the Prometheus UI.
See the list of command-line flags below.
Settings can also be passed through a configuration file. For example:
destination:
endpoint: https://otlp.io:443
headers:
Custom-Header: custom-value
attributes:
service.name: my-service-name
diagnostics:
endpoint: https://otlp.io:443
headers:
Custom-Header: custom-value
attributes:
service.name: my-service-name
prometheus:
wal: /prometheus/wal
endpoint: http://192.168.10.10:9191
See an example configuration yaml file here
The sidecar requires write access to the directory to store its progress between restarts.
To configure the sidecar for a Prometheus server installed using the Prometheus Community Helm Charts.
To configure the core components of the Prometheus sidecar, add the following definition to your custom values.yaml:
server:
sidecarContainers:
- name: otel-sidecar
image: lightstep/opentelemetry-prometheus-sidecar
imagePullPolicy: Always
args:
- --prometheus.wal=/data/wal
- --destination.endpoint=$(DESTINATION)
- --destination.header=lightstep-access-token=AAAAAAAAAAAAAAAA
- --diagnostics.endpoint=$(DIAGNOSTIC)
- --diagnostics.header=lightstep-access-token=AAAAAAAAAAAAAAAA
volumeMounts:
- name: storage-volume
mountPath: /data
ports:
- name: admin-port
containerPort: 9091
livenessProbe:
httpGet:
path: /-/health
port: admin-port
periodSeconds: 30
failureThreshold: 2
To configure the sidecar using the Prometheus Operator via the kube-prometheus-stack helm chart:
NOTE: the volume configured in the sidecar must be the same volume as prometheus uses
prometheus:
prometheusSpec:
containers:
- name: otel-sidecar
image: lightstep/opentelemetry-prometheus-sidecar:latest
imagePullPolicy: Always
args:
- --prometheus.wal=/prometheus/prometheus-db/wal
- --destination.endpoint=$(DESTINATION)
- --destination.header=lightstep-access-token=AAAAAAAAAAAAAAAA
- --diagnostics.endpoint=$(DIAGNOSTIC)
- --diagnostics.header=lightstep-access-token=AAAAAAAAAAAAAAAA
#####
ports:
- name: admin-port
containerPort: 9091
#####
livenessProbe:
httpGet:
path: /-/health
port: admin-port
periodSeconds: 30
failureThreshold: 2
#####
resources:
requests:
ephemeral-storage: "50M"
volumeMounts:
- name: prometheus-db
mountPath: /prometheus
The upstream Stackdriver Prometheus sidecar Kubernetes README contains more examples of how to patch an existing Prometheus deployment or deploy the sidecar without using Helm.
Most sidecar configuration settings can be set through command-line
flags, while a few more rarely-used options are only settable through
a yaml configuration file. To see all available command-line flags,
run opentelemetry-prometheus-sidecar --help. The printed usage is
shown below:
usage: opentelemetry-prometheus-sidecar [<flags>]
The OpenTelemetry Prometheus sidecar runs alongside the Prometheus
(https://prometheus.io/) Server and sends metrics data to an OpenTelemetry
(https://opentelemetry.io) Protocol endpoint.
Flags:
-h, --help Show context-sensitive help (also try
--help-long and --help-man).
--version Show application version.
--config-file=CONFIG-FILE A configuration file.
--destination.endpoint=DESTINATION.ENDPOINT
Destination address of a OpenTelemetry Metrics
protocol gRPC endpoint (e.g.,
https://host:port). Use "http" (not "https")
for an insecure connection.
--destination.attribute=DESTINATION.ATTRIBUTE ...
Destination resource attributes attached to
OTLP data (e.g., MyResource=Value1). May be
repeated.
--destination.header=DESTINATION.HEADER ...
Destination headers used for OTLP requests
(e.g., MyHeader=Value1). May be repeated.
--destination.timeout=DESTINATION.TIMEOUT
Destination timeout used for OTLP Export()
requests
--destination.compression=DESTINATION.COMPRESSION
Destination compression used for OTLP requests
(e.g., snappy, gzip, none).
--diagnostics.endpoint=DIAGNOSTICS.ENDPOINT
Diagnostics address of a OpenTelemetry Metrics
protocol gRPC endpoint (e.g.,
https://host:port). Use "http" (not "https")
for an insecure connection.
--diagnostics.attribute=DIAGNOSTICS.ATTRIBUTE ...
Diagnostics resource attributes attached to
OTLP data (e.g., MyResource=Value1). May be
repeated.
--diagnostics.header=DIAGNOSTICS.HEADER ...
Diagnostics headers used for OTLP requests
(e.g., MyHeader=Value1). May be repeated.
--diagnostics.timeout=DIAGNOSTICS.TIMEOUT
Diagnostics timeout used for OTLP Export()
requests
--diagnostics.compression=DIAGNOSTICS.COMPRESSION
Diagnostics compression used for OTLP requests
(e.g., snappy, gzip, none).
--prometheus.wal=PROMETHEUS.WAL
Directory from where to read the Prometheus
TSDB WAL. Default: data/wal
--prometheus.endpoint=PROMETHEUS.ENDPOINT
Endpoint where Prometheus hosts its UI, API,
and serves its own metrics. Default:
http://127.0.0.1:9090/
--prometheus.max-point-age=PROMETHEUS.MAX-POINT-AGE
Skip points older than this, to assist
recovery. Default: 25h0m0s
--prometheus.health-check-request-timeout=PROMETHEUS.HEALTH-CHECK-REQUEST-TIMEOUT
Timeout used for health-check requests to the prometheus endpoint. Default: 5s
--prometheus.scrape-interval=PROMETHEUS.SCRAPE-INTERVAL ...
Ignored. This is inferred from the Prometheus
via api/v1/status/config
--admin.port=ADMIN.PORT Administrative port this process listens on.
Default: 9091
--admin.listen-ip=ADMIN.LISTEN-IP
Administrative IP address this process listens
on. Default: 0.0.0.0
--security.root-certificate=SECURITY.ROOT-CERTIFICATE ...
Root CA certificate to use for TLS connections,
in PEM format (e.g., root.crt). May be
repeated.
--opentelemetry.max-bytes-per-request=OPENTELEMETRY.MAX-BYTES-PER-REQUEST
Send at most this many bytes per request.
Default: 65536
--opentelemetry.min-shards=OPENTELEMETRY.MIN-SHARDS
Min number of shards, i.e. amount of
concurrency. Default: 1
--opentelemetry.max-shards=OPENTELEMETRY.MAX-SHARDS
Max number of shards, i.e. amount of
concurrency. Default: 200
--opentelemetry.metrics-prefix=OPENTELEMETRY.METRICS-PREFIX
Customized prefix for exporter metrics. If not
set, none will be used
--filter=FILTER ... PromQL metric and attribute matcher which must
pass for a series to be forwarded to
OpenTelemetry. If repeated, the series must
pass any of the filter sets to be forwarded.
--startup.timeout=STARTUP.TIMEOUT
Timeout at startup to allow the endpoint to
become available. Default: 10m0s
--healthcheck.period=HEALTHCHECK.PERIOD
Period for internal health checking; set at a
minimum to the shortest Promethues scrape
period
--healthcheck.threshold-ratio=HEALTHCHECK.THRESHOLD-RATIO
Threshold ratio for internal health checking.
Default: 0.5
--log.level=LOG.LEVEL Only log messages with the given severity or
above. One of: [debug, info, warn, error]
--log.format=LOG.FORMAT Output format of log messages. One of: [logfmt,
json]
--log.verbose=LOG.VERBOSE Verbose logging level: 0 = off, 1 = some, 2 =
more; 1 is automatically added when log.level
is 'debug'; impacts logging from the gRPC
library in particular
--leader-election.enabled Enable leader election to choose a single writer.
--leader-election.k8s-namespace=LEADER-ELECTION.K8S-NAMESPACE
Namespace used for the leadership election lease.
--disable-supervisor Disable the supervisor.
--disable-diagnostics Disable diagnostics by default; if unset,
diagnostics will be auto-configured to the
primary destination
Two kinds of sidecar customization are available only through the configuration file. An example sidecar yaml configuration documents the available options.
Command-line and configuration files can be used at the same time, where command-line parameter values override configuration-file parameter values, with one exception. Configurations that support a map from string to string, including both request headers and resource attributes, are combined from both sources.
The sidecar waits until Prometheus finishes its first scrape(s) to begin processing the WAL, to ensure that target information is available before the sidecar tries loading its metadata cache.
This information is obtained through the Prometheus
api/v1/status/config endpoint. The sidecar will log which intervals
it is waiting for during startup. When using very long scrape
intervals, raise the --startup.timeout setting so the sidecar will
wait long enough to begin running.
The following settings give the user control over the amount of memory used by the sidecar for concurrent RPCs.
The sidecar uses a queue to manage distributing data points from the
Prometheus WAL to a variable number of workers, referred to as
"shards". Each shard assembles a limited size request, determined by
--opentelemetry.max-bytes-per-request (default: 64kB).
The number of shards varies in response to load, based on the observed
latency. Upper and lower bounds on the number of shards are
configured by --opentelemetry.min-shards and
--opentelemetry.max-shards.
CPU usage is determined by the number of shards and the workload. Use
--opentelemetry.max-shards to limit the maximum CPU used by the
sidecar.
The sidecar reports validation errors using conventions established by
Lightstep for conveying information about partial success when
writing to the OTLP destination. These errors are returned using gRPC
"trailers" (a.k.a. http2 response headers) and are output as metrics
and logs. See the sidecar.metrics.failing metric to diagnose
validation errors.
The sidecar may encounter errors between itself and Prometheus,
including failures to locate metadata about a targets that Prometheus
no longer knows about. Missing metadata, Prometheus API errors, and
other forms of inconsistency are reported using
sidecar.metrics.failing with key_reason and metric_name attributes.
Use the --destination.attribute=KEY=VALUE flag to add additional OpenTelemetry resource attributes to all exported timeseries.
Prometheus external labels are used for diagnostic purposes but are not attached to exported timeseries.
The --filter flag allows to provide filters which all series have to pass before being sent to the destination. Filters use the same syntax as Prometheus instant vector selectors, e.g.:
opentelemetry-prometheus-sidecar --filter='{__name__!~"cadvisor_.+",job="k8s"}' ...
This drops all series which do not have a job label k8s and all metrics that have a name starting with cadvisor_.
For equality filter on metric name you can use the simpler notation, e.g. --filter='metric_name{label="foo"}'.
The flag may be repeated to provide several sets of filters, in which case the metric will be forwarded if it matches at least one of them.
To change the name of a metric as it is exported, use the
metric_renames section in the configuration file:
metric_renames:
- from: original_metric_name
to: new_metric_name
# - ...To change the output type, value type, or description of a metric
instrument as it is exported, use the static_metadata section in the
configuration file:
static_metadata:
- metric: some_metric_name
type: counter # or gauge, or histogram
value_type: double # or int64
help: an arbitrary help string
# - ...Note:
- All
static_metadataentries must havetypespecified. - If
value_typeis specified, it will override the default value type for counters and gauges. All Prometheus metrics have a default type of double.
In a HA prometheus setup, a prometheus sidecar can be attached to each replica. All sidecars will write all metric points, it is responsibility of the backend of choice to deduplicate these points.
The leader election can be enabled in order to restrict which replica will send metrics to the Collector, reducing the amount of metrics transferred on the wire.
One of the sidecars will be elected as the Leader, this leader sidecar will tail the Prometheus WAL log, transform and send OTLP metrics to the Collector. All other non-leader sidecars will be in a stand-by mode, it will tail the Prometheus WAL log, but will not send any data to the Collector.
If the leader sidecar fails, a new Leader will be elected and will resume sending data to the collector.
The leader election uses the kubernetes coordination API to elect a leader. Ensure that there is a service account for Prometheus in Kubernetes and then bind it to the role with the following permissions:
rules:
- apiGroups:
- coordination.k8s.io
resources:
- leases
verbs:
- '*'After to the service account permissions are set up, set the argument flag --leader-election.enabled on the prometheus sidecar.
To change the namespace used for the leadership election lease, set --leader-election.k8s-namespace=LEADER-ELECTION.K8S-NAMESPACE.
When run in the default configuration, the sidecar will self-monitor for liveness and kill the process when it becomes unhealthy. Sidecar liveness can be monitored directly using the /-/health endpoint. We recommend a period of 30 seconds and failureThreshold: 2, for example in your Kubernetes deployment:
ports:
- name: admin-port
containerPort: 9091
livenessProbe:
httpGet:
path: /-/health
port: admin-port
periodSeconds: 30
failureThreshold: 2
The sidecar is instrumented with the OpenTelemetry-Go SDK and runs with standard instrumentation packages, including runtime and host metrics.
By default, diagnostics are autoconfigured to the primary destination. Configuration options are available to disable or configure alternative destinations and options.
Separate diagnostics settings can be configure to output OTLP similar to configuring the primary destination, for example:
diagnostics:
endpoint: https://otel-collector:443
headers:
Custom-Header: custom-value
timeout: timeout-value
attributes:
extra.resource: extra-value
Likewise, these fields can be accessed using --diagnostics.endpoint,
--diagnostics.header, --diagnostics.timeout, and --diagnostics.attribute.
The Prometheus sidecar provides options for logging in the case of diagnosing an issue.
- We recommend starting with setting the
--log.levelto bedebug,info,warn,error. - Additional options are available to set the output format of the logs (
--log.formatto belogfmtorjson), and the number of logs to recorded (--log.verboseto be0for off,1for some,2for more)
To disable diagnostics, set the argument flag --disable-diagnostics.
The Prometheus Sidecar has two main processes, the supervisor and a subordinate process. Diagnostic traces are sent from the supervisor process to monitor lifecycle events and diagnostic metrics are sent from the subordinate process.
Traces from the supervisor process are most helpful for diagnosing unknown problems. It signals lifecycle events and captures the stderr, attaching it to the trace.
The sidecar will output spans from its supervisor process with service.name=opentelemetry-prometheus-sidecar-supervisor. There are two kinds of spans: operation=health-client and operation=shutdown-report. These spans are also tagged with the attribute sidecar-health with values ok, not yet ready or first time ready.
Metrics from the subordinate process can help identify issues once the first metrics are successfully written. There are three standard host and runtime metrics to monitor:
Key Success Metrics
These metrics are key to understanding the health of the sidecar. They are periodically printed to the console log to assist in troubleshooting.
| Metric Name | Type | Description | Additional Attributes |
|---|---|---|---|
| sidecar.points.produced | counter | number of points read from the prometheus WAL | |
| sidecar.points.dropped | counter | number of points dropped due to errors | key_reason: metadata, validation |
| sidecar.points.skipped | counter | number of points skipped by filters | |
| sidecar.queue.outcome | counter | outcome of the sample in the queue | outcome: success, failed, retry, aborted |
| sidecar.series.dropped | counter | number of series or metrics dropped | key_reason: metadata, validation |
| sidecar.series.current | gauge | number of series in the cache | status: live, filtered, invalid |
| sidecar.metrics.failing | gauge | failing metric names and explanations | key_reason, metric_name |
Progress Metrics
Two metrics indicate the sidecar's progress in processing the
Prometheus write-ahead-log (WAL). These are measured in bytes and are
based on the assumption that each WAL segment is a complete 128MB.
Both of these figures are exported as current_segment_number * 128MB + segment_offset. The difference (i.e., sidecar.wal.size - sidecar.wal.offset) indicates how far the sidecar has to catch up,
assuming complete WAL segments.
| Metric Name | Type | Description |
|---|---|---|
| sidecar.wal.size | gauge | current writer position of the Prometheus write-ahead log |
| sidecar.wal.offset | gauge | current reader position in the Prometheus write-ahead log |
Host and Runtime Metrics
| Metric Name | Type | Description | Additional Attributes |
|---|---|---|---|
| process.cpu.time | counter | cpu seconds used | state: user, sys |
| system.network.io | counter | bytes sent and received | direction: read, write |
| runtime.go.mem.heap_alloc | gauge | memory in use |
Internal Metrics
These metrics are diagnostic in nature, meant for characterizing performance of the code and individual Prometheus installations. Operators can safely ignore these metrics except to better understand sidecar performance.
| Metric Name | Type | Description | Additional Attributes |
|---|---|---|---|
| sidecar.connect.duration | histogram | how many attempts to connect (and how long) | error: true, false |
| sidecar.export.duration | histogram | how many attempts to export (and how long) | error: true, false |
| sidecar.monitor.duration | histogram | how many attempts to scrape Prometheus /metrics (and how long) | error: true, false |
| sidecar.metadata.fetch.duration | histogram | how many attempts to fetch metadata from Prometheus (and how long) | mode: single, batch; error: true, false |
| sidecar.queue.capacity | gauge | number of available slots for samples (i.e., points) in the queue, counts buffer size times current number of shards | |
| sidecar.queue.running | gauge | number of running shards, those which have not exited | |
| sidecar.queue.shards | gauge | number of current shards, as set by the queue manager | |
| sidecar.queue.size | gauge | number of samples (i.e., points) standing in a queue waiting to export | |
| sidecar.series.defined | counter | number of series defined in the WAL | |
| sidecar.metadata.lookups | counter | number of calls to lookup metadata | error: true, false |
| sidecar.refs.collected | counter | number of WAL series refs removed from memory by garbage collection | error: true, false |
| sidecar.refs.notfound | counter | number of WAL series refs that were not found during lookup | |
| sidecar.segment.opens | counter | number of WAL segment open() calls | |
| sidecar.segment.reads | counter | number of WAL segment read() calls | |
| sidecar.segment.bytes | counter | number of WAL segment bytes read | |
| sidecar.segment.skipped | counter | number of skipped WAL segments | |
| sidecar.leadership | gauge | indicate if this sidecar is the leader or not |
This repository was copied into a private reposotitory from this upstream fork of stackdriver-prometheus-sidecar, dated July 31, 2020.
The matrix below lists the versions of Prometheus Server and other dependencies that have been qualified to work with releases of opentelemetry-prometheus-sidecar. If the matrix does not list whether they are compatible, please assume they are not verified yet but can be compatible. Feel free to contribute to the matrix if you have run the end-to-end test between a version of opentelemetry-prometheus-sidecar and Prometheus server.
| Sidecar Version | Compatible Prometheus Server Version(s) | Incompatible Prometheus Server Version(s) |
|---|---|---|
| 0.1.x | 2.15, 2.16, 2.18, 2.19, 2.21, 2.22, 2.23, 2.24 | 2.5 |
The following describes known scenarios that can be problematic for the sidecar.
It's possible for the sidecar to not have enough resources by default to keep up with the WAL in high throughput scenarios. When this case occurs, the following message will be displayed in the sidecar's logs:
past WAL segment not found, sidecar may have dragged behind. Consider increasing min-shards, max-shards and max-bytes-per-request value
This message means that the sidecar is looking for a WAL segment file that has been removed, usually due to Prometheus triggering a checkpoint. It's possible to look at the delta between sidecar.wal.size (total wal entries) and sidecar.wal.offset (where the sidecar currently is) to determine if the sidecar has enough resources to keep up. If the offset is increasingly further behind the size, it's recommended to increase the timeseries emitted per request using the following configuration options:
--opentelemetry.max-bytes-per-requestconfigures the maximum number of timeseries sent with each request from the sidecar to the OTLP backend.--opentelemetry.max-shardsconfigures the number of parallel go routines and grpc connections used to transmit the data.
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