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- # ADR 011: Monitoring
-
- ## Changelog
-
- 08-06-2018: Initial draft
- 11-06-2018: Reorg after @xla comments
- 13-06-2018: Clarification about usage of labels
-
- ## Context
-
- In order to bring more visibility into Tendermint, we would like it to report
- metrics and, maybe later, traces of transactions and RPC queries. See
- https://github.com/tendermint/tendermint/issues/986.
-
- A few solutions were considered:
-
- 1. [Prometheus](https://prometheus.io)
- a) Prometheus API
- b) [go-kit metrics package](https://github.com/go-kit/kit/tree/master/metrics) as an interface plus Prometheus
- c) [telegraf](https://github.com/influxdata/telegraf)
- d) new service, which will listen to events emitted by pubsub and report metrics
- 5. [OpenCensus](https://opencensus.io/go/index.html)
-
- ### 1. Prometheus
-
- Prometheus seems to be the most popular product out there for monitoring. It has
- a Go client library, powerful queries, alerts.
-
- **a) Prometheus API**
-
- We can commit to using Prometheus in Tendermint, but I think Tendermint users
- should be free to choose whatever monitoring tool they feel will better suit
- their needs (if they don't have existing one already). So we should try to
- abstract interface enough so people can switch between Prometheus and other
- similar tools.
-
- **b) go-kit metrics package as an interface**
-
- metrics package provides a set of uniform interfaces for service
- instrumentation and offers adapters to popular metrics packages:
-
- https://godoc.org/github.com/go-kit/kit/metrics#pkg-subdirectories
-
- Comparing to Prometheus API, we're losing customisability and control, but gaining
- freedom in choosing any instrument from the above list given we will extract
- metrics creation into a separate function (see "providers" in node/node.go).
-
- **c) telegraf**
-
- Unlike already discussed options, telegraf does not require modifying Tendermint
- source code. You create something called an input plugin, which polls
- Tendermint RPC every second and calculates the metrics itself.
-
- While it may sound good, but some metrics we want to report are not exposed via
- RPC or pubsub, therefore can't be accessed externally.
-
- **d) service, listening to pubsub**
-
- Same issue as the above.
-
- ### 2. opencensus
-
- opencensus provides both metrics and tracing, which may be important in the
- future. It's API looks different from go-kit and Prometheus, but looks like it
- covers everything we need.
-
- Unfortunately, OpenCensus go client does not define any
- interfaces, so if we want to abstract away metrics we
- will need to write interfaces ourselves.
-
- ### List of metrics
-
- | | Name | Type | Description |
- | - | --------------------------------------- | ------- | ----------------------------------------------------------------------------- |
- | A | consensus_height | Gauge | |
- | A | consensus_validators | Gauge | Number of validators who signed |
- | A | consensus_validators_power | Gauge | Total voting power of all validators |
- | A | consensus_missing_validators | Gauge | Number of validators who did not sign |
- | A | consensus_missing_validators_power | Gauge | Total voting power of the missing validators |
- | A | consensus_byzantine_validators | Gauge | Number of validators who tried to double sign |
- | A | consensus_byzantine_validators_power | Gauge | Total voting power of the byzantine validators |
- | A | consensus_block_interval | Timing | Time between this and last block (Block.Header.Time) |
- | | consensus_block_time | Timing | Time to create a block (from creating a proposal to commit) |
- | | consensus_time_between_blocks | Timing | Time between committing last block and (receiving proposal creating proposal) |
- | A | consensus_rounds | Gauge | Number of rounds |
- | | consensus_prevotes | Gauge | |
- | | consensus_precommits | Gauge | |
- | | consensus_prevotes_total_power | Gauge | |
- | | consensus_precommits_total_power | Gauge | |
- | A | consensus_num_txs | Gauge | |
- | A | mempool_size | Gauge | |
- | A | consensus_total_txs | Gauge | |
- | A | consensus_block_size | Gauge | In bytes |
- | A | p2p_peers | Gauge | Number of peers node's connected to |
-
- `A` - will be implemented in the fist place.
-
- **Proposed solution**
-
- ## Status
-
- Proposed.
-
- ## Consequences
-
- ### Positive
-
- Better visibility, support of variety of monitoring backends
-
- ### Negative
-
- One more library to audit, messing metrics reporting code with business domain.
-
- ### Neutral
-
- -
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