3 Commits (release/1.14)

Author	SHA1	Message	Date
Martin Holst Swende	8b6cf128af	metrics: refactor metrics (#28035) ... This change includes a lot of things, listed below. ### Split up interfaces, write vs read The interfaces have been split up into one write-interface and one read-interface, with `Snapshot` being the gateway from write to read. This simplifies the semantics _a lot_. Example of splitting up an interface into one readonly 'snapshot' part, and one updatable writeonly part: ```golang type MeterSnapshot interface { Count() int64 Rate1() float64 Rate5() float64 Rate15() float64 RateMean() float64 } // Meters count events to produce exponentially-weighted moving average rates // at one-, five-, and fifteen-minutes and a mean rate. type Meter interface { Mark(int64) Snapshot() MeterSnapshot Stop() } ``` ### A note about concurrency This PR makes the concurrency model clearer. We have actual meters and snapshot of meters. The `meter` is the thing which can be accessed from the registry, and updates can be made to it. - For all `meters`, (`Gauge`, `Timer` etc), it is assumed that they are accessed by different threads, making updates. Therefore, all `meters` update-methods (`Inc`, `Add`, `Update`, `Clear` etc) need to be concurrency-safe. - All `meters` have a `Snapshot()` method. This method is _usually_ called from one thread, a backend-exporter. But it's fully possible to have several exporters simultaneously: therefore this method should also be concurrency-safe. TLDR: `meter`s are accessible via registry, all their methods must be concurrency-safe. For all `Snapshot`s, it is assumed that an individual exporter-thread has obtained a `meter` from the registry, and called the `Snapshot` method to obtain a readonly snapshot. This snapshot is _not_ guaranteed to be concurrency-safe. There's no need for a snapshot to be concurrency-safe, since exporters should not share snapshots. Note, though: that by happenstance a lot of the snapshots _are_ concurrency-safe, being unmutable minimal representations of a value. Only the more complex ones are _not_ threadsafe, those that lazily calculate things like `Variance()`, `Mean()`. Example of how a background exporter typically works, obtaining the snapshot and sequentially accessing the non-threadsafe methods in it: ```golang ms := metric.Snapshot() ... fields := map[string]interface{}{ "count": ms.Count(), "max": ms.Max(), "mean": ms.Mean(), "min": ms.Min(), "stddev": ms.StdDev(), "variance": ms.Variance(), ``` TLDR: `snapshots` are not guaranteed to be concurrency-safe (but often are). ### Sample changes I also changed the `Sample` type: previously, it iterated the samples fully every time `Mean()`,`Sum()`, `Min()` or `Max()` was invoked. Since we now have readonly base data, we can just iterate it once, in the constructor, and set all four values at once. The same thing has been done for runtimehistogram. ### ResettingTimer API Back when ResettingTImer was implemented, as part of https://github.com/ethereum/go-ethereum/pull/15910, Anton implemented a `Percentiles` on the new type. However, the method did not conform to the other existing types which also had a `Percentiles`. 1. The existing ones, on input, took `0.5` to mean `50%`. Anton used `50` to mean `50%`. 2. The existing ones returned `float64` outputs, thus interpolating between values. A value-set of `0, 10`, at `50%` would return `5`, whereas Anton's would return either `0` or `10`. This PR removes the 'new' version, and uses only the 'legacy' percentiles, also for the ResettingTimer type. The resetting timer snapshot was also defined so that it would expose the internal values. This has been removed, and getters for `Max, Min, Mean` have been added instead. ### Unexport types A lot of types were exported, but do not need to be. This PR unexports quite a lot of them.	1 year ago
Exca-DK	b4dcd1a391	metrics: make gauge_float64 and counter_float64 lock free (#27025) ... Makes the float-gauges lock-free name old time/op new time/op delta CounterFloat64Parallel-8 1.45µs ±10% 0.85µs ± 6% -41.65% (p=0.008 n=5+5) --------- Co-authored-by: Exca-DK <dev@DESKTOP-RI45P4J.localdomain> Co-authored-by: Martin Holst Swende <martin@swende.se>	2 years ago
turboboost55	7dc100714d	metrics: add cpu counters (#26796) ... This PR adds counter metrics for the CPU system and the Geth process. Currently the only metrics available for these items are gauges. Gauges are fine when the consumer scrapes metrics data at the same interval as Geth produces new values (every 3 seconds), but it is likely that most consumers will not scrape that often. Intervals of 10, 15, or maybe even 30 seconds are probably more common. So the problem is, how does the consumer estimate what the CPU was doing in between scrapes. With a counter, it's easy ... you just subtract two successive values and divide by the time to get a nice, accurate average. But with a gauge, you can't do that. A gauge reading is an instantaneous picture of what was happening at that moment, but it gives you no idea about what was going on between scrapes. Taking an average of values is meaningless.	2 years ago