Convert client_java to OpenMetrics #615

brian-brazil · 2021-01-18T15:02:34Z

This switches the core data model to OM, adds support for negotiating and exposing OpenMetrics format, adds units, created time, and adds new direct instrumentation for Info and Enum.

This is done as gracefully as practical, but this will break users - in particular if a) they have counters lacking a _total suffix in which case the sample names will change or b) if they happen to be using UNTYPED which is now called UNKNOWN in which case they'll need up update their code.

Signed-off-by: Brian Brazil <brian.brazil@robustperception.io>

robskillington · 2021-01-21T04:14:18Z

simpleclient/src/main/java/io/prometheus/client/Collector.java

+      List<Sample> mungedSamples = samples;
+      // Deal with _total from pre-OM automatically.
+      if (type == Type.COUNTER) {
+        if (name.endsWith("_total")) {


nit: Worth making _total a const? Then can name.endsWith(counterSuffix) and name = name.substring(0, name.length() - counterSuffix.length()).

I don't like indirection like that, it only makes the code harder to understand for me as I have to bounce around the file for something that could be understood one its own line.

robskillington · 2021-01-21T04:14:33Z

simpleclient/src/main/java/io/prometheus/client/Collector.java

+        if (name.endsWith("_total")) {
+          name = name.substring(0, name.length() - 6);
+        }
+        String withTotal = name + "_total";


nit: This could also use the const.

robskillington · 2021-01-21T04:17:37Z

simpleclient/src/main/java/io/prometheus/client/CollectorRegistry.java

+          names.add(family.name + "_created");
+          names.add(family.name);
+          break;
+        case GAUGE_HISTOGRAM:


Believe gauge histogram should also have _created?

No, gauges don't have a created.

If so, should we change the proto then? HistogramValue can be used with GAUGE_HISTOGRAM:
https://github.com/OpenObservability/OpenMetrics/blob/master/proto/openmetrics_data_model.proto#L136-L138

I suppose implementors could enforce that's not combined together?

We should clarify that then.

robskillington · 2021-01-21T04:19:05Z

simpleclient/src/main/java/io/prometheus/client/Counter.java

+      if (name.endsWith("_total")) {
+        name = name.substring(0, name.length() - 6);


nit: These could reference the _total const?

robskillington · 2021-01-21T04:21:33Z

simpleclient/src/main/java/io/prometheus/client/Counter.java

+    /**
+     * Get the created time of the counter in milliseconds.
+     */
+    public long created() {


Should this maybe be a float in seconds? That way callers don't need to divide by 1000.0 to get the value they should expose, also since this accessor doesn't have the unit (seconds/milliseconds/etc) maybe it's best to return the unit that's expected to be exposed for exposition?

Java's current time function returns milliseconds, so that's the effective standard inside Java - and thus also what the client uses everywhere already.

robskillington · 2021-01-21T04:52:25Z

simpleclient/src/main/java/io/prometheus/client/SimpleCollector.java

@@ -209,6 +215,13 @@ public B namespace(String namespace) {
      this.namespace = namespace;
      return (B)this;
    }
+    /**
+     * Set the uit of the metric. Required.


Believe uit should be unit?

robskillington · 2021-01-21T04:54:11Z

simpleclient/src/test/java/io/prometheus/client/SimpleCollectorTest.java

+    Gauge g = Gauge.build().name("a").unit("seconds").help("h").create();
+    assertEquals("a_seconds", g.fullname);
+
+    Gauge g2 = Gauge.build().name("a_seconds").unit("seconds").help("h").create();
+    assertEquals("a_seconds", g2.fullname);


Worth adding a test to observe the unit being added if the name doesn't correctly have the unit on it already when built?

That's what the test right above this is doing.

robskillington · 2021-01-21T04:54:29Z

...nt_caffeine/src/test/java/io/prometheus/client/cache/caffeine/CacheMetricsCollectorTest.java

@@ -70,6 +70,7 @@ public void loadingCacheExposesMetricsForLoadsAndExceptions() throws Exception {
        }
        cache.get("user3");

+


nit: Probably could be removed this line change?

robskillington · 2021-01-21T04:56:07Z

simpleclient_common/src/main/java/io/prometheus/client/exporter/common/TextFormat.java

+    }
+
+    for (String accepts : acceptHeader.split(",")) {
+      if ("application/openmetrics-text".equals(accepts.split(";")[0].trim())) {


nit: Worth making this a const? It's used both in the content-type + version string const as well as here when detecting the accept type.

I don't think it'd aid readability to have a constant based on other constants, this is a well known string - I find it easier to have the raw text rather than digging through layers of indirection to see what this code is actually doing.

robskillington · 2021-01-21T04:57:47Z

simpleclient_common/src/main/java/io/prometheus/client/exporter/common/TextFormat.java

+      if (metricFamilySamples.type == Collector.Type.COUNTER) {
+        writer.write("_total");
+      }


Hm is Prometheus text version output also meant to have the suffixes appended? I thought only OpenMetrics format would get that?

Yes, no matter which format is negotiated the exact same samples should end up inside Prometheus.

robskillington · 2021-01-21T05:04:10Z

simpleclient_common/src/main/java/io/prometheus/client/exporter/common/TextFormat.java

@@ -53,6 +124,10 @@ public static void write004(Writer writer, Enumeration<Collector.MetricFamilySam
        writer.write('\n');
      }
    }
+    // Write out any OM-specific samples.
+    if (!omFamilies.isEmpty()) {
+      write004(writer, Collections.enumeration(omFamilies.values()));


Hm, could this not be recursive since this is in write004 method itself? i.e. could it not each time collect into omFamilies and recurse but not actually writing it in the child recursive call but simply recursing again infinitely?

Haven't looked to see if there's a test or not for this just yet.

The if is there for a reason. Java lacks inner functions, so this is the easy way to not repeat the rendering logic.

Ah yes, I see - and these will be gauges in the recurse function. Makes sense.

robskillington · 2021-01-21T05:07:59Z

simpleclient_common/src/main/java/io/prometheus/client/exporter/common/TextFormat.java

@@ -100,8 +175,101 @@ private static String typeString(Collector.Type t) {
        return "summary";
      case HISTOGRAM:
        return "histogram";
+      case GAUGE_HISTOGRAM:
+        return "histogram";


Hm, isn't this written out as a gauge? As per detecting if gsum/gcount is present?

Histogram is the closest structurally, even if it's technically a gauge. The Python client does the same.

beorn7 · 2021-01-21T13:10:42Z

Since the Prometheus server cannot be configured to not negotiate OpenMetrics, is it perhaps worth it to make OpenMetrics opt-in here, at least for a transition period? I assume this instrumentation library has loads of users, and many will naively update and then be taken by surprise by the changes in naming and the potential of name collisions.

The opt-in has worked quite well in client_golang. People still run into surprising (for them) issues, but at least they have very explicitly activated OpenMetrics and can easily switch it off again if needed.

brian-brazil · 2021-01-21T13:40:52Z

This PR is at its core a fundamental data model change, the addition of additional output formats and new metric types are incidental to that. No matter what format is negotiated, Prometheus will ultimately ingest the same samples. Having which internal data model to use would be non-trivial, and thus it does not make sense to make this configurable. I'm taking the same approach here as with client_python, clearing calling out the change in the release notes and announcements which is fine as this library is not 1.0. If users wish to continue to use the old code, they can not upgrade.

client_golang still uses the Prometheus data model internally, so it's not a good comparison.

beorn7 · 2021-01-21T14:06:01Z

My argument is purely from the users' perspective. They don't care about the internal data model.

I'm not disputing that we are technically entitled to any breaking changes in a pre-1.0 release. However, I think we should still try to be nice to our users if we can. And even if we are technically not breaking any promises, many users will still see it as "our fault" if things break unexpectedly (from their perspective).

The Python client already caused some trouble with the many added _created timeseries (which could only be prevented by not upgrading the Python client). That's however, just a load problem. Name collisions and suddenly enforced _total suffixes on counters are way more problematic. I'd expect client_java to run more commonly in large, complex, and highly critical production environments. I'm afraid releasing this as is under the current circumstances could hit the trust in the project quite a bit.

If at least Prometheus could have a configurable priority for content negotiation, we could at least offer a quick mitigation strategy.

RichiH · 2021-01-21T14:41:32Z

Would cutting a 0.10 (or 0.9.1) before merging this PR be a compromise?

beorn7 · 2021-01-21T14:59:00Z

It's technically a compromise, but it doesn't address the problem.

Users will suffer the same fate with 0.11. Please also take into account that instrumentation happens in code that is not your own, where you are not in control of which version to use. (See the recent Caddy issues as an example from the Go world. At least, Caddy could fix it by adding a configuration option for their users. And zero blame was put on the Prometheus project.)

I think the following migration path would be the least bad:

0.10 has OM as opt-in, so users can test it in their environments without any risk of activating OM without even knowing it.
0.11 has OM as opt-out, so whoever didn't test it and didn't get the message will now learn it the hard way, but can easily switch off.
0.12 will always negotiate OM if possible.

brian-brazil · 2021-01-21T15:31:10Z

I think the following migration path would be the least bad:

The problem with that suggested path is that it requires making a data model configurable, which is not a reasonable request as that's such a fundamental aspect of the code and would be a major amount of work. This PR was tricky enough as-is without having to duplicate all the relevant code and make it all cleanly and correctly interoperate somehow.

has OM as opt-in, ... has OM as opt-out, ... negotiate OM if possible.

Once again this is primarily a data model change, which metric format(s) can be negotiated is irrelevant as we'll always end up with the exact same samples being ingested into Prometheus. The way you can opt in or opt out is by choosing the version of client_java to use. If you don't like the change, it's easy to downgrade again.

Users will suffer the same fate with 0.11. Please also take into account that instrumentation happens in code that is not your own, where you are not in control of which version to use.

That's not a problem, as that's not how Java dependency resolution works. Whoever builds the final "binary" gets to choose which version is used, not the individual library developers. An end-user can also readily produce such a "binary" with a different version. You can't somehow end up with two different versions of the relevant code inside the binary claiming to both be the simpleclient. There's also no backwards incompatible ABI changes here (I'm always careful with that), so users can roll forwards/backwards as long as they don't write code that uses any of the new features.

Ultimately this is a change which has been carefully considered and publicly communicated for well over a year, including how users can migrate in this grace period. This is the PR that ends that ends the grace period Java, so if users choose to upgrade then they get the OM data model and new metric names with that. If they want to stay as-is, they're free to do that too.

juliusv · 2021-01-21T16:19:09Z

Without having reviewed the code or knowing Java, I'd tend to agree with @brian-brazil here if it's true that the binary author is in control of all dependency versions in Java, and if it's indeed a lot of extra effort to make the behavior configurable within the same version. But again, this is just my 2c without having taken a deep look at things.

roidelapluie · 2021-01-21T16:33:19Z

Thanks for this pull request.

By looking at the code, it seems that we still support prometheus text format. So it seems reasonable to add a feature to not check for _total, _unit and keep the original provided name. And that if you opt-in for OpenMetrics, we serve OM when negociated and run the checks about unit and total.

It also seems that the pre-om functions are not marked as @deprecated, which is something that I think we should do.

brian-brazil · 2021-01-25T13:20:28Z

Thanks for the discussion everyone, rollouts like these are always a bit tricky but all things considered I think this is the best path.

Prometheus is changing the naming scheme of some of their metrics in order to be compatible with the OpenMetrics standard. Part of this means that all counters will have `_total` or `_created` as a suffix. There is no way to create a counter without a `_total` suffix. See: prometheus/client_java#615

shakuzen · 2021-01-27T04:55:51Z

simpleclient/src/main/java/io/prometheus/client/SimpleCollector.java

@@ -209,6 +215,13 @@ public B namespace(String namespace) {
      this.namespace = namespace;
      return (B)this;
    }
+    /**
+     * Set the unit of the metric. Required.


Isn't a unit optional, not required? From the OpenMetrics spec:

If non-empty, it MUST be a suffix of the MetricFamily name separated by an underscore.

Indeed this is a copy&paste error, would you like to send a PR to fix this?

Sure. I've opened #619

It was incorrectly documented as required when initially introduced. See prometheus#615 (comment) Signed-off-by: Tommy Ludwig <8924140+shakuzen@users.noreply.github.com>

It was incorrectly documented as required when initially introduced. See #615 (comment) Signed-off-by: Tommy Ludwig <8924140+shakuzen@users.noreply.github.com>

justinabrahms · 2022-02-11T18:36:01Z

Just hopping in to mention that this broke a few services in my company due to the backwards incompatible change. :(

nobletrout · 2022-04-27T21:02:15Z

yup this broke stuff.

Prometheus is changing the naming scheme of some of their metrics in order to be compatible with the OpenMetrics standard. Part of this means that all counters will have `_total` or `_created` as a suffix. There is no way to create a counter without a `_total` suffix. See: prometheus/client_java#615

deepak-auto · 2022-06-13T14:59:49Z

We are blocked from upgrading to a newer version of Spring Boot because of this 🤷 Now our backlog involves fixing dozens, if not hundreds, of alerts and dashboards.

fwbrasil · 2022-06-22T16:16:50Z

We're also blocked from upgrading at Nubank. Fixing all of our alerts, dashboards, and integrations that consume prometheus data is going to be challenging. Would it be possible to provide a better migration path where the new behavior is configurable?

bwplotka · 2022-06-25T08:52:30Z

Ack, thanks for the reports (feel free to drop more of them or +1 the issue, it lets us know how important this issue is). 🤗

We are aware of this and we are actively discussing the way to unblock you and the way forward with OM transitions here and with other Prometheus clients.

fwbrasil · 2022-07-01T04:29:03Z

thank you @bwplotka! Please let me know if we can help. Upgrading the client would solve an important performance issue for us (#777)

fwbrasil · 2022-07-26T22:04:14Z

hi folks! any updates on this?

brian-brazil added 10 commits January 18, 2021 14:45

Add support for OM Units, and Counter naming.

819a857

Signed-off-by: Brian Brazil <brian.brazil@robustperception.io>

Get basic OM rendering working with HttpServer.

6847f9f

Signed-off-by: Brian Brazil <brian.brazil@robustperception.io>

Update and add tests and code for _total handling.

99e209d

Signed-off-by: Brian Brazil <brian.brazil@robustperception.io>

Get all the http servers working with OM.

d4f32a2

Signed-off-by: Brian Brazil <brian.brazil@robustperception.io>

Add OM output tests.

706672a

Signed-off-by: Brian Brazil <brian.brazil@robustperception.io>

Add handling for gsum/gcount/created in Prometheus exposition format.

801f91e

Signed-off-by: Brian Brazil <brian.brazil@robustperception.io>

Add _created for direct instrumentation.

5c0d1e7

Signed-off-by: Brian Brazil <brian.brazil@robustperception.io>

Add support for Enumeration.

92d34e3

Signed-off-by: Brian Brazil <brian.brazil@robustperception.io>

Add support for Info metrics

37fa7fb

Signed-off-by: Brian Brazil <brian.brazil@robustperception.io>

Make jvm_info use an Info. UNTYPED -> UNKNOWN.

784db17

Signed-off-by: Brian Brazil <brian.brazil@robustperception.io>

robskillington reviewed Jan 21, 2021

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brian-brazil merged commit 5c66e58 into master Jan 25, 2021

brian-brazil deleted the om branch January 25, 2021 13:20

isomarcte mentioned this pull request Jan 25, 2021

Update Prometheus Client To 0.10.0 And Fix Tests http4s/http4s#4273

Merged

shakuzen reviewed Jan 27, 2021

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shakuzen mentioned this pull request Jan 27, 2021

Document unit as optional #619

Merged

brian-brazil pushed a commit that referenced this pull request Jan 27, 2021

Document unit as optional (#619)

0196c28

It was incorrectly documented as required when initially introduced. See #615 (comment) Signed-off-by: Tommy Ludwig <8924140+shakuzen@users.noreply.github.com>

joe-elliott mentioned this pull request Jan 27, 2021

Add Exemplar Support to Client Java #622

Closed

Limess mentioned this pull request Jun 23, 2021

Support "Info" metrics clj-commons/iapetos#55

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hezhangjian mentioned this pull request Jan 20, 2022

Bump prometheus client version from 0.5.0 to 0.15.0 apache/pulsar#13785

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1 task

This was referenced Aug 18, 2022

How to use gauge histograms? #807

Open

Add direct support for new OpenMetrics types: GaugeHistogram, StateSet and Info micrometer-metrics/micrometer#3360

Open

kgann mentioned this pull request Sep 15, 2022

Add ::path-cache to registry collectors map metadata clj-commons/iapetos#59

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MartijnVisser mentioned this pull request Oct 13, 2022

[FLINK-29623][Metrics][Prometheus] Update Prometheus Java Client to 0.16.0 apache/flink#21047

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risdenk mentioned this pull request Mar 2, 2023

Update io.prometheus:* to v0.16.0 apache/solr#1419

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1 task

		if (name.endsWith("_total")) {
		name = name.substring(0, name.length() - 6);

		@@ -70,6 +70,7 @@ public void loadingCacheExposesMetricsForLoadsAndExceptions() throws Exception {
		}
		cache.get("user3");

Convert client_java to OpenMetrics #615

Convert client_java to OpenMetrics #615

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brian-brazil commented Jan 18, 2021

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beorn7 commented Jan 21, 2021 • edited Loading

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RichiH commented Jan 21, 2021

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