46 posts tagged with "performance-tracing"

High level summary​

• Benchmarking: Plutus memory budget scaling benchmarks; UTxO-HD benchmarks, leading to a fixed regression; Genesis benchmarks.
• Development: Ouroboros Genesis and UTxO-HD adjustments in workbench; Maintenance tasks.
• Infrastructure: Removing outdated deployments; Haskell profile definition merged; workbench simplification ongoing.
• Tracing: C library development ongoing; Feature implementation according to community feedback; test removeal of old system.

Low level overview​

Benchmarking​

We've run and analyzed scaling benchmarks of Plutus execution budgets. In this series of benchmarks, we measured the performance impact of changes to the memory budgets (both transaction and block). We observed an expected, and reasonable, increase in certain metrics only. Furthermore, we've shown this increase to be linearly correlated to the budget raise. This means that when exploring the headroom of those budgets, the performance cost for the network is alawys predictable. The benchmarks serve as a base for discussing potential changes to those budgets in Mainnet protocol parameters.

When building a performance baseline for UTxO-HD, we were able to locate a regression in its new in-memory backing store, LedgerDB V2. We created a local reproduction of that for the Consensus team, who was able to successfully adress the regression. A corresponding benchmarking report will be published on Cardano Updates.

Furthermore, we've performed benchmarks with the Ouroboros Genesis feature enabled and compared them to the release benchmark baseline. We could not detect any performance risk to the network during "normal operations", i.e. when all nodes are caught up with the chain tip.

Development​

During the course of building performance baselines for Ouroboros Genesis and UTxO-HD, we've developed various updates to the performance workbench to correctly handle the new Genesis consensus mode, as well as adjustments to the latest changes in the UTxO-HD node.

Additionally, we built several small quality-of-life improvements for the workbench, as well as investigated and fixed an inconsistent metric (Node Issue #6113).

Infrastructure​

The recent maintenance work also extended to the infrastructure: We've removed the dependency on deprecated environment definitions in iohk-nix by porting the relevant configurations over to the workbench. This facilitates a thorough cleanup of iohk-nix by the SRE team.

As the Haskell package defining benchmarking profiles has been merged, and all code replaced by it successfully removed, we're now working very hard on simplifying the interaction between the workbench and nix. This mostly covers removing redundancies that have lost their motivation, applying to both how workbench calls itself recursively multiple times, as well as how (and how many) corresponding nix store paths are created when evaluating derivations. This will both enhance maintainability, and result in much lighter workbench builds locally - but especially on CI runners.

Tracing​

Work on the self-contained C library implementing trace forwarding is ongoing. As forwarding is defined in terms of an OuroborosApplication, it's non-trivial to re-implement the feautures of the latter in C as well - such as handshake, version negotiation, and multiplexing. However, for the intended purpose of said library, it is unavoidable.

We've also started working on a new release of cardano-tracer, the trace / metrics consuming service in the new tracing system. This release is geared towards feature or change requests we've received from the community and found very valuable feedback. Having a seperate service to process all trace output enables us to react much quicker to this feedback, and decouple delivery from the Node's release cycle.

Last not least, we're doing an experimental run on creating a build of Node with the legacy tracing system removed. As the system is deeply woven into the code base, and some of the new system's components keep compatibility with the old one, untangling and removing these dependencies is a large endeavour. This build serves as a prototype to identify potential blockers, or decisions to be made, and eventually as a blueprint for removing the legacy system in some future Node release.

High level summary​

• Benchmarking: Release benchmarks and performance baselines on 10.2 for UTxO-HD, new GHC, Genesis; 'Perdiodic tracer' benchmarks.
• Development: Pervasive thread labeling in the Node; fix a race condition in monitoring dependency ekg-wai.
• Infrastructure: Haskell profile definition work passed testing, ready for merge; continued 'Byron' support in our tooling.
• Tracing: C library for trace forwarding reached prototype stage; last batch of documentation updates ready for publication.
• Community: Support and valuable feedback on Discord for new tracing system rollout.

Low level overview​

Benchmarking​

We've performed a full set of release benchmarks and analyses for Node version 10.2. We could not detect any performance risks, and expect network performance to be equivalent or slightly better than 10.1.x releases, albeit using slightly more CPU resources under rare conditions.

Furthermore, we're building several performance baselines with 10.2 to compare future changes, features or node flavours to. For comparative benchmarks, it's vital every change be measured individually, as to be able to discern their individual performance impact. For Node 10.3, there are several of those we want to capture, such as crypto class simplifications in Ledger, UTxO-HD with a new in-memory backend, Ouroboros Genesis, and last not least a new GHC9.6 release addressing a remaining performance blocker when building Cardano.

Additionally, we've validated the 'Periodic tracer' feature on cluster benchmarks and now have evidence of its positive impact on performance. This feature decorrelates gathering metrics from the ledger from the start of a block producer's forging loop, without sacrificing predictability of performance. By removing this competition on certain synchronization primitives, the hot code path in the forging loop now executes faster. The feature will be integrated in a future version of the Node.

Development​

We've tracked down a race condition in a community package that both tracing systems depend on for exposing metrics. In ekg-wai, a ThreadKilled exception could be re-thrown to the thread where it originated from. It is a low-risk condition, as it occurs only when then Node process terminates; however, when terminating due to an error condition, it caused the process to end prematurely, before the error could be logged. We've opened a PR (ekg-wai#12) against the package containing the fix and pre-released on CHaP.

Tracking down this condition could have been improved by providing pervasive, human-readable labels for all the threads that the Node process spawns. So in coordination with the Consensus team, we made sure this is the case for future builds of the Node - including locations in the code where dependency packages internally use forkIO to create green threads. This will enhance usability of debug output when looking into concurrency issues.

Infrastructure​

The Haskell definition of benchmarking workloads - and the removal of its bash/jq counterpart - is complete, and has passed testing phase. This includes a final alignment between all profile content defined using either option. Once merged, this will open up the path for simplification of how nix interacts with the performance workbench - and hopefully reduce complexity for our CI runners.

As cardano-api is deprecating some protocol parameter related data types which do not have relevance for Cardano anymore, we've had a discussion with stakeholders about the implications for our tooling: This would effectively disable our ability to benchmark clusters of BFT nodes which do not use a staking / reward-based consensus algorithm - as it used to be in Cardano's Byron era. The decision was made to not drop that ability from our tooling, as there are potential applications for the benchmarks outside of Cardano. As a consequence, we've startied porting those types to live on in our toolchain, representing an additonal maintenance item within our team.

Tracing​

The self-contained C library implementing trace forwarding is now in prototype state. It contains a pure C implementation of our forwarding protocol over socket, as well as pure C CBOR codecs for data payload to match the TraceObject schema used within the context Cardano. That ensures existing tooling can process traces emitted by non-Cardano applications, written in languages other than Haskell.

The latest updates to Developer Portal: cardano-tracer are ready to be published and awaiting a PR review on the Cardano Developer Portal.

Community​

We've been quite busy on our new Discord channel #tracing-monitoring on the IOG's Technical Community server. There's been an initial spike of interest and we've been able to provide support and explain various design decisions of the new tracing system. Additionally, we've gotten valuable feedback about potential features that would greatly help adoption of the new system. These are typically highly localized in their implementation, and non-breaking wrt. to API and design, such that addressing this feedback promptly adds much value at low risk - Thank You for your input!

High level summary​

• Benchmarking: Release benchmarks for Node 10.1.4; performance evaluation of ledger metrics trace location.
• Development: Database-backed quick queries for locli analysis tool.
• Infrastructure: Voting workload definition merged to master, work on Haskell profile definition now continues.
• Tracing: C library for trace forwarding and documentation ongoing; improved fallback configs.
• Community: new Discord channel #tracing-monitoring supporting new tracing system rollout.

Low level overview​

Benchmarking​

We've run and analyzed a full set of release benchmarks for Node version 10.1.4. We could not observe any performance risks, and expect network performance to very closely match that of previous 10.1.x releases.

Furthermore, we've been investigating the location on the 'hot code path' where metrics from ledger are traced - such as UTxO set size or delegation map size. This currently happens at slot start, when the block forging loop is kicked off. We aim to decouple emitting those traces from the forging loop, and instead moving them to a separate thread. This thread could potentially wake up after a pre-defined time has passed, like e.g. 2/3 of a slot's duration. That would ensure getting those values out of ledger does not occur simultaneously to block production proper.

Moreover, as a new feature, it would enable tracing those metrics on nodes that do not run a forging loop themselves. And last not least, it would free up the way to providing additional metrics at the new location - like DRep count, or DRep delegations - without negatively affecting performance. Initial prototyping has yielded promising results so far.

Development​

Parametrizable quick queries, a new feature of our analysis tool locli, have commenced development. They rely on the new database storage backend for raw benchmarking data to be efficient. These quick queries are based on a filter-reduce framework, with composable reducers, which provide a clean way to express exposing very specific points or correlations from the raw benchmarking data.

The quick query feature also incorporates ad-hoc plotting of the query results, and will incorporate exporting the result into exchange formats like CSV or JSON in the future.

Infrastructure​

The voting workload definition has been cleanly integrated with the workbench. This also includes an abstract definition of concurrent workloads - which was previously unnecessary, as exactly one workload would be handled by exactly one and the same service. The integration, along with the added flexibility, has been merged to master.

We're now actively working again on the Haskell definition of benchmarking workloads, including a test suite. Most of this improvement had already been done; it still needs final realignment with the current state of all existing workloads. It will allow us to trade hard-to-maintain large jq definitions with concise testable code, and recursive shell script invocations with using a well-defined command line interface only once.

Tracing​

Good progress has been made on the small, self-contained C library that implements trace forwarding. It will allow processes in any language that can call to C via a foreign function interface to use cardano-tracer as a target to forward traces and metrics. The initial prototype has already evolved into a library design, which intends to offer to the host application a simple way to encode to Cardano's schema of trace messages - and to use its forwarding protocol asynchronously, as to minimize interruption of the application's native control flow.

In preparation of the new tracing system's release, we've also revisited the fallback configuration values the system will use if it is accidentally misconfigured by the user. The forwarder component uses a bounded queue buffer for trace output to compensate for a possibly unreliable connection to cardano-tracer. The fallback bounds were chosen to conserve trace output at all cost - as it turns out, too high of a memory cost, if trace forwarding does not happen at all, due to faulty configuration. We've adjusted this and other fallback values to sensible defaults to guarantee a functional system even in case of configuration errors.

Community​

Our team will host a new channel #tracing-monitoring on IOG's Technical Community discord server. The migration to the new tracing system might affect existing automations built by the community, or how existing configuration need adjusting to achieve the intended outcome. In the channel, we'll offer support for the community in all those regards, as well as answer more general questions regarding the Node's tracing systems.

Additionally, we're currently releasing our documentation improvements to the excellent Cardano Developer Portal, linked below.

• Discord channel #tracing-monitoring
• Developer Portal: New Tracing quickstart
• Developer Portal: cardano-tracer

High level summary​

• Benchmarking: Finalized voting benchmarks on Node 10.0; workload implementation being generalized to be mergeable.
• Development: Database-backend for our analysis tool locli merged; several metrics improvements with new tracing.
• Tracing: C library for trace forwarding started; documentation improved; timing issue in forwarder fixed.

Low level overview​

Benchmarking​

The voting benchmarks have now finished. The exact implementation of how the voting workload is set up and submitted has been finalized and is currently being prepared for merging into master. This will add those benchmarks to the repertoire we can run on any future node version, and track potential performance changes of voting over time.

The setup allows us to add voting as an additional workload on top of the existing release benchmarking workloads - typically "value-only" and "Plutus loop". The value workload operates at 12TPS and always results in full blocks; we can draw a straight line comparison when a certain, constant percentage of each blocks is filled with vote transactions. The Plutus workload however is throttled by spending the block execution budget, and not so much by transaction size and TPS - contrary to voting submissions. This results in a large variance in block size that the network produces, and restricting analysis to the blocks that are actually comparable to each other greatly reduces sample size.

This means that in practice, we've found "voting on top of value-only" to represent the performance implications of voting most accurately. This workload will serve as a base for comparison over time, and will be run selectively on new versions, whenever the proposal / voting feature of the Conway ledger is touched.

As a conclusion to those benchmarks we've ascertained that:

1. there is a performance cost to voting, vote tallying and proposal enactment
2. on the system level, this cost is very reasonable and poses no operational risk
3. on the service level, processing an individual voting transaction is even slightly cheaper performance-wise than a transaction consuming and creating multiple UTxO entries

Development​

The analysis and reporting tool, locli ("LogObject CLI") now comes equipped with a database-backed persistence layer. This new backend has been validated by using it to re-analyse past benchmarks. Performance workbench integration has been completed, and by means of a new envvar this backend can be enabled for use in automations. It currently co-exists in locli with the default file system based persistence backend.

Apart from opening up raw benchmarking data to the full power of SQL queries, or quickly marshalling it into another format to feed into other applications, the new storage backend has considerable advantages regarding execution speed and resource usage. It both requires less RAM (around 30% less) during runtime, and less disk space - about 90% less! Standard analysis of a cluster run can now be performed in less than an hour, whereas it took around 2h before.

Currently, we're working on implementing parametrizable quick queries of that raw data - complete with adding plotting capabilities to locli. The queries are meant to easily extract and visualize very specific correlations that are not part of standard analysis, catering to the oftentimes investigative nature of performance analysis.

Furthermore, The new tracing system now provides direct insight into the chain tip's hash, exposing tipBlockHash, tipBlockParentHash and tipBlockIssuerVerificationKeyHash both as trace messages and metrics. Additionally, we've merged a fix for issue cardano-node#5751: the metric forging_enabled now correctly also observes the presence of the CLI option --non-producing-node.

Tracing​

The new tracing system allows for trace and metrics forwarding from some process to cardano-tracer. For any Haskell application, the forwarder package can easily be included as a library. For applications written in other programming languages, we've decided a small, self-contained C library that handles forwarding is a viable way to provide this functionality to a much wider range of ecosystems. The C library will implement protocol handshake and possibly muxing, the forwarder protocol messages being used, and CBOR-based encodings of trace messages and metrics - which only exists in Haskell currently. We've just started the prototype.

We've been working hard on updating and improving the documentation for the new tracing system on https://developers.cardano.org (not merged yet). The aim was to provide a quick start guide to "just get it set up and running", without presupposing any knowledge of tracing, or Haskell. Moreover, for users coming from the legacy tracing system, we wanted to highlight the key differences between systems - and possibly different assumptions when operating them.

Last not least, we caught a very interesting timing issue in the forwarder: each service connected to cardano-tracer bears both an internal and external name for the connection (both unique), where the external name is chosen by the service itself. Upon forwarder initialization, so called data points are set up within the service, into which data can then be traced (such as that external name), and which are actively polled / queried by cardano-tracer. As these are all concurrent events, the external name wasn't yet available in the data point, if initialization of forwarding happened "too fast". Once located, fixing this was trivial by enforcing a relative ordering of concurrent events just during initialization.

Happy New Year!​

It's been an amazing year for the Performance & Tracing team. We're proud to have contributed to Cardano's transition into the age of Voltaire, and reliably safeguarded performance of the Cardano network - and to have finalized our new tracing system. A huge thanks to all those who've been helpful, supportive - and who've presented us with new ideas and challanges.

Have a Happy New Year 2025!

High level summary​

• Benchmarking: Further Governance action / voting benchmarks on Node 10.0.
• Development: New protoype for database-backed persistence layer in our analysis tool locli.
• Workbench: More fine-grained genesis caching; export cluster topology for Leios simulation.
• Tracing: Final round of metrics alignment complete; prepared for typed-protocols-0.3 bump; new tracing system rollout starting with Node 10.2.

Low level overview​

Benchmarking​

We've been working on improving the voting workload for benchmarks along two axes: Firstly, reduce the (slight) overhead that decentralized vote submission induces. Secondly, introduce a scaling parameter - namely the number of votes submitted per transaction, and hence the number of proposals to be considered simultaneously for tallying and ratification. On the way, we improved upon timing of submissions, as this has caused benchmarks to abort mid-run every now and then: in those cases, a newly created UTxO entry just hadn't settled across the cluster when it was supposed to be reused for consumption.

Scaling of the voting workload is currently under analysis.

Development​

Our analysis and reporting tool, locli ("LogObject CLI") has a few drawbacks as far as system resource usage goes; it requires a huge amount of RAM, and initialization (i.e. loading and parsing trace output) is quite slow. Moreover, there is no intermediate, potentially exposable or queryable, representation of data besides the trace messages themselves.

We're working on a prototype that introduces a database persistence layer as that intermediate representation. Not only does that open up raw benchmarking data to other means of querying or processing outside locli. Initializing the tool from the database has also shown to require much less RAM, and to improve duration of the initialization phase. Furthermore, on-disk representation is much more efficient that way - which is no small benefit when raw benchmarking data for a single run can occupy north of 64GiB.

The prototype has yet to be fully integrated into the analysis pipeline for validation, however, initial observations are promising.

Workbench​

For our benchmarks, we rely on staked geneses, as the cluster needs control all stake, and such, block production, to yield meaningful performance metrics. As creating a staked genesis of that extent is an expensive operation, we use a caching mechanism for those. Small changes in the benchmarking profile, such as protocol version or parameters, Plutus cost models or execution budgets would usually trigger the creation of a new cache entry. We've now factored out from cache entry resolution all those variables that do not impact staking itself. We then created a mechnanism to patch those changes into genesis files after cache retrieval, when preparing them for a benchmarking run. This adds flexibility for creating profiles, and reduces the time to deploy a run to the cluster.

We also delivered a comprehensive description of our cluster to the Leios innovation team. This includes the definition of our artificially constrained topology, as well as a latency matrix for node connections in that topology, assigning a weight to all edges in the graph. The Leios team intends to use that material to implement a large-scale simulation of the algorithm, and thus gain representative timings for diffusion and propagation.

Tracing​

The alignment of metrics names between legacy and new tracing system is now complete - which should minimize the migration effort of existing dashboards for the community. The only differences that remain are motivated by increasing compliance with existing standards like e.g. OpenMetrics. Furthermore, a few metrics still missing in the new system have now been ported over, such as node.start.time or served.block.latest.

We're all set for the expected bump to typed-protocols-0.3: both forwarder packages trace-forward and ekg-forward for the new tracing system have been adapted to the new API and are passing all tests.

Last not least, we've settled on a rollout plan for the new tracing system. The new system will set to be the default with the upcoming Node release 10.2. This is achieved by a change of configuration only - there is no need for different Node builds. The cardano-node binary will contain both tracing systems for a considerable grace period: 3 - 6 months after release. This should give the community ample time to adjust for necessary changes in downstream services or dashboards that consume trace or metrics output.

We'll provide a comprehensive hands-on migration guide summarizing those changes for the user.