Chronos Ruby

Chronos Ruby is the framework-independent client for sending Ruby application errors and bounded telemetry to Chronos. Version 0.8 adds optional per-instance outbound Net::HTTP timing, privacy-safe cache identity, and one bounded dependency inventory per agent.

What the gem collects

Version 0.8 can collect:

exception class, message, structured backtrace, and chained causes;
timestamp, severity, tags, and an optional fingerprint;
application-supplied context, parameters, session, and user fields;
Ruby version, engine, platform, process ID, opaque thread ID, and hostname;
application version, environment, and service name.
Rack method, normalized route, status, duration, request ID, host, query-free path, optional user agent, controller/action, response size, trace ID, and already-parsed parameters when the middleware is used;
bounded breadcrumbs explicitly supplied by the application or integration.

See Data collected for the complete field table.

What is not collected by default

Chronos Ruby does not inspect environment variables, request/response bodies, cookies, Authorization headers, source code, database contents, lockfiles, or gem paths. Dependency reporting reads only already loaded gem names and versions once per agent. Application-supplied fields are recursively sanitized, but applications should still avoid sending unnecessary personal, health, financial, or authentication data.

Supported Ruby and Rails versions

Version 0.x targets Ruby 2.2.10 through Ruby 2.6. Version 0.5 provides best-effort Rails 4.2 through 5.2 integration through public framework APIs and feature detection. All supported combinations must pass dedicated CI before being listed as supported.

See Compatibility.

Plain Ruby installation

The current public build is a pre-release. Add its exact version to the application's Gemfile:

gem "chronos-ruby", "0.8.0.pre.1"

Install with a Bundler version compatible with the application. For the oldest supported runtime:

gem install bundler -v 1.17.3
bundle _1.17.3_ install

Without Bundler:

gem install chronos-ruby --pre

Rails installation

Version 0.5 exposes Rails support explicitly, keeping Rails and ActiveSupport out of plain Ruby applications:

gem "chronos-ruby", "0.8.0.pre.1", :require => "chronos/rails"

Generate the initializer with:

rails generate chronos:install

The Railtie installs the Rack middleware and notification subscribers idempotently. Automatic integration is disabled in test and console by default and can be controlled with rails_enabled, rails_capture_in_test, rails_capture_in_console, and rails_capture_user_agent. See Rails 4.2 and 5.2 integration.

Minimum configuration

project_id, project_key, and an HTTPS host are required while the agent is enabled:

require "chronos"

Chronos.configure do |config|
  config.project_id = ENV["CHRONOS_PROJECT_ID"]
  config.project_key = ENV["CHRONOS_PROJECT_KEY"]
  config.host = "https://chronos.example.com"
  config.environment = ENV["APP_ENV"] || "production"
  config.service_name = "billing"
  config.app_version = ENV["APP_VERSION"]
end

HTTPS verification is enabled by default. HTTP requires explicitly setting ssl_verify = false and should only be used with a local test server.

Automatic capture

Rack applications can capture unhandled exceptions automatically and preserve the application error semantics:

use Chronos::Integrations::Rack::Middleware,
    :include_user_agent => false

The middleware notifies asynchronously and re-raises the same exception. It never reads the request body, raw query string, cookies, authorization headers, or response body. See Rack integration and context.

Manual capture

Asynchronous capture is recommended for application code:

begin
  perform_payment
rescue StandardError => error
  Chronos.notify(error, :tags => ["payment"])
  raise
end

Synchronous capture waits for the HTTP result and is useful in scripts or controlled shutdown paths:

delivered = Chronos.notify_sync(RuntimeError.new("import failed"))

Both methods return false instead of allowing an internal agent error to escape.

User context

User data is opt-in and must contain only values your application is allowed to send:

Chronos.notify(error, :user => {"id" => "customer-42", "role" => "operator"})

Version 0.4 sanitizes this context before delivery and before it can enter retry storage. Data minimization remains the application's responsibility.

Breadcrumbs use a fixed circular buffer scoped to the current execution:

Chronos.add_breadcrumb(
  :category => "custom",
  :message => "payment started",
  :metadata => {"provider" => "example"}
)

No log, SQL, HTTP, cache, job, request body, or response body payload is collected automatically. Unknown categories become custom, and metadata is bounded and sanitized before queueing.

Filters and LGPD

Version 0.4 recursively redacts sensitive keys and detects Bearer tokens, JWTs, e-mail addresses, CPF, CNPJ, and valid payment-card candidates in free text. IPv4 addresses are anonymized by default. Applications can add blocklist matchers, hash selected identifiers, or install custom filters:

Chronos.configure do |config|
  # required options omitted
  config.blocklist_keys += [:medical_record, /bank_account/i]
  config.hash_keys += [:customer_id]
  config.filters << proc { |key, value| key.to_s == "internal_reference" ? "[REMOVED]" : value }
end

Sanitization runs before queueing and transport. See Privacy and LGPD for behavior, limitations, health and financial examples, and a payload audit procedure.

Ignore rules

Entire environments can be ignored:

Chronos.configure do |config|
  # required options omitted
  config.ignored_environments = ["development", "test"]
end

Local exception-specific ignore callbacks are not available in version 0.4. The server may provide a bounded list of exact fingerprints to ignore; it cannot provide regular expressions or executable rules.

Performance monitoring

Version 0.7 aggregates request, query, and job observations into bounded metric_batch events. Groups include count, error count/rate, total/min/max/average duration, fixed histogram buckets, status counts, and component breakdown. Percentiles are calculated in the SaaS without retaining every local duration.

SQL comments and literal values are removed before a bounded normalized query and SHA-256 fingerprint are produced. Binds are never read. Slow, repeated, possible N+1, long-transaction, connection-error, and deadlock signals are heuristic and require server-side confirmation. Group count, active trace count, fingerprints per trace, histogram buckets, and batch size all have fixed limits. See Essential APM aggregation.

Chronos.configure do |config|
  # required connection settings omitted
  config.apm_enabled = true
  config.apm_max_groups = 200
  config.apm_flush_count = 100
  config.apm_batch_size = 50
  config.apm_max_queries_per_request = 100
  config.apm_slow_query_threshold_ms = 500.0
  config.apm_n_plus_one_threshold = 5
end

Sidekiq and Active Job

Version 0.6.0.pre.1 adds optional Sidekiq 4/5 middleware:

gem "sidekiq", "~> 5.0"
gem "chronos-ruby", "0.8.0.pre.1", :require => "chronos/sidekiq"

The client middleware propagates only trace/request identifiers in a versioned Sidekiq-envelope field and never changes worker arguments. The server records class, queue, JID, retry count, duration, calculable queue latency, bounded arguments/tags, status, and error class. Values pass through the shared sanitizer before delivery. Failed jobs are notified once and the original exception is re-raised. See Sidekiq 4/5 legacy integration.

The Rails subscriber continues to record basic Active Job class, queue, and duration. Full Active Job context propagation plus optional Resque and Delayed Job adapters are subsequent version 0.6 increments.

External HTTP, cache, and dependencies

Version 0.8 instruments only explicitly selected Net::HTTP connection objects, avoiding a global monkey patch:

Chronos.configure do |config|
  # required connection settings omitted
  config.external_http_enabled = true
  config.external_http_trace_headers = true
end

http = Net::HTTP.new("payments.example.com", 443)
http.use_ssl = true
Chronos.instrument_net_http(http)

The wrapper records only sanitized host, method, status, duration, timeout, connection-error flag, and error class. It propagates X-Chronos-Trace-ID and X-Chronos-Request-ID when available and never reads URL path/query, Authorization, request body, response body, or error message.

Rails cache telemetry omits raw keys by default. Set cache_key_mode = :sha256 to emit a project-scoped hash; :none is the default. Dependency reporting is enabled by default, reads at most 100 already loaded gem specs, and emits one independent dependencies event per agent. Set dependency_reporting = false to disable it. See External HTTP, Cache observability, and Dependency inventory.

Deploy tracking

Deploy notifications are not implemented in version 0.8. app_version is included in event service metadata and the once-per-agent dependency inventory for release correlation.

Asynchronous queue

The queue has a fixed capacity and drops the newest event when full. Worker threads are created lazily after the first accepted event. The default capacity is 100 events with one worker.

flowchart LR
  E[Exception] --> N[Notice builder]
  N --> P[Privacy sanitizer]
  P --> S[Safe bounded serializer]
  S --> D[Delivery pipeline]
  D --> Q[Bounded queue]
  Q --> W[Fixed worker pool]
  W --> R[Retry and circuit breaker]
  R --> H[Net::HTTP transport]
  R --> B[Bounded memory backlog]

Use Chronos.flush(timeout) to wait for accepted events and Chronos.close(timeout) during shutdown. Workers are recreated after a process fork.

Retry and backlog

The resilience layer introduced in version 0.3 retries network errors, HTTP 408, 429, and 5xx responses with exponential backoff, bounded jitter, and a finite attempt count. Other 4xx responses are permanent and are not retried. A circuit breaker pauses requests after repeated failures, preventing retry storms.

After retries are exhausted, the already sanitized SerializedEvent may enter a fixed-capacity memory backlog. The backlog drops new items when full, is lost when the process exits, and never writes to disk. A later successful half-open probe drains backlog items as new events arrive.

The SaaS may return a JSON policy in the bounded X-Chronos-Remote-Configuration response header. Only sampling rate, enabled event types, a lower payload limit, exact ignored fingerprints, send interval, and kill switch are accepted. Remote values cannot change the host, project credentials, TLS, local maximums, code, or regular expressions. See Retry and backlog and Remote configuration.

How it works internally

The code follows hexagonal boundaries:

Chronos::Core contains immutable notices, sanitization, and safe normalization;
Chronos::Application coordinates capture;
Chronos::Application::DeliveryPipeline owns bounded retry and remote policy;
Chronos::Ports defines delivery behavior;
Chronos::Adapters implements Net::HTTP delivery and thread-local context;
Chronos::Integrations::Rack implements optional automatic Rack capture;
Chronos::Rails implements the optional Railtie, installer, generator, and public-notification adapters;
Chronos::Internal owns bounded queueing, workers, and defensive logging.

The core has no dependency on Rails, Rack, Sidekiq, or ActiveSupport. See Architecture.

Environment-specific configuration

Configuration values are explicit; the gem never scans the process environment. Read only the variables your application chooses:

Chronos.configure do |config|
  config.project_id = ENV["CHRONOS_PROJECT_ID"]
  config.project_key = ENV["CHRONOS_PROJECT_KEY"]
  config.host = ENV["CHRONOS_HOST"]
  config.environment = ENV["APP_ENV"] || "production"
  config.enabled = ENV["CHRONOS_ENABLED"] != "false"
  config.queue_size = 100
  config.workers = 1
  config.timeout = 5.0
  config.open_timeout = 2.0
  config.max_retries = 3
  config.retry_base_interval = 0.5
  config.retry_max_interval = 30.0
  config.retry_jitter = 0.25
  config.backlog_size = 100
  config.circuit_failure_threshold = 5
  config.circuit_reset_timeout = 30.0
  config.remote_configuration = true
  config.context_store = :thread_local
  config.breadcrumb_capacity = 20
  config.breadcrumb_max_bytes = 2048
  config.apm_enabled = true
  config.apm_max_groups = 200
  config.apm_flush_count = 100
  config.external_http_enabled = false
  config.cache_key_mode = :none
  config.dependency_reporting = true
end

All options are documented in Configuration.

Troubleshooting

Configuration errors are raised during Chronos.configure. Capture and delivery errors are contained and optionally reported to the configured logger. Verify credentials, HTTPS certificates, timeouts, and Chronos.flush results. See Troubleshooting.

Benchmark

Run the version 0.8 benchmarks with:

bundle _1.17.3_ exec ruby benchmarks/capture_exception.rb
bundle _1.17.3_ exec ruby benchmarks/serialization.rb
bundle _1.17.3_ exec ruby benchmarks/filtering.rb
bundle _1.17.3_ exec ruby benchmarks/queue.rb
bundle _1.17.3_ exec ruby benchmarks/retry_backlog.rb
bundle _1.17.3_ exec ruby benchmarks/request_overhead.rb
bundle _1.17.3_ exec ruby benchmarks/rails_notifications.rb
bundle _1.17.3_ exec ruby benchmarks/sidekiq_middleware.rb
bundle _1.17.3_ exec ruby benchmarks/apm_aggregation.rb
bundle _1.17.3_ exec ruby benchmarks/external_http.rb

Results depend on runtime, hardware, and payload. No performance comparison is claimed until repeatable measurements are published.

Migration from Airbrake

An Airbrake migration guide will be added before the legacy 1.0 release. Version 0.8 does not claim API compatibility or automatic replacement.

Local development

Clone the repository, install Bundler 1.17.3, and run setup:

gem install bundler -v 1.17.3
bin/setup

Open an interactive console:

bin/console

Install the current source locally:

bundle _1.17.3_ exec rake install

Tests

Run the complete suite on the current Ruby:

bundle _1.17.3_ exec rake

The legacy CI matrix covers Ruby 2.2.10, 2.3.8, 2.4.10, 2.5.9, and 2.6.10. Network integration tests use a local fake HTTP server.

Contributing

Open an issue before introducing a new public API or dependency. Every public class requires YARD documentation, tests, module documentation, and compatibility evidence. See CONTRIBUTING.md.

Security

Never include credentials in event context or logs. Report vulnerabilities privately according to SECURITY.md. Ruby 2.2 through 2.6 are end-of-life; Chronos provides technical compatibility, not runtime security maintenance.

License

Chronos Ruby is distributed under the terms of the MIT License. See LICENSE.txt.