Don't send unsampled transactions to APM server >= 8.0

lib/elastic_apm/config/server_info.rb

@@ -23,6 +23,9 @@ class Config
  class ServerInfo
  attr_reader :payload, :config, :http
 
+ VERSION_8_0 = '8.0'
+ VERSION_0 = '0'
+
  def initialize(config)
  @config = config
  @http = Transport::Connection::Http.new(config)
@@ -32,12 +35,14 @@ def execute
  resp = http.get(config.server_url)
  @payload = JSON.parse(resp.body)
  rescue
- @payload = {"version" => nil}
+ @payload = { "version" => VERSION_0 }
  end
 
  def version
- execute unless payload
- payload["version"]
+ @version ||= begin
+ execute
+ payload["version"] ? payload["version"].to_s : VERSION_0
+ end
  end
  end
  end

lib/elastic_apm/instrumenter.rb

@@ -150,7 +150,9 @@ def end_transaction(result = nil)
 
  transaction.done result
 
- enqueue.call transaction
+ if transaction.sampled? || @config.version < Config::ServerInfo::VERSION_8_0
+ enqueue.call transaction
+ end
 
  update_transaction_metrics(transaction)
 

spec/elastic_apm/config/server_info_spec.rb

@@ -0,0 +1,54 @@
+# Licensed to Elasticsearch B.V. under one or more contributor
+# license agreements. See the NOTICE file distributed with
+# this work for additional information regarding copyright
+# ownership. Elasticsearch B.V. licenses this file to you under
+# the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied. See the License for the
+# specific language governing permissions and limitations
+# under the License.
+
+# frozen_string_literal: true
+
+require "spec_helper"
+
+module ElasticAPM
+ class Config
+ RSpec.describe ServerInfo do
+ subject { described_class.new(Config.new) }
+
+ context 'when the request is successful' do
+ context 'when the version is in the response' do
+ it 'sets the version' do
+ WebMock.stub_request(:get, %r{^http://localhost:8200/$}).
+ to_return(body: '{"version":"7.17.4"}')
+ expect(subject.version).to eq('7.17.4')
+ end
+ end
+
+ context 'when the version is not in the response' do
+ it 'sets the version to 0' do
+ WebMock.stub_request(:get, %r{^http://localhost:8200/$}).
+ to_return(body: nil)
+ expect(subject.version).to eq('0')
+ end
+ end
+ end
+
+ context 'when the request is not successful' do
+ it 'sets the version to 0' do
+ WebMock.stub_request(:get, %r{^http://localhost:8200/$}).
+ to_raise(StandardError)
+ expect(subject.version).to eq('0')
+ end
+ end
+ end
+ end
+end

spec/elastic_apm/config_spec.rb

@@ -296,16 +296,16 @@ module ElasticAPM
  end
 
  describe "#version" do
- it "has no version if the server does not respond" do
+ it "has version 0 if the server does not respond" do
  WebMock.stub_request(:get, "http://localhost:8200/")
  .to_return(status: 404, body: "")
- expect(Config.new.version).to be_nil
+ expect(Config.new.version).to eq '0'
  end
 
  it "returns the version from the server" do
  WebMock.stub_request(:get, "http://localhost:8200/")
- .to_return(status: 200, body: '{"version": 8.0}')
- expect(Config.new.version).to eq 8.0
+ .to_return(status: 200, body: '{"version": 8.5}')
+ expect(Config.new.version).to eq '8.5'
  end
  end
  end

spec/elastic_apm/instrumenter_spec.rb

@@ -445,5 +445,29 @@ module ElasticAPM
  subject.stop
  end
  end
+
+ describe 'unsampled transactions' do
+ let(:config) { Config.new(transaction_sample_rate: '0') }
+
+ context 'when the server version is less than 8.0' do
+ it 'enqueues the transaction' do
+ stub_request(:get, "http://localhost:8200/")
+ .to_return(status: 200, body: '{"version": "7.17.4"}')
+ expect(subject.enqueue).to receive(:call).and_call_original
+ subject.start_transaction 'Test', config: config
+ subject.end_transaction
+ end
+ end
+
+ context 'when the server version is at least 8.0' do
+ it 'does not enqueue the transaction' do
+ stub_request(:get, "http://localhost:8200/")
+ .to_return(status: 200, body: '{"version": "8.5.3"}')
+ expect(subject.enqueue).not_to receive(:call)
+ subject.start_transaction 'Test', config: config
+ subject.end_transaction
+ end
+ end
+ end
  end
 end

spec/elastic_apm/middleware_spec.rb

@@ -115,6 +115,11 @@ class MiddlewareTestError < StandardError; end
  context 'with valid header' do
  it 'recognizes trace_context' do
  with_agent do
+ # The apm server version must be < 8.0 in order for a transaction
+ # to be enqueued when it's unsampled.
+ # See issue https://github.com/elastic/apm-agent-ruby/issues/1340
+ WebMock.stub_request(:get, %r{^http://localhost:8200/$}).
+ to_return(body: '{"version":"7.17.4"}')
  app.call(
  Rack::MockRequest.env_for(
  '/',
@@ -136,6 +141,11 @@ class MiddlewareTestError < StandardError; end
  context 'with tracestate' do
  it 'recognizes trace_context' do
  with_agent do
+ # The apm server version must be < 8.0 in order for a transaction
+ # to be enqueued when it's unsampled.
+ # See issue https://github.com/elastic/apm-agent-ruby/issues/1340
+ WebMock.stub_request(:get, %r{^http://localhost:8200/$}).
+ to_return(body: '{"version":"7.17.4"}')
  app.call(
  Rack::MockRequest.env_for(
  '/',
@@ -191,6 +201,11 @@ class MiddlewareTestError < StandardError; end
  context 'with a prefix-less header' do
  it 'recognizes trace_context' do
  with_agent do
+ # The apm server version must be < 8.0 in order for a transaction
+ # to be enqueued when it's unsampled.
+ # See issue https://github.com/elastic/apm-agent-ruby/issues/1340
+ WebMock.stub_request(:get, %r{^http://localhost:8200/$}).
+ to_return(body: '{"version":"7.17.4"}')
  app.call(
  Rack::MockRequest.env_for(
  '/',
@@ -212,6 +227,11 @@ class MiddlewareTestError < StandardError; end
  context 'with both types of headers' do
  it 'picks the prefixed' do
  with_agent do
+ # The apm server version must be < 8.0 in order for a transaction
+ # to be enqueued when it's unsampled.
+ # See issue https://github.com/elastic/apm-agent-ruby/issues/1340
+ WebMock.stub_request(:get, %r{^http://localhost:8200/$}).
+ to_return(body: '{"version":"7.17.4"}')
  app.call(
  Rack::MockRequest.env_for(
  '/',

spec/support/with_agent.rb

@@ -30,7 +30,7 @@ def with_agent(klass: ElasticAPM, args: [], **config)
 
  @server_version_stub =
  WebMock.stub_request(:get, %r{^http://localhost:8200/$}).
- to_return(body: '{"version":8.0}')
+ to_return(body: '{"version":"8.0"}')
 
  klass.start(*args, **config)
  yield