joining-new-teams

As a developer looking to join a new team, my user stories are:

1. I want to know what the main repos are (using git log --stat or git quickstats)
2. I want to know what the main classes and methods are in each repo
3. I want to understand what cross-repo dependence exists between components to identify cross-component risks
4. I want to understand what level of coverage already exists to identify general points of risk and coverage expectancy

By the end of step 3, there is enough information to create a prioritised list of classes and methods to dig into or have UML generated for (using Plant UML) to try and understand better.

I will be using real-logic as an example, because I've been playing with it recently and also it is a good example of a repo with possible cross-dependence between modules/sub projects (e.g. dependencies on Agrona across multiple projects). Please be aware that all results from tools are shortened or intended as samples only to illustrate my process.

Code metrics

Examples are below:

Method calls in aeron-client

Method	BRANCH	CALL	CALLED	CALLEDp
io.aeron.ChannelUri.get(String)	0	1	96	94
io.aeron.Aeron.nextCorrelationId()	0	2	111	77
io.aeron.ChannelUri.toString()	0	22	462	70
io.aeron.exceptions.AeronException.AeronException(String)	0	2	62	62

Classes

Class	Cyclic	Dcy	Dcy*	Dpt	Dpt*	PDcy	PDpt
io.aeron.Aeron	22	12	79	235	645	2	20
io.aeron.CommonContext	22	8	79	169	645	2	18
io.aeron.Publication	22	12	79	152	645	5	16
io.aeron.Subscription	22	16	79	142	645	4	15
io.aeron.logbuffer.Header	0	4	5	135	663	2	18
io.aeron.logbuffer.LogBufferDescriptor	0	2	4	102	684	2	8
io.aeron.protocol.DataHeaderFlyweight	0	1	2	101	701	1	11
io.aeron.Aeron.Context	22	13	79	97	645	2	14
io.aeron.Image	22	13	79	80	645	3	13

Interfaces

Interface	Cyclic	Dcy	Dcy*	Dpt	Dpt*	PDcy	PDpt
io.aeron.logbuffer.FragmentHandler	0	1	6	81	653	1	14
io.aeron.logbuffer.ControlledFragmentHandler	0	2	7	25	648	1	8
io.aeron.security.AuthorisationService	0	0	0	24	260	0	5
io.aeron.AvailableImageHandler	22	1	79	18	645	1	4
io.aeron.UnavailableImageHandler	22	1	79	16	645	1	4

Git log co-commit within a project

This is a measure of how often the same person is making commits within the same project within a window of time, ranked by those files which display the highest level of co-commit (filtered to remove some file types). This is to identify which files are likely to change together within the same project/repo. Here is an example for Agrona:

File	Most Co-Checked	coCheckTally	coCheckFileTally	firstFileTally
agrona/src/test/java/org/agrona/DeadlineTimerWheelTest.java	agrona/src/main/java/org/agrona/DeadlineTimerWheel.java	93	510	329
agrona/src/main/java/org/agrona/DeadlineTimerWheel.java	agrona/src/test/java/org/agrona/DeadlineTimerWheelTest.java	93	329	510
agrona/src/main/java/org/agrona/collections/Int2IntHashMap.java	agrona/src/main/java/org/agrona/collections/Int2ObjectHashMap.java	90	466	483
agrona/src/main/java/org/agrona/collections/Int2ObjectHashMap.java	agrona/src/main/java/org/agrona/collections/Int2IntHashMap.java	90	483	466
agrona/src/test/java/org/agrona/concurrent/DynamicCompositeAgentTest.java	agrona/src/main/java/org/agrona/concurrent/DynamicCompositeAgent.java	84	542	235
agrona/src/main/java/org/agrona/concurrent/DynamicCompositeAgent.java	agrona/src/test/java/org/agrona/concurrent/DynamicCompositeAgentTest.java	84	235	542
agrona/src/main/java/org/agrona/collections/ObjectHashSet.java	agrona/src/main/java/org/agrona/collections/IntHashSet.java	82	421	367
agrona/src/main/java/org/agrona/collections/IntHashSet.java	agrona/src/main/java/org/agrona/collections/ObjectHashSet.java	82	367	421
agrona/src/main/java/org/agrona/concurrent/AgentRunner.java	agrona/src/main/java/org/agrona/concurrent/DynamicCompositeAgent.java	80	542	438
agrona/src/main/java/org/agrona/collections/Object2IntHashMap.java	agrona/src/main/java/org/agrona/collections/Int2IntHashMap.java	69	483	336

Git log co-commit across a project

This is a measure of how often the same person is making commits across different repos within a window of time, ranked by those files which display the highest level of co-commit (filtered to remove some file types). This is to identify which files are likely changing together across projects/repos. The example data below combines a number of repos including Agrona and SBE. Your success at using this method will also vary upon project selection i.e. you have to be sensible when selecting which repos to analyse for cross-dependence otherwise you will get spurious results.

Most Probable Co-Checks:

File	Most Co-Checked	coCheckTally	coCheckFileTally	firstFileTally
src/main/java/uk/co/real_logic/agrona/concurrent/status/CountersReader.java	aeron-samples/src/main/java/uk/co/real_logic/aeron/samples/AeronStat.java	22	1282	42
sbe-tool/src/test/resources/issue835.xml	aeron-cluster/src/main/java/io/aeron/cluster/ConsensusModuleAgent.java	12	18911	27
src/main/java/org/agrona/concurrent/HighResolutionTimer.java	aeron-driver/src/main/java/io/aeron/driver/LossDetector.java	11	856	31
main/android/uk/co/real_logic/sbe/codec/java/CodecUtil.java	aeron-driver/src/main/java/uk/co/real_logic/aeron/driver/DriverConductor.java	29	13828	83
aeron-util/src/test/java/uk/co/real_logic/aeron/util/AgentTest.java	test/java/uk/co/real_logic/sbe/codec/java/DirectBufferTest.java	1	237	3
aeron-cluster/src/main/java/io/aeron/cluster/ConsensusModuleStateExport.java	sbe-tool/src/main/java/uk/co/real_logic/sbe/xml/XmlSchemaParser.java	5	1375	16
src/main/java/uk/co/real_logic/agrona/concurrent/SigInt.java	aeron-driver/src/main/java/uk/co/real_logic/aeron/driver/DriverConnection.java	15	5511	49
src/main/java/uk/co/real_logic/agrona/concurrent/SigIntBarrier.java	aeron-driver/src/main/java/uk/co/real_logic/aeron/driver/DriverConnection.java	15	5511	49
src/main/java/uk/co/real_logic/agrona/console/ContinueBarrier.java	aeron-driver/src/main/java/uk/co/real_logic/aeron/driver/DriverConnection.java	15	5511	50
src/main/java/uk/co/real_logic/agrona/concurrent/status/ReadOnlyPosition.java	aeron-driver/src/main/java/uk/co/real_logic/aeron/driver/DriverConnection.java	14	5511	47

Top Co-Checks

File	Most Co-Checked	coCheckTally	coCheckFileTally	firstFileTally
agrona/src/main/java/org/agrona/collections/IntArrayList.java	aeron-cluster/src/main/java/io/aeron/cluster/SequencerAgent.java	104	10770	1168
aeron-cluster/src/main/java/io/aeron/cluster/SequencerAgent.java	agrona/src/main/java/org/agrona/collections/IntArrayList.java	104	1168	10770
aeron-cluster/src/main/java/io/aeron/cluster/ConsensusModuleAgent.java	sbe-tool/src/main/java/uk/co/real_logic/sbe/generation/cpp/CppGenerator.java	90	7062	18911
sbe-tool/src/main/java/uk/co/real_logic/sbe/generation/cpp/CppGenerator.java	aeron-cluster/src/main/java/io/aeron/cluster/ConsensusModuleAgent.java	90	18911	7062
sbe-tool/src/main/java/uk/co/real_logic/sbe/generation/java/JavaGenerator.java	aeron-cluster/src/main/java/io/aeron/cluster/ConsensusModuleAgent.java	88	18911	6362
aeron-cluster/src/main/java/io/aeron/cluster/Election.java	sbe-tool/src/main/java/uk/co/real_logic/sbe/generation/cpp/CppGenerator.java	77	7062	11051
test/java/uk/co/real_logic/sbe/generation/java/JavaGeneratorTest.java	aeron-driver/src/main/java/uk/co/real_logic/aeron/driver/DriverConductor.java	73	13828	2239
aeron-driver/src/main/java/uk/co/real_logic/aeron/driver/DriverConductor.java	test/java/uk/co/real_logic/sbe/generation/java/JavaGeneratorTest.java	73	2239	13828
aeron-archive/src/main/java/io/aeron/archive/ArchiveConductor.java	sbe-tool/src/main/java/uk/co/real_logic/sbe/generation/java/JavaGenerator.java	70	6362	10390
aeron-cluster/src/main/java/io/aeron/cluster/service/ClusteredServiceAgent.java	agrona/src/main/java/org/agrona/collections/IntArrayList.java	69	1168	11345

Code coverage

The combined coverage is:

Package	Class, %	Method, %	Line, %
all classes	67.5% (865/1282)	26.5% (7673/28954)	37.4% (33457/89379)

Whilst the method coverage looks very low, approximatly 17k methods are auto-generated so if we account for that then the method coverage is closer to 63% and the line coverage also increases.

The combined project base requires unit tests across sub-projects to get that kind of coverage.

For example, if we look at the coverage for io.aeron.driver.media using the unit tests only in Aeron-driver we see the class and method level coverage is approximatly 65% whereas when we look at the coverage across all projects for that package then the coverage jumps.

Projects	Package	Class, %	Method, %	Line, %
Aeron-driver	io.aeron.driver.media	65.1% (28/43)	64.4% (224/348)	56.3% (880/1562)
All projects	io.aeron.driver.media	97.7% (42/43)	87.9% (306/348)	81.2% (1268/1562)

This means the coverage is dependent upon cross-project unit tests.