@contrast/core

Discovers Contrast configuration data (yaml, env vars, etc) and preconfigures a common set of APIs to be used for agent and tooling development.

Basic Usage

The module exports a factory function.

const core = require('@contrast/core')();

What You Get

• Logging

  core.logger.info('...');

  See more about the @contrast/logger service here.

• Monkey-patching

  core.patcher.patch(res, 'end', {
    name: 'http.ServerResponse.end',
    patchType: 'http-things',
    pre(data) {
      // ...
    }
  });

  See more about the @contrast/patcher service here.

• Code rewriting

  core.rewriter.addTransforms({
    CallExpression(path, state) {
      // ...
    };
  });
  core.rewriter.rewrite('function() { ...');

  See more about the @contrast/rewriter service here.

• Dependency hooks

  core.depHooks.resolve({ name: 'http' }, http => {
    // implemention details
  });

  See more about the @contrast/dep-hooks service here.

• Models and factories

  The construction of model data can rely on configuration and therefore can be stateful. So, we provide the models and their factories as services that can be used by consumers as if static.

  // stackframe filtration is configurable, thus stateful
  const snap = core.models.StacktraceFactory.createSnapshot();
  const frames = snap();

  See more about the @contrast/models service here.

• Report messages

  // configuration will tell which reporters become active
  core.reporters.install();
  core.messages.emit('ProtectInputTracingEvent', { ... });

  See more about the @contrast/reporter service here.

• Other stuff

  There are some utility-type functions that rely on configuration state.

  // This uses core.config.stack_trace_filters (new to v5)
  core.isAgentPath('/foo'); 

Related

• @contrast/agentify: Integrate core services and instrumentation into an application. See more here.