DODO - C++ framework for Docker applications

About

Dodo is a C++ framework to integrate seamlessly with Docker containers and k8s (kubernetes), hiding much of the red tape, as well as providing frameworks for typical demands such as DNS resolving, TLS-enabled TCP services, REST services, database accces and so on.

C++ offers high capability/requirement ratio, perfect for microservices.

Dodo applies c++17 features. It relies on and assumes the STL by using STL primitives such as std::string in interfaces. A dodo install comprises a bunch of header files and a shared library to which applications or 'services' are linked.

This is a pet project. Do not take it too seriously.

A skeleton for container services

The dodo::common::Application reads its run-time configuration from a YAML file, typically presented to the container as a ConfigMap. Framework objects can be iniltialized (constructed) with a YAML document fragment, so the application can retrieve its runtime configuration from a single source.

An dodo::common::Application instance implicitly installs signal handlers that are triggered on container stop requests, allowing the application to shutdown cleanly.

Logging (dodo::common::Logger) is implicit and can be configured to write to one or more of these targets:

A directory with a configured trail (size, history) of log files.
A syslog call to rsyslog.
Console aka standard out of the container entrypoint.

Docker healthchecks that run an in-container command (such as pidof myservice) are expensive on CPU, especially if the healthchecks need to be frequent or there are a lot of pods. The dodo::common::Application class starts a tiny TCP healthcheck listener (dodo::common::Application::HealthChecker) that responds to network-probes by the Docker host, which is much more efficient. The HealthChecker stops reponding when the Application exits.

High level APIs to common functionality

Most services will require at least some of the functionality dodo provides as high-level C++ abstractions without compromising low-level C/Linux performance.

Binary data as the dodo::common::Bytes datatype used as primitive by dodo interfaces.
Encryption and compression.
Transparent ipv4 and ipv6 Address classes, name resolution.
TCPSocket (insecure) and TLSSocket classes (encryption and trust).
TCPServer and TLSServer classes ready for subclassing a custom protocol.
Standard protocols:
- HTTP
- STOMP
HTTP(S)Server and HTTP(S)Client handling HTTP server and client red tape.
REST(S)Listener as a specialization of HTTP(S)Server where a YAML section specifies the REST API.
C++ APIs to persistency solutions:
- SQLite relational database
- PostgreSQL relational database
- MongoDB object store
Explicit persistent data stores implemented against SQLite
- Persistent key-value store
- Persistent fifo queue.
- Persistent Priority queue.

Dependencies

OpenSSL For TLS, hashing and encryption.
SQLite Persistent storage.
yaml-cpp Read and write YAML.
[rapidjson]() Read and write JSON.
crc32 CRC32 verfication codes (dependency included in the source tree).

Using the dodo framework

See the developer manual for an overview.

The source code is documented for Doxygen and automatically generated to github pages.

Maintaining the dodo framework

See the maintainer manual for an overview.

Build

git clone https://github.com/jmspit/dodo.git
cd dodo && \
   mkdir build && \
   cd build && \
   cmake ..  -DCMAKE_INSTALL_PREFIX=/opt/dodo && \
   cmake --build . && \
   cmake --install .

If installed to a location outside the system library paths, set the LD_LIBRARY_PATH to <CMAKE_INSTALL_PREFIX>/lib.

Build targets

In the configured build directory

target	build command	What
all	`cmake --build .`	builds the dodo library, examples and tests
dodo	`cmake --build . --target dodo`	Only builds `libdodo.so`
doc	`cmake --build . --target doc`	Creates the doxygen documentation in `./doxygen/html`.
cppcheck	`cmake --build . --target cppcheck`	Run cppcheck code quality check

Docker

A multistage build example (src/examples/docker/minideb/Dockerfile).

FROM bitnami/minideb:latest AS builder
 
RUN echo 'debconf debconf/frontend select Noninteractive' | debconf-set-selections
RUN apt-get update && \
    apt-get install -y apt-utils && \
    apt-get install -y libssl-dev git g++ cmake
 
RUN mkdir -p /opt/dodo/build && mkdir -p /opt/dodo/bin && mkdir -p /opt/dodo/lib
WORKDIR /opt/dodo/build
RUN git clone --branch latest https://github.com/jmspit/dodo.git
RUN cd dodo && \
    mkdir build && \
    cd build && \
    cmake ..  -DCMAKE_INSTALL_PREFIX=/opt/dodo && \
    make && \
    make install
 
FROM bitnami/minideb:latest
ENV LD_LIBRARY_PATH=${LD_LIBRARY_PATH}/opt/dodo/lib
ENV PATH=${PATH}:/opt/dodo/bin
RUN apt-get update && \
    apt-get install -y openssl
COPY --from=builder /opt/dodo/lib /opt/dodo/lib
COPY --from=builder /opt/dodo/bin /opt/dodo/bin
WORKDIR /opt/dodo

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