Polishing deployment of Docker image

* Ahead compilation of Cython modules (so that "pyximport" finds modules already compiled)
* Use of Named Lock to avoid database initialization problems with multiple gunicorn workers starting at the same

Dockerfile

@@ -8,6 +8,7 @@ FROM python:3.7.3-slim-stretch
 # docker build -t magicnexush2020/magic-nis-backend .
 #
 # 1.bis) REFRESH image into Docker Hub:
+# ("docker login" first)
 # docker push magicnexush2020/magic-nis-backend:<TAGNAME>
 #
 # Usage example:
@@ -113,4 +114,6 @@ CMD ["/usr/local/bin/gunicorn", "--workers=3", "--log-level=debug", "--timeout=2
 #CMD ["supervisord", "-c", "/etc/supervisord.conf"]
 
 COPY nexinfosys /app/nexinfosys
+RUN cythonize -a -i /app/nexinfosys/restful_service/helper_accel.pyx && \
+    cythonize -a -i /app/nexinfosys/command_generators/parser_spreadsheet_utils_accel.pyx
 

README.md

@@ -81,7 +81,7 @@ The pip version is obviously for execution as package, and does not include the
 
 `pip install nexinfosys`
 
-* Use class class *NIS*, with methods similar to *NISClient* class in [nexinfosys-client](https://github.com/MAGIC-nexus/nis-python-client) package.
+* Use class **NIS**, with methods similar to **NISClient** class in [nexinfosys-client](https://github.com/MAGIC-nexus/nis-python-client) package.
 
 #### Docker image
 

nexinfosys/restful_service/service_main.py

@@ -15,6 +15,7 @@
 # from flask import (jsonify, abort, redirect, url_for,
 #
 #                    )
+from NamedAtomicLock import NamedAtomicLock
 from flask import (Response, request, session as flask_session, send_from_directory, redirect
                    )
 from flask.helpers import get_root_path
@@ -124,7 +125,13 @@ def construct_session_persistence_backend():
 # >>>> THE INITIALIZATION CODE <<<<
 #
 
-initialize_databases()
+lock = NamedAtomicLock("nis-backend-lock")
+lock.acquire()
+try:
+    initialize_databases()
+finally:
+    lock.release()
+
 nexinfosys.data_source_manager = register_external_datasources()
 
 d = construct_session_persistence_backend()

requirements.txt

@@ -64,6 +64,7 @@ jsonpickle==1.2
 python_magic>=0.4.13  # To be removed, it is used only by the Magic Box file type detection
 dotted>=0.1.8 # <- Dotted notation: !!Fantastic!!
 sympy>=1.1.1
+NamedAtomicLock==1.1.3
 #sympy==1.3
 #cachier==1.2.2
 #tablib <- dictmapper (convert nested dict's to CSV)