Bugfix/schema and timeout

[YaphetKG]

• Fixes "List out of Index" showing up when redis is empty and schema graph computed is also empty

SELECT a:gene->b:disease
FROM "/schema"
WHERE a="curie:ismissing"

Fix makes behavior return an empty response with the query graph evaluated from the query.

• Adds timeouts to queries this is configurable as per deployment via
  "REDIS_QUERY_TIMEOUT" env variable. And value is in milliseconds.

• Adds get parameter for /schema endpoint so we can do force refresh through an api call. Could be useful when roger pipeline finishes building graph we can let tranql recompute the schema. And don't need to wait till the next update interval.

[waTeim]

A minor thing If in query_redis question doesn't contain options then the get on line 628 will throw an exception.

I really wish there was a more efficient way to update the cache only if a change occurs rather than blindly recalculating every x seconds.

[YaphetKG]

Hi @waTeim , thanks for the review. Just added a default to options as empty dict.
WRT schema computation, the main reason for re-doing the schema is i think when graph has changed in redisgraph.

• One of the ways we can detect this change maybe using counts of nodes and edges per type maybe.
  Something like

grab node types and counts for each,
grab edge types and counts for each, 
make a hash value
if hash value is diff from previous one recalc schema

• Another way maybe having a meta node in the graph , that the roger pipeline would write out , something with version and time graph was build. That way we can check if this node has changed.

• A third option is increasing interval that we do this calc. This wouldn't change the efficiency but would reduce the frequency of making schema calc cypher query calls to redisgraph. Since we have the api endpoint to force update the schema, we can make http request to that endpoint. In this scenario , roger pipeline on airflow would build the graph and make a force_update schema call to tranql once the graph has done building.

[stevencox]

@YaphetKG - please let me know when this is tested in heal-dev - i.e. ensuring search/indexing/etc is working as expected.