Moving to a micro-service architecture, I have separated an AppEngine module into two services (the big one and a smaller one, still part of the same AppEngine project). Next, I want to separate the database into two, so allowing the small micro-service to have only the needed tables in its own db. The problem is one of the tables is needed by both micro-services. The smaller service only reads data from this table (has multiple select queries which join on data from this table)
Option 1: I can leave this table in the bigger service which uses it the most and make the smaller service make an http request to get the data that it needs, cache this data and be notified when this data changes by the owner service of that table. Then, to refresh its cache, the smaller service makes an http request again. In order to communicate from service A to service B, I was thinking between using Google PubSub or Task Queue. And I am not sure which one to use here. In this case, receiving the message in order is not important since the message will be generic "table_state_changed, query for new data", so both could be used.. Option 2: I can duplicate the table in both databases (this will allow the service to have all the necessary data closer). When the bigger service modifies data in the table, it will notify the smaller service to perform the same modification on its version of the table. In this case, the order of the messages is important, since it specifies exact crud operations to perform on the table. Can PubSub be modified to maintain order, somehow insert ordering information in the message payload to contain previous messages sent? Retries are also important, we don't want to end up having inconsistencies between the two tables. Option 3: Is there a way to create Read Replicas with ignored tables in AppEngine (so that I include only the tables I need in one of the services and leave the other one with the entire db as it is currently) and set a specific service to only use that replica? This does not sound as a good idea, however it leaves CloudSql the burden of maintaining same data in both versions of the table). Which option is better in your opinion and most importantly which one is better suited for this case? PubSub or TaskQueues. Also, this is only the first step to separate the monolith, there will be other services in the future, that would probably encounter the same problem. -- You received this message because you are subscribed to the Google Groups "Google App Engine" group. To unsubscribe from this group and stop receiving emails from it, send an email to google-appengine+unsubscr...@googlegroups.com. To post to this group, send email to google-appengine@googlegroups.com. Visit this group at https://groups.google.com/group/google-appengine. To view this discussion on the web visit https://groups.google.com/d/msgid/google-appengine/fee2b32c-42ef-4ce6-a1fb-346ff01f4b73%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
