![Javascript Patching
var result = documentStore.DatabaseCommands.UpdateByIndex("Raven/DocumentsByEntityName",
new IndexQuery
{
Query = "Tag: OrderDeliveries"
},
new ScriptedPatchRequest
{
Script = @"
var customerLookup = JSON.parse('customers');
this.Expedited = customerLookup[this.CustomerId].IsPreferred;",
Values = new Dictionary<string, object>
{
{ "customers", JsonConvert.SerializeObject(customers) }
}
});
result.WaitForCompletion();](https://image.slidesharecdn.com/lessonsfromthetrenches-160530114130/85/Lessons-from-the-Trenches-Building-Enterprise-Applications-with-RavenDB-9-320.jpg)
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Lessons from the Trenches - Building Enterprise Applications with RavenDB
- 1. Lessons from theTrenches Dan Bishop RavenHQ [email protected] github.com/bishbulb twitter.com/bishbulb
- 2. Typical Project Lifecycle Technical Discovery Convince Stakeholders Prototype Iterate Launch MVP Iterate Life is good! Life is good, right?
- 3. Reality Sets In โข Business is not โfinishedโ with the MVP solution โข Users are never satisfied โข User hacks are conceived and proliferated โข Small gaps grow into chasms โข Production support issues start coming in โข Things arenโt shiny anymore
- 4. Data Conversions โข Properties are added and removed โข Data types change โข Class names and namespaces change โข Documents are split or merged โข Indexes change
- 5. Data Conversions โ Adding Properties public class OrderDelivery { public string Id { get; set; } public string Address { get; set; } public DateTime DeliveryDate { get; set; } } { "Address": "100 First St, NY, NY", "DeliveryDate": "2016-05-30T12:30:00" } public class OrderDelivery { public string Id { get; set; } public string Address { get; set; } public DateTime DeliveryDate { get; set; } public bool Expedited { get; set; } }
- 6. Data Conversions โ Adding Properties public class OrderDeliveriesIndex : AbstractIndexCreationTask<OrderDelivery> { public OrderDeliveriesIndex() { Map = docs => from doc in docs select new { doc.Address, doc.DeliveryDate, doc.Expedited }; } }
- 7. Data Conversions โ Adding Properties var expeditedDeliveries = session .Query<OrderDelivery, OrderDeliveriesIndex>() .Where(x => x.Expedited); if (expeditedDeliveries.Count > 10) { // email delivery manager }
- 8. Javascript Patching var result = documentStore.DatabaseCommands.UpdateByIndex("Raven/DocumentsByEntityName", new IndexQuery { Query = "Tag: OrderDeliveries" }, new ScriptedPatchRequest { Script = "this.Expedited = true;" }, new BulkOperationOptions { AllowStale = false }); result.WaitForCompletion();
- 9. Javascript Patching var result = documentStore.DatabaseCommands.UpdateByIndex("Raven/DocumentsByEntityName", new IndexQuery { Query = "Tag: OrderDeliveries" }, new ScriptedPatchRequest { Script = @" var customerLookup = JSON.parse('customers'); this.Expedited = customerLookup[this.CustomerId].IsPreferred;", Values = new Dictionary<string, object> { { "customers", JsonConvert.SerializeObject(customers) } } }); result.WaitForCompletion();
- 10. Javascript Patching โข Patch scripts always run against an index โข Make patch scripts idempotent โข Consider rollback strategy โข Split changes into multiple releases โข Debugging โข Test in the Studio, use output() function โข View patch progress in RavenDB 3.5
- 11. Data Conversions โ Removing Properties โข Safe by default โข Properties in the underlying document are retained documentStore.Conventions.PreserveDocumentPropertiesNotFoundOnModel = true; โข Clutter by default โข Keep track of the properties being removed โข Run Javascript patch scripts in the next release to remove the properties
- 12. You Want All the Data? โข Raven intentionally makes this hard with the normal APIs โข Indexes can be stale, query results limited to 1024 results โข Streaming to the rescue var results = session.Advanced.Stream<OrderDelivery>("orderdeliveries-"); session.Advanced.LoadStartingWith<OrderDelivery>("orderdeliveries-", start: 0, pageSize: 1000); var query = session.Query<OrderDelivery, OrderDeliveriesIndex>() .Where(x => !x.Delivered); var results = session.Advanced.Stream(query); โข Other tips session.Advanced.MaxNumberOfRequestsPerSession = int.MaxValue;
- 13. Semantic Document Identifiers โข Identifiers that have embedded data/context โข employees/1/deliveryroutes/2016-06-01 โข Prevents logical duplicates โข Enables multi-load with one round-trip โข employees/1/preferences โข employees/1/workschedule โข deliveryroutes/2016-06-01/employees/1 โข Enables you to bypass indexes altogether โข Example: Get all delivery routes for a particular day
- 14. LoadDocument Manager Employee1 Employee2 EmployeeN public EmployeesIndex() { Map = employeees => from employee in employeees let manager = LoadDocument<Manager>(employee.ManagerId) select new { employee.Id, ManagerName = manager.Name }; }
- 15. LoadDocument Manager CompanyVehicle public CompanyVehiclesIndex() { Map = vehicles => from vehicle in vehicles let manager = LoadDocument<Manager>(vehicle.ManagerId) select new { vehicle.Id, ManagerName = manager.Name }; }
- 16. LoadDocument โข One to many relationships could cause problems โข Only when updating the document that has many other documents referencing it โข One to one relationships are fine โข Look for alternatives โข Transformers โข Data duplication
- 17. Auto vs Static Indexes โข Auto indexes are great for prototyping โข Consider the implications <appSettings> <add key="Raven/CreateAutoIndexesForAdHocQueriesIfNeeded" value="false" /> </appSettings> โข Indexes are resource intensive โข Be aware of the indexes you have
- 18. WaitForNonStaleResults โข Gives you up-to-date results from an index โข Dealing with CRUD views โข Make the writer wait for indexes, not the reader var results = session .Query<OrderDelivery, OrderDeliveriesIndex>() .Customize(x => x.WaitForNonStaleResultsAsOfNow());
- 19. Consistency Issues โข ACID provides specific guarantees โข DistributedTransactions โข DTC commit and rollback happen in a separate thread from updates โข Rather than locking the underlying documents, Raven will allow you to access them but will return an HTTP 203 Non-Authoritative response โข Scenario: NServiceBus processing chain of messages UpdateUserProfile ConfirmPhoneNumber session.Advanced.AllowNonAuthoritativeInformation = false;
- 20. Replication Failover Create Order Upgrade to Expedited Delivery Schedule Delivery Failover to secondary node โข Consider multi-transaction business workflows โข What happens if the Raven client fails over to another node midway through the processing sequence?
- 21. Replication Failover โข Consider the risk/reward of allowing automatic failover โข Manual failover is an option โข Secondary nodes are treated as โhot standbyโ nodes โข Mix-and-match failover behaviors โข Consider SLAs and business needs when deciding on failover strategies โข These tradeoffs are not specific to RavenDB โข All distributed systems have similar challenges
- 22. Questions