FAQ

How to choose the back-end storage? RocksDB or distributed storage?
HugeGraph supports multiple deployment modes. Choose based on your data scale and scenario:
- Standalone Mode: Server + RocksDB, suitable for development/testing and small to medium-scale data (≤ 2 TB)
- Distributed Mode: HugeGraph-PD + HugeGraph-Store (HStore), for deployments that require horizontal scaling and multiple replicas, supporting data scales up to 1 PB
Version 1.7.0 supports RocksDB, HStore, HBase, and Memory. Legacy backends such as Cassandra, ScyllaDB, MySQL, and PostgreSQL require version 1.5.x or earlier.
Prompt when starting the service: xxx (core dumped) xxx
First confirm that the JDK version is Java 11 or later. HugeGraph 1.7.0 no longer supports Java 8.
The service is started successfully, but there is a prompt similar to “Unable to connect to the backend or the connection is not open” when operating the graph
Persistent local backends such as RocksDB and HBase must be initialized with init-store before their first startup. HStore is managed by PD and Store and does not use this script.
Do all backends need to be executed before use init-store, and can the serialization options be filled in at will?
Memory and HStore do not use init-store; persistent local backends such as RocksDB and HBase must be initialized before first use. The serializer must match the backend, for example RocksDB uses binary.
Execution init-store error: Exception in thread "main" java.lang.UnsatisfiedLinkError: /tmp/librocksdbjni3226083071221514754.so: /usr/lib64/libstdc++.so.6: version `GLIBCXX_3.4.10' not found (required by /tmp/librocksdbjni3226083071221514754.so)
RocksDB requires gcc 4.3.0 (GLIBCXX_3.4.10) and above
The bin directory contains start-hugegraph.sh, start-restserver.sh and start-gremlinserver.sh. These scripts seem to be related to startup. Which one should be used?
Current release packages retain only start-hugegraph.sh as the Server startup script. GremlinServer and the REST Server run in the same process.
Two graphs are configured, the names are hugegraph and hugegraph1, and the command to start the service is start-hugegraph.sh. Is only the hugegraph graph opened?
The script name is unrelated to the graph name. To load multiple local graphs from the graphs directory, set graph.load_from_local_config=true in rest-server.properties; its default value in the source code is false.
After the service starts successfully, garbled characters are returned when using curl to query all vertices
The batch vertices/edges returned by the server are compressed (gzip), and can be redirected to gunzip for decompression (curl http://example | gunzip), or can be sent with the postman of Firefox or the restlet plug-in of Chrome browser. request, the response data will be decompressed automatically.
When using the vertex Id to query the vertex through the RESTful API, it returns empty, but the vertex does exist
Check the type of the vertex ID. If it is a string type, the “id” part of the API URL needs to be enclosed in double quotes, while for numeric types, it is not necessary to enclose the ID in quotes.
Vertex Id has been double quoted as required, but querying the vertex via the RESTful API still returns empty
Check whether the vertex id contains +, space, /, ?, %, &, and = reserved characters of these URLs. If they exist, they need to be encoded. The following table gives the coded values:
```
special character | encoded value
------------------| -------------
+                 | %2B
space             | %20
/                 | %2F
?                 | %3F
%                 | %25
#                 | %23
&                 | %26
=                 | %3D
```
Timeout when querying vertices or edges of a certain category (query by label)
Since the amount of data belonging to a certain label may be relatively large, please add a limit limit.
It is possible to operate the graph through the RESTful API, but when sending Gremlin statements, an error is reported: Request Failed(500)
It may be that the configuration of GremlinServer is wrong, check whether the host and port of gremlin-server.yaml match the gremlinserver.url of rest-server.properties, if they do not match, modify them, and then Restart the service.
When using Loader to import data, a Socket Timeout exception occurs, and then Loader is interrupted
Continuously importing data will put too much pressure on the Server, which will cause some requests to time out. The pressure on Server can be appropriately relieved by adjusting the parameters of Loader (such as: number of retries, retry interval, error tolerance, etc.), and reduce the frequency of this problem.
How to delete all data from a graph
An administrator can call DELETE /graphspaces/{graphspace}/graphs/{graph}/clear?confirm_message=I'm sure to delete all data. The confirm_message query parameter must match that value exactly, otherwise the request is rejected. See the Graph API for details. This operation removes schemas, vertices, edges, and indexes.
The database has been cleared and init-store has been executed, but when trying to add a schema, the prompt “xxx has existed” appeared.
There is a cache in the HugeGraphServer, and it is necessary to restart the Server when the database is cleared, otherwise the residual cache will be inconsistent.
An error is reported during the process of inserting vertices or edges: The max length of vertex id is 16384, but got xxx {yyy} or The max length of edge id is 65536, but got xxx {yyy}
In order to ensure query performance, the current backend storage limits the length of the id column. The vertex id cannot exceed 16384 bytes and the edge id cannot exceed 65536 bytes. An index id longer than 32 bytes is stored as a hash instead of being rejected.
Is there support for nested attributes, and if not, are there any alternatives?
Nested attributes are currently not supported. Alternative: Nested attributes can be taken out as individual vertices and connected with edges.
Can an EdgeLabel connect multiple pairs of VertexLabel, such as “investment” relationship, which can be “individual” investing in “enterprise”, or “enterprise” investing in “enterprise”?
Yes. Call link(sourceLabel, targetLabel) once per pair when building the EdgeLabel; every pair is kept, so one “investment” label can cover both “individual” to “enterprise” and “enterprise” to “enterprise”. The older sourceLabel() and targetLabel() builder methods are deprecated and accept only a single pair.
Prompt HTTP 415 Unsupported Media Type when sending a request through RestAPI
Content-Type: application/json needs to be specified in the request header

Other issues can be searched in the issue area of the corresponding project, such as Server-Issues / Loader Issues