FAQ
How to choose the back-end storage? Choose RocksDB, Cassandra, ScyllaDB, Hbase or Mysql?
The choice of backend storage depends on specific needs. For installations on a single machine (node) with data volumes under 10 billion records, RocksDB is generally recommended. However, if a distributed backend is needed for scaling across multiple nodes, other options should be considered. ScyllaDB, designed as a drop-in replacement for Cassandra, offers protocol compatibility and better hardware utilization, often requiring less infrastructure. HBase, on the other hand, requires a Hadoop ecosystem to function effectively. Finally, while MySQL supports horizontal scaling, managing it in a distributed setup can be challenging.
Prompt when starting the service:
xxx (core dumped) xxx
Please check if the JDK version is Java 11, at least Java 8 is required
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
init-storeBefore starting the service for the first time, you need to use the initialization backend first , and subsequent versions will prompt more clearly and directly.
Do all backends need to be executed before use init-store, and can the serialization options be filled in at will?
Before running the
init-store.sh
command to create the databases that will host the graphs defined in the configuration file, the back-end must be properly configured and running. The only exception is when using memory as the back-end. Supported back-ends includecassandra
,hbase
,rocksdb
,scylladb
, etc. It’s important to note that serialization must maintain a strict one-to-one correspondence and cannot be assigned differntly than the recommended values.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 error
NoHostAvailableException
occurred while executinginit-store.sh
.NoHostAvailableException
means that theCassandra
service cannot be connected to. If you are sure that you want to use the Cassandra backend, please install and start this service first. As for the message itself, it may not be clear enough, and we will update the documentation to provide further explanation.The
bin
directory containsstart-hugegraph.sh
,start-restserver.sh
andstart-gremlinserver.sh
. These scripts seem to be related to startup. Which one should be used?Since version 0.3.3, GremlinServer and RestServer have been merged into HugeGraphServer. To start, use start-hugegraph.sh. The latter two will be removed in future versions.
Two graphs are configured, the names are
hugegraph
andhugegraph1
, and the command to start the service isstart-hugegraph.sh
. Is only the hugegraph graph opened?start-hugegraph.sh
will open all graphs under the graphs ofgremlin-server.yaml
. The two have no direct relationship in nameAfter the service starts successfully, garbled characters are returned when using
curl
to query all verticesThe 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 thepostman
ofFirefox
or therestlet
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 existCheck 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 theseURLs
. 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 sendingGremlin
statements, an error is reported:Request Failed(500)
It may be that the configuration of
GremlinServer
is wrong, check whether thehost
andport
ofgremlin-server.yaml
match thegremlinserver.url
ofrest-server.properties
, if they do not match, modify them, and then Restart the service.When using
Loader
to import data, aSocket Timeout
exception occurs, and thenLoader
is interruptedContinuously importing data will put too much pressure on the
Server
, which will cause some requests to time out. The pressure onServer
can be appropriately relieved by adjusting the parameters ofLoader
(such as: number of retries, retry interval, error tolerance, etc.), and reduce the frequency of this problem.How to delete all vertices and edges. There is no such interface in the RESTful API. Calling
g.V().drop()
ofgremlin
will report an errorVertices in transaction have reached capacity xxx
At present, there is really no good way to delete all the data. If the user deploys the
Server
and the backend by himself, he can directly clear the database and restart theServer
. You can use the paging API or scan API to get all the data first, and then delete them one by one.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 theServer
when the database is cleared, otherwise the residual cache will be inconsistent.An error is reported during the process of inserting vertices or edges:
Id max length is 128, but got xxx {yyy}
orBig id max length is 32768, but got xxx
In order to ensure query performance, the current backend storage limits the length of the id column. The vertex id cannot exceed 128 bytes, the edge id cannot exceed 32768 bytes, and the index id cannot exceed 128 bytes.
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 ofVertexLabel
, such as “investment” relationship, which can be “individual” investing in “enterprise”, or “enterprise” investing in “enterprise”?An
EdgeLabel
does not support connecting multiple pairs ofVertexLabels
, users need to split theEdgeLabel
into finer details, such as: “personal investment”, “enterprise investment”.Prompt
HTTP 415 Unsupported Media Type
when sending a request throughRestAPI
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