apache/skywalking · error · UnexpectedException

Can't split instance id into 2 parts, {}

Error message

Can't split instance id into 2 parts, {}

What it means

UnexpectedException thrown by IDManager.ServiceInstanceID.analysisId(String) when an instance id does not split into exactly 2 parts by Const.ID_PARSER_SPLIT. Instance ids are produced by buildId(serviceId, instanceName) as serviceId + '.' + encode(instanceName); analysisId inverts this and rejects any other shape, echoing the bad id in the message.

Source

Thrown at oap-server/server-core/src/main/java/org/apache/skywalking/oap/server/core/analysis/IDManager.java:147

         * @param serviceId built by {@link ServiceID#buildId(String, boolean)}
         * @return service instance id
         */
        public static String buildId(String serviceId, String instanceName) {
            if (StringUtil.isBlank(instanceName)) {
                instanceName = Const.BLANK_ENTITY_NAME;
            }
            return serviceId
                + Const.ID_CONNECTOR
                + encode(instanceName);
        }

        /**
         * @return service instance id object decoded from {@link #buildId(String, String)} result
         */
        public static ServiceInstanceID.InstanceIDDefinition analysisId(String id) {
            final String[] strings = id.split(Const.ID_PARSER_SPLIT);
            if (strings.length != 2) {
                throw new UnexpectedException("Can't split instance id into 2 parts, " + id);
            }
            return new ServiceInstanceID.InstanceIDDefinition(
                strings[0],
                decode(strings[1])
            );
        }

        /**
         * @return encoded service instance relation id
         */
        public static String buildRelationId(ServiceInstanceRelationDefine define) {
            return define.sourceId + Const.RELATION_ID_CONNECTOR + define.destId;
        }

        /**
         * @return encoded instance hierarchy relation id
         */
        public static String buildInstanceHierarchyRelationId(InstanceHierarchyRelationDefine define) {

View on GitHub (pinned to 102af09b4a)

Solutions

1. Build ids exclusively via IDManager.ServiceInstanceID.buildId(serviceId, instanceName) and pass only its output to analysisId
2. Verify instance names are URL-encoded on the build side (buildId already does this)
3. Inspect the failing id in the exception message to find the producing code path
4. For legacy stored ids, reindex or decode with the historical format

Example fix

// before
InstanceIDDefinition def = IDManager.ServiceInstanceID.analysisId(instanceName);

// after
String id = IDManager.ServiceInstanceID.buildId(serviceId, instanceName);
InstanceIDDefinition def = IDManager.ServiceInstanceID.analysisId(id);

if (id == null || id.split("\\.").length != 2) {
    throw new IllegalArgumentException("Not an instance id produced by IDManager.ServiceInstanceID.buildId: " + id);
}

boolean isInstanceId(String id) {
    return id != null && id.split("\\.").length == 2 && id.endsWith(".") == false;
}

try {
    InstanceIDDefinition def = IDManager.ServiceInstanceID.analysisId(id);
} catch (UnexpectedException e) {
    LOGGER.warn("Skipping malformed instance id: {}", id, e);
}

When it happens

Trigger: Passing a raw instance name, an id where the instance name was not URL-encoded (so embedded separators shift the split), an id carrying extra segments, or null/empty into analysisId.

Common situations: Custom receiver/analysis code assembling instance ids by string concatenation instead of buildId; names containing the connector character '.' unencoded; stale data from an older encoding scheme after upgrade.

Related errors

• Can't split service id into 2 parts, {}
• Illegal Service Relation entity id
• Illegal Service Instance Relation entity id
• Can't split endpoint id into 2 parts, {}
• Illegal endpoint Relation entity id, {}

AI-assisted analysis of apache/skywalking@102af09b4a (2026-08-14). Data as JSON: /api/errors/9ae6440fb7934fcd. Report an issue: GitHub.