This is archived documentation for InfluxData product versions that are no longer maintained. For newer documentation, see the latest InfluxData documentation.
What is a continuous query?
A continuous query (CQ) is an InfluxQL query that the system periodically executes in batches.
Each batch contains one or more queries where each query covers a single GROUP BY time() interval.
InfluxDB always generates a query for the current GROUP BY time() interval (the one containing now()) and it generates zero or more queries for recent GROUP BY time() intervals.
The time ranges of the generated queries have round-number boundaries.
For example, if the CQ’s GROUP BY time() interval is 30 minutes long, the start and end times for each query (in MM:SS) are always 00:00 or 30:00.
The CQ schedule
The rate at which InfluxDB generates batches of queries and the number of queries generated per batch depend on the CQ’s GROUP BY time() interval and on the following configuration options (shown with their default settings):
compute-runs-per-interval = 10compute-no-more-than = "2m0s"recompute-previous-n = 2recompute-no-older-than = "10m0s"
Frequency of batch creation
InfluxDB compares compute-runs-per-interval and compute-no-more-than to determine the rate at which it generates batches for a CQ.
compute-runs-per-interval is the upper bound of the number of incremental queries generated per GROUP BY time() interval.
compute-no-more-than is the maximum frequency at which InfluxDB generates batches.
compute-no-more-than takes precedence over compute-runs-per-interval.
In the default settings, InfluxDB generates batches for a CQ as often as 10 times per the GROUP BY time() interval.
However, it will not generate batches more often than every two minutes, regardless of the value of GROUP BY time() divided by 10.
For example, if the CQ has a GROUP BY time(30m) interval, then compute-runs-per-interval sets a maximum batch frequency of 3m, since 30m / 10 = 3m.
This is less frequent than the maximum frequency of 2m, as set by compute-no-more-than, so the system generates a batch of that CQ every 3m.
If the CQ has a GROUP BY time(30s) interval, then compute-runs-per-interval sets a maximum batch frequency of 3s, since 30s / 10 = 3s.
However, compute-no-more-than takes precedence and thus the system generates batches every 2m.
Number of queries per batch
InfluxDB uses recompute-previous-n and recompute-no-older-than to determine the number queries generated per batch for a CQ.
All batches include at least one generated query with the time range that spans now().
The maximum number of additional queries with time ranges that span intervals prior to now() is determined by recompute-previous-n.
Therefore recompute-previous-n + 1 is the maximum number of queries per batch.
recompute-no-older-than puts a limit on the age of the previous query interval, such that the upper boundary of each generated query must be greater than now() - recompute-no-older-than.
recompute-no-older-than takes precedence over recompute-previous-n.
In the default settings, InfluxDB generates at most three queries per batch: one spanning now() and up to two queries spanning older time intervals, as set by recompute-previous-n.
In addition, the upper boundary of the query time range for each generated query must be less than 10m in the past.
For example, if the CQ has a GROUP BY time(30s) interval, then InfluxDB generates three queries for each batch.
However, if the CQ has a GROUP BY time(30m) interval, then InfluxDB generates only one or two queries for a given batch, since the third query would have an upper boundary at least 30m in the past, which exceeds the recompute-no-older-than setting.
Depending on your CQ’s GROUP BY time() interval you may want to make changes to the default configuration settings.
The next sections present example CQs and discuss how they work with the configuration options:
- CQ 1 is an introductory example CQ that shows how the default configuration settings work with a CQ’s
GROUP BY time()interval. - CQ 2 is an example of a CQ with a shorter term
GROUP BY time()interval that doesn’t work well with the default configuration settings. This section also covers how to alter the configuration settings to fix the issue. - CQ 3 is an example of a CQ with a longer term
GROUP BY time()interval. This section shows how to alter the configuration settings to take into account lagged data.
CQ 1: 4 minute GROUP BY time() interval
Create CQ 1
CREATE CONTINUOUS QUERY cq1 ON telegraf BEGIN SELECT MEAN(value) INTO cq_4m FROM cpu_usage_idle WHERE cpu='cpu-total' GROUP BY time(4m) ENDFor our purposes the only important part of that statement is the 4m GROUP BY time() interval.
For more on the syntax for creating CQs, see Continuous Queries.
The default CQ schedule
Default configuration settings:compute-runs-per-interval = 10compute-no-more-than = "2m0s"recompute-previous-n = 2recompute-no-older-than = "10m0s"
InfluxDB generates batches of CQ 1 every 2 minutes.
compute-runs-per-interval sets a maximum batch frequency of 0.4m, since 4m / 10 = 0.4m.
This is more frequent than the maximum frequency of 2m, as set by compute-no-more-than, so the system generates a batch of CQ 1 every 2m.
InfluxDB generates 3 queries per batch of CQ 1.
InfluxDB generates one query that spans now() and two additional queries that span older time intervals because recompute-no-older-than=10m always exceeds the recent time range covered by recompute-previous-n=2: 2 intervals * 4m = 8m, which is less than the 10m maximum.
CQ 1 in practice
A sample of CQ 1’s frequency of batch creation and the number of queries per batch on 2015/11/24 starting at 18:19:45 (UTC):
InfluxDB generates three queries at 18:19:45:
SELECT MEAN(value) INTO "telegraf"."default".cq_4m FROM "telegraf"."default".cpu_usage_idle WHERE cpu = 'cpu-total' AND time >= '2015-11-24T18:16:00Z' AND time < '2015-11-24T18:20:00Z' GROUP BY time(4m)
SELECT MEAN(value) INTO "telegraf"."default".cq_4m FROM "telegraf"."default".cpu_usage_idle WHERE cpu = 'cpu-total' AND time >= '2015-11-24T18:12:00Z' AND time < '2015-11-24T18:16:00Z' GROUP BY time(4m)
SELECT MEAN(value) INTO "telegraf"."default".cq_4m FROM "telegraf"."default".cpu_usage_idle WHERE cpu = 'cpu-total' AND time >= '2015-11-24T18:08:00Z' AND time < '2015-11-24T18:12:00Z' GROUP BY time(4m)InfluxDB generates another three queries two minutes later at 18:21:45:
SELECT MEAN(value) INTO "telegraf"."default".cq_4m FROM "telegraf"."default".cpu_usage_idle WHERE cpu = 'cpu-total' AND time >= '2015-11-24T18:20:00Z' AND time < '2015-11-24T18:24:00Z' GROUP BY time(4m)
SELECT MEAN(value) INTO "telegraf"."default".cq_4m FROM "telegraf"."default".cpu_usage_idle WHERE cpu = 'cpu-total' AND time >= '2015-11-24T18:16:00Z' AND time < '2015-11-24T18:20:00Z' GROUP BY time(4m)
SELECT MEAN(value) INTO "telegraf"."default".cq_4m FROM "telegraf"."default".cpu_usage_idle WHERE cpu = 'cpu-total' AND time >= '2015-11-24T18:12:00Z' AND time < '2015-11-24T18:16:00Z' GROUP BY time(4m)In both cases, the first query has the relevant time range that spans now(): 18:19:45 falls within the four minute interval between 18:16:00 and 18:20:00, and 18:21:45 falls within the four minute interval between 18:20:00 and 18:24:00.
The second two queries span older four minute time intervals.
Notice that the queries that cover the time ranges 18:16:00 through 18:20:00 and 18:12:00 through 18:16:00 appear in both the first batch of generated queries and in the second batch of generated queries.
The more recent CQ results overwrite previously calculated values.
This ensures that if data points arrive with a timestamp a few minutes in the past they are still incorporated into the CQ results.
CQ 2: 30 second GROUP BY time() interval
Create CQ 2
CREATE CONTINUOUS QUERY cq2 ON telegraf BEGIN SELECT MEAN(value) INTO "telegraf"."default".cq_30s FROM "telegraf"."default".cpu_usage_idle WHERE cpu = 'cpu-total' GROUP BY time(30s) ENDFor our purposes the only important part of that statement is the 30s GROUP BY time() interval.
For more on the syntax for creating CQs, see Continuous Queries.
The default CQ schedule
Default configuration settings:compute-runs-per-interval = 10compute-no-more-than = "2m0s"recompute-previous-n = 2recompute-no-older-than = "10m0s"
InfluxDB generates batches of CQ 2 every 2 minutes.
compute-runs-per-interval sets a maximum batch frequency of 3s, since 30s / 10 = 3s.
This is more frequent than the maximum frequency of 2m, as set by compute-no-more-than, so the system generates a batch of CQ 2 every 2m.
InfluxDB generates 3 queries per batch of CQ 2.
InfluxDB generates one query that spans now() and two additional queries that span older time intervals because recompute-no-older-than=10m always exceeds the recent time range covered by recompute-previous-n=2: 2 intervals * 30s = 1m, which is less than the 10m maximum.
CQ 2 in practice
A sample of CQ 2’s frequency of batch creation and the number of queries per batch on 2015/11/24 starting at 19:41:17 (UTC):
InfluxDB generates three queries at 19:41:17:
SELECT MEAN(value) INTO "telegraf"."default".cq_30s FROM "telegraf"."default".cpu_usage_idle WHERE cpu = 'cpu-total' AND time >= '2015-11-24T19:41:00Z' AND time < '2015-11-24T19:41:30Z' GROUP BY time(30s)
SELECT MEAN(value) INTO "telegraf"."default".cq_30s FROM "telegraf"."default".cpu_usage_idle WHERE cpu = 'cpu-total' AND time >= '2015-11-24T19:40:30Z' AND time < '2015-11-24T19:41:00Z' GROUP BY time(30s)
SELECT MEAN(value) INTO "telegraf"."default".cq_30s FROM "telegraf"."default".cpu_usage_idle WHERE cpu = 'cpu-total' AND time >= '2015-11-24T19:40:00Z' AND time < '2015-11-24T19:40:30Z' GROUP BY time(30s)InfluxDB generates another three queries two minutes later at 19:43:17:
SELECT MEAN(value) INTO "telegraf"."default".cq_30s FROM "telegraf"."default".cpu_usage_idle WHERE cpu = 'cpu-total' AND time >= '2015-11-24T19:43:00Z' AND time < '2015-11-24T19:43:30Z' GROUP BY time(30s)
SELECT MEAN(value) INTO "telegraf"."default".cq_30s FROM "telegraf"."default".cpu_usage_idle WHERE cpu = 'cpu-total' AND time >= '2015-11-24T19:42:30Z' AND time < '2015-11-24T19:43:00Z' GROUP BY time(30s)
SELECT MEAN(value) INTO "telegraf"."default".cq_30s FROM "telegraf"."default".cpu_usage_idle WHERE cpu = 'cpu-total' AND time >= '2015-11-24T19:42:00Z' AND time < '2015-11-24T19:42:30Z' GROUP BY time(30s)In both cases, the first query has the revelant time range that spans now(): 19:41:17 falls within the 30 second interval between 19:41:00 and 19:41:30, and 19:43:17 falls within the 30 second interval between 19:43:00 and 19:43:30.
The second two queries span older 30 second time intervals.
Because of CQ 2’s small GROUP BY time() interval, leaving the default configuration settings as-is causes InfluxDB to skip a 30 second interval.
In the example above, the system never queries the time range between 19:41:30 and 19:42:00.
The next two sections offer different ways to solve the missing interval problem.
Change the frequency of batch creation
New configuration settings:compute-runs-per-interval = 10compute-no-more-than = "1m30s"recompute-previous-n = 2recompute-no-older-than = "10m0s"
InfluxDB now generates batches of CQ 2 every 1.5 minutes.
compute-runs-per-interval sets a maximum batch frequency of 3s, since 30s / 10 = 3s.
This is more frequent than the maximum frequency of 1.5m, as set by compute-no-more-than, so the system generates a batch of CQ 2 every 1.5m.
Now a sample of CQ 2’s frequency of batch creation and the number of queries per batch on 2015/11/24 starting at 19:41:17 (UTC) looks like this:
InfluxDB generates three queries at 19:41:17:
SELECT MEAN(value) INTO "telegraf"."default".cq_30s FROM "telegraf"."default".cpu_usage_idle WHERE cpu = 'cpu-total' AND time >= '2015-11-24T19:41:00Z' AND time < '2015-11-24T19:41:30Z' GROUP BY time(30s)
SELECT MEAN(value) INTO "telegraf"."default".cq_30s FROM "telegraf"."default".cpu_usage_idle WHERE cpu = 'cpu-total' AND time >= '2015-11-24T19:40:30Z' AND time < '2015-11-24T19:41:00Z' GROUP BY time(30s)
SELECT MEAN(value) INTO "telegraf"."default".cq_30s FROM "telegraf"."default".cpu_usage_idle WHERE cpu = 'cpu-total' AND time >= '2015-11-24T19:40:00Z' AND time < '2015-11-24T19:40:30Z' GROUP BY time(30s)InfluxDB generates another three queries 1.5 minutes later at 19:42:47:
SELECT MEAN(value) INTO "telegraf"."default".cq_30s FROM "telegraf"."default".cpu_usage_idle WHERE cpu = 'cpu-total' AND time >= '2015-11-24T19:42:30Z' AND time < '2015-11-24T19:43:00Z' GROUP BY time(30s)
SELECT MEAN(value) INTO "telegraf"."default".cq_30s FROM "telegraf"."default".cpu_usage_idle WHERE cpu = 'cpu-total' AND time >= '2015-11-24T19:42:00Z' AND time < '2015-11-24T19:42:30Z' GROUP BY time(30s)
SELECT MEAN(value) INTO "telegraf"."default".cq_30s FROM "telegraf"."default".cpu_usage_idle WHERE cpu = 'cpu-total' AND time >= '2015-11-24T19:41:30Z' AND time < '2015-11-24T19:42:00Z' GROUP BY time(30s)Notice that because of the new frequency of batch creation, InfluxDB no longer misses the query that covers the time range from 19:41:30 through 19:42:00.
Change the number of queries per batch
New configuration settings:compute-runs-per-interval = 10compute-no-more-than = "2m0s"recompute-previous-n = 3recompute-no-older-than = "10m0s"
InfluxDB generates 4 queries per batch of CQ 2.
InfluxDB generates one query that spans now() and three additional queries that span older time intervals because recompute-no-older-than=10m always exceeds the recent time range covered by recompute-previous-n=3: 3 intervals * 30s = 1.5m, which is less than the 10m maximum.
Now a sample of CQ 2’s frequency of batch creation and the number of queries per batch on 2015/11/24 starting at 19:41:17 (UTC) looks like this:
InfluxDB generates four queries at 19:41:17:
SELECT MEAN(value) INTO "telegraf"."default".cq_30s FROM "telegraf"."default".cpu_usage_idle WHERE cpu = 'cpu-total' AND time >= '2015-11-24T19:41:00Z' AND time < '2015-11-24T19:41:30Z' GROUP BY time(30s)
SELECT MEAN(value) INTO "telegraf"."default".cq_30s FROM "telegraf"."default".cpu_usage_idle WHERE cpu = 'cpu-total' AND time >= '2015-11-24T19:40:30Z' AND time < '2015-11-24T19:41:00Z' GROUP BY time(30s)
SELECT MEAN(value) INTO "telegraf"."default".cq_30s FROM "telegraf"."default".cpu_usage_idle WHERE cpu = 'cpu-total' AND time >= '2015-11-24T19:40:00Z' AND time < '2015-11-24T19:40:30Z' GROUP BY time(30s)
SELECT MEAN(value) INTO "telegraf"."default".cq_30s FROM "telegraf"."default".cpu_usage_idle WHERE cpu = 'cpu-total' AND time >= '2015-11-24T19:39:30Z' AND time < '2015-11-24T19:40:00Z' GROUP BY time(30s)InfluxDB generates another four queries two minutes later at 19:43:17:
SELECT MEAN(value) INTO "telegraf"."default".cq_30s FROM "telegraf"."default".cpu_usage_idle WHERE cpu = 'cpu-total' AND time >= '2015-11-24T19:43:00Z' AND time < '2015-11-24T19:43:30Z' GROUP BY time(30s)
SELECT MEAN(value) INTO "telegraf"."default".cq_30s FROM "telegraf"."default".cpu_usage_idle WHERE cpu = 'cpu-total' AND time >= '2015-11-24T19:42:30Z' AND time < '2015-11-24T19:43:00Z' GROUP BY time(30s)
SELECT MEAN(value) INTO "telegraf"."default".cq_30s FROM "telegraf"."default".cpu_usage_idle WHERE cpu = 'cpu-total' AND time >= '2015-11-24T19:42:00Z' AND time < '2015-11-24T19:42:30Z' GROUP BY time(30s)
SELECT MEAN(value) INTO "telegraf"."default".cq_30s FROM "telegraf"."default".cpu_usage_idle WHERE cpu = 'cpu-total' AND time >= '2015-11-24T19:41:30Z' AND time < '2015-11-24T19:42:00Z' GROUP BY time(30s)Notice that because of the new number of queries per batch, InfluxDB no longer misses the query that covers the time range from 19:41:30 through 19:42:00.
CQ 3: 1 hour GROUP BY time() interval
Create CQ 3
CREATE CONTINUOUS QUERY cq3 ON telegraf BEGIN SELECT MEAN(value) INTO cq_1h FROM cpu_usage_idle WHERE cpu='cpu-total' GROUP BY time(1h) ENDFor our purposes the only important part of that statement is the 1h GROUP BY time() interval.
For more on the syntax for creating CQs, see Continuous Queries.
The default CQ schedule
Default configuration settings:compute-runs-per-interval = 10compute-no-more-than = "2m0s"recompute-previous-n = 2recompute-no-older-than = "10m0s"
InfluxDB generates batches of CQ 3 every 6 minutes.
compute-runs-per-interval sets a maximum batch frequency of 6m, since 60m / 10 = 6m.
This is less frequent than the maximum frequency of 2m, as set by compute-no-more-than, so the system generates a batch of CQ 3 every 6m.
InfluxDB generates at most 2 queries per batch of CQ 3.
InfluxDB generates one query that spans now() and at most 1 additional query that spans an older time interval because the third query would have an upper boundary at least 1h in the past, which exceeds the recompute-no-older-than (10m) setting.
CQ 3 in practice
A sample of CQ 3’s frequency of batch creation and the number of queries per batch on 2015/11/24 starting at 22:09:55 (UTC):
InfluxDB generates two queries at 22:09:55:
SELECT MEAN(value) INTO "telegraf"."default".cq_1h FROM "telegraf"."default".cpu_usage_idle WHERE cpu = 'cpu-total' AND time >= '2015-11-24T22:00:00Z' AND time < '2015-11-24T23:00:00Z' GROUP BY time(1h)
SELECT MEAN(value) INTO "telegraf"."default".cq_1h FROM "telegraf"."default".cpu_usage_idle WHERE cpu = 'cpu-total' AND time >= '2015-11-24T21:00:00Z' AND time < '2015-11-24T22:00:00Z' GROUP BY time(1h)InfluxDB generates one query six minutes later at 22:15:55:
SELECT MEAN(value) INTO "telegraf"."default".cq_1h FROM "telegraf"."default".cpu_usage_idle WHERE cpu = 'cpu-total' AND time >= '2015-11-24T22:00:00Z' AND time < '2015-11-24T23:00:00Z' GROUP BY time(1h)At 22:09:55, InfluxDB generates two queries; one query covers the time range that spans now() and one query covers the previous GROUP BY time() interval.
InfluxDB generates the second query because now() - 10m falls in the previous GROUP BY time() interval (22:09:55 - 10m = 21:59:55).
At 22:15:55, InfluxDB generates only one query.
That query covers the time range that spans now().
InfluxDB doesn’t generate a second query because now() - 10m falls in the interval that spans now() (22:15:55 - 10m = 22:05:55).
If you have lagged data, generating, at most, one query for a previous interval may not take into account all of your data. The next section offers one way to adjust the configuration settings so that a query batch always includes a query for one previous time interval.
Change the number queries per batch
New configuration settings:compute-runs-per-interval = 10compute-no-more-than = "2m0s"recompute-previous-n = 1recompute-no-older-than = 120m0s
InfluxDB generates 2 queries per batch of CQ 3.
InfluxDB generates one query that spans now() and one additional query that spans an older time interval because recompute-no-older-than=120m always exceeds the recent time range covered by recompute-previous-n=1: 1 interval * 1h = 60m, which is less than the 120m maximum.
Now, a sample of CQ 3’s frequency of batch creation and the number of queries per batch on 2015/11/24 starting at 22:09:55 (UTC) looks like this:
InfluxDB generates two queries at 22:09:55:
SELECT MEAN(value) INTO "telegraf"."default".cq_1h FROM "telegraf"."default".cpu_usage_idle WHERE cpu = 'cpu-total' AND time >= '2015-11-24T22:00:00Z' AND time < '2015-11-24T23:00:00Z' GROUP BY time(1h)
SELECT MEAN(value) INTO "telegraf"."default".cq_1h FROM "telegraf"."default".cpu_usage_idle WHERE cpu = 'cpu-total' AND time >= '2015-11-24T21:00:00Z' AND time < '2015-11-24T22:00:00Z' GROUP BY time(1h)InfluxDB generates two queries six minutes later at 22:15:55:
SELECT MEAN(value) INTO "telegraf"."default".cq_1h FROM "telegraf"."default".cpu_usage_idle WHERE cpu = 'cpu-total' AND time >= '2015-11-24T22:00:00Z' AND time < '2015-11-24T23:00:00Z' GROUP BY time(1h)
SELECT MEAN(value) INTO "telegraf"."default".cq_1h FROM "telegraf"."default".cpu_usage_idle WHERE cpu = 'cpu-total' AND time >= '2015-11-24T21:00:00Z' AND time < '2015-11-24T22:00:00Z' GROUP BY time(1h)Because of the new settings, InfluxDB always includes in a batch one query that spans an older time interval in addition to the query that spans now().